Temperature diagnostic line ratios of Fe XVII
International Nuclear Information System (INIS)
Raymond, J.C.; Smith, B.W.; Los Alamos National Lab., NM)
1986-01-01
Based on extensive calculations of the excitation rates of Fe XVII, four temperature-sensitive line ratios are investigated, paying special attention to the contribution of resonances to the excitation rates and to the contributions of dielectronic recombination satellites to the observed line intensities. The predictions are compared to FPCS observations of Puppis A and to Solar Maximum Mission (SMM) and SOLEX observations of the sun. Temperature-sensitive line ratios are also computed for emitting gas covering a broad temperature range. It is found that each ratio yields a differently weighted average for the temperature and that this accounts for some apparent discrepancies between the theoretical ratios and solar observations. The effects of this weighting on the Fe XVII temperature diagnostics and on the analogous Fe XXIV/Fe XXV satellite line temperature diagnostics are discussed. 27 references
Laboratory measurements of the x-ray line emission from neon-like Fe XVII
International Nuclear Information System (INIS)
Brown, G V; Beiersdorfer, P; Chen, H; Scofield, J; Boyce, K R; Kelley, R L; Kilbourne, C A; Porter, F S; Gu, M F; Kahn, S M; Szymkowiak, A E
2006-01-01
The authors have conducted a systematic study of the dominant x-ray line emission from Fe XVII. These studies include relative line intensities in the optically thin limit, intensities in the presence of radiation from satellite lines from lower charge states of iron, and the absolute excitation cross sections of some of the strongest lines. These measurements were conducted at the Lawrence Livermore National Laboratory electron beam ion trap facility using crystal spectrometers and a NASA-Goddard Space Flight Center microcalorimeter array
Photoionization and electron-ion recombination of Fe XVII for high temperature plasmas
International Nuclear Information System (INIS)
Nahar, Sultana N.
2012-01-01
Earlier studies on electron-ion recombination of Fe XVII, e+FeXVIII→FeXVII, concentrated on low temperature region. However, due to its higher abundance, recombination in the high temperature region is of great importance. Total and level-specific recombination cross sections and rates of Fe XVII are presented from the detailed study in the high temperature. The calculations were carried out using the unified method which incorporates both the radiative recombination (RR) and dielectronic recombination (DR) including the interference effects. The method also yields self-consistent set of recombination rates and photoionization cross sections. Unified method is implemented through relativistic Breit-Pauli R-matrix (BPRM) method and close coupling (CC) approximation. For the details of the high energy and high temperature features a CC wave function expansion consisting of 60 levels from n=2 and 3 complexes of the core Fe XVIII was considered. Earlier study included core excitations to n=2 levels only. It is found that the resonances due to core excitations to n=3 levels are much more extensive and stronger than those to n=2 levels and increase the recombination considerably in the high temperature region. While earlier study of 3-level calculations agree very well with the experimentally derived low temperature recombination, the high temperature rate shows a broad peak at about 5×10 6 K, near the maximum abundance of the ion, due to dominance of DR via PEC (photo-excitation-of-core) resonances of n=3 levels. Level-specific recombination rate coefficients, which include both the RR and DR, are presented for 454 levels (n≤10, l≤9, 0 ≤J≤8 with even and odd parities) of Fe XVII. This is the first large-scale BPRM calculations for recombination of a complex atomic system beyond He- and Li-like ions. The results are expected to be accurate with 10-20% uncertainty and provide accurate modelings of ultraviolet to X-ray spectra.
Discrepancies between calculated and observed Fe XVII and Ni XIX solar coronal lines
Energy Technology Data Exchange (ETDEWEB)
Loulergue, M [Observatoire de Paris, Section de Meudon, 92 (France); Nussbaumer, H [Eidgenoessische Technische Hochschule, Zurich (Switzerland)
1975-12-01
The 36-levels model atom Fe/sup +16/ of Loulergue and Nussbaumer (1973) is extended to a 51-levels atom including n=4 configuration. The earlier conclusion that relative intensities among the Fe XVII lines are not sufficiently sensitive to variations in electron densities and electron temperature to deduce these parameters from observed intensity ratios still holds. Discrepancies between calculated and observed relative intensities in Fe XVII and Ni XIX are attributed to blends or misidentifications.
Atomic data and spectral line intensities for Fe XVII
International Nuclear Information System (INIS)
Bhatia, A.K.; Doschek, G.A.
2003-01-01
Electron impact collision strengths and spontaneous radiative decay rates are calculated for Fe XVII. The data pertain to the 73 levels of the configurations, 2s 2 2p 6 , 2s 2 2p 5 3s, 2s 2 2p 5 3p 2s 2 2p 5 3d, 2s2p 6 3s, 2s2p 6 3p, 2s2p 6 3d, 2s 2 2p 5 4s, 2s 2 2p 5 4p, 2s 2 2p 5 4d, 2s2p 6 4s, 2s2p 6 4p, and 2s2p 6 4d. Collision strengths are calculated at 11 incident electron energies: 58.5, 65.0, 70.0, 76.0, 85.0, 127.5, 170.0, 212.5, 255.0, 340.0, and 425.0 Ry. This work is an improvement over our earlier work on Fe XVII in two respects: (1) configurations involving 4s, 4p, and 4d electrons have been added and (2) a broader range of incident electron energies is used in the computation of collision strengths and excitation rate coefficients. Relative spectral line intensities are calculated for astrophysically important transitions. These are obtained by computing the excitation rate coefficients (cm 3 s -1 ), i.e., the collision strengths integrated over a Maxwellian electron distribution, and then solving the equations of detailed balance for the populations of the 73 energy levels, assuming a collisional excitation model and an electron temperature of 4 x 10 6 K. This temperature is typical for Fe XVII when formed in equilibrium by collisional ionization and recombination. Using the excitation rate coefficients and the radiative decay rates, level populations are computed for five electron densities and are given in this paper
Intensity ratio among Ne-like FeXVII n=3-2 transitions
International Nuclear Information System (INIS)
Morita, Shigeru; Oishi, Tetsutarou; Murakami, Izumi; Goto, Motoshi; Huang, Xianli; Zhang, Hongming
2016-01-01
Radial profiles of FeXVII 3s-2p and 3d-2p transitions emitted in wavelength range of 15-17A have been observed in Large Helical Device (LHD). The Chord-integrated radial profiles are converted into radial emissivity profile by means of Abel inversion. The emissivity ratios among FeXVII n=3-2 transitions calculated from the radial emissivity profile are compared with calculation based on a collisional-radiative (CR) model developed for Fe ions. The result reasonably confirms the effect of electron temperature and density on the emissivity ratios. However, the emissivity of 3C (2p"53d "1P_1 → 2p"6) transition is obviously lower than the prediction from the CR model. This discrepancy is consistent with measurements in the solar corona and other laboratory plasmas. (author)
Loch, S. D.; Ballance, C. P.; Li, Y.; Fogle, M.; Fontes, C. J.
2015-03-01
Recent measurements using an X-ray Free Electron Laser (XFEL) and an Electron Beam Ion Trap at the Linac Coherent Light Source facility highlighted large discrepancies between the observed and theoretical values for the Fe xvii 3C/3D line intensity ratio. This result raised the question of whether the theoretical oscillator strengths may be significantly in error, due to insufficiencies in the atomic structure calculations. We present time-dependent spectral modeling of this experiment and show that non-equilibrium effects can dramatically reduce the predicted 3C/3D line intensity ratio, compared with that obtained by simply taking the ratio of oscillator strengths. Once these non-equilibrium effects are accounted for, the measured line intensity ratio can be used to determine a revised value for the 3C/3D oscillator strength ratio, giving a range from 3.0 to 3.5. We also provide a framework to narrow this range further, if more precise information about the pulse parameters can be determined. We discuss the implications of the new results for the use of Fe xvii spectral features as astrophysical diagnostics and investigate the importance of time-dependent effects in interpreting XFEL-excited plasmas.
Measurement of the Radiative Decay of the Longest-Lived Level in the Fe XVII Spectrum
Brown, Gregory V.; Beiersdorfer, Peter; Träbert, Elmar
2014-08-01
The Fe XVII emission spectrum comprises several very prominent X-ray lines that play an important role in the study of many astrophysical objects. Among the Fe XVII X-ray lines, those emanating from a 3s level, i.e., lines 3F, 3G, and M2, invariably appear too strong compared to the lines emanating from a 3d level, i.e., lines 3C and 3D, when compared to theory. Two of the four 3s levels are metastable, which means they have a rather long radiative decay time compared to collisional processes. The decay rate of the 2p^53s J=2 level has recently been measured at the Livermore EBIT facility [J. R. Crespo López-Urrutia and P. Beiersdorfer, ApJ 721, 576 (2010)], and the scatter of predictions by a factor of 1.7 has been reduced to a measurement uncertainty of merely a few percent. Even longer-lived is the J=0 level of the same 2p^53s configuration. Theory predicts an exclusive magnetic dipole decay to the lowest J=1 level of the same 2p^53s configuration, i.e. to the upper level of line 3G. There appear to be fewer predictions for this rate than for the rates associated with the other Fe XVII levels. Various calculations yield a decay rate near 16 000 s-1 for this level (or a level lifetime near 63 µs). If this value is correct, electron-impact collisions affect line ratios tied to this level at densities between about 10^10 cm-3 and 10^13 cm-3, that is, exactly at many coronal densities of present interest. We have used the Livermore EBIT facility to measure the M1 decay rate of the 2p^53s J=0 level. We find a value commensurate with the value predicted by the Flexible Atomic Code.Work performed under auspices of U.S. D.o.E. by DE-AC52-07NA27344 and supported by NASA's APRA progam under Interagency Agreement NNG13WF991.
Large Enhancement in High-Energy Photoionization of Fe XVII and Missing Continuum Plasma Opacity
Nahar, Sultana N.; Pradhan, Anil K.
2016-06-01
Aimed at solving the outstanding problem of solar opacity, and radiation transport plasma models in general, we report substantial photoabsorption in the high-energy regime due to atomic core photoexcitations not heretofore considered. In extensive R -matrix calculations of unprecedented complexity for an important iron ion Fe xvii (Fe16 + ), with a wave function expansion of 99 Fe xviii (Fe17 + ) LS core states from n ≤4 complexes (equivalent to 218 fine structure levels), we find (i) up to orders of magnitude enhancement in background photoionization cross sections, in addition to strongly peaked photo-excitation-of-core resonances not considered in current opacity models, and ii) demonstrate convergence with respect to successive core excitations. The resulting increase in the monochromatic continuum, and 35% in the Rosseland mean opacity, are compared with the "higher-than-predicted" iron opacity measured at the Sandia Z -pinch fusion device at solar interior conditions.
Structure and magnetism in Co/X, Fe/Si, and Fe/(FeSi) multilayers
Franklin, Michael Ray
Previous studies have shown that magnetic behavior in multilayers formed by repeating a bilayer unit comprised of a ferromagnetic layer and a non-magnetic spacer layer can be affected by small structural differences. For example, a macroscopic property such as giant magnetoresistance (GMR) is believed to depend significantly upon interfacial roughness. In this study, several complimentary structural probes were used to carefully characterize the structure of several sputtered multilayer systems-Co/Ag, Co/Cu, Co/Mo, Fe/Si, and Fe//[FeSi/]. X-ray diffraction (XRD) studies were used to examine the long-range structural order of the multilayers perpendicular to the plane of the layers. Transmission electron diffraction (TED) studies were used to probe the long-range order parallel to the layer plane. X-ray Absorption Fine Structure (XAFS) studies were used to determine the average local structural environment of the ferromagnetic atoms. For the Co/X systems, a simple correlation between crystal structure and saturation magnetization is discovered for the Co/Mo system. For the Fe/X systems, direct evidence of an Fe-silicide is found for the /[FeSi/] spacer layer but not for the Si spacer layer. Additionally, differences were observed in the magnetic behavior between the Fe in the nominally pure Fe layer and the Fe contained in the /[FeSi/] spacer layers.
57Fe Moessbauer and magnetic studies of ErFe12-xNbx
International Nuclear Information System (INIS)
Wang, J L; Campbell, S J; Cadogan, J M; Tegus, O; Edge, A V J
2005-01-01
The structural and magnetic properties of ErFe 12-x Nb x compounds (x 0.6, 0.7 and 0.8) have been investigated by x-ray diffraction, ac susceptibility and dc magnetization measurements and 57 Fe Moessbauer spectroscopy. Refinements of the x-ray diffraction patterns show that the Nb atoms preferentially occupy the 8i sites; this can be understood in the terms of enthalpy effects and differences in the metallic radii. The average Fe-Fe distance at the different sites is found to behave as d Fe-Fe (8i)> d Fe-Fe (8j)> d Fe-Fe (8f). The unit cell volume increases slightly with increasing Nb content, consistent with the larger radius of Nb compared with Fe. A spin reorientation from easy-axis at room temperature to easy-cone at low temperatures has been detected for all compounds. The spin reorientation temperatures T sr in ErFe 12-x Nb x compounds remain essentially unchanged (T sr ∼42-44 K) with increasing Nb concentration, whereas a significant decrease in T sr (T sr1 ∼236-204 K; T sr2 ∼154-94 K) is obtained in DyFe 12-x Nb x from x = 0.6 to 0.8. This can be understood by taking the different crystal-field terms responsible for the spin reorientation in the two systems into account. We find that the spin-reorientation process is particularly sensitive to the sixth-order term B 60 O 60 of the crystal field acting on the Er 3+ ion, due to its large and positive value of γ J . 57 Fe hyperfine interaction parameters and magnetic moments values have been determined for the 8i, 8j and 8f sites from the Moessbauer spectra. The weighted average 57 Fe hyperfine field values were found to follow a T 2 dependence; this suggests that a single-particle excitation mechanism is responsible for reduction of the 3d-sublattice magnetization with increasing temperature
Fe L-shell Excitation Cross Section Measurements on EBIT-I
Chen, Hui; Beiersdorfer, P.; Brown, G.; Boyce, K.; Kelley, R.; Kilbourne, C.; Porter, F.; Gu, M. F.; Kahn, S.
2006-09-01
We report the measurement of electron impact excitation cross sections for the strong iron L-shell 3-2 lines of Fe XVII to Fe XXIV at the LLNL EBIT-I electron beam ion trap using a crystal spectrometer and NASA-Goddard Space Flight Center's 6x6 pixel array microcalorimeter. The cross sections were determined by direct normalization to the well-established cross sections for radiative electron capture. Our results include the excitation cross section for over 50 lines at multiple electron energies. Although we have found that for 3C line in Fe XVII the measured cross sections differ significantly from theory, in most cases the measurements and theory agree within 20%. This work was performed under the auspices of the U.S. DOE by LLNL under contract No. W-7405-Eng-48 and supported by NASA APRA grants to LLNL, GSFC, and Stanford University.
Energy Technology Data Exchange (ETDEWEB)
Tsuchiya, Yuu, E-mail: tsuchiya.yuu1990@gmail.com; Ikeda, Shugo; Kobayashi, Hisao [University of Hyogo (Japan)
2016-12-15
We have investigated the physical properties of single-crystalline K{sub x}Fe{sub 2-y}S{sub 2} and K{sub x}Fe{sub 2-y}Se{sub 2} samples using {sup 57}Fe Mössbauer spectroscopy. The observed {sup 57}Fe Mössbauer spectra were reconstructed using a major antiferromagnetic ordered K{sub 2}Fe{sub 4}Se{sub 5} phase and a minor paramagnetic phase down to 5 K, despite being superconducting below 32.2 K in K{sub x}Fe{sub 2-y}Se{sub 2}. The analysis of {sup 57}Fe Mössbauer spectrum for K{sub x}Fe{sub 2-y}S{sub 2} at 290 K confirms the presence of a major antiferromagnetic ordered K{sub 2}Fe{sub 4}S{sub 5} phase and a minor paramagnetic phase in the K{sub x}Fe{sub 2-y}S{sub 2} single crystal. The derived hyperfine interaction parameters of the paramagnetic phase in K{sub x}Fe{sub 2-y}S{sub 2} suggest that the microstructure of this phase in K{sub x}Fe{sub 2-y}S{sub 2} is similar to that of the superconducting phase in K{sub x}Fe{sub 2-y}Se{sub 2} although the K{sub x}Fe{sub 2-y}S{sub 2} single crystals exhibit no superconductivity down to 5 K.
Tropeano, M.; Pallecchi, I.; Cimberle, M. R.; Ferdeghini, C.; Lamura, G.; Vignolo, M.; Martinelli, A.; Palenzona, A.; Putti, M.
2010-05-01
In this paper we carry out a direct comparison between transport and superconducting properties—namely resistivity, magnetoresistivity, Hall effect, Seebeck effect, thermal conductivity, upper critical field—of two different families of Fe-based superconductors, which can be viewed in many respects as end members: SmFeAsO1 - xFx with the largest Tc and the largest anisotropy and Fe1 + yTe1 - xSex, with the largest Hc2, the lowest Tc and the lowest anisotropy. In the case of the SmFeAsO1 - xFx series, we find that a single-band description allows us to extract an approximate estimation of band parameters such as carrier density and mobility from experimental data, although the behaviour of the Seebeck effect as a function of doping demonstrates that a multiband description would be more appropriate. On the contrary, experimental data for the Fe1 + y(Te1 - x, Sex) series exhibit a strongly compensated behaviour, which can be described only within a multiband model. In the Fe1 + y(Te1 - x, Sex) series, the role of the excess Fe, tuned by Se stoichiometry, is found to be twofold: on one hand it dopes electrons in the system and on the other hand it introduces localized magnetic moments, responsible for Kondo like scattering and likely pairbreaking of Cooper pairs. Hence, Fe excess also plays a crucial role in determining superconducting properties such as the Tc and the upper critical field Hc2. The huge Hc2 values of the Fe1 + yTe1 - xSex samples are described by a dirty limit law, opposed to the clean limit behaviour of the SmFeAsO1 - xFx samples. Hence, magnetic scattering by excess Fe seems to drive the system in the dirty regime, but its detrimental pairbreaking role seems not to be as severe as predicted by theory. This issue has yet to be clarified, addressing the more fundamental issue of the interplay between magnetism and superconductivity.
Preparation and characterization of sputtered Fe1-xN x films
International Nuclear Information System (INIS)
Easton, E. Bradley; Buhrmester, Th.; Dahn, J.R.
2005-01-01
Iron nitride films have been prepared by reactive DC magnetron sputtering. The composition of Fe 1-x N x was varied over a range of 0 ≤ x ≤ 0.5 by controlling the nitrogen flow rate during sputtering. These films were characterized using powder X-ray diffraction (XRD), thermogravimetric and electron microprobe analysis. We found that the nitrogen content in the films increased with nitrogen gas partial pressure. XRD experiments revealed an evolution through the α-Fe, γ'-Fe 4 N, ε-Fe 2+z N, ζ-Fe 2 N, γ'''-FeN and γ'-FeN phases, when the nitrogen gas mole percentage was increased from 0% up to 70%. Above 70%, only the γ'-FeN phase was formed despite a measurable increase in the nitrogen content of the film with nitrogen gas partial pressure. Rietveld analysis of powder X-ray diffraction patterns revealed that this behavior is due to an increase in the nitrogen site occupation factor within the lattice
Microstructure and Properties of Fe3Al-Fe3AlC x Composite Prepared by Reactive Liquid Processing
Verona, Maria Nalu; Setti, Dalmarino; Paredes, Ramón Sigifredo Cortés
2018-04-01
A Fe3Al-Fe3AlC x composite was prepared using reactive liquid processing (RLP) through controlled mixture of carbon steel and aluminum in the liquid state. The microstructure and phases of the composite were assessed using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, optical microscopy, and differential scanning calorimetry. In addition, the density, hardness, microhardness, and elastic modulus were evaluated. The Fe3Al-Fe3AlC x composite consisted of 65 vol pct Fe3Al and 35 vol pct Fe3AlC x ( κ). The κ phase contained 10.62 at. pct C, resulting in the stoichiometry Fe3AlC0.475. The elastic modulus of the Fe3Al-Fe3AlC0.475 composite followed the rule of mixtures. The RLP technique was shown to be capable of producing Fe3Al-Fe3AlC0.475 with a microstructure and properties similar to those achieved using other processing techniques reported in the literature.
Gas phase synthesis of core-shell Fe@FeO{sub x} magnetic nanoparticles into fluids
Energy Technology Data Exchange (ETDEWEB)
Aktas, Sitki, E-mail: aksitki61@gmail.com; Thornton, Stuart C.; Binns, Chris [University of Leicester, Department of Physics and Astronomy (United Kingdom); Denby, Phil [Ensol As, Nesttun (Norway)
2016-12-15
Sorbitol, short chain molecules, have been used to stabilise of Fe@FeO{sub x} nanoparticles produced in the gas phase under the ultra-high vacuum (UHV) conditions. The sorbitol coated Fe@FeO{sub x} nanoparticles produced by our method have a narrow size distribution with a hydrodynamic diameter of 35 nm after NaOH is added to the solution. Magnetisation measurement shows that the magnetic nanoparticles are superparamagnetic at 100 K and demonstrate hysteresis at 5 K with an anisotropy constant of 5.31 × 10{sup 4} J/m{sup 3} (similar to bulk iron). Also, it is shown that sorbitol is only suitable for stabilising the Fe@FeO{sub x} suspensions, and it does not prevent further oxidation of the metallic Fe core. According to MRI measurement, the nanoparticles have a high transverse relaxation rate of 425 mM{sup −1} s{sup −1}.
Thermodynamic Description Of Ternary Fe-B-X Systems. Part 2: Fe-B-Ni
Directory of Open Access Journals (Sweden)
Miettinen J.
2014-06-01
Full Text Available Przedstawiono termodynamiczny opis trójskładnikowego układu Fe-B-Ni w kontekście nowej bazy danych dla układów Fe-B-X (X = Cr, Ni, Mn, Si, Ti, V, C. Parametry termodynamiczne dwuskładnikowych stopów Fe-B. Fe-Ni i B-Ni zostały są zaczerpnięte z wcześniejszych opracowań, przy tym opis B-Ni został nieznacznie zmodyfikowany. Parametry dla układu Fe-B-Ni zostały zoptymalizowane w tej pracy w oparciu o eksperymentalne równowagi fazowe i dane termodynamiczne zaczerpnięte z literatury. Roztwory stałe w układzie Fe-B-Ni opisano przy użyciu modelu roztworu substytucyjnego, a borki traktowane są jako fazy stechiometryczne lub półstechiometryczne typu (A.BpCq opisane przy użyciu modelu dwu podsieci.
Studies on electrodeposited Cd1-xFe xS thin films
International Nuclear Information System (INIS)
Deshmukh, S.K.; Kokate, A.V.; Sathe, D.J.
2005-01-01
Thin films of Cd 1-x Fe x S have been prepared on stainless steel and fluorine doped tin oxide (FTO) coated glass substrates using electrodeposition technique. Double distilled water containing precursors of Cd, Fe and S are used with ethylene diamine tetra-acetic acid (EDTA) disodium salt as a complexing agent to obtain good quality deposits by controlling the rate of reactions. The different preparative parameters like concentration of bath, deposition time, pH of the bath and Fe content in the bath have been optimized by photoelectrochemical (PEC) technique in order to get good quality thin films. Different techniques have been used to characterize electrodeposited Cd 1-x Fe x S thin films. The X-ray diffraction (XRD) analysis reveals that the films Cd 1-x Fe x S are polycrystalline in nature with crystallite size 282 A for the films deposited with optimized preparative parameters. Scanning electron microscopy (SEM) study for the sample deposited at optimized preparative parameters reveals that all grains uniformly distributed over the surface of stainless steel substrate indicates well defined growth of polycrystalline Cd-Fe-S material. Optical absorption shows the presence of direct transition and band gap energy decreases from 2.43 to 0.81 eV with the increase of Fe content from 0 to 1. PEC study shows the films of Cd 1-x Fe x S with x = 0.2 are more photosensitive than other compositions
A study of the Fe-based superconductor SmFeAsO{sub 1-x}F{sub x} by x-ray photoelectron spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Zhang, Y; Chen, Y L; Cui, Y J; Cheng, C H; Zhao, Y [Key Laboratory of Magnetic Levitation Technologies and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhang, H [Department of Physics, Peking University, Beijing 100871 (China)], E-mail: yzhao@swjtu.edu.cn
2009-01-15
The electronic structure of the Fe-based superconductor SmFeAsO{sub 1-x}F{sub x} (x = 0 and 0.2) is studied with x-ray photoemission spectroscopy (XPS) through comparing the band structures of the nonsuperconducting parent material SmFeAsO and the superconducting SmFeAsO{sub 0.8}F{sub 0.2} (T{sub c} = 52.5 K). A small peak centered at 0.2 eV below the Fermi level, E{sub F}, in the valence band is observed in the parent material SmFeAsO, which is due to the low-spin state of the Fe 3d electrons. With fluorine doping, the peak at 0.2 eV disappears and a broad plateau forms near the Fermi level; in the meantime, the density of states at E{sub F} is slightly suppressed. The O 1s and Sm 3d core levels shift towards high energy by {approx}0.55 eV with fluorine doping, but in a sharp comparison, the Fe 2p and As 3d core levels do not shift significantly (the binding energy shift is less than 0.01 eV). It is deduced from the core-level shifts that the Fermi level of the system moves up by 0.55 eV by fluorine doping.
International Nuclear Information System (INIS)
Deb, Aniruddha; Bergmann, Uwe; Cramer, S.P.; Cairns, Elton J.
2005-01-01
Fe K-edge X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) have been performed on electrodes containing LiFePO 4 to determine the local atomic and electronic structure and their stability with electrochemical cycling. A versatile electrochemical in situ cell has been constructed for long-term soft and hard X-ray experiments for the structural investigation on battery electrodes during the lithium-insertion/extraction processes. The device is used here for an X-ray absorption spectroscopic study of lithium insertion/extraction in a LiFePO 4 electrode, where the electrode contained about 7.7 mg of LiFePO 4 on a 20 μm thick Al-foil. Fe K-edge X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) have been performed on this electrode to determine the local atomic and electronic structure and their stability with electrochemical cycling. The initial state (LiFePO 4 ) showed iron to be in the Fe 2+ state corresponding to the initial state (0.0 mAh) of the cell, whereas in the delithiated state (FePO 4 ) iron was found to be in the Fe 3+ state corresponding to the final charged state (3 mAh). XANES region of the XAS spectra revealed a high spin configuration for the two states (Fe (II), d 6 and Fe (III), d 5 ). The results confirm that the olivine structure of the LiFePO 4 and FePO 4 is retained by the electrodes in agreement with the XRD observations reported previously. These results confirm that LiFePO 4 cathode material retains good structural short-range order leading to superior cycling capability
Ordering phenomena in FeCo-films and Fe/Cr-multilayers: an X-ray and neutron scattering study
Energy Technology Data Exchange (ETDEWEB)
Nickel, B.
2001-07-01
The following topics are covered: critical phenomena in thin films, critical adsorption, finite size scaling, FeCo Ising model, kinematical scattering theory for thin films, FeCo thin films, growth and characterisation of single crystal FeCo thin films, X-ray study of ordering in FeCo films, antiferromagnetic coupling in Fe/Cr multilayers, neutron scattering on Fe/Cr multilayers (WL)
Study of Moessbauer effect on LiFe5-x Alx O8, LiFe 5-x Gax O8 and LiGa5-x Fex O8 systems
International Nuclear Information System (INIS)
Barthem, V.M.T.S.
1982-01-01
The measures obtained by Moessbauer spectroscopy from LiFe 5-x Ga x O 8 and LiFe 5-x Al x O 8 systems are presented. A comparative study of the influences of dopant diamagnetic ions on magnetic structures of lithium ferrite was performed. The LiGa 5-x Fe x O 8 systems were analysed based on the existing data from LiAl 5-x Fe x O 8 systems, otaining informations about the iron ion behaviour in both matrices. (M.C.K.) [pt
Selective Magnetic Evolution of MnxFe1-xO Nanoplates
Song, Hyon-Min
2015-04-27
Iron-manganese oxide (MnxFe1-xO) nanoplates were prepared by thermal decomposition method. Irregular development of crystalline phases was observed with the increase of annealing temperature. Magnetic properties are in accordance with their respective crystalline phases, and the selective magnetic evolution from their rich magnetism of MnxFe1-xO and MnFe2O4 is achieved by controlling the annealing conditions. Rock-salt structure of MnxFe1-xO (space group Fm-3m) is observed in as-synthesized nanoplates, while MnFe2O4 and MnxFe1-xO with significant magnetic interactions between them are observed at 380 °C. In nanoplates annealed at 450 °C, soft ferrites of Mn0.48Fe2.52O4 with MnxFe1-xO are observed. It is assumed that the differential and early development of crystalline phase of MnxFe1-xO, and the inhomogeneous cation mixing between Mn and Fe cause this rather extraordinary magnetic development. In particular, the prone nature of divalent metal oxides to cation vacancy and the prolonged annealing time of 15 hours which enables ordering are also thought to contribute to these irregularities.
Selective Magnetic Evolution of MnxFe1-xO Nanoplates
Song, Hyon-Min; Zink, Jeffrey I.; Khashab, Niveen M.
2015-01-01
Iron-manganese oxide (MnxFe1-xO) nanoplates were prepared by thermal decomposition method. Irregular development of crystalline phases was observed with the increase of annealing temperature. Magnetic properties are in accordance with their respective crystalline phases, and the selective magnetic evolution from their rich magnetism of MnxFe1-xO and MnFe2O4 is achieved by controlling the annealing conditions. Rock-salt structure of MnxFe1-xO (space group Fm-3m) is observed in as-synthesized nanoplates, while MnFe2O4 and MnxFe1-xO with significant magnetic interactions between them are observed at 380 °C. In nanoplates annealed at 450 °C, soft ferrites of Mn0.48Fe2.52O4 with MnxFe1-xO are observed. It is assumed that the differential and early development of crystalline phase of MnxFe1-xO, and the inhomogeneous cation mixing between Mn and Fe cause this rather extraordinary magnetic development. In particular, the prone nature of divalent metal oxides to cation vacancy and the prolonged annealing time of 15 hours which enables ordering are also thought to contribute to these irregularities.
Moessbauer studies of the LiAl sub(5-x) Fe sub(x) O8 and LiGa sub(5-x) Fe sub(x) O8 systems
International Nuclear Information System (INIS)
Barthem, V.M.T.S.; Maria Neto, J.; Souza Barros, F. de
1982-01-01
Comparative Moessbauer studies of the LiGa sub(5-x) Fe sub(x) O 8 and LiAl sub(5-x) Fe sub(x) O 8 systems are shown. The characteristics of the Moessbauer spectra, obtained with LiGa 5 O 8 samples with 0,1% of Fe 3+ , differ drastically from that observed with LiAl 5 O 8 with the same three-valent iron concentration. All these differences are related to the more covalent character of the gallium-oxygen binding, when compared with the aluminium-oxygen one. (L.C.) [pt
International Nuclear Information System (INIS)
Doschek, G.A.; Feldman, U.; Cowan, R.D.
1981-01-01
We discuss high-resolution solar flare iron line spectra recorded between 1.82 and 1.97 A by a spectrometer flown by the Naval Research Laboratory on an Air Force spacecraft launched on 1979 February 24. The emission line spectrum is due to inner-shell transitions in the ions Fe XX-Fe XXV. Using theoretical spectra and calculations of line intensities obtained by methods discussed by Merts, Cowan, and Magee, we derive electron temperatures as a function for time of two large class X flares. These temperatures are deduced from intensities of lines of Fe XXIII, Fe XXII, and Fe XXIV. Previous measurements by us have involved only lines of Fe XXIV and Fe XXV. We discuss the determination of the differential emission measure between about 12 x 10 6 K and 20 x 10 6 K using these temperatures. The possibility of determining electron densities in flare and tokamak plasmas using the inner-shell spectra of Fe XXI and Fe XX is discussed. We also discuss recent theoretical work by Mewe and Schrijver based on atomic data of Grineva, Safronova, and Urnov
Structure and magnetic properties of Y2Fe17-xMnx compounds (x=0-6)
International Nuclear Information System (INIS)
Wang Yingang; Zhejiang Univ., Hangzhou; Yang Fuming; Chen Changpin; Tang Ning; Pan Hongge; Zhejiang Univ., Hangzhou; Wang Qidong
1996-01-01
The effect of Mn on structure and magnetic properties of Y 2 Fe 17-x Mn x compounds has been studied. Substitution of Mn for Fe does not change the structure of Y 2 Fe 17 , and all the Y 2 Fe 17-x Mn x compounds crystallize in Th 2 Ni 17 structure. The lattice constants first increase, then slightly decrease, and finally increase again. The Curie temperature of Y 2 Fe 17-x Mn x compounds first increases, shows a maximum at x=0.3, and then decreases again. The saturation magnetization of Y 2 Fe 17-x Mn x compounds decreases dramatically with increasing Mn content. The moments of Mn atoms in these compounds are also discussed. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Yan, Su-Yuan; Wang, Cheng-Yang [Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineer (Tianjin), Tianjin University, Tianjin 300072 (China); Gu, Rong-Min [Department of Chemistry, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineer (Tianjin), Tianjin University, Tianjin 300072 (China); Sun, Shuai [Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineer (Tianjin), Tianjin University, Tianjin 300072 (China); Li, Ming-Wei, E-mail: mingweili@tju.edu.cn [Department of Chemistry, Tianjin University, Tianjin 300072 (China); Collaborative Innovation Center of Chemical Science and Engineer (Tianjin), Tianjin University, Tianjin 300072 (China)
2015-04-15
Highlights: • LiMn{sub 0.6}Fe{sub 0.4}PO{sub 4}/C cathode material shows enhanced rate capability. • The Fe doped in the partial Mn sites could significantly facilitate the Li ions transfer. • The enhanced Li{sup +} ions diffusion contributes to the optimized rate capability of LiMn{sub 0.6}Fe{sub 0.4}PO{sub 4}. • ACM carbonization forms well carbon coating and a 3D carbon network structure. - Abstract: To enhance the rate and cyclic performances of LiMnPO{sub 4} cathode material for lithium-ion batteries, Mn is partially substituted with Fe, and LiMn{sub 1−x}Fe{sub x}PO{sub 4} (x = 0.2, 0.3, 0.4, 0.5) solid solutions are synthesized and investigated. Amphiphilic carbonaceous material (ACM) forms well carbon coating and connects the LiMn{sub 1−x}Fe{sub x}PO{sub 4} crystallites by a three-dimensional (3D) carbon network. The synergetic Fe substitution and carbon connection obviously improve the samples’ rate capacities and cyclic stability. The optimized LiMn{sub 0.6}Fe{sub 0.4}PO{sub 4}/C sample delivers discharge capacities of 160 mA h g{sup −1} at 0.05 C, 148 mA h g{sup −1} at 1 C, and 115 mA h g{sup −1} at 20 C. All samples have well capacity retention (>92%) after 50 charge/discharge cycles at 1 C. The enhanced electrochemical properties are mainly attributed to the improvement of Li ion and electron transport in the LiMn{sub 1−x}Fe{sub x}PO{sub 4}/C samples, respectively mainly resulting from their modified crystal structures caused by Fe substitution and the 3D carbon coating/connection originating from ACM carbonization. LiMn{sub 1−x}Fe{sub x}PO{sub 4} materials exhibit two discharge plateaus at ∼4.0 and ∼3.5 V (vs. Li{sup +}/Li), whose heights respectively reflect the redox potentials of Mn{sup 3+}/Mn{sup 2+} and Fe{sup 3+}/Fe{sup 2+} couples. The plateaus’ lengths correspond to the Mn/Fe ratio in LiMn{sub 1−x}Fe{sub x}PO{sub 4} and are affected by the kinetic behavior of samples. Though the ∼4.0 V plateau shrinks with
International Nuclear Information System (INIS)
Nkoma, J.S.; Ekosse, G.
1998-05-01
The X-ray Diffraction (XRD) technique is applied to study five samples of Cu-Ni orebodies, and it is shown that they contain chalcopyrite CuFeS 2 as the source of Cu, pentlandite (Fe,Ni) 9 S 8 as the source of Ni and pyrrhotite Fe 1-x S as a dominant compound. There are also other less dominant compounds such as bunsenite NiO, chalcocite Cu 2 S, penrosite (Ni, Cu)Se 2 and magnetite Fe 3 O 4 . Using the obtained XRD data, we obtain the lattice parameters for tetragonal chalcopyrite as a=b=5.3069A and c=10.3836A, cubic pentlandite as a=b=c=10.0487A, and hexagonal pyrrhotite as a=b=6.8820A and c=22.8037A. (author)
Mn and Fe Impurities in Si$_{1-x}$ Ge$_{x}$ alloys
2002-01-01
Following our investigations of Mn and Fe impurities in elemental semiconductors and in silicon in particular by means of on-line $^{57}$Fe Mössbauer spectroscopy, utilizing radioactive $^{57}$Mn$^{+}$ ion beams at ISOLDE, we propose to extend these studies to bulk and epitaxially-grown Si$_{1-x}$Ge$_{x}$ alloys. In these materials, although already successfully employed in electronic devices, little is known about point defects and important harmful 3d impurities. The experiments aim to determine a variety of fundamental properties: The lattice location of ion-implanted Mn/Fe, the electronic and vibrational properties of dilute Fe impurities in different lattice sites, the charge-state and composition dependence of the diffusivity of interstitial Fe on an atomic scale, the reactions and formation of complexes with lattice defects created by the $^{57}$Mn implantation or by the recoil effect in the nuclear decay to the Mössbauer state of $^{57m}$Fe. Feasibility studies in 2003 indicate that these aims can b...
Reid, Jean-Philippe
ommaire La structure du gap supraconducteur et sa modulation sont intimement liees au potentiel d'interaction responsable de l'appariement des electrons d'un supraconducteur. Ainsi, l'etude de la structure du gap-SC et de sa modulation permettent de faire la lumiere sur la nature du mecanisme d'appariement des electrons. A cet egard, les resultats experimentaux des supraconducteurs a base de fer ne cadrent pas dans un seul ensemble, ce qui est en opposition au gap-SC universel des cuprates. Dans ce qui suit, nous presenterons une etude systematique du gap-SC pour plusieurs pnictides. En effet, en utilisant la conductivite thermique, une sonde directionnelle du gap-SC, nous avons ete en mesure de reveler la structure du gap-SC pour les composes suivants : Ba1-xKxFe 2As2, Ba(Fe1-xCo x)2As2, LiFeAs et Fe1-deltaTe 1-xSex. L'etude de ces quatre composes, de trois differentes familles structurales, a pu etablir un tableau partiel mais tres exhaustif de la structure du gap-SC de pnictides. En effet, tel qu'illustre dans cette these, ces quatre composes ne possedent aucun noeud dans leur structure du gap-SC a dopage optimal. Toutefois, a une concentration differente de celle optimale pour les composes K-Ba122 et Co-Ba122, des noeuds apparaissent sur la surface de Fermi, aux extremites 'du dome supraconducteur. Ceci suggere fortement que, pour ces composes, la presence de noeuds sur la surface de Fermi est nuisible a la phase supraconductrice. Mots-cles: Supraconducteurs a base de fer, Pnictides, Structure du gap supraconducteur, Conductivite thermique
Magnetic properties of CeyFe4-xNixSb12
International Nuclear Information System (INIS)
Viennois, R.; Ravot, D.; Tedenac, J.C.; Charar, S.; Mauger, Alain
2005-01-01
The structural and magnetic properties of the metallic skutterudite CeFe 4 Sb 12 have been investigated, with those of Ce y Fe 4-x Ni x Sb z with compositions approaching the relations y=(4-2x)/3, z=12 for which the materials are semiconductors. The large and temperature-dependent contribution of Fe to the magnetic susceptibility of CeFe 4 Sb 12 has been isolated from the Ce contribution, which makes possible a quantitative analysis of the Kondo lattice behavior. In CeFe 4 Sb 12 the Wilson-Sommerfeld ratio is modified by a factor two with respect to former analyses where the magnetic contribution of Fe had been neglected. The main effect of the reduction of the free carrier (hole) concentration in Ce y Fe 4 Sb 12 is to suppress the Kondo effect and the Fe contribution to the magnetic susceptibility. The samples with theoretical hole concentration per unit cell p*=z-8-3y-2x smaller than 0.5 behave like semiconductors in which the exchange between localized Ce 3+ spins is negligible, and are most promising for a potential use as thermoelements
Structure and magnetic transition of LaFe13-xSix compounds
International Nuclear Information System (INIS)
Bo Liuxu; Altounian, Z; Ryan, D H
2003-01-01
Structure and magnetic transitions were investigated by x-ray diffraction and Moessbauer spectroscopy in LaFe 13-x Si x compounds with x = 1.6, 2.0 and 2.6. With increasing Si content, the La-Fe interatomic distance decreased while the average Fe-Fe distance increased. These changes affect the structural stability and the magnetic properties of the compounds. The temperature dependence of the hyperfine field for the compound with x = 2.6 can be fitted very well using a mean field model with a Brillouin function (BF) while that for the compounds with x = 1.6 and 2.0 changes more sharply than that predicted by the BF relation near the Curie temperature. The different nature of the magnetic transition with different Si content originates from the spatial distribution of the Si atoms and related variation of the La-(Fe, Si) and the Fe-Fe distances in the cubic NaZn 13 structure
Electronic structure of LaFe{sub 2}X{sub 2} (X = Si,Ge)
Energy Technology Data Exchange (ETDEWEB)
Hase, I., E-mail: i.hase@aist.go.jp [Electronics and Photonics Research Institute, AIST, Tsukuba, Ibaraki 305-8568 (Japan); Yanagisawa, T. [Electronics and Photonics Research Institute, AIST, Tsukuba, Ibaraki 305-8568 (Japan)
2011-11-15
We have calculated the electronic structure of LaFe{sub 2}Si{sub 2} and LaFe{sub 2}Ge{sub 2} from first-principles. The obtained Fermi surfaces of LaFe{sub 2}Si{sub 2} and LaFe{sub 2}Ge{sub 2} resemble those of LaRu{sub 2}Ge{sub 2}, which well explains the result of the dHvA experiments of CeRu{sub 2}Ge{sub 2}. Their density of states curves show the common feature with CaFe{sub 2}As{sub 2}. D(E{sub F}) strongly depends on the distortion of the FeX{sub 4} tetrahedra and/or the height of the X atom, as also found in iron-pnictide system. Recently found iron-pnictide superconductor (Ba,K)Fe{sub 2}As{sub 2} and the heavy-fermion superconductor CeCu{sub 2}Si{sub 2} both have the same crystal structure. In this paper we have calculated the electronic structure of LaFe{sub 2}Si{sub 2} and LaFe{sub 2}Ge{sub 2} from first-principles. These compounds also have the same crystal structure and closely related to both of (Ba,K)Fe{sub 2}As{sub 2} and CeRu{sub 2}Ge{sub 2}. The obtained Fermi surfaces of LaFe{sub 2}Si{sub 2} and LaFe{sub 2}Ge{sub 2} resemble those of LaRu{sub 2}Ge{sub 2}, which are already found that they well explain the results of the dHvA experiments of CeRu{sub 2}Ge{sub 2}. Their density of states curves show the common feature with CaFe{sub 2}As{sub 2}. The density of states at the Fermi level strongly depends on the distortion of the FeX{sub 4} tetrahedra and/or the height of the X atom from the two-dimensional Fe plane, as also found in iron-pnictide system. The electronic specific heat coefficient is 11.8 mJ/mol K{sup 2} for LaFe{sub 2}Si{sub 2} and 12.5 mJ/mol K{sup 2} for LaFe{sub 2}Ge{sub 2}, which is about 1/3 and 1/2 of experimental results, respectively.
Oliynyk, Anton O; Lomnytska, Yaroslava F; Dzevenko, Mariya V; Stoyko, Stanislav S; Mar, Arthur
2013-01-18
Construction of the isothermal section in the metal-rich portion (ternary phases: (Mo(1-x)Fe(x))(2)P (x = 0.30-0.82) and (Mo(1-x)Fe(x))(3)P (x = 0.10-0.15). The occurrence of a Co(2)Si-type ternary phase (Mo(1-x)Fe(x))(2)P, which straddles the equiatomic composition MoFeP, is common to other ternary transition-metal phosphide systems. However, the ternary phase (Mo(1-x)Fe(x))(3)P is unusual because it is distinct from the binary phase Mo(3)P, notwithstanding their similar compositions and structures. The relationship has been clarified through single-crystal X-ray diffraction studies on Mo(3)P (α-V(3)S-type, space group I42m, a = 9.7925(11) Å, c = 4.8246(6) Å) and (Mo(0.85)Fe(0.15))(3)P (Ni(3)P-type, space group I4, a = 9.6982(8) Å, c = 4.7590(4) Å) at -100 °C. Representation in terms of nets containing fused triangles provides a pathway to transform these closely related structures through twisting. Band structure calculations support the adoption of these structure types and the site preference of Fe atoms. Electrical resistivity measurements on (Mo(0.85)Fe(0.15))(3)P reveal metallic behavior but no superconducting transition.
International Nuclear Information System (INIS)
Duc, N.H.; Huong Giang, D.T.; Chau, N.
2004-01-01
Studies of the naturally formed nanostructure and magnetization reversal process were performed for the sputtered Tb(Fe 0.55 Co 0.45 ) 1.5 /Y x (Fe 0.7 Co 0.3 ) 1-x multilayers (0≤x≤0.2) with a TbFeCo layer thickness t TbFeCo =12 nm and YFeCo layer thickness t YFeCo =10 nm. The structural investigations showed that nanocrystals are naturally formed and coexist within the amorphous matrix in Y 0.1 (FeCo) 0.9 layers. In this state, low magnetic coercivity and large parallel magnetostrictive susceptibility are observed. The results are discussed in terms of the crystalline discontinuity of the soft YFeCo layers
Fe-moment instability in Ti{sub 1-x}Sc{sub x}Fe{sub 2} Laves-phase compounds
Energy Technology Data Exchange (ETDEWEB)
Ouladdiaf, B. [Institut Laue-Langevin, BP 156, 38042 GRENOBLE Cedex 09 (France); Deportes, J. [Lab. Louis Neel, CNRS, BP 166, 38042 GRENOBLE Cedex 09 (France); Saoudi, M. [Centre Universitaire de Guelma, GUELMA 24 000 (Algeria)
2002-07-01
The magnetic properties of the pseudo-binary Laves-phase compounds Ti{sub 1-x}Sc{sub x}Fe{sub 2} were investigated by means of magnetisation and high-resolution powder neutron diffraction techniques. For x<0.2 a transition from an antiferromagnetic state to a canted one with a ferromagnetic component in the basal plane is observed, while for 0.2<x<0.27 the transition is from a collinear ferromagnetic state along the c-axis to a canted one. For x{proportional_to}0.3, an additional first-order transition is observed at low temperature accompanied by a large magnetovolume anomaly due to the increase of the intrinsic moment of the Fe atoms at the 2a site. (orig.)
Structure and grindability of cast Ti-5Cr-xFe alloys
International Nuclear Information System (INIS)
Hsu, H.-C.; Pan, C.-H.; Wu, S.-C.; Ho, W.-F.
2009-01-01
The purpose of this study was to investigate the structure, microhardness and grindability of Ti-5Cr and a series of ternary Ti-5Cr-xFe alloys with 0.1, 0.5, 1, 3 and 5 wt.% Fe, respectively. This study evaluated the phase and structure of Ti-5Cr and Ti-5Cr-xFe alloys, using an X-ray diffraction (XRD) for phase analysis and optical microscope for microstructure of the etched alloys. In addition, grindability was evaluated by measuring the amount of metal volume removed after grinding for 1 min at each of the four rotational speeds of the wheel (500, 750, 1000 or 1200 m/min), with the goal of developing a titanium alloy with better machinability than commercially pure titanium (c.p. Ti). The results showed that the structure of Ti-5Cr-xFe alloys is sensitive to the Fe content. With Fe contents higher than 0.5 wt.%, the equi-axed β phase is entirely retained, while ω phase was found in the Ti-5Cr, Ti-5Cr-0.1Fe, Ti-5Cr-0.5Fe and Ti-5Cr-1Fe alloys. The largest quantity of ω phase and highest microhardness were found in Ti-5Cr-0.5Fe and Ti-5Cr-1Fe alloys. The grinding rates of the Ti-5Cr and Ti-5Cr-xFe alloys showed a similar tendency to the microhardness. The Ti-5Cr, Ti-5Cr-0.1Fe, Ti-5Cr-0.5Fe and Ti-5Cr-1Fe alloys exhibited the best grindability, especially at 500, 750 and 1000 m/min. Furthermore, the grindability of the tested metals increased in proportion to grinding speed up to 1000 m/min, with a decrease after 1200 m/min. This study concluded that Fe may be used to harden titanium and improve the grindability
Longitudinal recording on FePt and FePtX (X = B, Ni) intermetallic compounds
Li, Ning
1999-11-01
Near field recording on high coercivity FePt intermetallic compound media using a high Bsat write element was investigated. Untextured FePt media were prepared by magnetron sputtering on ZrO2 disks at a substrate temperature of 450°C, with post annealing at 450°C for 8 hrs. Both multilayer and cosputtered precursors produced the ordered tetragonal L10 phase with high coercivity between 5kOe and 12kOe. To improve readback noise decrease magnetic domain size, FePtB media were subsequently prepared by cosputtering. Over-write, roll-off, signal to noise ratio and non-linear transition shift (NLTS) ere measured by both metal in gap (MIG) and merged MR heads. FePtB media showed similar NLTS to commercial CoCrPtTa longitudinal media, but 5dB lower signal to noise ratio. By operating recording transducers in near contact, reasonable values of (>30dB) could be obtained. VSM Rotational Transverse Magnetization has been used for measuring the anisotropy field of magnetic thin films. Magnetization reversal during rotation of a 2D isotropic an applied field is discussed. The relationship between the transverse magnetization My and the applied field H was numerically solved. An excellent approximation for the transverse magnetization is found to be: My/Ms=A(1- H/Hk) 2.5, where A = 1.1434, and Hk is the anisotropy field. For curve fitting to experimental data, both A and Hk were used as fitting parameters. Comparison between a constructed torque hysteresis method and this VSM RTM method have been made theoretically and experimentally. Both results showed that VSM RTM will give better extrapolation of the anisotropy field. The torque measurement will slightly overestimate the anisotropy field. The anisotropy fields of FePt and FePtX (X = B, Ni) films were characterized using this VSM RTM technique with comparison to a CoCrTaPt disk. Anisotropy energy was derived. Hc/Hk was used as an indicator for coherent rotation of a single domain. Interactions between magnetic domains were
Energy Technology Data Exchange (ETDEWEB)
Calta, Nicholas P. [Department of Chemistry, Northwestern University (United States); Kanatzidis, Mercouri G., E-mail: m-kanatzidis@northwestern.edu [Department of Chemistry, Northwestern University (United States); Materials Science Division, Argonne National Laboratory (United States)
2016-04-15
This article reports two new Hf-rich intermetallics synthesized using Sn flux: Hf{sub 3}Fe{sub 4}Sn{sub 4} and Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x}. Hf{sub 3}Fe{sub 4}Sn{sub 4} adopts an ordered variant the Hf{sub 3}Cu{sub 8} structure type in orthorhombic space group Pnma with unit cell edges of a=8.1143(5) Å, b=8.8466(5) Å, and c=10.6069(6) Å. Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x}, on the other hand, adopts a new structure type in Cmc2{sub 1} with unit cell edges of a=5.6458(3) Å, b=35.796(2) Å, and c=8.88725(9) Å for x=0. It exhibits a small amount of phase width in which Sn substitutes on one of the Fe sites. Both structures are fully three-dimensional and are characterized by pseudo one- and two-dimensional networks of Fe–Fe homoatomic bonding. Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x} exhibits antiferromagnetic order at T{sub N}=46(2) K and its electrical transport behavior indicates that it is a normal metal with phonon-dictated resistivity. Hf{sub 3}Fe{sub 4}Sn{sub 4} is also an antiferromagnet with a rather high ordering temperature of T{sub N}=373(5) K. Single crystal resistivity measurements indicate that Hf{sub 3}Fe{sub 4}Sn{sub 4} behaves as a Fermi liquid at low temperatures, indicating strong electron correlation. - Graphical abstract: Slightly different growth conditions in Sn flux produce two new intermetallic compounds: Hf{sub 3}Fe{sub 4}Sn{sub 4} and Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x}. - Highlights: • Single crystals of both Hf{sub 3}Fe{sub 4}Sn{sub 4} and Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x} were grown using Sn flux. • The crystal structures were determined using single crystal X-ray diffraction. • The Fe moments in Hf{sub 3}Fe{sub 4}Sn{sub 4} display AFM order below T{sub N}=373 K. • The Fe moments in Hf{sub 9}Fe{sub 4−x}Sn{sub 10+x} display AFM order below T{sub N}=46 K.
Electronic, optical, and thermoelectric properties of Fe2+xV1−xAl
Directory of Open Access Journals (Sweden)
D. P. Rai
2017-04-01
Full Text Available We report the electronic, optical, and thermoelectric properties of full-Heusler alloy Fe2VAl with Fe antisite doping (Fe2+xV1−xAl as obtained from the first-principles Tran-Blaha modified Becke-Johnson potential. The results are discussed in relation to the available experimental data and show good agreements for the band gap, magnetic moment, and optical spectra. Exploring our transport data for thermoelectric applicability suggest that Fe2+xV1−xAl is a good candidate with a high figure of merit (ZT 0.75(0.65 for x = 0.25(0.50 at room temperature.
Energy Technology Data Exchange (ETDEWEB)
Fokwa, Boniface P.T. [Institut fuer Anorganische Chemie, Rheinisch-Westfaelische Technische Hochschule Aachen, D-52056 Aachen (Germany); Dronskowski, Richard [Institut fuer Anorganische Chemie, Rheinisch-Westfaelische Technische Hochschule Aachen, D-52056 Aachen (Germany)]. E-mail: drons@HAL9000.ac.rwth-aachen.de
2007-01-31
Single crystals of the borides Fe {sub x}Rh{sub 7-x}B{sub 3} (1 < x < 1.5) and Fe {sub x}Ru{sub 7-x}B{sub 3} (0 < x < 1) have been synthesized by arc-melting the elements in a water-cooled copper crucible under argon atmosphere. The silver-like products, structurally characterized by single-crystal X-ray analysis, adopt the hexagonal Th{sub 7}Fe{sub 3} structure type (space group P6{sub 3} mc, no. 186) with Z = 2. Their structures consist of layers of boron-centered trigonal prisms of rhodium or ruthenium (Rh;Ru) and iron on the one side, and one-dimensional channels of face-sharing octahedral (Rh;Ru){sub 6} clusters on the other. Unlike in FeRh{sub 6}B{sub 3}, the iron substitution takes place at two (6c and 2b) of the three available rhodium/ruthenium positions, with a preference for the 6c site in the case of the Fe {sub x}Rh{sub 7-x}B{sub 3} compounds but not for Fe {sub x}Ru{sub 7-x}B{sub 3}.
Magnetic properties of fcc (Co95Fe5)1-xAlx ribbons
International Nuclear Information System (INIS)
Makhlouf, Salah A.; Parker, F.T.; Benameur, T.
1999-01-01
Rapidly quenched (Co 95 Fe 5 ) 1-x Al x ribbons are investigated by X-ray diffraction, magnetization, and Moessbauer effect measurements. A single fcc phase is obtained for all ribbons x ≤ 10 at.%. The lattice constant increases linearly with x and is discussed in connection with magnetic moment. The influence of Al substitution on both magnetization and Fe-atom hyperfine field (H) is studied. At 296 K, the magnetization decreases linearly while H drops nonlinearly as x increases. Al substitution leads to substantial differences in iron hyperfine fields in bcc and fcc systems. Fe moment is perturbed differently by Al substitution in fcc (Co 95 Fe 5 ) 1-x Al x and bcc Fe-Al systems
Ferromagnetism in Fe{sub 3-x-y}Ni{sub x}GeTe{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Stahl, Juliane; Johrendt, Dirk [Muenchen Univ. (Germany). Dept. Chemie; Pomjakushin, Vladimir [Paul Scherrer Institute, Villigen (Switzerland). Lab. for Neutron Scattering
2016-07-01
Polycrystalline samples of Fe{sub 3-y}GeTe{sub 2} (0.08 ≤ y ≤ 0.29) and the solid solutions Fe{sub 3-x-y}Ni{sub x}GeTe{sub 2} (0.24 ≤ x ≤ 1.32; 0.14 ≤ y ≤ 0.41) were synthesized at 898-973 K in a resistance furnace and characterized by X-ray and neutron powder diffraction with Rietveld analysis (Fe{sub 3}GeTe{sub 2} type, P6{sub 3}/mmc, a = 402.665(3), c = 1632.820(14) pm for x = 0, y = 0.08). Fe{sub 3}Ge layers with planar FeGe hexagons and additional iron atoms above and below the rings are separated by double layers of tellurium atoms. Fe{sub 3}GeTe{sub 2} is ferromagnetic below T{sub C} = 230 K with magnetic moments aligned along the c axis. T{sub C} depends on the iron content and decreases with increasing iron vacancies continuously to 153 K in Fe{sub 2.71}GeTe{sub 2}. Further reduction of T{sub C} is possible by nickel substitution until magnetic ordering is nearly absent in Fe{sub 1.33}Ni{sub 1.32}GeTe{sub 2}. The suppression of the magnetic ordering is caused by random dilution of the magnetic iron atoms either by vacancies or by non-magnetic nickel atoms.
Mossbauer spectral study of NdFe1-xGaxO3 perovskites
International Nuclear Information System (INIS)
Rubin, J.; Piquer, C.; Filoti, G.; Parra-Borderias, M.; Bartolome, F.; Bartolome, J.
2007-01-01
The 57 Fe Mossbauer spectra of NdFe 1-x Ga x O 3 (x=0, 0.1, 0.2, 0.25, 0.5 and 0.7) have been measured at room temperature (RT). For x<0.5 the spectra have been fitted with magnetic sextets with their areas following a binomial distribution of Fe surroundings with Ga neighbours. The spectra for x=0.5 and 0.7 show paramagnetic doublets, which account for the percolation effect induced by the non-magnetic Ga substitution for Fe, which has been estimated to be x=0.43 at RT. The analysis of the hyperfine field values as a function of the Ga concentration shows the effect of the variations of the antiferromagnetic sublattice magnetization. Moreover, the dependence of this field with the number of susbstituted neighbours suggests an increase of the average Fe-O-Fe exchange interaction as a consequence of the lattice contraction when Ga susbtitutes for Fe
Energy Technology Data Exchange (ETDEWEB)
Misra, Sushil K., E-mail: skmisra@alcor.concordia.ca [Physics Department, Concordia University, Montreal, QC, Canada H3G 1M8 (Canada); Andronenko, S.I. [Physics Institute, Kazan Federal University, Kazan 420008 (Russian Federation); Thurber, A.; Punnoose, A. [Department of Physics, Boise State University, Boise, ID 83725-1570 (United States); Nalepa, A. [Max-Planck-Institut für Chemische Energie Konversion, Stifstrasse 34-36, 45470 Mülheim an der Ruhr (Germany)
2014-08-01
EPR studies on two types of nanoparticles of Fe{sup 3+} doped, 0.1–10%, ZnO, NL and QJ, prepared using similar chemical hydrolysis methods, in diethylene glycol, and in denatured ethanol solutions, respectively, were carried out at X-band (∼9.5 GHz) at 77 K and at Q-band (∼34.0 GHz) at 10, 80, and 295 K. To interpret the experimental results, EPR spectra were simulated by exact diagonalization of the spin-Hamiltonian matrix to identify the Fe ions at different magnetically active sites in these samples. The simulation for NL samples revealed that they contained (i) Fe{sup 3+} ions, which substituted for Zn ions, the zero-field splitting (ZFS) parameter which has a large distribution over the sample due to oxygen vacancies in the second coordination sphere; (ii) EPR signal from surface oxygen defects; and (iii) ferromagnetically (FM) coupled Fe ions with concentration of Fe more than 1%. The EPR spectra for QJ samples are very different from those for NL samples, exhibiting only rather intense FM EPR lines. The FM and EPR spectra in NL and/or QJ samples are found to vary strongly with differences in the surface morphology of nanoparticles. - Highlights: • X and Q band EPR studies on NL and QJ nanoparticles of Fe{sup 3+} doped ZnO at 10, 80, and 295 K. • Fe ions are present at different magnetically active sites in these samples. • NL samples consist of paramagnetic Fe{sup 3+} ions, and ferromagnetically coupled Fe ions. • QJ samples exhibit only intense ferromagnetic lines, different from QJ. • Spectra vary strongly with the surface morphology of nanoparticles.
Oxidation states of Fe in LaNi1-xFexO3
International Nuclear Information System (INIS)
Goeta, A.E.; Falcon, H.; Carbonio, R.
1994-01-01
The distribution of oxidation states in perovskites of the type LaA 1-x B x O 3 (A and B transition metal ions) can be ''tailored'' by x variation. In particular, in LaNiO 3 it has been shown that Fe substitution for Ni foces some Ni 3+ into Ni 2+ , while some Fe 3+ changes into the unusual Fe 4+ state. In addition, the existence of mixed oxidation states of Fe and/or Ni in LaNi 1-x Fe x O 3 has been related to its catalytic activity in hydrogen peroxide decomposition. The Fe 4+ population, obtained using Moessbauer spectroscopy, was found to be constant for all the analyzed annealing temperatures for x = 0.25 concentration, where the isomer shift difference for both states is the highest and the catalytic activity is maximum. (orig.)
Directory of Open Access Journals (Sweden)
Fabiano Magalhães
2008-09-01
Full Text Available In this work two perovskites were prepared: LaMn1-xFe xO3, and LaMn0.1-x Fe0.90Mo xO3. XRD and Mössbauer spectroscopy suggest the formation of pure phase perovskite with the incorporation of Fe and Mo in the structure. The catalytic activity of these materials was studied in two reactions with H2O2: the decomposition to O2, and the oxidation of the model organic contaminant methylene blue. The perovskite composition strongly affects the catalytic activity, while Fe decreases the H2O2 decomposition Mo strongly improves dye oxidation.
Microemulsion synthesis and magnetic properties of Fe{sub x}Ni{sub (1−x)} alloy nanoparticles
Energy Technology Data Exchange (ETDEWEB)
Beygi, H., E-mail: hossein.beygi@stu-mail.um.ac.ir; Babakhani, A.
2017-01-01
This paper investigates synthesis of Fe{sub x}Ni{sub (1−x)} bimetallic nanoparticles by microemulsion method. Through studying the mechanism of nanoparticles formation, it is indicated that synthesis of nanoparticles took placed by simultaneous reduction of metal ions and so nanoparticles structure is homogeneous alloy. Fe{sub x}Ni{sub (1−x)} nanoparticles with different sizes, morphologies and compositions were synthesized by changing the microemulsion parameters such as water/surfactant/oil ratio, presence of co-surfactant and NiCl{sub 2}·6H{sub 2}O to FeCl{sub 2}·4H{sub 2}O molar ratio. Synthesized nanoparticles were characterized by transmission electron microscopy, particle size analysis, X-ray diffraction, atomic absorption and thermogravimetric analyses. The results indicated that, presence of butanol as co-surfactant led to chain-like arrangement of nanoparticles. Also, finer nanoparticles were synthesized by decreasing the amount of oil and water and increasing the amount of CTAB. The results of vibrating sample magnetometer suggested that magnetic properties of Fe{sub x}Ni{sub (1−x)} alloy nanoparticles were affected by composition, size and morphology of the particles. Spherical and chain-like Fe{sub x}Ni{sub (1−x)} alloy nanoparticles were superparamagnetic and ferromagnetic, respectively. Furthermore, higher iron in the composition of nanoparticles increases the magnetic properties. - Highlights: • Fe{sub x}Ni{sub (1−x)} alloy NPs synthesized by simultaneous metal ions reduction in microemulsion. • Finer NPs synthesized at lower amount of oil and water and higher amount of CTAB. • Chain-like Fe{sub x}Ni{sub (1−x)} NPs are ferromagnetic; higher aspect ratio, more magnetization. • Spherical Fe{sub x}Ni({sub 1−x)} NPs with smaller size (7 nm) are superparamagnetic. • Spherical Fe{sub x}Ni{sub (1−x)} nanoparticles with higher x had increased magnetic properties.
New Insights into Mn1−xZnxFe2O4 via Fabricating Magnetic Photocatalyst Material BiVO4/Mn1−xZnxFe2O4
Directory of Open Access Journals (Sweden)
Taiping Xie
2018-02-01
Full Text Available BiVO4/Mn1−xZnxFe2O4 was prepared by the impregnation roasting method. XRD (X-ray Diffractometer tests showed that the prepared BiVO4 is monoclinic crystal, and the introduction of Mn1−xZnxFe2O4 does not change the crystal structure of BiVO4. The introduction of a soft-magnetic material, Mn1−xZnxFe2O4, was beneficial to the composite photocatalyst’s separation from the liquid solution using an extra magnet after use. UV-vis spectra analysis indicated that Mn1−xZnxFe2O4 enhanced the absorption intensity of visible light for BiVO4. EIS (electrochemical impedance spectroscopy investigation revealed that the introduction of Mn1−xZnxFe2O4 enhanced the conductivity of BiVO4, further decreasing its electron transfer impedance. The photocatalytic efficiency of BiVO4/Mn1−xZnxFe2O4 was higher than that of pure BiVO4. In other words, Mn1−xZnxFe2O4 could enhance the photocatalytic reaction rate.
Alzate-Cardona, J. D.; Barco-Rios, H.; Restrepo-Parra, E.
2018-02-01
The magnetocaloric behavior of La{2/{3}} Ca{1/{3}} Mn1-x Fe x O3 for x = 0.00, 0.02, 0.03, 0.05, 0.07, 0.08 and 0.10 under the influence of an external magnetic field was simulated and analyzed. Simulations were carried out using the Monte Carlo method and the classical Heisenberg model under the Metropolis algorithm. These mixed valence manganites are characterized by having three types of magnetic ions corresponding to Mn4+≤ft(S=\\frac{3}{2}\\right) , which are bonded with Ca2+ , and Mneg3+ and Mneg\\prime3+ (S=2) , related to La3+ . The Fe ions were randomly included, replacing Mn ions. With this model, the magnetic entropy change, Δ S , in an isothermal process was determined. -Δ Sm showed maximum peaks around the paramagnetic-ferromagnetic transition temperature, which depends on Fe doping. Relative cooling power was computed for different Fe concentrations varying the magnetic applied field. Our model and results show that the Fe doping decreases the magnetocaloric effect in the La{2/{3}} Ca{1/{3}} Mn1-x Fe x O3, making this a bad candidate for magnetic refrigeration. The strong dependence of the magnetocaloric behavior on Fe doping and the external magnetic field in La{2/{3}} Ca{1/{3}} Mn1-x Fe x O3 can boost these materials for the future technological applications.
Energy Technology Data Exchange (ETDEWEB)
Sun, Y.W.; Yan, J.L., E-mail: yjl@gxu.edu.cn; Feng, E.L.; Tang, G.W.; Zhou, K.W.
2017-01-15
The structure and magnetocaloric effect of Mn{sub 5−x}Fe{sub x}GeSi{sub 2} compounds were studied. Analysis of X-ray powder diffraction and energy dispersive X-Ray spectroscopy revealed that Mn{sub 5−x}Fe{sub x}GeSi{sub 2} alloys with x<1 crystallize in the Mn{sub 5}Si{sub 3}-type structure (space group P6{sub 3}/mcm), maintaining the structure of Mn{sub 5}Ge{sub 3}; and alloys with x=1.5 and 2 consist of the major Mn{sub 5}Si{sub 3}-type phase and the minor Ni{sub 2}In-type phase (space group P6{sub 3}/mmc). The results of Rietveld refinement showed that the cell parameters for the Mn{sub 5}Si{sub 3}-type phase decrease with increasing Fe content. The positive slopes in Arrott plots indicate that a second-order ferromagnetic to paramagnetic transition occurs. The Curie temperature increases with increasing Fe content from 182 K for x=0.6 to 224 K for x=2. The maximum magnetic entropy change of 3.7 J/(kg K) for x=0.8 was found under a magnetic field change of 0–20 kOe. - Highlights: • Mn{sub 5−x}Fe{sub x}GeSi{sub 2} alloys with x<1 crystallize in the hexagonal Mn{sub 5}Si{sub 3}-type structure. Alloys with x=1.5 and 2 consist of a major Mn{sub 5}Si{sub 3}-type phase and a secondary Ni{sub 2}In-type phase. • The cell parameters decrease and the Curie temperature increases with increasing x in Mn{sub 5−x}Fe{sub x}GeSi{sub 2} alloys. • The maximum -∆S{sub M} of 3.7 J/(kg K) and RCP of 211 J/kg for x=0.8 was found under a magnetic field change of 0–20 kOe.
Recommended data on proton-ion collision rate coefficients for Fe X-Fe XV ions
International Nuclear Information System (INIS)
Skobelev, I.; Murakami, I.; Kato, T.
2006-01-01
The proton-ion collisions are important for excitation of some ion levels in a high-temperature low density plasma. In the present work evaluation of data obtained for proton-induced transitions in Fe X - Fe XV ions with the help of different theoretical methods is carried out. It is suggested a simple analytical formula with 7 parameters allowing to describe dependency of proton rate coefficient on proton temperature in an enough wide temperature range. The values of free parameters have been determined by fitting of approximation formula to numerical data and are presented for recommended data together with fitting accuracies. By comparing of proton collision rates with electron ones it is shown that proton impact excitation processes may be important for Fe X, XI, XIII-XV ions. The results obtained can be used for plasma kinetics calculations and for development of spectroscopy methods of plasma diagnostics. (author)
Thermal plasma synthesis of Fe1−xNix alloy nanoparticles
International Nuclear Information System (INIS)
Raut, Suyog A.; Kanhe, Nilesh S.; Bhoraskar, S. V.; Mathe, V. L.; Das, A. K.
2014-01-01
Fe-Ni alloy nanoparticles are of great interest because of diverse practical applications in the fields such as magnetic fluids, high density recording media, catalysis and medicine. We report the synthesis of Fe-Ni nanoparticles via thermal plasma route. Thermal plasma assisted synthesis is a high temperature process and gives high yields of production. Here, we have used direct arc thermal plasma plume of 6kw as a source of energy at operating pressure 500 Torr. The mixture of Fe-Ni powder in required proportion (Fe 1−x Ni x ; x=0.30, 0.32, 0.34, 0.36, 0.38 and 0.40) was made to evaporate simultaneously from the graphite anode in thermal plasma reactor to form Fe-Ni bimetallic nanoparticles. The as synthesized particles were characterized by X-Ray Diffraction (XRD), Thermo-Gravimetric Analysis/Differential Scanning Calorimtry (TGA/DSC)
International Nuclear Information System (INIS)
Williams, J.M.; Adetunji, J.; Gregori, M.
2000-01-01
We report the distribution of magnetic moments of Fe 3+ and Co 2+ in Co 2+ -, Ti 4+ -substituted M-type barium hexaferrite, Ba(Co,Ti) x Fe (12-2x) O 19 , as a function of doping rate, x. The substitution, x, for iron has been varied with x=0, 0.25, 0.50, 0.70 and 0.85. The magnetic moments of Fe 3+ and Co 2+ were calculated from the combined results of Moessbauer measurements for Fe 3+ ions in the sublattices and neutron diffraction data for the total moments of Fe 3+ and Co 2+ . A comparison of the signs of the magnetic moments of Fe 3+ and Co 2+ ions enabled us to attribute spin directions of the Co 2+ ions in the sublattices of the substituted ferrite samples. The spin directions of Co 2+ are opposite to those of Fe 3+ in the 4f 2 and 2b sublattices. They are reversed from the original directions in the 4f 1 and 12K sublattices when the value of x≥0.70. A quantitative analysis shows that Co 2+ and Ti 4+ ions are preferably substituted into 4f 2 and 12K sublattices, respectively. In addition, while the hyperfine field of Fe 3+ in the 2b sublattice gives rise to the 2b-4f 2 interaction it is the partially substituted Co 2+ ions in the 4f 1 and 12K sublattices that contribute to the near neighbour 2a-4f 1 and 2b-12K types of interaction
An X-ray absorption spectroscopic study of the metal site preference in Al1−xGaxFeO3
International Nuclear Information System (INIS)
Walker, James D.S.; Grosvenor, Andrew P.
2013-01-01
Magnetoelectric materials have potential for being introduced into next generation technologies, especially memory devices. The AFeO 3 (Pna2 1 ; A=Al, Ga) system has received attention to better understand the origins of magnetoelectric coupling. The magnetoelectric properties this system exhibits depend on the amount of anti-site disorder present, which is affected by the composition and the method of synthesis. In this study, Al 1−x Ga x FeO 3 was synthesized by the ceramic method and studied by X-ray absorption spectroscopy. Al L 2,3 -, Ga K-, and Fe K-edge spectra were collected to examine how the average metal coordination number changes with composition. Examination of XANES spectra from Al 1−x Ga x FeO 3 indicate that with increasing Ga content, Al increasingly occupies octahedral sites while Ga displays a preference for occupying the tetrahedral site. The Fe K-edge spectra indicate that more Fe is present in the tetrahedral site in AlFeO 3 than in GaFeO 3 , implying more anti-site disorder is present in AlFeO 3 . - Graphical abstract: Al 1−x Ga x FeO 3 has been investigated by XANES. Through examination of Al L 2,3 -, Ga K-, and Fe K-edge XANES spectra, it was found that more anti-site disorder of the Fe atoms is present in AlFeO 3 compared to in GaFeO 3 . Highlights: ► Al 1−x Ga x FeO 3 was investigated by X-ray absorption spectroscopy. ► Ga prefers to occupy the tetrahedral site in Al 1−x Ga x FeO 3 . ► Fe prefers to occupy the octahedral sites in Al 1−x Ga x FeO 3 as x increases. ► More anti-site disorder is present in AlFeO 3 compared to in GaFeO 3.
X-ray fluorescence analysis of Fe - Ni - Mo systems
International Nuclear Information System (INIS)
Belyaev, E.E.; Ershov, A.V.; Mashin, A.I.; Mashin, N.I.; Rudnevskij, N.K.
1998-01-01
Procedures for the X-ray fluorescence determination of the composition and thickness of Fe - Ni - Mo thin films and the concentration of elements in thick films of the Fe - Ni - Mo alloy are developed [ru
Phase transitions and magnetocaloric effects in intermetallic compounds MnFeX (X=P, As, Si, Ge)
International Nuclear Information System (INIS)
Tegus, O.; Bao Li-Hong; Song Lin
2013-01-01
Since the discovery of giant magnetocaloric effect in MnFeP 1−x As x compounds, much valuable work has been performed to develop and improve Fe 2 P-type transition-metal-based magnetic refrigerants. In this article, the recent progress of our studies on fundamental aspects of theoretical considerations and experimental techniques, effects of atomic substitution on the magnetism and magnetocalorics of Fe 2 P-type intermetallic compounds MnFeX (X=P, As, Ge, Si) is reviewed. Substituting Si (or Ge) for As leads to an As-free new magnetic material MnFeP 1−x Si(Ge) x . These new materials show large magnetocaloric effects resembling MnFe(P, As) near room temperature. Some new physical phenomena, such as huge thermal hysteresis and ‘virgin’ effect, were found in new materials. On the basis of Landau theory, a theoretical model was developed for studying the mechanism of phase transition in these materials. Our studies reveal that MnFe(P, Si) compound is a very promising material for room-temperature magnetic refrigeration and thermo-magnetic power generation. (topical review - magnetism, magnetic materials, and interdisciplinary research)
The atomic structure of Fe100-xCux nanoalloys: X-ray absorption analysis
International Nuclear Information System (INIS)
Kravtsova, A.N.; Yalovega, G.E.; Soldatov, A.V.; Yan, W.S.; Wei, S.Q.
2009-01-01
The local atomic structure of Fe 100-x Cu x nanoalloys (x = 0, 10, 20, 40, 60, 70, 80 and 100%) has been investigated by X-ray absorption near edge structure (XANES) analysis. Local environment around copper and iron atoms in Fe 100-x Cu x has been studied by comparing the experimental XANES with corresponding theoretical spectra calculated for several structural models. It has been established that the most probable structure of the Fe 100-x Cu x nanoalloys for a low concentration of copper (x = 10-20%) is a homogenous bcc structure, for a high copper concentration (x = 60-80%)-a homogenous fcc structure, while at an intermediate copper concentration (about 40%) the nanoalloys have an inhomogeneous structure consisting of clusters of fcc solid solution (90%) and of clusters of bcc solid solution (10%)
Energy Technology Data Exchange (ETDEWEB)
Rettenwander, D., E-mail: daniel.rettenwander@sbg.ac.at [Department of Materials Research and Physics, University of Salzburg, 5020 Salzburg (Austria); Geiger, C.A. [Department of Materials Research and Physics, University of Salzburg, 5020 Salzburg (Austria); Tribus, M.; Tropper, P. [Institute of Mineralogy and Petrography, Faculty of Geo- and Atmospheric Sciences, University of Innsbruck, Innrain 52, 6020 Innsbruck (Austria); Wagner, R.; Tippelt, G.; Lottermoser, W.; Amthauer, G. [Department of Materials Research and Physics, University of Salzburg, 5020 Salzburg (Austria)
2015-10-15
A series of Fe{sup 3+}-bearing Li{sub 7}La{sub 3}Zr{sub 2}O{sub 12} (LLZO) garnets was synthesized using solid-state synthesis methods. The synthetic products were characterized compositionally using electron microprobe analysis and inductively coupled plasma optical emission spectroscopy (ICP-OES) and structurally using X-ray powder diffraction and {sup 57}Fe Mössbauer spectroscopy. A maximum of about 0.25 Fe{sup 3+} pfu could be incorporated in Li{sub 7−3x}Fe{sub x}La{sub 3}Zr{sub 2}O{sub 12} garnet solid solutions. At Fe{sup 3+} concentrations lower than about 0.16 pfu, both tetragonal and cubic garnets were obtained in the synthesis experiments. X-ray powder diffraction analysis showed only a garnet phase for syntheses with starting materials having intended Fe{sup 3+} contents lower than 0.52 Fe{sup 3+} pfu. Back-scattered electron images made with an electron microprobe also showed no phase other than garnet for these compositions. The lattice parameter, a{sub 0}, for all solid-solution garnets is similar with a value of a{sub 0}≈12.98 Å regardless of the amount of Fe{sup 3+}. {sup 57}Fe Mössbauer spectroscopic measurements indicate the presence of poorly- or nano-crystalline FeLaO{sub 3} in syntheses with Fe{sup 3+} contents greater than 0.16 Fe{sup 3+} pfu. The composition of different phase pure Li{sub 7−3x}Fe{sub x}La{sub 3}Zr{sub 2}O{sub 12} garnets, as determined by electron microprobe (Fe, La, Zr) and ICP-OES (Li) measurements, give Li{sub 6.89}Fe{sub 0.03}La{sub 3.05}Zr{sub 2.01}O{sub 12}, Li{sub 6.66}Fe{sub 0.06}La{sub 3.06}Zr{sub 2.01}O{sub 12}, Li{sub 6.54}Fe{sub 0.12}La{sub 3.01}Zr{sub 1.98}O{sub 12}, and Li{sub 6.19}Fe{sub 0.19}La{sub 3.02}Zr{sub 2.04}O{sub 12}. The {sup 57}Fe Mössbauer spectrum of cubic Li{sub 6.54}Fe{sub 0.12}La{sub 3.01}Zr{sub 1.98}O{sub 12} garnet indicates that most Fe{sup 3+} occurs at the special crystallographic 24d position, which is the standard tetrahedrally coordinated site in garnet. Fe{sup 3+} in smaller
The Moessbauer effect in Fe(III) HEDTA, Fe(III) EDTA, and Fe(III) CDTA compounds
International Nuclear Information System (INIS)
Prado, F.R.
1989-01-01
The dependence of Moessbauer spectra with pH value of Fe(III)HEDTA and Fe(III)CDTA compounds is studied. Informations on formation processes of LFe-O-FeL (L=ligand) type dimers by the relation of titration curves of Fe(III)EDTA, Fe(III)HEDTA and Fe(III)CDTA compounds with the series of Moessbauer spectra, are obtained. Some informations on Fe-O-Fe bond structure are also obtained. Comparing the titration curves with the series of Moessbauer spectra, it is concluded that the dimerization process begins when a specie of the form FeXOH α (X = EDTA, HEDTA, CDTA; α = -1, -2) arises. (M.C.K.) [pt
Energy Technology Data Exchange (ETDEWEB)
Stromberg, Frank
2009-07-07
In line with this work the structural and magnetic properties of the exchange coupled layered systems Fe/FeSn{sub 2} and Fe/FeSi/Si and of the Fe ion implanted diluted magnetic semiconductor (DMS) SiC(Fe) were investigated. The main measuring method was the isotope selective {sup 57}Fe conversion electron Moessbauer spectroscopy (CEMS), mostly in connection with the {sup 57}Fe tracer layer technique, in a temperature range from 4.2 K to 340 K. Further measurement techniques were X-ray diffraction (XRD), electron diffraction (LEED, RHEED), SQUID magnetometry and FMR (Ferromagnetic Resonance). In the first part of this work the properties of thin AF FeSn{sub 2}(001) films and of the exchange-bias system Fe/FeSn{sub 2}(001) on InSb(001) were investigated. With the application of {sup 57}Fe-tracer layers and CEMS both the Fe-spin structure and the temperature dependence of the magnetic hyperfine field (B{sub hf}) of FeSn{sub 2} could be examined. The evaporation of Fe films on the FeSn{sub 2} films produced in the latter ones a high perpendicular spin component at the Fe/FeSn{sub 2} interface. In some distance from the interface the Fe spins rotate back into the sample plane. Furthermore {sup 57}Fe-CEMS provided a correlation between the absolute value of the exchange field vertical stroke He vertical stroke and the amount of magnetic defects within the FeSn{sub 2}. Temperature dependent CEMS-measurements yielded informations about the spin dynamics within the AF. The transition temperatures T{sub B}{sup *}, which were interpreted as superparamagnetic blocking temperatures, obtain higher values compared to the temperatures T{sub B} of the exchange-bias effect, obtained with magnetometry measurements. The second part of this work deals with the indirect exchange coupling within Fe/FeSi/Si/FeSi/Fe multilayers and FeSi diffusion barriers. The goal was to achieve Fe free Si interlayers. The CEMS results show that starting from a thickness of t{sub FeSi}=10-12 A of the
Zhou, Mingfei; Andrews, Lester
1999-06-01
Laser-ablated iron atoms, cations, and electrons have been reacted with CO molecules during condensation in excess neon. The FeCO molecule is observed at 1933.7 cm-1 in solid neon. Based on isotopic shifts and density functional calculations, the FeCO molecule has the same 3Σ- ground state in solid neon that has been observed at 1946.5 cm-1 in a recent high resolution gas phase investigation [Tanaka et al., J. Chem. Phys. 106, 2118 (1997)]. The C-O stretching vibration of the Fe(CO)2 molecule is observed at 1917.1 cm-1 in solid neon, which is in excellent agreement with the 1928.2 cm-1 gas phase value for the linear molecule. Anions and cations are also produced and trapped, absorptions at 1782.0, 1732.9, 1794.5, and 1859.7 cm-1 are assigned to the linear FeCO-, Fe(CO)2-, trigonal planar Fe(CO)3-, and C3v Fe(CO)4- anions, respectively, and 2123.0, 2134.0 cm-1 absorptions to the linear FeCO+ and Fe(CO)2+ cations. Doping these experiments with CCl4 virtually eliminates the anion absorptions and markedly increases the cation absorptions, which confirms the charge identifications. Higher iron carbonyl Fe(CO)3, Fe(CO)4, and Fe(CO)5 absorptions are produced on photolysis.
Fluorescence x-ray absorption fine structure studies of Fe-Ni-S and Fe-Ni-Si melts to 1600 K
Manghnani, M. H.; Hong, X.; Balogh, J.; Amulele, G.; Sekar, M.; Newville, M.
2008-04-01
We report NiK -edge fluorescence x-ray absorption fine structure spectra (XAFS) for Fe0.75Ni0.05S0.20 and Fe0.75Ni0.05Si0.20 ternary alloys from room temperature up to 1600 K. A high-temperature furnace designed for these studies incorporates two x-ray transparent windows and enables both a vertical orientation of the molten sample and a wide opening angle, so that XAFS can be measured in the fluorescence mode with a detector at 90° with respect to the incident x-ray beam. An analysis of the Ni XAFS data for these two alloys indicates different local structural environments for Ni in Fe0.75Ni0.05S0.20 and Fe0.75Ni0.05Si0.20 melts, with more Ni-Si coordination than Ni-S coordination persisting from room temperature through melting. These results suggest that light elements such as S and Si may impact the structural and chemical properties of Fe-Ni alloys with a composition similar to the earth’s core.
Energy Technology Data Exchange (ETDEWEB)
Shafia, Ehsan [Politecnico di Torino, Department of Applied Science and Technology and INSTM Unit of Torino-Politecnico (Italy); Esposito, Serena [Università degli Studi di Cassino e del Lazio Meridionale, Department of Civil and Mechanical Engineering (Italy); Manzoli, Maela; Chiesa, Mario [Università di Torino, Dipartimento di Chimica and Centro Interdipartimentale NIS (Italy); Tiberto, Paola [Electromagnetism, I.N.Ri.M. (Italy); Barrera, Gabriele [Università di Torino, Dipartimento di Chimica and Centro Interdipartimentale NIS (Italy); Menard, Gabriel [Harvard University, Department of Chemistry and Chemical Biology (United States); Allia, Paolo, E-mail: paolo.allia@polito.it [Politecnico di Torino, Department of Applied Science and Technology and INSTM Unit of Torino-Politecnico (Italy); Freyria, Francesca S. [Massachusetts Institute of Technology, Department of Chemistry (United States); Garrone, Edoardo; Bonelli, Barbara, E-mail: barbara.bonelli@polito.it [Politecnico di Torino, Department of Applied Science and Technology and INSTM Unit of Torino-Politecnico (Italy)
2015-08-15
Textural, magnetic and spectroscopic properties are reported of Fe-doped aluminosilicate nanotubes (NTs) of the imogolite type, IMO, with nominal composition (OH){sub 3}Al{sub 2−x}Fe{sub x}O{sub 3}SiOH (x = 0, 0.025, 0.050). Samples were obtained by either direct synthesis (Fe-0.025-IMO, Fe-0.050-IMO) or post-synthesis loading (Fe-L-IMO). The Fe content was either 1.4 wt% (both Fe-0.050-IMO and Fe-L-IMO) or 0.7 wt% (Fe-0.025-IMO). Textural properties were characterized by High-Resolution Transmission Electron Microscopy, X-ray diffraction and N{sub 2} adsorption/desorption isotherms at 77 K. The presence of different iron species was studied by magnetic moment measurements and three spectroscopies: Mössbauer, UV–Vis and electron paramagnetic resonance, respectively. Fe{sup 3+}/Al{sup 3+} isomorphic substitution (IS) at octahedral sites at the external surface of NTs is the main process occurring by direct synthesis at low Fe loadings, giving rise to the formation of isolated high-spin Fe{sup 3+} sites. Higher loadings give rise, besides IS, to the formation of Fe{sub 2}O{sub 3} clusters. IS occurs up to a limit of Al/Fe atomic ratio of ca. 60 (corresponding to x = 0.032). A fraction of the magnetism related to NCs is pinned by the surface anisotropy; also, clusters are magnetically interacting with each other. Post-synthesis loading leads to a system rather close to that obtained by direct synthesis, involving both IS and cluster formations. Slightly larger clusters than with direct synthesis samples, however, are formed. The occurrence of IS indicates a facile cleavage/sealing of Al–O–Al bonds: this opens the possibility to exchange Al{sup 3+} ions in pre-formed IMO NTs, a much simpler procedure compared with direct synthesis.
Energy Technology Data Exchange (ETDEWEB)
Galindo-Hernández, Félix, E-mail: felixgalindo@gmail.com [Universidad Nacional Autónoma de México (U.N.A.M.), A.P. 20-364, México City, D.F. 01000 (Mexico); Instituto Mexicano del Petróleo (I.M.P.), Eje Central Lázaro Cárdenas Norte 152 Col. San Bartolo Atepehuacan, México City, D.F. 07730 (Mexico); ESIQIE, Instituto Politécnico Nacional, Col. Zacatenco, Av. Politécnico s/n, México City, D.F. 07738 (Mexico); Wang, Jin-An; Chen, Lifang [ESIQIE, Instituto Politécnico Nacional, Col. Zacatenco, Av. Politécnico s/n, México City, D.F. 07738 (Mexico); Bokhimi, Xim [Universidad Nacional Autónoma de México (U.N.A.M.), A.P. 20-364, México City, D.F. 01000 (Mexico); Gómez, Ricardo; Pérez-Larios, Alejandro [Department of Chemistry, Universidad Autónoma Metropolitana-Iztapalapa, San Rafael Atlixco 186, A.P. 55-534, México City, D.F. 09340 (Mexico); Nava Entzana, Noel [Instituto Mexicano del Petróleo (I.M.P.), Eje Central Lázaro Cárdenas Norte 152 Col. San Bartolo Atepehuacan, México City, D.F. 07730 (Mexico)
2013-12-15
Graphical abstract: In Fe{sub x}O{sub y}/C photocatalyts important effect of Fe{sup 3+} ions in the photodehydrogenation of the ethano was noticed. -- Highlights: • Iron oxides supported on carbon are photoactive catalysts. • Photoactivity in dehydrogenation of ethanol depends of the amount of Fe{sup 3+} ions present in the catalysts. • The capacity of UV–vis absorbance by the Fe{sub x}O{sub y}/C catalysts is significantly dependent of the amount of Fe{sup 3+} ions. • A maximum of rate constant, K = 2125 μmol h{sup −1}, was obtained from the sample with 30 wt% Fe. -- Abstract: Fe{sub x}O{sub y}/C photocatalysts at different iron content were prepared by the incipient wet impregnation method and calcined at 773 K. The photocatalysts were characterized by means of nitrogen adsorption–desorption isotherms, surface fractal dimension, non-local density functional theory, X-ray diffraction, Rietveld refinement and UV–vis spectroscopy. The photocatalytic activity was evaluated using the photodehydrogenation of ethanol as a model reaction for the production of hydrogen. The specific surface areas of Fe{sub x}O{sub y}/C substrates, with 15, 20 and 30 wt% iron content, diminished from 638 to 490 m{sup 2}/g, as the iron content increased. X-ray diffraction analysis showed that iron oxides coexist as wustite and magnetite in samples with Fe contents of 15 and 20 wt%; for sample with 30 wt% Fe, wustite, magnetite and hematite phases were observed. The photophysical, textural and structural properties were modified by the hematite phase formed by thermal treatment. The Rietveld refinements denoted changes in occupancy of Fe{sup 3+} and Fe{sup 2+} in Fe{sub x}O{sub y} crystallites. A relationship between the Fe{sup 3+} ions content and the reactivity for the hydrogen production from the photodehydrogenation of ethanol (from 1360 to 2125 μmol h{sup −1}), was evidenced.
Magnetic properties of the Ce2Fe17-x Mn x helical magnets up to high magnetic fields
International Nuclear Information System (INIS)
Kuchin, A.G.; Mushnikov, N.V.; Bartashevich, M.I.; Prokhnenko, O.; Khrabrov, V.I.; Lapina, T.P.
2007-01-01
Magnetic properties of the Ce 2 Fe 17- x Mn x , x=0-2, alloys in magnetic fields up to 40 T are reported. The compounds with x=0.5-1 are helical antiferromagnets and those with 1 B that couple antiparallelly to the Fe moments. Easy-plane magnetic anisotropy in the Ce 2 Fe 17- x Mn x compounds weakens upon substitution of Mn for Fe. The absolute value of the first anisotropy constant in the Ce 2 Fe 17- x Mn x helical ferromagnets decreases slower with increasing temperature than that calculated from the third power of the spontaneous magnetization. Noticeable magnetic hysteresis in the Ce 2 Fe 17- x Mn x , x=0.5-2, helical magnets over the whole range of magnetic fields reflects mainly irreversible deformation of the helical magnetic structure during the magnetization of the compounds. A contribution from short-range order (SRO) magnetic clusters to the magnetic hysteresis of the helical magnets has been also estimated
Crystallization study of amorphous system Fe84-xWxB16 (x = 3;5)
International Nuclear Information System (INIS)
Novakova, A.A.; Sidorova, G.V.; Kiseleva, T.Yu.; Szasz, A.
1992-01-01
A complex study of the crystallization process of the amorphous system was carried out by Moessbauer spectroscopy, X-ray diffraction and DTA. Alloy samples crystallized at 600deg C contain the following phases: α-Fe, Fe 3 B and solid solution (Fe, W) 3 B. (orig.)
Structural and magnetic study of mechanically deformed Fe rich FeAlSi ternary alloys
International Nuclear Information System (INIS)
Legarra, E.; Apiñaniz, E.; Plazaola, F.
2012-01-01
Highlights: ► Addition of Si to binary Fe–Al alloys makes the disordering more difficult. ► Si addition opposes the large volume increase found in FeAl alloys with deformation. ► Disordering induces a redistribution of non-ferrous atoms around Fe atoms in Fe 75 Al 25−x Si x and Fe 70 Al 30−x Si x . ► Addition of Si to binary Fe 75 Al 25 and Fe 70 Al 30 alloys opposes the magnetic behavior induced by Al in the magnetism of Fe. ► Si inhibits the para-ferro transition found in Fe 60 Al 40 alloy with disordering. - Abstract: In this work we study systematically the influence of different Al/Si ratios on the magnetic and structural properties of mechanically disordered powder Fe 75 Al 25−x Si x , Fe 70 Al 30−x Si x and Fe 60 Al 40−x Si x alloys by means of Mössbauer spectroscopy, X-ray diffraction and magnetic measurements. In order to obtain different stages of disorder the alloys were deformed by different methods: crushing induction melted alloys and ball milling annealed (ordered) alloys using different number of balls and speed. X-ray and Mössbauer data show that mechanical deformation induces the disordered A2 structure in these alloys. The results indicate that addition of Si to binary Fe–Al alloys makes the disordering more difficult. In addition, X-ray diffraction patterns show that the normalized lattice parameter variation of the disordered alloys of each composition decreases monotonically with Si content, indicating clearly that Si addition opposes the large volume increase found in FeAl alloys with deformation. The study of the hyperfine fields indicates that there is a redistribution of non-ferrous atoms around Fe atoms with the disordering; indeed, there is an inversion of the behavior of the hyperfine field of the Fe atoms. On the other hand, the magnetic measurements indicate that addition of Si to binary Fe 75 Al 25 and Fe 70 Al 30 alloys opposes the magnetic behavior induced by Al in the magnetism of Fe.
Diffraction and spectroscopic study of pyrochlores Bi{sub 2−x}Fe{sub 1+x}SbO{sub 7}
Energy Technology Data Exchange (ETDEWEB)
Zhou, Qingdi; Blanchard, Peter E.R. [School of Chemistry, The University of Sydney, Sydney, NSW 2006 (Australia); Kennedy, Brendan J., E-mail: kennedyb@chem.usyd.edu.au [School of Chemistry, The University of Sydney, Sydney, NSW 2006 (Australia); Ling, Chris D.; Liu, Samuel [School of Chemistry, The University of Sydney, Sydney, NSW 2006 (Australia); Avdeev, Max [Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales 2234 (Australia); Aitken, Jade B. [Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168 (Australia); Institute of Materials Structure Science, KEK, Tsukuba, Ibaraki 305-0801 (Japan); School of Chemistry, The University of Sydney, Sydney, NSW 2006 (Australia); Tadich, Anton; Brand, Helen E.A. [Australian Synchrotron, 800 Blackburn Road, Clayton, Victoria 3168 (Australia)
2014-03-15
Highlights: • Fe rich pyrochlores of the type Bi{sub 2−x}Fe{sub 1+x}SbO{sub 7} were prepared by solid state methods. • Structures determined using a combination of neutron and synchrotron X-ray diffraction. • Fe partially occupies the 8-coordinate site. • Dispacive disorder of the Bi cations observed as a consequence of the 6s{sup 2} electrons. • Non-Vegard behaviour seen at low Fe contents due to disorder. -- Abstract: The structural and electronic properties of the series Bi{sub 2−x}Fe{sub 1+x}SbO{sub 7} (0 ⩽ x ⩽ 0.6) were investigated using a combination of diffraction and spectroscopy. Synchrotron and neutron diffraction analysis show that Fe{sup 3+} cations substitute for Bi{sup 3+} onto the A site with increasing x, which was further confirmed by analysis of the Fe K/L-edge X-ray absorption near-edge spectra. The diffraction analysis indicated the presence of displacive disorder along the A{sub 2}O chains, likely the result of the Bi{sup 3+} 6s{sup 2} lone pair, as well as non-Vegard-like behaviour of the lattice parameters in the Fe-poor region. Fe K-edge extended X-ray absorption fine-structure analysis of Bi{sub 2}FeSbO{sub 7} confirmed the displacive disorder of the Bi{sup 3+} cations as well as Sb{sup 5+} and Fe{sup 3+} disorder on the B site.
International Nuclear Information System (INIS)
Wu, Jiangtao; Xu, Jun; Li, Nan; Jiang, Yaqi; Xie, Zhaoxiong
2015-01-01
Single phase Co and Ti co-doped Bi_1_−_xFeO_3−La_xFeO_3 (x = 0–1) solid solutions were prepared by the sol–gel method. Room temperature x-ray powder diffraction (XRD) patterns showed that the structures of as-prepared Bi_1_−_xLa_xFe_0_._9_0Co_0_._0_5Ti_0_._0_5O_3 solid solutions transformed from rhombohedral R3c to tetragonal P4mm and then to orthorhombic Pnma, with increasing La concentration from 0 to 1. In situ high-temperature XRD (HTXRD) analysis further revealed that rhombohedral structure R3c (x ≤ 0.16) and tetragonal structure P4mm (0.17 ≤ x ≤ 0.40) changed to orthorhombic Pnma along with increasing temperature, and the phase transition temperature decreased with the increase of La doping concentration. However, the orthorhombic structure Pnma (x ≥ 0.41) kept stable even when the temperature reached 850 °C. The phase diagram of as-prepared binary solid solutions of Bi_1_−_xLa_xFe_0_._9_0Co_0_._0_5Ti_0_._0_5O_3(x = 0–1) was drawn on the basis of XRD and HTXRD analysis. Magnetic measurement revealed that the magnetic properties are greatly enhanced with the increase of La content. - Highlights: • Single phase Co and Ti co-doped (1−x)BiFeO_3–xLaFeO_3 (x = 0–1) solid solutions were synthesized. • The phase transitions were investigated by tuning composition and temperature. • Phase diagram was constructed according to the results of XRD for the first time. • The magnetization of solid solution can be enhanced when increasing La content.
Fe K-EDGE X-RAY ABSORPTION SPECTROSCOPY OF SILICATE MINERALS AND GLASSES
Binsted , N.; Greaves , G.; Henderson , C.
1986-01-01
Structural parameters determined for crystalline iron, fayalite and aegirine agree closely with X-ray crystallograhic data. A glass of NaFeSi2O6 composition has Fe predominantly present as Fe3+ in tetrahedral coordination i.e. as a network former. CaFeSiO4 and CaFeSi2O6 glasses have about 1/3 of the total Fe in octahedral coordination i.e. as a network modifier.
Elemental moment variation of bcc Fe{sub x}Mn{sub 1−x} on MgO(001)
Energy Technology Data Exchange (ETDEWEB)
Bhatkar, H.; Snow, R.J. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Arenholz, E. [Advanced Light Source, Lawrence Berkeley National Laboratories, Berkeley, CA 94720 (United States); Idzerda, Y.U., E-mail: idzerda@montana.edu [Department of Physics, Montana State University, Bozeman, MT 59717 (United States)
2017-02-01
We report the growth, structural characterization, and electronic structure evolution of epitaxially grown bcc Fe{sub x}Mn{sub 1−x} on MgO(001). It is observed that the 20 nm thick Fe{sub x}Mn{sub 1−x} alloy films remained bcc from 0.65≤x≤1, much beyond the bulk stability range of 0.88≤x≤1. X-ray absorption spectroscopy and X-ray magnetic circular dichroism show that both the Fe and Mn L{sub 3} binding energies slightly increase with Mn incorporation and that the elemental moment of Fe in the 20 nm crystalline bcc alloy film remain nearly constant, then shows a dramatic collapse near x~0.84. The Mn MCD intensity is found to be small at all compositions that exhibit ferromagnetism - Highlights: • Bcc Fe{sub x}Mn{sub 1−x} films were stabilized beyond bulk range by epitaxial growth on MgO. • XMCD shows negligible moment in Mn regardless of composition. • Fe moment stays constant until 84% Mn concentration. • Magnetic moment suddenly collapses before any structural change seen in RHEED.
Energy Technology Data Exchange (ETDEWEB)
Barik, S K; Krishnamoorthi, C [Department of Physics and NUS Nanoscience and Nanotechnology Initiative, 2 Science Drive 3, National University of Singapore, Singapore 117542, Singapore. (Singapore); Mahendiran, R [Department of Physics and NUS Nanoscience and Nanotechnology Initiative, 2 Science Drive 3, National University of Singapore, Singapore 117542, Singapore. (Singapore)
2011-04-15
We have studied the effect of Fe substitution on magnetic and magnetocaloric properties in La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3} (x=0.05, 0.07, 0.10, 0.15, and 0.20) over a wide temperature range (T=10-400 K). It is shown that substitution by Fe gradually decreases the ferromagnetic Curie temperature (T{sub C}) and saturation magnetization up to x=0.15 but a dramatic change occurs for x=0.2. The x=0.2 sample can be considered as a phase separated compound in which both short-range ordered ferromagnetic and antiferromagnetic phases coexist. The magnetic entropy change (-{Delta}S{sub m}) was estimated from isothermal magnetization curves and it decreases with increase of Fe content from 4.4 J kg{sup -1} K{sup -1} at 343 K (x=0.05) to 1.3 J kg{sup -1} K{sup -1} at 105 K (x=0.2), under {Delta}H=5 T. The La{sub 0.7}Sr{sub 0.3}Mn{sub 0.93}Fe{sub 0.07}O{sub 3} sample shows negligible hysteresis loss, operating temperature range over 60 K around room temperature with refrigerant capacity of 225 J kg{sup -1}, and magnetic entropy of 4 J kg{sup -1} K{sup -1} which will be an interesting compound for application in room temperature refrigeration. - Research highlights: > We report magnetocaloric effect in La{sub 0.7}Sr{sub 0.3}Mn{sub 1-x}Fe{sub x}O{sub 3} (x=0-0.2). > Magnetic entropy change ({Delta}S{sub m}) decreases with increasing x. > A large {Delta}S{sub m} and refrigeration capacity are found around 300 K in x=0.07.
Multiferroic properties of nanocrystalline BiFe1−xNixO3 (x=0.0–0.15) perovskite ceramics
International Nuclear Information System (INIS)
Chaudhari, Yogesh; Mahajan, Chandrashekhar M.; Singh, Amrita; Jagtap, Prashant; Chatterjee, Ratnamala; Bendre, Subhash
2015-01-01
Ni doped BiFeO 3 (x=0, 0.05, 0.1 and 0.15) nanocrystalline ceramics were synthesized by the solution combustion method (SCM) to obtain optimal multiferroic properties. The effect of Ni doping on structural, morphological, ferroelectric, magnetic and dielectric properties of BiFeO 3 was studied. The structural investigations by using X-ray diffraction (XRD) pattern confirmed that BiFe 1−x Ni x O 3 ceramics have rhombhohedral perovskite structure. The ferroelectric hysteresis measurements for BiFe 1−x Ni x O 3 (x=0, 0.05, 0.1, 0.15) compound at room temperature found to exhibit unsaturated behavior and presents partial reversal of polarization. The magnetic measurements demonstrated an enhancement of ferromagnetic property due to Ni doping in BiFeO 3 when compared with undoped BiFeO 3 . The variation of dielectric constant with temperature in BiFe 0.9 Ni 0.1 O 3 and BiFe 0.85 Ni 0.15 O 3 samples evidenced an apparent dielectric anomaly around 350 °C and 300 °C which corresponds to antiferromagnetic to paramagnetic phase transition of (T N ) of BiFeO 3 . The dependence of room temperature dielectric properties on frequency signifies that both dielectric constant (ε) and dielectric loss (tan δ) are the strong function of frequency. The results show that solution combustion method leads to synthesis of an excellent and reproducible BiFe 1−x Ni x O 3 multiferroic ceramics. - Highlights: • Synthesis of BiFe 1−x Ni x O 3 (x=0, 0.05, 0.1 and 0.15) multiferroic ceramics. • Solution Combustion Method (SCM). • Ferroelectric and dielectric properties of undoped and Ni doped BiFeO 3 ceramics. • High temperature synthesis of BiFe 1−x Ni x O 3 multiferroic ceramics. • First detailed report about SCM synthesized the BiFe 1−x Ni x O 3 ceramics
Pr2Fe14B/α-Fe nanocomposites for thermal applications
International Nuclear Information System (INIS)
Silva, Suelanny Carvalho da
2012-01-01
In this work, Pr x Fe 94 - x B 6 (x = 6, 8, 10 and 12) nanostructured powders were prepared by a combination of hydrogenation, disproportionation, desorption and recombination (HDDR) process with high energy milling applied to the mixture of an as-cast alloy (Pr 14 Fe 80 B 6 ) and α-Fe. The produced nanoparticles showed magnetic properties comparable to those reported in hyperthermia studies. The optimal time to obtain the magnetic nanoparticles is 5 hours (at 900 rpm). It was verified that longer milling times cause an increase in carbon percentage on the particles. The carbon is derived from oleic acid added as a surfactant in the milling step. The nanocomposites exhibit coercive force ranging from 80 Oe (6.5 kAm -1 ) to 170 Oe (13.5 kAm -1 ) and magnetic moments in the range of 81 129 Am2kg -1 . From the X-ray diffraction analyses, only two phases were found in all samples: α-Fe and the magnetic phase Pr 2 Fe 14 B. Individual nanoparticles with diameter of about 20 nm were verified. The samples studied presented heating when exposed to an alternating magnetic field (f = 222 kHz e H max ∼3.7 kAm -1 ) comparable to reported in literature. Temperature variations (ΔT) of the powders were: 51 K for Pr 6 Fe 88 B 6 , 41 K for Pr 8 Fe 86 B 6 , 38 K for Pr 10 Fe 8 4 B 6 and T = 34 K for Pr 12 Fe 82 B 6 . The specific absorption rates (SARs) of the powders were 201 Wkg -1 for Pr 6 Fe 88 B 6 composition, 158 Wkg -1 on the composition Pr 8 Fe 86 B 6 , and 114 Wkg -1 for Pr 10 Fe 84 B 6 and Pr 12 Fe 82 B 6 compositions. (author)
First-principles study of electronic properties of FeSe{sub 1-x}S{sub x} alloys
Energy Technology Data Exchange (ETDEWEB)
Kumar, Sandeep, E-mail: sandeep@phy.iitb.ac.in; Singh, Prabhakar P. [Department of Physics, Indian Institute of Technology-Bombay, Mumbai-400076 (India)
2016-05-06
We have studied the electronic and superconducting properties of FeSe{sub 1-x}S{sub x} (x = 0.0, 0.04) alloys by first-principles calculations using the Korringa-Kohn-Rostoker Atomic Sphere Approximation within the coherent potential approximation (KKR-ASA-CPA). The electronic structure calculations show the ground states of S-doped FeSe to be nonmagnetic. We present the results of our unpolarized calculations for these alloys in terms of density of states (DOS), band structures, Fermi surfaces and the superconducting transition temperature of FeSe and FeSe{sub 0.96}S{sub 0.04} alloys. We find that the substitution of S at Se site into FeSe exhibit the subtle changes in the electronic structure with respect to the parent FeSe. We have also estimated bare Sommerfeld constant (γ{sub b}), electron-phonon coupling constant (λ) and the superconducting transition temperature (T{sub c}) for these alloys, which were found to be in good agreement with experiments.
Moessbauer study of (Fe1-x Cu x )4N (0.05≤x≤0.15) films
International Nuclear Information System (INIS)
El Khiraoui, S.; Sajieddine, M.; Vergnat, M.; Bauer, Ph.; Mabrouki, M.
2007-01-01
In this work, we have prepared nitrogenated Fe 1- x Cu x alloys by reactive evaporation under a flow of nitrogen ions. After annealing, X-ray diffraction shows that we have synthesized the γ'-(Fe 1- x Cu x ) 4 N (0.05≤x≤0.15) compounds. The films were investigated by Moessbauer spectroscopy. The crystallographic structure and the respective positions of the Fe and Cu atoms in the compounds have been determined
X-ray magnetic absorption in Fe-Tb amorphous thin films
Kim, Chan Wook; Watanabe, Yasuhiro
1999-01-01
In order to investigate the magnetic structure of Fe-Tb amorphous thin films, we have performed magnetic circular dichroism (MCD) measurements by using the circularly polarized X-ray at the Fe K- and the Tb L2,3-edges in Fe sub 8 sub 8 Tb sub 1 sub 2 , Fe sub 8 sub 0 Tb sub 2 sub 0 , and Fe sub 6 sub 2 Tb sub 3 sub 8. In all samples, the spin-dependent absorption effects, DELTA mu t, were observed. Also, elementary information was obtained on the spin polarizations of the p- and the d-projected electrons lying in the unoccupied states near the Fermi levels in the samples.
Energy Technology Data Exchange (ETDEWEB)
Shen Jiang [Institute of Applied Physics, University of Science and Technology Beijing, 30 Xueyuou Road, HaiDian District, Beijing 100083 (China)]. E-mail: shenj@sas.ustb.edu.cn; Qian Ping [Institute of Applied Physics, University of Science and Technology Beijing, 30 Xueyuou Road, HaiDian District, Beijing 100083 (China); Chen Nanxian [Institute of Applied Physics, University of Science and Technology Beijing, 30 Xueyuou Road, HaiDian District, Beijing 100083 (China); Department of Physics, Tsinghua University, Beijing 100084 (China)
2005-03-15
We have investigated the structural properties of Pr{sub 2}Fe{sub 17-} {sub x} Mn {sub x} compounds by using quasi-ab initio pair potentials {phi} {sub Fe-Fe}(r), {phi} {sub Pr-Fe}(r), {phi} {sub Pr-Pr}(r), {phi} {sub Pr-Mn}(r), {phi} {sub Fe-Mn}(r) and {phi} {sub Mn-Mn}(r). In Pr{sub 2}Fe{sub 17-} {sub x} Mn {sub x} , the ternary elements Mn substitute for Fe atoms without changing the crystal structure. The calculated cohesive energy curves show that for all values of x, Mn preferentially substitutes for Fe in the 6c site and randomly substitutes for Fe in the 18f and 18h site. The calculated lattice constants coincide quite well with experimental values. Furthermore, the phonon density, specific heat and vibrational entropy of these compounds are also calculated. It is interesting that simple pair potentials can describe these extremely anisotropic materials.
Energy Technology Data Exchange (ETDEWEB)
Bindu, K.; Nagaraja, H. S., E-mail: hosakoppa@gmail.com [Material Research Laboratory, Department of Physics, National Institute of Technology Karnataka, Surathkal, Srinivasnagar, Mangalore-575 025, Karnataka (India); Chowdhury, P. [Nanomaterials Research Laboratory, Surface Engineering Division, National Aerospace Laboratories, Council of Scientific and Industrial Research, Bangalore-560 017, Karnataka (India); Ajith, K. M. [Computational Physics Laboratory, Department of Physics, National Institute of Technology Karnataka, Surathkal, Srinivasnagar, Mangalore-575 025, Karnataka (India)
2016-05-06
Hematite (α-Fe{sub 2}O{sub 3}) doped with tetravalent ions have potential applications in various fields such as gas sensors, memories, energy storage devices because of their electrical and magnetic properties. Microwave assisted synthesis was used to prepare Tin doped α-Fe{sub 2}O{sub 3} [α-Sn{sub x}Fe{sub 2-x}O{sub 3}]. The structural and morphological studies were investigated using X-ray diffraction (XRD) and Scanning electron microscopy (SEM). XRD patterns revealed that α-Fe{sub 2}O{sub 3} and α-Sn{sub x}Fe{sub 2-x}O{sub 3} were having rhombohedral structure. The compositional study was done by Energy dispersive X-ray Spectroscopy (EDS). The magnetic properties were studied by Vibrating Sample Magnetometry (VSM). Results shows that the prepared samples were found to be antiferromagnetic in nature and the results are discussed in detail.
Metamagnetic behaviour of La1-xGdxFe12B6 compounds
International Nuclear Information System (INIS)
Li, Q.A.; Groot, C.H. de; Boer, F.R. de; Buschow, K.H.J.
1997-01-01
The magnetic properties of compounds of the type La 1-x Gd x Fe 12 B 6 have been studied in high magnetic fields at 4.2 K. LaFe 12 B 6 is a compound with Fe moments close to magnetic instability and values not larger than about 0.5 μ B . Substitution of Gd for part of the La and application of high magnetic fields enhance the Fe moments to values in excess of 2 μ B . The high-moment state in LaFe 12 B 6 is reached via a metamagnetic transition. This first-order transition is associated with an extremely large hysteresis of nearly 7 T at 4.2 K. (orig.)
International Nuclear Information System (INIS)
Ye Qing; Zhou Jing; Zhao Haifeng; Chen Xing; Chu Wangsheng; Zheng Xusheng; Marcelli, Augusto; Wu Ziyu
2013-01-01
The hydrated shell of both Fe 2+ and Fe 3+ aqueous solutions are investigated by using the molecular dynamics (MD) and X-ray absorption structure (XAS) methods. The MD simulations show that the first hydrated shells of both Fe 2+ and Fe 3+ are characterized by a regular octahedron with an Fe-O distance of 2.08Å for Fe 2+ and 1.96Å for Fe 3+ , and rule out the occurrence of a Jahn-Teller distortion in the hydrated shell of an Fe 2+ aqueous solution. The corresponding X-ray absorption near edge fine structure (XANES) calculation successfully reproduces all features in the XANES spectra in Fe 2+ and Fe 3+ aqueous solution. A feature that is located at energy 1 eV higher than the white line (WL) in an Fe 3+ aqueous solution may be assigned to the contribution of the charge transfer. (authors)
Study on adsorption of 99Tc on Fe, Fe2O3 and Fe3O4
International Nuclear Information System (INIS)
Liu Dejun; Fan Xianhua; Zhang Yingjie; Yao Jun; Zhou Duo; Wang Yong
2004-01-01
The absorption behavior of 99 Tc on Fe, Fe 2 O 3 and Fe 3 O 4 powders from aqueous 99 TcO 4 - solutions is studied by batch method in atmospheric conditions. After the adsorption reaches equilibrium, the valence state of 99 Tc in the aqueous solution is examined by extraction with tetraphenylarsonium chloride. The experimental results show that the adsorption ratio of 99 Tc on iron powders decreases with the increase of pH (in the range of 5-8) and of CO 3 2- concentration (in the range of 1 x 10 -8 -1 x 10 -2 mol/L). In opposite, the two factors have no significant influence on the absorption of 99 Tc on both Fe 2 O 3 and Fe 3 O 4 powders. The adsorption isotherms of 99 TcO 4 - on Fe, Fe 2 O 3 and Fe 3 O 4 powders can be well described by the Freundlich's equation. The major valence state of 99 Tc is deduced to be Tc(IV) when iron powders is used as the absorbent. In the case of Fe 2 O 3 or Fe 3 O 4 as an absorbent, the 99 Tc remains as the TcO 4 - form
Electrical resistivity surface for FeO-Fe2O3-P2O5 glasses
Vaughan, J. G.; Kinser, D. L.
1975-01-01
The dc electrical properties and microstructure of x(FeO-Fe2O3)-(100-x)P2O5 glasses were investigated up to a maximum of x = 75 mol %. Results indicate that, in general, the minimum resistivity of the glass does not occur at equal Fe(2+) and Fe(3+) concentrations, although for the special case where x = 55 mol % the minimum does occur at Fe(2+)/Fe total = 0.5, as reported by other investigators. Evidence presented shows that the position of the minimum resistivity is a function of total iron content. The minimum shifts to glasses richer in Fe(2+) at higher total iron concentrations.
Structural and magnetic properties of NdFeB and NdFeB/Fe films with Mo addition
Energy Technology Data Exchange (ETDEWEB)
Urse, M; Grigoras, M; Lupu, N; Chiriac, H, E-mail: urse@phys-iasi.ro [National Institute of R and D for Technical Physics, 47 Mangeron Blvd., 700050 Iasi (Romania)
2011-07-06
The influence of the Mo addition on the microstructure and magnetic properties of Nd-Fe-B and Nd-Fe-B/Fe films was studied. The coercivity is a key parameter in the control of technical performances of Nd-Fe-B films. A small amount of about 1 at.% Mo can enhance the coercivity of Nd-Fe-B film by controlling the growth of soft and hard magnetic grains. A coercivity of 22.1 kOe, a remanence ratio, M{sub r}/M{sub s}, of 0.83 and a maximum energy product of 8 MGOe were obtained for Ta/[NdFeBMo(1at.%)(540nm)/Ta films annealed at 650{sup 0}C for 20 minutes due to Mo precipitates formed at the Nd{sub 2}Fe{sub 14}B phase boundaries which prevent the nucleation and expansion of the magnetic domains. Simultaneous use of Mo as addition and the stratification of Nd-Fe-B-Mo films using Fe as spacer layer are important tools for the improvement of the hard magnetic properties of Nd-Fe-B films. The Ta/[NdFeBMo(1at.%)(180nm)/Fe(1nm)]x3/Ta multilayer film annealed at 620{sup 0}C exhibits an increase in the coercivity from 12.1 kOe to 22.8 kOe, in the remanence ratio from 0.77 to 0.80, and in the maximum energy product from 4.5 to 7.1 MGOe in comparison with Ta/Nd-Fe-B/Ta film. As compared to Ta/Nd-Fe-B/Ta film, the Ta/[NdFeBMo(1at.%)(180nm)/Fe(1nm)]x3/Ta film presents a decrease in the crystallization temperature of about 30{sup 0}C.
Electrochemical reduction of nitrous oxide on La1-xSrxFeO3 perovskites
DEFF Research Database (Denmark)
Kammer Hansen, Kent
2010-01-01
The electrochemical reduction of nitrous oxide and oxygen has been studied on cone-shaped electrodes of La1-xSrxFeO3-delta perovskites in an all solid state cell, using cyclic voltammetry. It was shown that the activity of the La1-xSrxFeO3-delta perovskites for the electrochemical reduction...... of nitrous oxide mainly depends on the amount of Fe(III) and oxide ion vacancies. The activity of the La1-xSrxFeO3-delta perovskites towards the electrochemical reduction of nitrous oxide is much lower than the activity of the La1-xSrxFeO3-delta perovskites towards the electrochemical reduction of oxygen...
Hyperfine interactions in dilute Se doped Fe{sub x}Sb{sub 1−x} bulk alloy
Energy Technology Data Exchange (ETDEWEB)
Sarkar, Mitesh, E-mail: miteshsarkar-msu@yahoo.com; Agrawal, Naveen [The M. S. University of Baroda, Department of Physics (India); Chawda, Mukesh [Polytechnic, The M. S. University of Baroda, Department of Applied Physics (India)
2016-12-15
Hyperfine Interaction technique like Moessbauer spectroscopy is a very sensitive tool to study the local probe interactions in Iron doped alloys and compounds. We report here the Moessbauer study of the effect of Fe concentration variations in dilute magnetic semiconducting Se{sub 0.004}Fe{sub x}Sb{sub 1−x} alloys for x = 0.002, 0.004 and 0.008. The materials were characterized using X-ray diffraction technique (XRD), Fourier Transform Infra-red spectroscopy (FTIR), Neutron depolarization and Moessbauer spectroscopy. The FTIR result shows the semiconducting behavior of the alloys with band gap of 0.18 eV. From Moessbauer spectroscopy two magnetic sites (A and B) were observed. The value of hyperfine magnetic fields (HMF) of ∼ 308 kOe (site A) and 270 kOe (site B) was constant with increase in Fe concentration. A nonmagnetic interaction was also observed with quadrupole splitting (QS) of 1.26 mm/sec (site C) for x = 0.004 and x = 0.008. The Neutron depolarization studies indicate that the clusters of Fe or Fe based compounds having net magnetic moments with a size greater than 100 Å is absent.
Role of PO4 tetrahedron in LiFePO4 and FePO4 system.
Zeng, Yuewu
2015-06-01
Using high resolution transmission electron microscopy with image simulation and Fourier analysis, the Li1- x FePO4 (x < 0.01), Li1- x FePO4 (x ∼ 0.5), and FePO4 particles, prepared by charging or discharging the 053048 electrochemical cells (thickness: 5 mm, width: 30 mm, height: 48 mm) and dismantled inside an Ar-filled dry box, were investigated. The high resolution images reveal: (1) the solid solution of Li1- x FePO4 (x < 0.01) contains some missing Li ions leading PO4 group distorted around M1 tunnel of the unit cell; (2) the texture of the particles of Li1- x FePO4 (x ∼0.5) has homogeneously distributed compositional domains of LiFePO4 and FePO4 resulting from spinodal decomposition which promote Li ion easily getting into the particle due to uphill diffusion, (3) the particles of FePO4 formed in charging have heavily distorted lattice and contain some isolated LiFePO4 , (4) interface between LiFePO4 and FePO4 and between amorphous and crystal region provides the lattice distortion of small polarons. © 2015 Wiley Periodicals, Inc.
Energy Technology Data Exchange (ETDEWEB)
Chaudhari, Yogesh [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon 425001, Maharastra (India); Department of Physics, Shri. Pancham Khemaraj Mahavidyalaya, Sawantwadi 416510, Maharastra (India); Mahajan, Chandrashekhar M. [Department of Engineering Sciences and Humanities (DESH), Vishwakarma Institute of Technology, Pune 411 016, Maharastra (India); Singh, Amrita [Magnetics and Advanced Ceramics Laboratory, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India); Jagtap, Prashant [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon 425001, Maharastra (India); Chatterjee, Ratnamala [Magnetics and Advanced Ceramics Laboratory, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India); Bendre, Subhash, E-mail: bendrest@gmail.com [Department of Physics, School of Physical Sciences, North Maharashtra University, Jalgaon 425001, Maharastra (India)
2015-12-01
Ni doped BiFeO{sub 3} (x=0, 0.05, 0.1 and 0.15) nanocrystalline ceramics were synthesized by the solution combustion method (SCM) to obtain optimal multiferroic properties. The effect of Ni doping on structural, morphological, ferroelectric, magnetic and dielectric properties of BiFeO{sub 3} was studied. The structural investigations by using X-ray diffraction (XRD) pattern confirmed that BiFe{sub 1−x}Ni{sub x}O{sub 3} ceramics have rhombhohedral perovskite structure. The ferroelectric hysteresis measurements for BiFe{sub 1−x}Ni{sub x}O{sub 3} (x=0, 0.05, 0.1, 0.15) compound at room temperature found to exhibit unsaturated behavior and presents partial reversal of polarization. The magnetic measurements demonstrated an enhancement of ferromagnetic property due to Ni doping in BiFeO{sub 3} when compared with undoped BiFeO{sub 3}. The variation of dielectric constant with temperature in BiFe{sub 0.9}Ni{sub 0.1}O{sub 3} and BiFe{sub 0.85}Ni{sub 0.15}O{sub 3} samples evidenced an apparent dielectric anomaly around 350 °C and 300 °C which corresponds to antiferromagnetic to paramagnetic phase transition of (T{sub N}) of BiFeO{sub 3}. The dependence of room temperature dielectric properties on frequency signifies that both dielectric constant (ε) and dielectric loss (tan δ) are the strong function of frequency. The results show that solution combustion method leads to synthesis of an excellent and reproducible BiFe{sub 1−x}Ni{sub x}O{sub 3} multiferroic ceramics. - Highlights: • Synthesis of BiFe{sub 1−x}Ni{sub x}O{sub 3} (x=0, 0.05, 0.1 and 0.15) multiferroic ceramics. • Solution Combustion Method (SCM). • Ferroelectric and dielectric properties of undoped and Ni doped BiFeO{sub 3} ceramics. • High temperature synthesis of BiFe{sub 1−x}Ni{sub x}O{sub 3} multiferroic ceramics. • First detailed report about SCM synthesized the BiFe{sub 1−x}Ni{sub x}O{sub 3} ceramics.
Energy Technology Data Exchange (ETDEWEB)
Trunova, Anastasia
2009-05-25
This work is dedicated to investigations of structural and magnetic properties of the colloidal Fe/Fe{sub x}O{sub y} nanocubes (13 nm) and the Fe{sub x}Rh{sub 100-x} core/shell nanoparticles (2 nm). As compared with other works, where the measurements on oxidized nanoparticles were carried out, we additionally performed investigations on nanoparticles in an oxide free state. In order to make the measurements on oxide free particles possible, oxygen- and hydrogenplasma was used to remove the ligands and reduce the oxide shell of the Fe nanocubes. The oxide free Fe nanocubes were covered with a Ag/Pt protective coating to prevent them from new oxidation. This method allowed carrying out the magnetic measurements on oxide free Fe nanocubes. Micromagnetic simulations as well as simulations of the high frequency susceptibility were used for the data analysing. It was found that both the g-factor g=2.09{+-}0.01 and the anisotropy constant K{sub 4}=(4.8{+-}0.5).10{sup 4} J/m{sup 3} coincide with that of bulk iron. However, the saturation magnetization M{sub S}(5 K)=(1.2{+-}0.12).10{sup 6} A/m differs from the bulk value by 30%. The reduction by 30% compared to the bulk value in the case of nanoparticles may be caused by the following possible reasons: a) the presence of inner oxide layer (approx. 10 at.%) that cannot be reduced; b) the anti-parallel order between magnetic moments of iron core and magnetic moments of antiferomagnetic iron oxide; c) some structural changes of the surface after plasma treatment. The obtained damping parameter {alpha}=0.03{+-}0.005 is ten times larger than that of the Fe layers as it is known for nanoparticles systems in general. The core/shell Fe{sub x}Rh{sub 100-x} nanoparticles (x=80,50) were produced under Ar-atmosphere and were sealed into a quartz tube to prevent oxidation. The analysis of g-factors shows that the value for the FePh nanoparticles with Fe-rich core is larger (g=2.08{+-}0.01) than that for the nanoparticles with Rh
Magnetic Properties and Microstructure of FeOx/Fe/FePt and FeOx/FePt Films
Directory of Open Access Journals (Sweden)
Jai-Lin Tsai
2013-01-01
Full Text Available The Fe(6 nm/FePt film with perpendicular magnetization was deposited on the glass substrate. To study the oxygen diffusion effect on the coupling of Fe/FePt bilayer, the plasma oxidation with 0.5~7% oxygen flow ratio was performed during sputtered part of Fe layer and formed the FeOx(3 nm/Fe(3 nm/FePt trilayer. Two-step magnetic hysteresis loops were found in trilayer with oxygen flow ratio above 1%. The magnetization in FeOx and Fe/FePt layers was decoupled. The moments in FeOx layer were first reversed and followed by coupled Fe/FePt bilayer. The trilayer was annealed again at 500°C and 800°C for 3 minutes. When the FeOx(3 nm/Fe(3 nm/FePt trilayer was annealed at 500°C, the layers structure was changed to FeOx(6 nm/FePt bilayer due to oxygen diffusion. The hard-magnetic FeOx(6 nm/FePt film was coupled with single switching field. The FeOx/(disordered FePt layer structure was observed with further annealing at 800°C and presented soft-magnetic loop. In summary, the coupling between soft-magnetic Fe, FeOx layer, and hard-magnetic L10 FePt layer can be controlled by the oxygen diffusion behavior, and the oxidation of Fe layer was tuned by the annealing temperature. The ordered L10 FePt layer was deteriorated by oxygen and became disordered FePt when the annealed temperature was up to 800°C.
Structure and mechanical properties of as-cast Ti-5Nb-xFe alloys
International Nuclear Information System (INIS)
Hsu, Hsueh-Chuan; Hsu, Shih-Kuang; Wu, Shih-Ching; Lee, Chih-Jhan; Ho, Wen-Fu
2010-01-01
In this study, as-cast Ti-5Nb and a series of Ti-5Nb-xFe alloys were investigated and compared with commercially pure titanium (c.p. Ti) in order to determine their structure and mechanical properties. The series of Ti-5Nb-xFe alloys contained an iron content ranging from 1 to 5 mass% and were prepared by using a commercial arc-melting vacuum-pressure casting system. Additionally, X-ray diffraction (XRD) for phase analysis was conducted with a diffractometer, and three-point bending tests were performed to evaluate the mechanical properties of all specimens. The fractured surfaces were observed by using scanning electron microscopy (SEM). The experimental results indicated that these alloys possessed a range of different structures and mechanical properties dependent upon the various additions of Fe. With an addition of 1 mass% Fe, retention of the metastable β phase began. However, when 4 mass% Fe or greater was added, the β phase was entirely retained with a bcc crystal structure. Moreover, the ω phase was only detected in the Ti-5Nb-2Fe, Ti-5Nb-3Fe and Ti-5Nb-4Fe alloys. The largest quantity of ω phase and the highest bending modulus were found in the Ti-5Nb-3Fe alloy. The Ti-5Nb-2Fe alloy had the lowest bending modulus, which was lower than that of c.p. Ti by 20%. This alloy exhibited the highest bending strength/modulus ratio of 26.7, which was higher than that of c.p. Ti by 214%, and of the Ti-5Nb alloy (14.4 ) by 85%. Additionally, the elastically recoverable angles of the ductile Ti-5Nb-1Fe (19.9 o ) and Ti-5Nb-5Fe (29.5 o ) alloys were greater than that of c.p. Ti (2.7 o ) by as much as 637% and 993%, respectively. Furthermore, the preliminary cell culturing results revealed that the Ti-5Nb-xFe alloys were not only biocompatible, but also supported cell attachment.
Structure and mechanical properties of as-cast Ti-5Nb-xFe alloys
Energy Technology Data Exchange (ETDEWEB)
Hsu, Hsueh-Chuan; Hsu, Shih-Kuang; Wu, Shih-Ching [Department of Dental Laboratory Technology, Central Taiwan University of Science and Technology, Taichung 40605, Taiwan (China); Institute of Biomedical Engineering and Material Science, Central Taiwan University of Science and Technology, Changhua 51591, Taiwan (China); Lee, Chih-Jhan [Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan (China); Ho, Wen-Fu, E-mail: fujii@mail.dyu.edu.tw [Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan (China)
2010-09-15
In this study, as-cast Ti-5Nb and a series of Ti-5Nb-xFe alloys were investigated and compared with commercially pure titanium (c.p. Ti) in order to determine their structure and mechanical properties. The series of Ti-5Nb-xFe alloys contained an iron content ranging from 1 to 5 mass% and were prepared by using a commercial arc-melting vacuum-pressure casting system. Additionally, X-ray diffraction (XRD) for phase analysis was conducted with a diffractometer, and three-point bending tests were performed to evaluate the mechanical properties of all specimens. The fractured surfaces were observed by using scanning electron microscopy (SEM). The experimental results indicated that these alloys possessed a range of different structures and mechanical properties dependent upon the various additions of Fe. With an addition of 1 mass% Fe, retention of the metastable {beta} phase began. However, when 4 mass% Fe or greater was added, the {beta} phase was entirely retained with a bcc crystal structure. Moreover, the {omega} phase was only detected in the Ti-5Nb-2Fe, Ti-5Nb-3Fe and Ti-5Nb-4Fe alloys. The largest quantity of {omega} phase and the highest bending modulus were found in the Ti-5Nb-3Fe alloy. The Ti-5Nb-2Fe alloy had the lowest bending modulus, which was lower than that of c.p. Ti by 20%. This alloy exhibited the highest bending strength/modulus ratio of 26.7, which was higher than that of c.p. Ti by 214%, and of the Ti-5Nb alloy (14.4 ) by 85%. Additionally, the elastically recoverable angles of the ductile Ti-5Nb-1Fe (19.9{sup o}) and Ti-5Nb-5Fe (29.5{sup o}) alloys were greater than that of c.p. Ti (2.7{sup o}) by as much as 637% and 993%, respectively. Furthermore, the preliminary cell culturing results revealed that the Ti-5Nb-xFe alloys were not only biocompatible, but also supported cell attachment.
International Nuclear Information System (INIS)
Sun, Song; Ye, Rongchang; Long, Yi
2013-01-01
Graphical abstract: M–T curves show that all the compounds undergo a ferromagnetic–paramagnetic magnetic phase transition process. Besides, the Curie temperature T c of La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) compounds increase monotonously from 195 K to 219 K when Ni content x varies from 0 to 0.03. Highlights: ► We substituted Fe by new element Ni in La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds. ► The microstructure evolution, magnetic phase transition and Curie temperature of La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds were investigated. ► The small substitution of Ni for Fe in La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds enhances the formation of 1:13 phase and helps the elimination of impurity phase significantly. ► The Curie temperature T C of La(Fe 1−x Ni x ) 11.5 Si 1.5 compounds increase monotonously from 195 K to 219 K when x varies from 0 to 0.03. - Abstract: The influence of Ni substitution on the microstructure evolution and magnetic phase transition has been investigated in La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) compounds. Results show that partial substitution of Ni for Fe in La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) alloys promotes fining of the as-cast microstructure. Besides, the formation of 1:13 phase and the elimination of impurity phases is facilitated significantly when annealed at 1373 K for 5 days. Large amounts of inhomogeneities are present in the annealed LaFe 11.5 Si 1.5 alloy. While almost single 1:13 phase is obtained in La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0.02, 0.03) alloys. Moreover, the Curie temperature T C of La(Fe 1−x Ni x ) 11.5 Si 1.5 (x = 0, 0.01, 0.02, 0.03) compounds increase monotonously from 195 K to 219 K when Ni content x varies from 0 to 0.03.
Energy Technology Data Exchange (ETDEWEB)
Han, Ru-shuai; Qi, Li-qian; Hou, Xue; Liu, Li-hu; Liu, Hui-yuan [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang, Hebei 050024 (China); Xian, Xiao-Ning [Department of Information technology, Yuncheng Agricultural College, Shanxi 044000 (China); Guo, Ge-Xin [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang, Hebei 050024 (China); Sun, Hui-yuan, E-mail: huiyuansun@126.com [College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050024 (China); Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang, Hebei 050024 (China)
2016-12-15
In this work, a solid phase reaction method was used to fabricate (1−x)Bi{sub 0.85}La{sub 0.15}FeO{sub 3}–xCoFe{sub 2}O{sub 4} (x=0.1, 0.2, 0.3, 0.4) composite powders. X-ray diffraction patterns showed that no chemical reaction occurred between the separate Bi{sub 0.85}La{sub 0.15}FeO{sub 3} and CoFe{sub 2}O{sub 4} phases and indicated that the powder samples had two distinct phases with a CoFe{sub 2}O{sub 4} spinel phase and a Bi{sub 0.85}La{sub 0.15}FeO{sub 3} perovskite phase. The average crystallite sizes of the Bi{sub 0.85}La{sub 0.15}FeO{sub 3} in the composite powder were almost unchanged as the CoFe{sub 2}O{sub 4} content was increased. By comparing the experimental and theoretical values for the magnetization, we found that the Bi{sub 0.85}La{sub 0.15}FeO{sub 3} phase contributed to the magnetization of the composite powders. In addition, it also provides a new way to prove the existence of magnetoelectric coupling in the sample. - Highlights: • Theoretical magnetic value of the samples was calculated. • The experimental value of the magnetism was greater than the theoretical value. • The effect of the crystallite sizes on the magnetism was eliminated by calculating the crystallite sizes of BLFO. • The BLFO contributed to the magnetic moment through the magnetoelectric coupling.
Structural and magnetic properties of the (Ca1-xNax)(Fe2-xTix)O4 solid solution (0 ≤ x ≤ 1)
International Nuclear Information System (INIS)
Zouari, S.; Ranno, L.; Cheikh-Rouhou, A.; Isnard, O.; Wolfers, P.; Bordet, P.; Strobel, P.
2008-01-01
New compounds corresponding to the (Ca 1-x Na x )(Fe 2-x Ti x )O 4 formula with 0 ≤ x ≤ 1 were prepared by solid state reactions at 1100 deg. C in air. A continuous solid solution was found between end members CaFe 2 O 4 and NaFeTiO 4 . The evolution of structural parameters and bonding geometry with composition is discussed in detail. Magnetic measurements show that the antiferromagnetic ordering known in CaFe 2 O 4 is suppressed for all x values investigated (x ≥ 0.2). The absence of crystallographic transition at low temperature was checked by X-ray diffraction down to 10 K. The magnetic structure of CaFe 2 O 4 was redetermined from powder neutron diffraction. Spins on the two iron sites order antiparallel (F z F z spin arrangement), as described previously. The difference in magnetic moments on Fe 1 and Fe 2 sites result in a ferrimagnetic configuration with net moment 2.72μ B at 2 K
Dopant spin states and magnetism of Sn{sub 1−x}Fe{sub x}O{sub 2} nanoparticles
Energy Technology Data Exchange (ETDEWEB)
Punnoose, A., E-mail: apunnoos@boisestate.edu; Dodge, Kelsey; Reddy, K. M.; Franco, Nevil; Chess, Jordan; Eixenberger, Josh [Department of Physics, Boise State University, Boise, Idaho 83725-1570 (United States); Beltrán, J. J. [Department of Physics, Boise State University, Boise, Idaho 83725-1570 (United States); Grupo de Estado Sólido, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No 52-21, Medellín (Colombia); Barrero, C. A. [Grupo de Estado Sólido, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No 52-21, Medellín (Colombia)
2014-05-07
This work reports detailed investigations of a series of ∼2.6 nm sized, Sn{sub 1−x}Fe{sub x}O{sub 2} crystallites with x = 0–0.10 using Mossbauer spectroscopy, x-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectroscopy (EPR), and magnetometry to determine the oxidation state of Fe dopants and their role in the observed magnetic properties. The magnetic moment per Fe ion μ was the largest ∼6.48 × 10{sup −3} μ{sub B} for the sample with the lowest (0.001%) Fe doping, and it showed a rapid downward trend with increasing Fe doping. Majority of the Fe ions are in 3+ oxidation state occupying octahedral sites. Another significant fraction of Fe dopant ions is in 4+ oxidation state and a still smaller fraction might be existing as Fe{sup 2+} ions, both occupying distorted sites, presumably in the surface regions of the nanocrystals, near oxygen vacancies. These studies also suggest that the observed magnetism is not due to exchange coupling between Fe{sup 3+} spins. A more probable role for the multi-valent Fe ions may be to act as charge reservoirs, leading to charge transfer ferromagnetism.
Green, R J; Regier, T Z; Leedahl, B; McLeod, J A; Xu, X H; Chang, G S; Kurmaev, E Z; Moewes, A
2015-10-16
Dilute magnetic semiconductors (DMSs) show great promise for applications in spin-based electronics, but in most cases continue to elude explanations of their magnetic behavior. Here, we combine quantitative x-ray spectroscopy and Anderson impurity model calculations to study ferromagnetic Fe-substituted In2O3 films, and we identify a subset of Fe atoms adjacent to oxygen vacancies in the crystal lattice which are responsible for the observed room temperature ferromagnetism. Using resonant inelastic x-ray scattering, we map out the near gap electronic structure and provide further support for this conclusion. Serving as a concrete verification of recent theoretical results and indirect experimental evidence, these results solidify the role of impurity-vacancy coupling in oxide-based DMSs.
Onari, Seiichiro; Yamakawa, Youichi; Kontani, Hiroshi
2014-05-09
The isostructural transition in the tetragonal phase with a sizable change in the anion height, is realized in heavily H-doped LaFeAsO and (La,P) codoped CaFe2As2. In these compounds, the superconductivity with higher Tc (40-50 K) is realized near the isostructural transition. To find the origin of the anion-height instability and the role in realizing the higher-Tc state, we develop the orbital-spin fluctuation theory by including the vertex correction. We analyze LaFeAsO(1-x)H(x) and find that the non-nematic orbital fluctuations, which induce the anion-height instability, are automatically obtained at x∼0.5, in addition to the conventional nematic orbital fluctuations at x∼0. The non-nematic orbital order triggers the isostructural transition, and its fluctuation would be a key ingredient to realize higher-Tc superconductivity of order 50 K.
Crystallization study of amorphous system Fe[sub 84-x]W[sub x]B[sub 16] (x = 3; 5)
Energy Technology Data Exchange (ETDEWEB)
Novakova, A.A.; Sidorova, G.V.; Kiseleva, T.Yu.; Szasz, A. (Dept. of Physics, State Univ., Moscow (Russia) Inst. of Metallurgy, Academy of Science, Moscow (Russia) Eoetvoes Univ., Budapest (Hungary))
1992-10-01
A complex study of the crystallization process of the amorphous system was carried out by Moessbauer spectroscopy, X-ray diffraction and DTA. Alloy samples crystallized at 600deg C contain the following phases: [alpha]-Fe, Fe[sub 3]B and solid solution (Fe, W)[sub 3]B. (orig.).
Thermodynamics and long-range order of nitrogen in gamma'-Fe4N1-x
Kooi, BJ; Somers, MAJ; Mittemeijer, EJ
Models are given for the description of the chemical potential of nitrogen in gamma'-Fe4N1-x. In previous work, gamma'-Fe4N1-x was treated as a (sub)regular solution, thereby assuming that the N atoms are distributed randomly on the sites of their own sublattice. However, in gamma'-Fe4N1-x,
Magnetic and Moessbauer studies of amorphous Fe72-xYxHo8B20 alloys
International Nuclear Information System (INIS)
Krishnan, R.; Dumond, Y.; Ajan, A.; Shringi, S.N.; Prasad, S.
1996-01-01
We have carried out magnetic and Moessbauer studies of amorphous Fe 72-x Y x Ho 8 B 20 alloys. The Fe moment decreases with the addition of Y and a magnetic compensation occurs at 4 K for x=16. The temperature and field dependences of the magnetization have been interpreted using the mean field theory and Chudnovsky's model, respectively. These analyses yield some interesting parameters such as the random anisotropy, the exchange interactions J Fe-Fe , J Fe-Ho , etc. The Moessbauer studies show that the average hyperfine field decreases linearly with the addition of Y, in accordance with the decrease in the Fe moment. (orig.)
LiFePO4 Nanostructures Fabricated from Iron(III) Phosphate (FePO4 x 2H2O) by Hydrothermal Method.
Saji, Viswanathan S; Song, Hyun-Kon
2015-01-01
Electrode materials having nanometer scale dimensions are expected to have property enhancements due to enhanced surface area and mass/charge transport kinetics. This is particularly relevant to intrinsically low electronically conductive materials such as lithium iron phosphate (LiFePO4), which is of recent research interest as a high performance intercalation electrode material for Li-ion batteries. Many of the reported works on LiFePO4 synthesis are unattractive either due to the high cost of raw materials or due to the complex synthesis technique. In this direction, synthesis of LiFePO4 directly from inexpensive FePO4 shows promise.The present study reports LiFePO4 nanostructures prepared from iron (III) phosphate (FePO4 x 2H2O) by precipitation-hydrothermal method. The sintered powder was characterized by X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Inductive coupled plasma-optical emission spectroscopy (ICP-OES), and Electron microscopy (SEM and TEM). Two synthesis methods, viz. bulk synthesis and anodized aluminum oxide (AAO) template-assisted synthesis are reported. By bulk synthesis, micro-sized particles having peculiar surface nanostructuring were formed at precipitation pH of 6.0 to 7.5 whereas typical nanosized LiFePO4 resulted at pH ≥ 8.0. An in-situ precipitation strategy inside the pores of AAO utilizing the spin coating was utilized for the AAO-template-assisted synthesis. The template with pores filled with the precipitate was subsequently subjected to hydrothermal process and high temperature sintering to fabricate compact rod-like structures.
Magnetic and Mössbauer studies of amorphous Fe 72- xY xHo 8B 20 alloys
Krishnan, R.; Driouch, L.; Lassri, H.; Dumond, Y.; Ajan, Antony; Shringi, S. N.; Prasad, Shiva
1996-11-01
We have carried out magnetic and Mössbauer studies of amorphous Fe 72- xY xHo 8B 20 alloys. The Fe moment decreases with the addition of Y and a magnetic compensation occurs at 4 K for x = 16. The temperature and field dependences of the magnetization have been interpreted using the mean field theory and Chudnovsky's model, respectively. These analyses yield some interesting parameters such as the random anisotropy, the exchange interactions JFe-Fe, JFe-Ho, etc. The Mössbauer studies show that the average hyperfine field decreases linearly with the addition of Y, in accordance with the decrease in the Fe moment.
NMR and Moessbauer studies of the amorphous system Fe79P/sub 21-x/B/sub x/
International Nuclear Information System (INIS)
Amamou, A.; Durand, J.
1977-05-01
Combined NMR, spin-echo and Moessbauer experiments have been performed to obtain hyperfine field distributions of the transition metal and metalloid elements in splat-cooled amorphous Fe 79 P 21 /sub -x/B/sub x/ alloys. These distributions are related to the local environments of the elements. The NMR signals are observed in the low frequency range 20-60 MHz and all the nuclei, i.e. Fe, P and B, may contribute to the spectral distribution. The resolution of the spectra into that due to Fe and (P + B) nuclei was made possible by using samples prepared with an Fe 56 isotope. The Fe distribution thus obtaned shows general agreement with the Moessbauer field distribution. From a careful analysis of the NMR data, the hyperfine field at the B nuclei in these amorphous alloys is found to range from 24 to 26 KG increasing with B content. An upper limit of 8 KG for the half-width is attributed to this distribution. The Moessbauer spectra of the Fe 57 nuclei resemble those for the crystalline Fe 75 P 25 /sub -x/B/sub x/ alloys. A fit of the spectra shows a field distribution which suggests the presence of structure. Such a structure may correspond to various Fe sites, also seen in the crystalline alloys. The distributions generally lie between about 160 and 330 KG, with a maximum at about 260 KG. These spectra do not show the presence of Fe nuclei with essentially zero hyperfine field as was obtained for amorphous Fe-Pd-P by Sharon et al. and for amorphous Fe-P by Logan et al. With increasing B content the center of gravity of the Fe distribution shifts to higher values. From a systematic study of the NMR lines and other considerations it is concluded that the P field distribution is broad and its hyperfine field is between 20 and 35 KG for the higher P concentration alloys
Fabrication of Mg-X-O (X = Fe, Co, Ni, Cr, Mn, Ti, V, and Zn) barriers for magnetic tunnel junctions
Yakushiji, K.; Kitagawa, E.; Ochiai, T.; Kubota, H.; Shimomura, N.; Ito, J.; Yoda, H.; Yuasa, S.
2018-05-01
We fabricated magnetic tunnel junctions with a 3d-transition material(X)-doped MgO (Mg-X-O) barrier, and evaluated the effect of the doping on magnetoresistance (MR) and microstructure. Among the variations of X (X = Fe, Co, Ni, Cr, Mn, Ti, V, and Zn), X = Fe and Mn showed a high MR ratio of more than 100%, even at a low resistance-area product of 3 Ωμm2. The microstructure analysis revealed that (001) textured orientation formed for X = Fe and Mn despite substantial doping (about 10 at%). The elemental mappings indicated that Fe atoms in the Mg-Fe-O barrier were segregated at the interfaces, while Mn atoms were evenly involved in the Mg-Mn-O barrier. This suggests that MgO has high adaptability for Fe and Mn dopants in terms of high MR ratio.
Synthesis and electrochemical properties of Ti4+ doped Li3-xFe2-xTix(PO4)3/C cathode materials
International Nuclear Information System (INIS)
Liu Zhanqiang; Huang Fuqiang; Sun Junkang
2011-01-01
Highlights: → Li 3-x Fe 2-x Ti x (PO 4 ) 3 /C composite cathodes were prepared by ball-milling method. Ti-doping can improve the electrochemical property of Li 3 Fe 2 (PO 4 ) 3 . → The optimized doping level was found to be x = 0.2. → The second phase of LiTi 2 (PO 4 ) 3 will emerge if the doping level higher than 0.2. - Abstract: Li 3-x Fe 2-x Ti x (PO 4 ) 3 /C (x = 0-0.4) cathodes designed with Fe doped by Ti was studied. Both Li 3 Fe 2 (PO 4 ) 3 /C (x = 0) and Li 2.8 Fe 1.8 Ti 0.2 (PO 4 ) 3 /C (x = 0.2) possess two plateau potentials of Fe 3+ /Fe 2+ couple (around 2.8 V and 2.7 V vs. Li + /Li) upon discharge observed from galvanostatic charge/discharge and cyclic voltammetry. Li 2.8 Fe 1.8 Ti 0.2 (PO 4 ) 3 /C has higher reversibility and better capacity retention than that of the undoped Li 3 Fe 2 (PO 4 ) 3 /C. A much higher specific capacity of 122.3 mAh/g was obtained at C/20 in the first cycle, approaching the theoretical capacity of 128 mAh/g, and a capacity of 100.1 mAh/g was held at C/2 after the 20th cycle.
Shape memory effect of Fe-17%Mn-X alloys
International Nuclear Information System (INIS)
Lee, S.-H.; Kim, H.-J.; Choi, C.-S.; Baik, S.-H.
2000-01-01
SME of Fe-17%Mn-X alloy decreased with increasing Ni and Cr contents. This is because the occurrence of stress-induced martensite transformation of γ to ε is difficult due to the increase in stability of retained austenite with increasing Ni and Cr contents. SME of Fe-17%Mn-X alloy increased with increasing the number of thermal cycles. The reason is that the prior bending deformation for SME is associated with coalescence of the pre-existing ε plates due to their rearrangement, thereby the more the ε content, the greater the SME. (orig.)
Single crystal neutron diffraction study of SrFeOsub(3-x)(x=0. 1)
Energy Technology Data Exchange (ETDEWEB)
Oda, H; Yamaguchi, Y; Takei, H; Watanabe, H [Tohoku Univ., Sendai (Japan). Research Inst. for Iron, Steel and Other Metals
1977-01-01
Neutron diffraction study was carried out on single crystals of the perovskite oxide SrFeOsub(3-x)(x=0.1). SrFeOsub(3-x)(x=0.1) has a proper screw spin structure with the propagation vector parallel to (111) direction and its Neel temperature is 118 K. The electron configuration of Fe/sup 4 +/(3d/sup 4/) ion is close to the low-spin state (tsub(2g)sup(4)) and the oxygen ion has the unpaired electron with the magnetic moment of 0.3..mu..sub(B) antiparallel to the vector sum of the magnetic moments of two iron ions lying on the neighbouring planes perpendicular to the screw axis. The absolute value of the propagation vector is almost constant. 0.130x..sqrt..3.2..pi../a A/sup -1/, at temperatures below 50 K, while it decreases gradually at higher temperatures reaching 0.118x..sqrt..3.2..pi../a A/sup -1/ at Tsub(N).
Spin injection into semiconductors: the role of Fe/AlxGa1-xAs interface
International Nuclear Information System (INIS)
Fitzsimmons, M.R.; Park, S.
2004-01-01
The influence of the growth and post-growth annealing temperatures of Fe/Al x Ga 1-x As-based spin light-emitting diodes (LEDs) on the spin injection efficiency is discussed. The extent of interfacial reactions during molecular beam epitaxial growth of Fe on GaAs was determined from in-situ x-ray photoelectron spectroscopy studies. The Fe/GaAs interface results in ≤ 3 monolayers of reaction for Fe grown at -15 C. Intermediate growth temperatures (95 C) lead to ∼5 monolayers of interfacial reactions, and high growth temperatures of 175 C lead to a ∼9 monolayer thick reacted layer. Polarized neutron reflectivity was used to determine the interfacial magnetic properties of epitaxial Fe 0.5 Co 0.5 /GaAs heterostructures grown under identical conditions. No interfacial magnetic dead layer is detected at the interface for Fe 0.5 Co 0.5 films grown at -15 C, an ∼6 (angstrom) thick nonmagnetic layer formed at the interface for 95 C growth and an ∼5 (angstrom) thick magnetic interfacial reacted layer formed for growth at 175 C. Spin injection from Fe contacts into spin LEDs decreases sharply when reactions result in a nonmagnetic interfacial layer. Significant spin injection signals are obtained from Fe contacts grown between -5 C and 175 C, although the higher Fe growth temperatures resulted in a change in the sign of the spin polarization. Post-growth annealing of the spin LEDs is found to increase spin injection efficiency for low Fe growth temperatures and to a sign reversal of the spin polarization for high growth temperature (175 C). An effective Schottky barrier height increase indicates that post growth annealing modifies the Fe/Al x Ga 1-x As interface.
Thermodynamics and Long-Range Order of Nitrogen in γ'-Fe4N1-x
Kooi, Bart J.; Somers, Marcel A.J.; Mittemeijer, Eric J.
1996-01-01
Models are given for the description of the chemical potential of nitrogen in γ'-Fe4N1-x. In previous work, γ'-Fe4N1-x was treated as a (sub)regular solution, thereby assuming that the N atoms are distributed randomly on the sites of their own sublattice. However, in γ'-Fe4N1-x, long-range ordering
Magnetothermopower in A2−xLaxFeMoO6 (A = Sr, Ba
Directory of Open Access Journals (Sweden)
G. V. M. Williams
2017-01-01
Full Text Available A magnetothermopower has been observed in electronically spin-polarized polycrystalline Sr2-xLaxFeMoO6 and Ba2FeMoO6. The magnetothermopower is linear up to ~50 K for Sr2-xLaxFeMoO6 and linear up to ~270 K for Ba2FeMoO6. We suggest that the magnetothermopower may arise from a spin-tunneling magnetothermopower between the grains.
Magnetic nanowires (Fe, Fe-Co, Fe-Ni – magnetic moment reorientation in respect of wires composition
Directory of Open Access Journals (Sweden)
Kalska-Szostko Beata
2015-03-01
Full Text Available Magnetic nanowires of Fe, Fe-Co, and Fe-Ni alloy and layered structure were prepared by electrochemical alternating current (AC deposition method. The morphology of the nanowires in and without the matrix was studied by energy dispersive X-ray spectroscopy (EDX, scanning electron microscopy (SEM, and X-ray diffraction (XRD, respectively. The wires either show strong dependence on the combination of elements deposition (alloy or layered or chemical composition (Co or Ni. The magnetic properties of the nanostructures were determined on the basis of Mössbauer spectroscopy (MS.
Magnetism and large magnetocaloric effect in HoFe{sub 2-x}Al{sub x}
Energy Technology Data Exchange (ETDEWEB)
Mican, S., E-mail: sever.mican@ubbcluj.ro [Babes-Bolyai University Cluj-Napoca, RO-400084 Cluj-Napoca (Romania); Benea, D., E-mail: diana.benea@phys.ubbcluj.ro [Babes-Bolyai University Cluj-Napoca, RO-400084 Cluj-Napoca (Romania); Tetean, R., E-mail: romulus.tetean@phys.ubbcluj.ro [Babes-Bolyai University Cluj-Napoca, RO-400084 Cluj-Napoca (Romania)
2013-02-05
Highlights: Black-Right-Pointing-Pointer Structural, magnetic and magnetocaloric properties of HoFe{sub 2-x}Al{sub x} compounds are reported. Black-Right-Pointing-Pointer Electronic structure calculations show a good agreement between theory and experiment. Black-Right-Pointing-Pointer Magnetic transitions close to room temperature for the Fe-rich samples. Black-Right-Pointing-Pointer High values of the relative cooling power for all of the investigated samples. Black-Right-Pointing-Pointer No hysteresis losses in applied fields of up to 4 T. - Abstract: The structural, magnetic and magnetocaloric properties of several HoFe{sub 2-x}Al{sub x} compounds were investigated. The compounds in the Fe-rich region (0.36 Less-Than-Or-Slanted-Equal-To x Less-Than-Or-Slanted-Equal-To 0.4) crystallize in the cubic MgCu{sub 2} (C15) structure, while for the ones in the intermediate region (0.75 Less-Than-Or-Slanted-Equal-To x Less-Than-Or-Slanted-Equal-To 1.125) the hexagonal MgZn{sub 2} (C14) structure was observed. Electronic structure calculations were performed, showing a good agreement between theory and experiment. The Curie temperatures were found to decrease with Al content. For the Fe-rich compounds, these are close to room temperature, while for the compounds in the intermediate region, transition temperatures are well below 300 K. No magnetic hysteresis was found around the Curie temperature for applied magnetic fields of up to 4 T. All of the investigated compounds undergo a second-order magnetic phase transition at the Curie temperature. A maximum magnetic entropy change value of 7.6 J/kg K was obtained for the sample with x = 1.125, all of the samples displaying rather large RCP values. The possibility of incorporating these materials in magnetic refrigeration devices is discussed.
dos Santos, A. V.; Samudio Pérez, C. A.; Muenchen, D.; Anibele, T. P.
2015-01-01
The ground state properties of Fe/N/Fe and Fe/O/Fe multilayers were investigated using the first principles calculations. The calculations were performed using the Linearized Augmented Plane Wave (LAPW) method implemented in the Wien2k code. A supercell consisting of one layer of nitride (or oxide) between two layers of Fe in the bcc structure was used to model the structure of the multilayer. The research in new materials also stimulated theoretical and experimental studies of iron-based nitrides due to their variety of structural and magnetic properties for the potential applications as in high strength steels and for high corrosion resistance. It is obvious from many reports that magnetic iron nitrides such as γ-Fe4N and α-Fe16N2 have interesting magnetic properties, among these a high magnetisation saturation and a high density crimp. However, although Fe-N films and multilayers have many potential applications, they can be produced in many ways and are being extensively studied from the theoretical point of view there is no detailed knowledge of their electronic structure. Clearly, efforts to understand the influence of the nitrogen atoms on the entire electronic structure are needed as to correctly interpret the observed changes in the magnetic properties when going from Fe-N bulk compounds to multilayer structures. Nevertheless, the N atoms are not solely responsible for electronics alterations in solid compounds. Theoretical results showed that Fe4X bulk compounds, where X is a variable atom with increasing atomic number (Z), the nature of bonding between X and adjacent Fe atoms changes from more covalent to more ionic and the magnetic moments of Fe also increase for Z=7, i.e. N. This is an indicative that atoms with a Z number higher than 7, i.e., O, can produce several new alterations in the entire magnetic properties of Fe multilayers. This paper presents the first results of an ab-initio electronic structure calculations, performed for Fe-N and Fe
Moessbauer effect study on mechanically alloyed amorphous Fe1-xTix alloys
International Nuclear Information System (INIS)
Chen Hong; Xu Zuxiong; Ma Ruzhang; Zhao Zhongtao; Ping Jueyun
1994-01-01
Amorphous Fe 1-x Ti x (x = 0.50, 0.60) powders were produced by mechanical alloying from pure elemental powders in a vibratory ball-mill. X-ray diffraction (XRD) and Moessbauer effect (ME) were used to study the progress of amorphization and the property of hydrogen absorption in Fe-Ti alloys. The amorphization process and the properties of the amorphous phase are discussed. (orig.)
Moessbauer spectroscopy on amorphous Fe/sub x/Ni/sub 80-x/B20 after neutron irradiation
International Nuclear Information System (INIS)
Sitek, J.; Miglierini, M.
1985-01-01
Amorphous Fe/sub x/Ni/sub 80-x/B 20 glassy alloys (x = 40, 50, 60, and 70) irradiated with fast neutrons in a fluence range of 10 14 to 10 19 cm -2 were investigated by Moessbauer spectroscopy. There were some significant changes in the Moessbauer spectrum parameters of the 10 19 cm -2 irradiated samples except Fe 40 Ni 40 B 20 . This corresponds to a change in the direction of the easy axis of magnetization. The measurements show that the resistance of the Fe-Ni-B system against neutron irradiation improves with increasing Ni content up to a certain point
Magnetic spin configuration in Fe{sub 50}Pt{sub 50-x}Rh{sub x} alloys
Energy Technology Data Exchange (ETDEWEB)
Fenske, J.; Lott, D.; Schreyer, A. [GKSS Research Centre (Germany); Mankey, G.J. [University of Alabama, MINT Center (United States); Schmidt, W.; Schmalzl, K. [Juelich Research Centre (Germany); Tartakowskaya, E. [Institute for Magnetism, National Ukrainian Accademy of Science (Ukraine)
2010-07-01
FePt-based alloys are typically the material of choice for magnetic information storage media. The high magnetic moment of Fe gives a large magnetization and the large atomic number of Pt results in a high magnetic anisotropy. This combination enables the written bits to be smaller than ever before. One way to control the magnetic properties in these materials is through the introduction of a third element into the crystal matrix e.g. Rh. When Rh is added to replace Pt in the equiatomic alloy, new magnetic phases emerge. Bulk samples of Fe{sub 50}Pt{sub 50-x}Rh{sub x} studied by magnetization measurements refer to three different phase transitions with increasing temperature: (I) An antiferromagnetic (AF)-paramagnetic (PM) transition for 30<x<14.25, (II), an AF-ferromagnetic (FM) transition for 14.25<x<9.5 and, (III), a FM-PM transition 9.5<x<0. Here we present results on a series of 200 nm Fe{sub 50}Pt{sub 50-x}Rh{sub x} films with different Rh concentrations. These films were examined by neutron diffraction in dependence of temperature and magnetic field. By the use of polarized and unpolarized neutron diffraction we could develop a detailed model of the magnetic spin structure in these thin films.
Studies on the KTa1-xFe xO3-δ system
International Nuclear Information System (INIS)
Ciriaco, M. Lurdes F.; Silva Pereira, M.I. da; Nunes, M.R.; Mendonca, M.H.; Costa, F.M.
2006-01-01
In this work we have prepared by ceramic route, polycrystalline powders samples derived from the KTaO 3 perovskite by the partial replacement of tantalum by iron with nominal composition KTa 1-x Fe x O 3-δ (0 ≤ x ≤ 1), in order to evaluate the consequence of these substitution on the properties of the compounds. Two synthesis temperatures were used, 973 and 1373 K. From the powders (x = 0.1) iron coatings were prepared and tested, as electrode materials, in alkaline solutions. The characterisation of the powder samples was made by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrical conductivity measurements. Cyclic voltammetry was used in the electrodes characterisation. The results show that the partial replacement of Ta by Fe and the synthesis temperature affect the properties of the system
An X-ray absorption spectroscopic study of the metal site preference in Al1-xGaxFeO3
Walker, James D. S.; Grosvenor, Andrew P.
2013-01-01
Magnetoelectric materials have potential for being introduced into next generation technologies, especially memory devices. The AFeO3 (Pna21; A=Al, Ga) system has received attention to better understand the origins of magnetoelectric coupling. The magnetoelectric properties this system exhibits depend on the amount of anti-site disorder present, which is affected by the composition and the method of synthesis. In this study, Al1-xGaxFeO3 was synthesized by the ceramic method and studied by X-ray absorption spectroscopy. Al L2,3-, Ga K-, and Fe K-edge spectra were collected to examine how the average metal coordination number changes with composition. Examination of XANES spectra from Al1-xGaxFeO3 indicate that with increasing Ga content, Al increasingly occupies octahedral sites while Ga displays a preference for occupying the tetrahedral site. The Fe K-edge spectra indicate that more Fe is present in the tetrahedral site in AlFeO3 than in GaFeO3, implying more anti-site disorder is present in AlFeO3.
NMR study of spin fluctuations and superconductivity in LaFeAsO1-xHx
Fujiwara, Naoki; Sakurai, Ryosuke; Iimura, Soushi; Matsuishi, Satoru; Hosono, Hideo; Yamakawa, Yoichi; Kontani, Hiroshi
2013-03-01
We have performed NMR measurements in LaFeAsO1-xHx, an isomorphic compound of LaFeAsO1-xFx. LaFeAsO1-xHx is most recently known for having double superconducting (SC) domes on H doping. LaFeAsO1-xHx is an electron- doped system, and protons act as H-1 as well as F-1. The first SC dome is very similar between F and H doping, suggesting that H doping supplies the same amount of electrons as F doping. Interestingly, an excess amount of H up to x=0.5 can be replaced with O2-. In the H-overdoped regime (x > 0 . 2), LaFeAsO1-xHx undergoes the second superconducting state. We measured the relaxation rate of LaFeAsO1-xHx for x=0.2 and 0.4, and fond an anomalous electronic state; spin fluctuations measured from 1 /T1 T is enhanced with increasing the doping level from x = 0 . 2 to 0.4. The enhancement of spin fluctuations with increasing carrier doping is a new phenomenon that has not observed in LaFeAsO1-xFx in which the upper limit of the doping level is at most x = 0 . 2 . We will discuss the phenomenon in relation to superconductivity. Grant (KAKENHI 23340101) from the Ministry of Education, Sports and Science, Japan
Fe-vacancy and superconductivity in FeSe-based superconductors
Wang, C. H.; Chen, T. K.; Chang, C. C.; Lee, Y. C.; Wang, M. J.; Huang, K. C.; Wu, P. M.; Wu, M. K.
2018-06-01
This review summarizes recent advancements in FeSe and related systems. The FeSe and related superconductors are currently receiving considerable attention for the high Tcs observed and for many similar features to the high Tc cuprate superconductors. These similarities suggest that understanding the FeSe based compounds could potentially help our understanding of the cuprates. We shall first review the common features observed in the FeSe-based system. It was found that with a careful control of material synthesizing processes, numerous rich phases have been observed in the FeSe-based system. Detailed studies show that the Fe-vacancy ordered phases found in the FeSe based compounds, which are non-superconducting Mott insulators, are the parent compounds of the superconductors. Superconductivity emerges from the parent phases by disordering the Fe vacancy order, often by a simple annealing treatment. Recent high temperature X-ray diffraction experiments show that the degree of structural distortion associated with the disorder of Fe-vacancy is closely related to volume fraction of the superconductivity observed. These results suggest the strong lattice to spin coupling are important for the occurrence of superconductivity in FeSe based superconductors.
Ternary NiFeX as soft biasing film in a magnetoresistive sensor
Chen, Mao-Min; Gharsallah, Neila; Gorman, Grace L.; Latimer, Jacquie
1991-04-01
The properties of NiFeX ternary films (X being Al, Au, Nb, Pd, Pt, Si, and Zr) have been studied for soft-film biasing of the magnetoresistive (MR) trilayer sensor. In general, the addition of the element X into the NiFe alloy film decreases the saturation magnetization Bs and magnetoresistance coefficient of the film, while increasing the film's electrical resistivity ρ. One of the desirable properties of a soft film for biasing is high sheet resistance for minimum current flow. A figure of merit Bsρ that takes into account both the rate of increase in Bs and the rate of decrease in ρ when adding X element was derived to compare the effectiveness of various X elements in reducing the current shunting through the soft-film layer. Using this criterion, NiFeNb and NiFeZr emerge as good soft-film materials having a maximum sheet resistance relative to the MR layer. Other critical properties such as magnetoresistance coefficient, magnetostriction, coercivity, and anisotropy field were also examined and are discussed in this paper.
Surfactant-induced layered growth in homoepitaxy of Fe on Fe(100)-c(2 x 2)O reconstruction surface
International Nuclear Information System (INIS)
Kamiko, Masao; Mizuno, Hiroyuki; Chihaya, Hiroaki; Xu, Junhua; Kojima, Isao; Yamamoto, Ryoichi
2007-01-01
In this study, the effects of several surfactants (Pb, Bi, and Ag) on the homoepitaxial growth of Fe(100) were studied and compared. The reflection high-energy electron diffraction measurements clearly reveal that these surfactants enhance the layer-by-layer growth of Fe on an Fe(100)-c(2 x 2)O reconstruction surface. The dependence of growth on the surfactant layer thickness suggests that there exists a suitable amount of surfactant layer that induces a smoother layer-by-layer growth. Comparisons between the atomic force microscopy images reveal that the root-mean-square surface roughness of Fe films mediated by Pb and Bi surfactants are considerably smaller than those of the films mediated by Ag surfactant. The Auger electron spectra show that Pb and Bi segregate at the top of the surface. It has been concluded that Pb and Bi are effective surfactants for enhancing layer-by-layer growth in Fe homoepitaxy. Ag has the same effect, but it is less efficient due to the weak surface segregation of Ag
International Nuclear Information System (INIS)
Shi, H L; Yang, H X; Tian, H F; Lu, J B; Wang, Z W; Qin, Y B; Song, Y J; Li, J Q
2010-01-01
The SrFe 2 As 2-x P x (0.0 ≤ x ≤ 1.0) and CaFe 2 As 2-y P y (0.0 ≤ y ≤ 0.3) materials were prepared by a solid-state reaction method. X-ray diffraction measurements indicate that the single-phase samples can be successfully obtained for SrFe 2 As 2-x P x (0.0 ≤ x ≤ 0.8) and CaFe 2 As 2-y P y (0.0 ≤ y ≤ 0.3). Visible contraction of the lattice parameters is determined due to the relatively smaller radius of P ions in comparison with that of As. The spin-density-wave (SDW) instability associated with the tetragonal to orthorhombic phase transition is suppressed noticeably in both systems following the increase in P content. The highest superconducting transitions are observed at about 27 K in SrFe 2 As 1.3 P 0.7 and at about 13 K in CaFe 2 As 1.925 P 0.075 , respectively. Structural analysis suggests that lattice contraction could notably affect the superconductivity in these materials.
Ab initio studies of Co{sub 2}FeAl{sub 1−x}Si{sub x} Heusler alloys
Energy Technology Data Exchange (ETDEWEB)
Szwacki, N. Gonzalez, E-mail: gonz@fuw.edu.pl; Majewski, Jacek A., E-mail: jam@fuw.edu.pl
2016-07-01
We present results of extensive theoretical studies of Co{sub 2}FeAl{sub 1−x}Si{sub x} Heusler alloys, which have been performed in the framework of density functional theory employing the all-electron full-potential linearized augmented plane-wave scheme. It is shown that the Si-rich alloys are more resistive to structural disorder and as a consequence Si stabilizes the L2{sub 1} structure. Si alloying changes position of the Fermi level, pushing it into the gap of the minority spin-band. It is also shown that the hyperfine field on Co nuclei increases with the Si concentration, and this increase originates mostly from the changes in the electronic density of the valence electrons. - Highlights: • GGA+U calculations: μ and E{sub g} dependence on the value of U for Co{sub 2}FeAl and Co{sub 2}FeSi. • Behavior of magnetic hyperfine fields on the Co site of Co{sub 2}FeAl{sub 1−x}Si{sub x} versus x. • DFT proof of suppression of formation of antisites defects with x in Co{sub 2}FeAl{sub 1−x}Si{sub x}.
Fe-N{sub x}/C assisted chemical–mechanical polishing for improving the removal rate of sapphire
Energy Technology Data Exchange (ETDEWEB)
Xu, Li, E-mail: xl0522@126.com [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Shenzhen Key Laboratory of Micro/Nano Manufacturing, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057 (China); Zou, Chunli; Shi, Xiaolei [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Shenzhen Key Laboratory of Micro/Nano Manufacturing, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057 (China); Pan, Guoshun, E-mail: pangs@tsinghua.edu.cn [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Shenzhen Key Laboratory of Micro/Nano Manufacturing, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057 (China); Luo, Guihai; Zhou, Yan [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084 (China); Shenzhen Key Laboratory of Micro/Nano Manufacturing, Research Institute of Tsinghua University in Shenzhen, Shenzhen 518057 (China)
2015-07-15
Highlights: • A novel non-noble metal catalyst (Fe-N{sub x}/C) was prepared. • Fe-N{sub x}/C shows remarkable catalytic activity for improving the removal rate of sapphire in alkaline solution. • The optimum CMP removal by Fe-N{sub x}/C yielded a superior surface finish of 0.078 nm the average roughness. • Fe{sub 2}O{sub 3}, Fe{sub 3}O{sub 4}, pyridinic N as well as pyrrolic N group possibly serving as the catalytic sites. • A soft hydration layer (boehmite, AlO(OH)) was generated on the surface of sapphire during CMP process. - Abstract: In this paper, a novel non-noble metal catalyst (Fe-N{sub x}/C) is used to improve the removal mass of sapphire as well as obtain atomically smooth sapphire wafer surfaces. The results indicate that Fe-N{sub x}/C shows good catalytic activity towards sapphire removal rate. And the material removal rates (MRRs) are found to vary with the catalyst content in the polishing fluid. Especially that when the polishing slurry mixes with 16 ppm Fe-N{sub x}/C shows the maximum MRR and its removal mass of sapphire is 38.43 nm/min, more than 15.44% larger than traditional CMP using the colloidal silicon dioxide (SiO{sub 2}) without Fe-N{sub x}/C. Catalyst-assisted chemical–mechanical polishing of sapphire is studied with X-ray photoelectron spectroscopy (XPS). It is found that the formation of a soft hydration layer (boehmite, γ-AlOOH or γ-AlO(OH)) on sapphire surface facilitates the material removal and achieving fine surface finish on basal plane. Abrasives (colloid silica together with magnetite, ingredient of Fe-N{sub x}/C) with a hardness between boehmite and sapphire polish the c-plane of sapphire with good surface finish and efficient removal. Fe{sub 2}O{sub 3}, Fe{sub 3}O{sub 4}, pyridinic N as well as pyrrolic N group would be the catalytical active sites and accelerate this process. Surface quality is characterized with atomic force microscopy (AFM). The optimum CMP removal by Fe-N{sub x}/C also yields a superior
Polaronic transport and thermoelectricity in Fe1 -xCoxSb2S4 (x =0 , 0.1, and 0.2)
Liu, Yu; Kang, Chang-Jong; Stavitski, Eli; Du, Qianheng; Attenkofer, Klaus; Kotliar, G.; Petrovic, C.
2018-04-01
We report a study of Co-doped berthierite Fe1 -xCoxSb2S4 (x =0 , 0.1, and 0.2). The alloy series of Fe1 -xCoxSb2S4 crystallize in an orthorhombic structure with the Pnma space group, similar to FeSb2, and show semiconducting behavior. The large discrepancy between activation energy for conductivity, Eρ (146 ˜270 meV ), and thermopower, ES (47 ˜108 meV ), indicates the polaronic transport mechanism. Bulk magnetization and heat-capacity measurements of pure FeSb2S4 (x =0 ) exhibit a broad antiferromagnetic transition (TN=46 K ) followed by an additional weak transition (T*=50 K ). Transition temperatures (TN and T*) slightly decrease with increasing Co content x . This is also reflected in the thermal conductivity measurement, indicating strong spin-lattice coupling. Fe1 -xCoxSb2S4 shows relatively high value of thermopower (up to ˜624 μ V K-1 at 300 K) and thermal conductivity much lower when compared to FeSb2, a feature desired for potential applications based on FeSb2 materials.
Magneto-optical imaging of polycrystalline FeTe1-xSex prepared at various conditions
International Nuclear Information System (INIS)
Ding, Q.; Taen, T.; Mohan, S.; Nakajima, Y.; Tamegai, T.
2011-01-01
High-quality FeTe 1-x Se x polycrystals with T c ∼ 14 K were prepared by sintering at different temperatures. Intragranular critical current density of FeTe 1-x Se x polycrystals estimated from M-H curve is 5 x 10 4 A/cm 2 at 5 K under zero field. The observed intragranular J c value was confirmed by the magneto-optical images in the remanent state. The weak-link feature of FeTe 1-x Se x polycrystals is also revealed through magneto-optical imaging. We have prepared high-quality polycrystalline FeTe 1-x Se x by sintering at different temperatures and characterized their structural and magnetic properties with X-ray diffraction, magnetization measurements, and magneto-optical imaging. The intragranular J c was estimated to be 5 x 10 4 A/cm 2 , which is smaller than the single crystal, but still in the range for practical applications.
Crystal growth of Sm0.3Tb0.7FeO3 and spin reorientation transition in Sm1−xTbxFeO3 orthoferrite
International Nuclear Information System (INIS)
Wu, Anhua; Wang, Bo; Zhao, Xiangyang; Xie, Tao; Man, Peiwen; Su, Liangbi; Kalashnikova, A.M.; Pisarev, R.V.
2017-01-01
In this work, Sm 0.3 Tb 0.7 FeO 3 single crystal was successfully grown by optical floating zone method. Sm 0.3 Tb 0.7 FeO 3 samples with a-, b-, and c-orientation were manufactured by means of Laue photograph. Magnetic properties of Sm 0.3 Tb 0.7 FeO 3 single crystals are studied over a wide temperature range from 2 to 400 K. Spin reorientation transition from Γ 2 to Γ 4 are observed by means of the temperature dependence of magnetization It indicated the reorientation transition temperature of Sm 1−x Tb x FeO 3 single crystals is lowered with the contents of Tb contents rising based on this work and our previous works, thus the spin reorientation transition temperature can be adjusted through changing the compound in orthoferrites materials, which means that we can get orthoferrites single crystals with high magnetism property in various temperature through material design. - Highlights: • Sm 0.3 Tb 0.7 FeO 3 single crystals with various compounds were successfully grown by optical floating zone method. • The relation between SRT temperature and composition in Sm 1−x Tb x FeO 3 orthoferrite was indicated. • The spin reorientation transition temperature of Sm 1−x Tb x FeO 3 single crystals can be adjusted through changing the compound in orthoferrites materials.
MIL-100-Fe derived N-doped Fe/Fe3C@C electrocatalysts for efficient oxygen reduction reaction
Guo, Dakai; Han, Sancan; Wang, Jiacheng; Zhu, Yufang
2018-03-01
N-doped porous Fe/Fe3C@C electrocatalysts were prepared by the pyrolysis of the hexamethylenetetramine (HMT)-incorporated MIL-100-Fe at different temperatures (700-1000 °C) under N2 atmosphere. Rotary evaporation of MIL-100-Fe and HMT solution could make more N-enriched HMT molecules enter into the pores of MIL-100-Fe, thus improving nitrogen contents of the final pyrolyzed samples. All pyrolyzed samples show porous textures with middle specific surface areas. The X-ray photoelectron spectroscopy (XPS) results demonstrate the successful introduction of N atoms into carbon framework. Sample Fe-N2-800 prepared by annealing the precursors with the HMT/MIL-100-Fe weight ratio of 2 at 800 °C exhibits the best electrocatalytic activity towards the oxygen reduction reaction (ORR) in terms of onset potential and current density because of high graphitic N and pyridinic N content. The enwrapped Fe/Fe3C nanoparticles and Fe-Nx active sites in these samples could also boost the ORR activity synergistically. Moreover, sample Fe-N2-800 demonstrates a dominant four electron reduction process, as well as excellent long-term operation stability and methanol crossover resistance. Thus, the N-doped Fe/Fe3C@C composites derived from the HMT-incorporated MIL-100-Fe are promising electrocatalysts to replace Pt/C for ORR in practical applications.
Magnetoresistance Versus Oxygen Deficiency in Epi-stabilized SrRu1 - x Fe x O3 - δ Thin Films
Dash, Umasankar; Acharya, Susant Kumar; Lee, Bo Wha; Jung, Chang Uk
2017-03-01
Oxygen vacancies have a profound effect on the magnetic, electronic, and transport properties of transition metal oxide materials. Here, we studied the influence of oxygen vacancies on the magnetoresistance (MR) properties of SrRu1 - x Fe x O3 - δ epitaxial thin films ( x = 0.10, 0.20, and 0.30). For this purpose, we synthesized highly strained epitaxial SrRu1 - x Fe x O3 - δ thin films with atomically flat surfaces containing different amounts of oxygen vacancies using pulsed laser deposition. Without an applied magnetic field, the films with x = 0.10 and 0.20 showed a metal-insulator transition, while the x = 0.30 thin film showed insulating behavior over the entire temperature range of 2-300 K. Both Fe doping and the concentration of oxygen vacancies had large effects on the negative MR contributions. For the low Fe doping case of x = 0.10, in which both films exhibited metallic behavior, MR was more prominent in the film with fewer oxygen vacancies or equivalently a more metallic film. For semiconducting films, higher MR was observed for more semiconducting films having more oxygen vacancies. A relatively large negative MR ( 36.4%) was observed for the x = 0.30 thin film with a high concentration of oxygen vacancies ( δ = 0.12). The obtained results were compared with MR studies for a polycrystal of (Sr1 - x La x )(Ru1 - x Fe x )O3. These results highlight the crucial role of oxygen stoichiometry in determining the magneto-transport properties in SrRu1 - x Fe x O3 - δ thin films.
Energy Technology Data Exchange (ETDEWEB)
Steyaert, S.; Breton, J.-M. le; Teillet, J. [Rouen Univ. (France). Groupe de Metall. Phys.; Kubis, M.; Handstein, A.; Mueller, K.H. [Rouen Univ. (France). Groupe de Metall. Phys.]|[Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany). Inst. fuer Metallische Werkstoffe
1998-07-01
Sm{sub 2}Fe{sub 17-x}Ga{sub x} powders (x=0,0.5,1,2) obtained at different steps of the HDDR process were analysed by Moessbauer spectrometry. For the homogenised powders, the mean hyperfine field of the Sm{sub 2}Fe{sub 17-x}Ga{sub x} contribution increases with Ga content in agreement with a lattice expansion. The anisotropy change from planar to uniaxial is confirmed in samples with x = 2. In the hydrogenated powders, the value of the mean hyperfine field of Sm{sub 2}Fe{sub 17-x}Ga{sub x}H{sub y} is greater than that of Sm{sub 2}Fe{sub 17-x}Ga{sub x} in the corresponding homogenised powders, in agreement with the presence of hydrogen in the 2:17 structure. It decreases with increasing Ga amount, suggesting that the H content in the Sm{sub 2}Fe{sub 17-x}Ga{sub x}H{sub y} phase decreases with increasing Ga content. In the disproportionated powders, the disproportionation reaction is incomplete for x {>=} 1 as the contributions of both the Sm{sub 2}Fe{sub 17-x}Ga{sub x}H{sub y} and {alpha}-Fe(Ga) phases are observed in the corresponding Moessbauer spectra. This indicates that for x {>=} 1 the hydrogen diffusion is inhibited during hydrogenation. (orig.)
Magnetic vacancies; simulations and TDPAD experiments with 19 F in Al(x) Fe(1-x)
International Nuclear Information System (INIS)
Ekwall, B.; Johansson, K.; Lidbjoerk, P.; Lindgren, B.; Norlin, L.O.
1984-04-01
Al(x) Fe(1-x) alloys with less or equal 4.2 at percent have been studied by the TDPAD method utilising 19 F as probe. The hyperfine field was found to increase with 0.39(6) percent per at percent Al. A Monte Carlo simulation of the dipolar distribution, due to the missing Fe moments, agrees well with the experimental results.(author)
Energy Technology Data Exchange (ETDEWEB)
Eastwood, D.S. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Ali, M.; Hickey, B.J. [Department of Physics and Astronomy, University of Leeds, Leeds LS2 1JT (United Kingdom); Tanner, B.K., E-mail: b.k.tanner@dur.ac.uk [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom)
2013-12-15
The relaxation of Fe/MgO/Fe tunnel junctions grown epitaxially on (001) MgO substrates has been measured by in-situ grazing incidence in-plane X-ray diffraction during the thermal annealing cycle. We find that the Fe layers are fully relaxed and that there are no irreversible changes during annealing. The MgO tunnel barrier is initially strained towards the Fe but on annealing, relaxes and expands towards the bulk MgO value. The strain dispersion is reduced in the MgO by about 40% above 480 K post-annealing. There is no significant change in the “twist” mosaic. Our results indicate that the final annealing stage of device fabrication, crucial to attainment of high TMR, induces substantial strain relaxation at the MgO barrier/lower Fe electrode interface. - Highlights: • Lattice relaxation of Fe/MgO/Fe epitaxial magnetic tunnel junctions measured. • In-plane lattice parameter of Fe equal to bulk value; totally relaxed. • MgO barrier initially strained towards the Fe but relaxes on annealing. • Reduction in strain dispersion in the MgO barrier by 40% above about 470 K. • No change in the in-plane “twist” mosaic throughout the annealing cycle.
Synthesis and characterization of perovskites type La(Fe_xV_1_-_x)O_3
International Nuclear Information System (INIS)
Tupan, Lilian Felipe da Silva
2014-01-01
Perovskites of the La(Fe_xV_1_-_x)O_3 type were synthesized by solid state reaction and by arc-melting. The samples prepared were structurally characterized by X-ray diffraction and regarding the magnetic and hyperfine properties by "5"7Fe Mössbauer spectroscopy. The results revealed that the samples crystallized mostly with orthorhombic structure, in the Pbnm space group. The lattice parameters of the pseudo-ternary compounds decreased linearly with the progressive substitution of iron by vanadium, in agreement with the Vegard's law. It was also observed the reduction of the hyperfine magnetic field which changes from a well defined sextet of 51,8 T, obtained for LaFeO_3, to a magnetic field distribution and, further, to a paramagnetic component for the richest vanadium samples. Low temperature Mössbauer spectroscopy measurements were additionally performed for the La(Fe_0_,_2V_0_,_8)O_3 sample. It was shown that the sample recovers the magnetic order with decreasing temperature. These results reveal that the coexistence of iron-vanadium results in an even more complicated magnetic behavior, decreasing the magnetic transition temperature, as replacement of iron by vanadium in orthoferrite increases. (author)
Singh, Neera; Parkash, Om; Kumar, Devendra
2018-03-01
In the present investigation, Fe(100-x) Ni(x) alloys (x = 10, 20, 30, 40 and 50 wt%) were synthesized through the evolution of γ-taenite and α-kamacite phases by powder metallurgy route using commercially available Fe and Ni powders. Mechanically mixed powders of Fe and Ni were compacted at room temperature and sintered at three different temperatures 1000, 1200 and 1250 °C for 1 h. Both Ni concentration and sintering temperature have shown a strong impact on the phase formation, tribological and electrochemical behavior. Micro structural study has shown the formation of taenite (γ-Fe,Ni) and kamacite (α-Fe,Ni) phases in the sintered specimens. An increase in Ni fraction resulted in formation of more taenite which reduces hardness and wear resistance of specimens. Increasing the sintering temperature decreased the defect concentration with enhanced taenite formation, aiding to higher densification. Taenite formed completely in Fe50Ni50 after sintering at 1250 °C. Tribological test revealed the maximum wear resistance for Fe70Ni30 specimen due to the presence of both kamacite and taenite in significant proportions. The formation of taenite as well as the decrease in defect concentration improves the corrosion resistance of the specimens significantly in 1M HCl solution. A maximum corrosion protection efficiency of around ∼87% was achieved in acidic medium for Fe50Ni50, sintered at 1250 °C.
Co{sub 100−x}Fe{sub x} magnetic thick films prepared by electrodeposition
Energy Technology Data Exchange (ETDEWEB)
Aguirre, M. del C., E-mail: carmenaguirre@famaf.unc.edu.ar [Instituto de Física Enrique Gaviola-Conicet-Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina); Farías, E. [Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina); Abraham, J.; Urreta, S.E. [Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba (Argentina)
2015-04-05
Highlights: • Low iron containing films are compact, with rounded, relatively uniform surfaces. • Larger Fe contents exhibit nanowall networks covering the surface. • Coercivity in the out of plane configuration is larger than in the easy axis direction. • Co-rich films nucleate and grow by a 3DP diffusion controlled mechanism. • For equiatomic Fe{sub 50}Co{sub 50} films, nucleation tends to become instantaneous. - Abstract: Co–Fe films are grown onto plane pre-treated Cu foils; the effects of the alloy composition on the morphology and the crystal texture of the electrodeposited films and their anisotropic magnetic hysteresis properties are explored. Nucleation and crystallization mechanisms in these Co-rich layers are also investigated with pulse-reverse plating techniques, using the first cathodic pulse current–time transients. In the diffusion controlled regime the deposition mechanism is found to involve progressive nucleation with three-dimensional (3D) growth, except for the equiatomic Fe{sub 50}Co{sub 50} solution where nucleation tends to become instantaneous. The different morphologies and size scales observed are described and correlated with coercivity. The films are electrodeposited onto electrochemically pre-treated Cu substrates from feeds of nominal Fe/Co mol ratios between 0/100 and 50/50. The composition of the deposited layers, as determined by energy dispersive X-ray spectroscopy, are quite close to the nominal values. Cyclic voltammetry determinations exhibit only a single reduction process on the cathode, indicating that a unique (Co{sub 100−x}Fe{sub x}) phase grows. Depending on composition and on the substrate pre-treatment, these layers exhibit textures with features of different sizes. X ray diffraction patterns indicate that the nanostructures with Fe contents above 20 at.% crystallize in a body-centered cubic cell, while samples with Fe contents below this value are fcc. Regarding the effect of composition on the
Photoelectron spectroscopy study of Fe-diluted Au-Fe alloys
Nahm, T U; Choi, B; Park, J S; Oh, S J; Cho, E J
2003-01-01
The electronic structure of Fe-diluted Au-Fe alloys has been studied by taking core-level and valence-band spectra using x-ray photoemission spectroscopy and synchrotron radiation. From the core-level spectroscopy, we found that the Fe 2p spectrum is composed of d sup 6 and d sup 7 multiplets from Fe impurity atoms. This behaviour is qualitatively discussed within the context of electron-electron interaction. In order to explore the electron-correlation effects in the valence band, we obtained Fe 3d partial spectral weights by taking advantage of the Cooper-minimum phenomenon of an Au 5d photoionization cross section. It was found that the spin-down states have an appreciable amount of spectral weights throughout the host Au 5d band, contrary to previous one-electron calculations predicting two-peak structure of the Fe 3d states. We suggest that this discrepancy results from the correlation effect of the Fe 3d electrons.
Accurate solid solution range of BiMnxFe3-xO6 and low temperature magnetism
Jiang, Pengfei; Yue, Mufei; Cong, Rihong; Gao, Wenliang; Yang, Tao
2017-11-01
BiMnxFe3-xO6 (x = 1) represents a new type of oxide structure containing Bi3+ and competing magnetic super-exchanges. In literature, multiple magnetic states were realized at low temperatures in BiMnFe2O6, and the hypothetical parent compounds (BiMn3O6, BiFe3O6) were predicted to be different in magnetism. Herein, we performed a careful study on the syntheses of BiMnxFe3-xO6 at ambient pressure, and the solid solution range was determined to be 0.9 ≤ x ≤ 1.3 by Rietveld refinements on high-quality powder X-ray diffraction data. Due to the very similar cationic size of Mn3+ and Fe3+, and possibly the structural rigidity, there was no significant structure change in the whole range of solid solution. The magnetic behavior of BiMnxFe3-xO6 (x = 1.2, 1.22, 1.26, 1.28 and 1.3) was generally similar to BiMnFe2O6, while the relative higher concentration of Mn3+ led to the decreasing of the antiferromagnetic ordering temperature.
Energy Technology Data Exchange (ETDEWEB)
Oyola Lozano, D., E-mail: doyola@ut.edu.co [University of Tolima, Department of Physics (Colombia); Zamora, L. E.; Perez Alcazar, G. A. [University of Valle, Department of Physics (Colombia); Rojas, Y. A.; Bustos, H. [University of Tolima, Department of Physics (Colombia); Greneche, J. M. [Universite du Maine, Laboratoire de Physique de l' Etat Condense, UMR CNRS 6087 (France)
2006-04-15
In this work the magnetic and structural properties are investigated by Moessbauer spectrometry, Vibrating Sample Magnetometry and X-ray diffraction of Nd{sub 2}(Fe{sub 100-x}Nb{sub x}){sub 14}B powdered alloys with x = 0, 2 and 4 prepared by arc melting. The Moessbauer spectra of the samples were fitted with several contributions from: Nd{sub 2}Fe{sub 14}B, {alpha}-Fe and a paramagnetic phase associated with Nd{sub 1.1}Fe{sub 4}B{sub 4} for x = 0 and additionally from NbFeB and Nd{sub 2}Fe{sub 17} for x = 2 and x = 4. The relative fractions of {alpha}-Fe and Nd{sub 2}Fe{sub 14}B are smaller for x = 4 than for x = 0, indicating that the amount of these two phases is reduced with increasing Nb content, while the relative fraction of Nd{sub 2}Fe{sub 17} increases. The {alpha}-Fe grain size slightly decreases while that of the Nd{sub 2}Fe{sub 14}B phase is increasing, when the Nb content increases. The hysteresis loops indicate that these samples behave as hard ferromagnets, with a coercive field which decreases when the Nb content increases, but with rather low remanent magnetization.
Magnetic and structural properties of the Nd2(Fe100-xNbx)14B system prepared by arc melting
International Nuclear Information System (INIS)
Oyola Lozano, D.; Zamora, L. E.; Perez Alcazar, G. A.; Rojas, Y. A.; Bustos, H.; Greneche, J. M.
2006-01-01
In this work the magnetic and structural properties are investigated by Moessbauer spectrometry, Vibrating Sample Magnetometry and X-ray diffraction of Nd 2 (Fe 100-x Nb x ) 14 B powdered alloys with x = 0, 2 and 4 prepared by arc melting. The Moessbauer spectra of the samples were fitted with several contributions from: Nd 2 Fe 14 B, α-Fe and a paramagnetic phase associated with Nd 1.1 Fe 4 B 4 for x = 0 and additionally from NbFeB and Nd 2 Fe 17 for x = 2 and x = 4. The relative fractions of α-Fe and Nd 2 Fe 14 B are smaller for x = 4 than for x = 0, indicating that the amount of these two phases is reduced with increasing Nb content, while the relative fraction of Nd 2 Fe 17 increases. The α-Fe grain size slightly decreases while that of the Nd 2 Fe 14 B phase is increasing, when the Nb content increases. The hysteresis loops indicate that these samples behave as hard ferromagnets, with a coercive field which decreases when the Nb content increases, but with rather low remanent magnetization.
Mn doping effect on structure and magnetism of epitaxial (FePt)1-xMnx films
International Nuclear Information System (INIS)
Huang, J.C.A.; Chang, Y.C.; Yu, C.C.; Yao, Y.D.; Hu, Y.M.; Fu, C.M.
2003-01-01
We study the structure and perpendicular magnetism of molecular beam epitaxy grown (FePt) 1-x Mn x films with doping concentration x=0, 1%, 2%, 3%, 4%, and 5%. The (FePt) 1-x Mn x films were made by multilayers growth of [Fe/Pt/Mn]xN at 100 deg. C and annealed at 600 deg. C. X-ray diffraction scans indicate that relatively better L1 0 ordered structure for low Mn doping (x 3%. The perpendicular magnetic anisotropy effect of the (FePt) 1-x Mn x films tends to decrease with the increase of Mn doping for x>1%. However, the x=1% doped films possess slightly better perpendicular magnetic anisotropy effect than the zero doped film. The perpendicular magnetic anisotropy constant are of about 1.3x10 7 and 1.6x10 7 erg/cm 3 for x=0% and x=1%, respectively
Forming a structure of the CoNiFe alloys by X-ray irradiation
Valko, Natalia; Kasperovich, Andrey; Koltunowicz, Tomasz N.
The experimental data of electrodeposition kinetics researches and structure formation of ternary CoNiFe alloys deposited onto low-carbon steel 08kp in the presence of X-rays are presented. Relations of deposit rate, current efficiencies, element and phase compositions of CoNiFe coatings formed from sulfate baths with respect to cathode current densities (0.5-3A/dm2), electrolyte composition and irradiation were obtained. It is shown that, the CoNiFe coatings deposited by the electrochemical method involving exposure of the X-rays are characterized by more perfect morphology surfaces with less developed surface geometry than reference coatings. The effect of the X-ray irradiation on the electrodeposition of CoNiFe coatings promotes formatting of alloys with increased electropositive component and modified phase composition.
Preparation and properties of Fe{sub 80−x}Ni{sub x}P{sub 14}B{sub 6} bulk metallic glasses
Energy Technology Data Exchange (ETDEWEB)
Zhang, Ling; Ma, XiuHua [School of Physics Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046 (China); Li, Qiang, E-mail: qli@xju.edu.cn [School of Physics Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046 (China); Zhang, Jijun [School of Physics Science and Technology, Xinjiang University, Urumqi, Xinjiang 830046 (China); Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Dong, Yaqiang; Chang, Chuntao [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China)
2014-09-01
Highlights: • Fe{sub 80−x}Ni{sub x}P{sub 14}B{sub 6} (x = 20–50 at.%) BMGs were prepared by fluxing and J-quenching techniques. • The highest GFA is reached at x = 40 and the corresponding critical diameter is up to 2.5 mm. • The present FeNi-based BMGs exhibit very large ε{sub p} and the ε{sub p} of Fe{sub 30}Ni{sub 50}P{sub 14}B{sub 6} BMG is 11.7%. • The present FeNi-based BMGs have much higher corrosion resistance than stainless steel. - Abstract: Bulk Fe{sub 80−x}Ni{sub x}P{sub 14}B{sub 6} (x = 20, 30, 40, 50 at.%) glassy alloy rods with the diameters of 1.0–2.5 mm were synthesized by combining fluxing technique and J-quenching technique. The glassy alloy rods were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). It is found that the range of supercooled liquid region (ΔT{sub x}) is 27–32 K. The saturation magnetization of Fe{sub 80−x}Ni{sub x}P{sub 14}B{sub 6} (x = 20, 30, 40, 50 at.%) bulk glassy alloys gradually decreases from 1.13 T to 0.58 T with increasing Ni content from x = 20 to x = 50. More importantly, the present quaternary FeNiPB bulk metallic glasses (BMGs) shows a significant plastic strain, in particular, the plastic strain of Fe{sub 30}Ni{sub 50}P{sub 14}B{sub 6} BMG reaches as high as 11.7%. The corrosion resistance of the present FeNiPB BMGs was studied by weight-loss method, potentiodynamic polarization curves and scanning electron microscopy (SEM). It is shown that the corrosion resistance of the present FeNiPB BMGs in 0.5 M NaCl and 1 M HCl solution increases with Ni content, and further the present FeNiPB BMGs exhibit larger E{sub corr} values and lower I{sub corr} values, i.e. higher corrosion resistances, than that of stainless steel.
Moessbauer Investigation of Spin Arrangements in Er2-xCexFe14B
International Nuclear Information System (INIS)
Bogacz, B.F.; Pedziwiatr, A.T.
2008-01-01
It was theoretically postulated earlier that in compounds Er 2-x Ce x Fe 14 B it may be possible to observe not only axial and planar spin arrangements but also a conical one. In order to experimentally verify this hypothesis, 57 Fe Moessbauer spectroscopy analysis was used to study the polycrystalline compounds Er 2-x Ce x Fe 14 B in the postulated composition region (x = 1.0, 1.1, 1.2, 1.3) in the wide range of temperatures. The obtained experimental data do not clearly support the suggestion of conical arrangement occurrence in the postulated compositions. They indicate that such phenomenon may be shifted towards higher Ce content. (authors)
Zhang, Yuanlei; Li, Zhe; He, Xijia; Huang, Yinsheng; Xu, Kun; Jing, Chao
2018-02-01
A series of Ni55-x Fe x Mn20Ga25 (0 ⩽ x ⩽ 5) Heusler alloys was prepared to investigate their phase transitions and magnetic properties. At room temperature, these alloys present various crystal structures, and the unit cell volume enlarges with increase of Fe content in both austenite and martensite. Multiple magneto-structural transformations were observed in the parent alloy (x = 0). In the process of cooling, it undergoes martensitic transformation (MT) from L21-type paramagnetic austenite to L10-type ferromagnetic martensite, accompanying an intermartensitic transformation (IMT, 7M → L10). By establishing a detailed phase diagram, we found that both MT and IMT shift to lower temperature simultaneously, while the ferromagnetic (FM) transition of austenite moves to higher temperature as Fe increases. With the further increase of Fe content beyond a critical value, both the IMT and the FM transitions split off from MT, and the former follows with the transforming sequence of 7M → 5M. Based on the experimental data, some key magnetic parameters have been obtained in this system. The calculated magnetocrystalline anisotropy constant ({{K}1} ) of martensite quickly increases as Fe increases, and then it almost reaches a saturated value (~5.5 × 105 J m-3) for the alloys with x > 3. However, the spontaneous magnetic moment ({μs} ) attains a peak value of about 4.2 μ B/f.u. in the alloy with x = 4, which is not consistent with the linear increasing of effective magnetic moment ({μef f} ). Further magnetic measurements with hydrostatic pressure indicate that such a discrepancy could be ascribed to the competition between the magnetic exchange interaction and the volume change of unit cell governed by the dopant Fe content.
How oxygen attacks [FeFe] hydrogenases from photosynthetic organisms
Stripp, Sven T.; Goldet, Gabrielle; Brandmayr, Caterina; Sanganas, Oliver; Vincent, Kylie A.; Haumann, Michael; Armstrong, Fraser A.; Happe, Thomas
2009-01-01
Green algae such as Chlamydomonas reinhardtii synthesize an [FeFe] hydrogenase that is highly active in hydrogen evolution. However, the extreme sensitivity of [FeFe] hydrogenases to oxygen presents a major challenge for exploiting these organisms to achieve sustainable photosynthetic hydrogen production. In this study, the mechanism of oxygen inactivation of the [FeFe] hydrogenase CrHydA1 from C. reinhardtii has been investigated. X-ray absorption spectroscopy shows that reaction with oxygen results in destruction of the [4Fe-4S] domain of the active site H-cluster while leaving the di-iron domain (2FeH) essentially intact. By protein film electrochemistry we were able to determine the order of events leading up to this destruction. Carbon monoxide, a competitive inhibitor of CrHydA1 which binds to an Fe atom of the 2FeH domain and is otherwise not known to attack FeS clusters in proteins, reacts nearly two orders of magnitude faster than oxygen and protects the enzyme against oxygen damage. These results therefore show that destruction of the [4Fe-4S] cluster is initiated by binding and reduction of oxygen at the di-iron domain—a key step that is blocked by carbon monoxide. The relatively slow attack by oxygen compared to carbon monoxide suggests that a very high level of discrimination can be achieved by subtle factors such as electronic effects (specific orbital overlap requirements) and steric constraints at the active site. PMID:19805068
Phase relationships of the system Fe-Ni-S and structure of the high-pressure phase of (Fe1-xNix)3S2
Urakawa, Satoru; Kamuro, Ryota; Suzuki, Akio; Kikegawa, Takumi
2018-04-01
The phase relationships of the Fe-Ni-S system at 15 GPa were studied by high pressure quench experiments. The stability fields of (Fe,Ni)3S and (Fe,Ni)3S2 and the melting relationships of the Fe-Ni-S system were determined as a function of Ni content. The (Fe,Ni)3S solid solution is stable in the composition of Ni/(Fe + Ni) > 0.7 and melts incongruently into an Fe-Ni alloy + liquid. The (Fe,Ni)3S2 makes a complete solid solution and melts incongruently into (Fe,Ni)S + liquid, whose structure was determined to show Cmcm-orthorhombic symmetry by in situ synchrotron X-ray diffraction experiments. The eutectic contains about 30 at.% of S, and its temperature decreases with increasing Ni content with a rate of ∼5 K/at.% from 1175 K. The density of the Fe-FeS eutectic composition (Fe70S30) liquid is evaluated to be 6.93 ± 0.08 g/cm3 at 15 GPa and 1200 K based on the Clausius-Clapeyron relations and densities of subsolidus phases. The Fe-Ni-S liquids are a primary sulfur-bearing phase in the deep mantle with a reducing condition (250-660 km depth), and they would play a significant role in the carbon cycle as a carbon host as well as in the generation of diamond.
Energy Technology Data Exchange (ETDEWEB)
Li, Jianan; Jing, Panpan; Zhang, Xinlei; Cao, Derang; Wei, Jinwu; Pan, Lining [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Liu, Zhenlin [Analysis and researching center of Gansu province, Lanzhou 730000 (China); Wang, Jianbo [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Key Laboratory for Special Function Materials and Structural Design of the Ministry of the Education, Lanzhou University, Lanzhou 730000 (China); Liu, Qingfang, E-mail: liuqf@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000 (China)
2017-03-01
NiFe{sub 2−x}Ce{sub x}O{sub 4} (x = 0–0.03) nanoribbons have been successfully fabricated using electrospinning technique and followed by calcining in air at 500 °C. The crystalline, morphologies and compositions of NiFe{sub 2−x}Ce{sub x}O{sub 4} nanoribbons are characterized by X-ray diffraction, selected area electron diffraction, transmission electron microscope, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy (EDX). The results show that the components, mean crystallite sizes and morphologies change along with the content of Ce{sup 3+}. A formation mechanism of NiFe{sub 2-x}Ce{sub x}O{sub 4} nanoribbons is proposed. The magnetic hysteresis loops of NiFe{sub 2−x}Ce{sub x}O{sub 4} nanoribbons reveals that the coercivity changes from 165 Oe to 64 Oe and saturation magnetizations change from 40.97 emu/g to 25.05 emu/g at room temperature. Morevover, the Mössbauer spectra of {sup 57}Fe in NiFe{sub 2−x}Ce{sub x}O{sub 4} nanoribbons is discussed in detail. It is believed that this work will play important role in magnetic application with the advantage of excellent magnetic properties, efficient functionalization and relatively low cost. - Highlights: • The NiFe{sub 2−x}Ce{sub x}O{sub 4} nanoribbons have been fabricated using electrospinning technique. • Ce{sup 3+} ions occupy B sites by replacing Fe{sup 3+} ions. • The coercivity changes from 165 Oe to 64 Oe. • The saturation magnetizations change from 40.97 emu/g to 25.05 emu/g.
Enhancement of plasticity of Fe-based bulk metallic glass by Ni substitution for Fe
Energy Technology Data Exchange (ETDEWEB)
Guo, S.F. [State Key Laboratory of Material Processing and Die and Mould Technology, Huazhong University of Science and Technology, 430074 Wuhan (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Li, N.; Zhang, C. [State Key Laboratory of Material Processing and Die and Mould Technology, Huazhong University of Science and Technology, 430074 Wuhan (China); Liu, L., E-mail: sfguo2005@163.co [State Key Laboratory of Material Processing and Die and Mould Technology, Huazhong University of Science and Technology, 430074 Wuhan (China)
2010-08-15
Bulk metallic glasses (BMGs) (Fe{sub 1-x}Ni{sub x}){sub 71}Mo{sub 5}P{sub 12}C{sub 10}B{sub 2} (x = 0, 0.1 and 0.2) with a diameter of 3 mm were synthesized by copper mold casting. The effect of Ni substitution for Fe on the structure, thermal and mechanical properties has been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and compressive testing. It was found that the substitution of Ni for Fe enhances the glass forming ability, and improves the plasticity of Fe{sub 71}Mo{sub 5}P{sub 12}C{sub 10}B{sub 2} BMG as indicated by the increase in the plastic strain from 3.1% (x = 0) to 5.2% (x = 0.2). The improvement of the plasticity is discussed in term of the reduction of glass transition temperature and the supercooled liquid region due to the substitution of Ni for Fe.
Magnetic properties and configuration of Fe{sub 50}Pt{sub 50*x}Rh{sub x} films
Energy Technology Data Exchange (ETDEWEB)
Fenske, Jochen; Lott, Dieter; Schreyer, Andreas [Helmholt-Zentrum, Geesthacht (Germany); Schmidt, Wolfgang; Schmalzl, Karin [IFF Forschungszentrum, Juelich (Germany); JCNS at ILL (France); Mankey, Gary J. [MINT Center, University of Alabama (United States); Klose, Frank [Ansto, Bragg Institute (Australia); Tartakowskaya, Helena [Institute for Magnetism, National Accademy of Scinece (Ukraine)
2011-07-01
Ordered FePt alloys with L1{sub 0} structure are known as materials with FM order and a high magnetic moment of Fe providing a large magnetization. The large atomic number of Pt on the other hand results in a high magnetic anisotropy. If grown in thin films, the high anisotropy often results in perpendicular magnetization which is the preferred orientation for current magnetic recording media. One way to control the magnetic properties in these materials is through the introduction of a third element into the crystal matrix e.g. Rh. When Rh is added to replace Pt in the equiatomic alloy, new magnetic phases emerge. Here we present neutron diffraction studies on the magnetic properties of different 200nm thick Fe{sub 50}Pt{sub 50*x}Rh{sub x} films in dependence of the temperature and external magnetic fields. Additional resonant x-ray measurements on the Fe and Pt absorption edges provide additional information about the magnetic moments on these sites.
Energy Technology Data Exchange (ETDEWEB)
Alcover, Ignacio Blazquez; David, Rénald; Daviero-Minaud, Sylvie; Filimonov, Dmitry; Huvé, Marielle; Roussel, Pascal; Kabbour, Houria; Mentré, Olivier [CNRS-UMR
2015-08-12
We show here that the exsolution of Fe2+ ions out of two-dimensional (2D) honeycomb layers of BaFe2(PO4)2 into iron-deficient BaFe2–x(PO4)2 phases and nanometric α-Fe2O3 (typically 50 nm diameter at the grain surface) is efficient and reversible until x = 2/3 in mild oxidizing/reducing conditions. It corresponds to the renewable conversion of 12 wt % of the initial mass into iron oxide. After analyzing single crystal X-ray diffraction data of intermediate members x = 2/7, x = 1/3, x = 1/2 and the ultimate Fe-depleted x = 2/3 term, we then observed a systematic full ordering between Fe ions and vacancies (VFe) that denote unprecedented easy in-plane metal diffusion driven by the Fe2+/Fe3+ redox. Besides the discovery of a diversity of original depleted triangular ∞{Fe2/3+2–xO6} topologies, we propose a unified model correlating the x Fe-removal and the experimental Fe/VFe ordering into periodic one-dimensional motifs paving the layers, gaining insights into predictive crystahemistry of complex low dimensional oxides. When we increased the x values it led to a progressive change of the materials from 2D ferromagnets (Fe2+) to 2D ferrimagnets (Fe2/3+) to antiferromagnets for x = 2/3 (Fe3+).
Energy Technology Data Exchange (ETDEWEB)
Wuest, H., E-mail: holger.wuest@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Bommer, L., E-mail: lars.bommer@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Huber, A.M., E-mail: arne.huber@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Goll, D., E-mail: dagmar.goll@htw-aalen.de [Aalen University, Materials Research Institute, Beethovenstr. 1, 73430 Aalen (Germany); Weissgaerber, T., E-mail: thomas.weissgaerber@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Kieback, B., E-mail: bernd.kieback@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Technische Universität Dresden, Institute for Materials Science, Helmholtzstraße 7, 01069 Dresden (Germany)
2017-04-15
Permanent magnetic materials based on Ce(Fe, Co){sub 12−x}Ti{sub x} with the ThMn{sub 12} structure are promising candidates for replacing NdFeB magnets. Its intrinsic magnetic properties are not far below the values of Nd{sub 2}Fe{sub 14}B, and the high amount of Fe and the fact that Ce is much more abundant and less expensive than Nd encourages the reasonable interest in these compounds. Nanocrystalline magnetic material of the composition Ce{sub 1−x}Sm{sub x}Fe{sub 11−y}Co{sub y}Ti (x=0−1 and y=0; 1.95) has been produced by both melt spinning and mechanical alloying. Alloys containing only Ce as rare earth element (x=0) show coercivities below 77 kA/m, while for x=1 H{sub c,J} values up to 392 kA/m are reached. Coercivity shows rather an exponential than a linear dependence on the gradual substitution of Ce by Sm. - Highlights: • CeFe{sub 11}Ti nanocrystalline samples demonstrate values of H{sub c,J} up to 77 kA/m. • SmFe{sub 11}Ti nanocrystalline samples demonstrate values of H{sub c,J} up to 392 kA/m. • Dependence of H{sub c,J} on x in Ce{sub 1−x}Sm{sub x(}Fe, Co){sub 11}Ti obeys non-linear dependence. • Optimum annealing shifts to from 800 °C for CeFe{sub 11}Ti to 900 °C for SmFe{sub 11}Ti.
The effect of magnetic ordering on the giant magnetoresistance of Cr-Fe-V and Cr-Fe-Mn
International Nuclear Information System (INIS)
Somsen, Ch.; Acet, M.; Nepecks, G.; Wassermann, E.F.
2000-01-01
Cr-rich Cr 1-x Fe x alloys with compositions in the vicinity of mixed ferromagnetic and antiferromagnetic exchange (x=0.18) exhibit giant magnetoresistance. In order to understand the influence of the antiferromagnetism of Cr on the giant magnetoresistance one can manipulate the antiferromagnetic exchange either by adding vanadium, which destroys the antiferromagnetism of Cr, or by adding manganese, which enhances it. Cr-Fe-V and Cr-Fe-Mn alloys also have Curie temperatures that lie between low temperatures and room temperature in the concentration region where giant magnetoresistance is observed. Therefore, they are also used as samples to study the magnetoresistance as a function of the strength of FM exchange. We discuss these points in the light of temperature and concentration-dependent magnetoresistance experiments on Cr 0.99-x Fe x V 0.01 , Cr 0.96-x Fe x V 0.04 , Cr 0.90-x Fe x Mn 0.10 and Cr 0.55 Fe x Mn 0.45-x alloys. Results indicate that the most favorable condition for a large magnetoresistance in these alloys occurs at temperatures near the Curie temperature
Structure and magnetic properties of Gd{sub x}Y{sub 1−x}FeO{sub 3} obtained by mechanosynthesis
Energy Technology Data Exchange (ETDEWEB)
Bolarín-Miró, A.M. [Área Académica de Ciencias de la Tierra y Materiales, Universidad Autónoma del Estado de Hidalgo Mineral de la Reforma, Hidalgo 42184 (Mexico); Sánchez-De Jesús, F., E-mail: fsanchez@uaeh.edu.mx [Área Académica de Ciencias de la Tierra y Materiales, Universidad Autónoma del Estado de Hidalgo Mineral de la Reforma, Hidalgo 42184 (Mexico); Cortés-Escobedo, C.A. [Centro de Investigación e Innovación Tecnológica del IPN, Distrito Federal 02250 (Mexico); Valenzuela, R. [Depto. de Materiales Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, México D.F. 04510 (Mexico); Ammar, S. [ITODYS, UMR 7086, Université de Paris-Diderot, 75250 Paris Cedex (France)
2014-02-15
Highlights: • Orthohombic GDxY1-xFeO3 was obtained by mechanosynthesis after 5 h of milling. • Mechanosynthesized GdxY1-xFeO3 show weak ferromagnetic behavior. • Mechanosynthesis promotes unexpected magnetic properties in GdxY1-xFeO3. • The maximum magnetization that was reached 7.7 emu/g for Gdo.75Y0.25FeO3. • For Gd0.5Y0.5FeO3, the magnetization decreases down to 2.1 emu/g. -- Abstract: Solid solutions of yttrium–gadolinium orthoferrites Gd{sub x}Y{sub 1−x}FeO{sub 3} (0 ⩽ x ⩽ 1) were prepared by high-energy ball milling. The aim of this work was to study the influence of the synthesis parameters on the crystal structure and the magnetic behavior of these solid solutions. The precursors, Fe{sub 2}O{sub 3}, Y{sub 2}O{sub 3} and Gd{sub 2}O{sub 3}, mixed in a stoichiometric ratio to obtain these orthoferrites, were milled for different times (up to 5 h). X-ray diffraction and Rietveld refinement were used to elucidate the phase transformation as a function of the milling time. Results showed the complete formation of orthoferrite with an orthorhombic structure (S.G. Pbnm) without any annealing after 5 h of milling for all of the compositions. The effect of the synthesis process and the x value on the crystal structure and the magnetic properties were also studied. All of the synthesized powders demonstrated weak ferromagnetic behavior. In particular, an increase in the maximum magnetization for all the compositions was found, with a maximum that reached 7.7 emu/g for Gd{sub 0.75}Y{sub 0.25}FeO{sub 3}. For Gd{sub 0.5}Y{sub 0.5}FeO{sub 3}, the magnetization decreases down to 2.1 emu/g. A small contamination of metallic Fe was confirmed through electron spin resonance experiments.
Lattice dynamics of Ru2FeX (X = Si, Ge) Full Heusler alloys
Rizwan, M.; Afaq, A.; Aneeza, A.
2018-05-01
In present work, the lattice dynamics of Ru2FeX (X = Si, Ge) full Heusler alloys are investigated using density functional theory (DFT) within generalized gradient approximation (GGA) in a plane wave basis, with norm-conserving pseudopotentials. Phonon dispersion curves and phonon density of states are obtained using first-principles linear response approach of density functional perturbation theory (DFPT) as implemented in Quantum ESPRESSO code. Phonon dispersion curves indicates for both Heusler alloys that there is no imaginary phonon in whole Brillouin zone, confirming dynamical stability of these alloys in L21 type structure. There is a considerable overlapping between acoustic and optical phonon modes predicting no phonon band gap exists in dispersion curves of alloys. The same result is shown by phonon density of states curves for both Heusler alloys. Reststrahlen band for Ru2FeSi is found smaller than Ru2FeGe.
Frustrated magnetization in PrxLa1-xBaCuO5Fe
International Nuclear Information System (INIS)
Ortiz, W.A.; Araujo-Moreira, F.M.; Prassides, K.
1999-01-01
The crystal structure of the system Pr x La 1-x BaCuO 5 Fe has been recently reviewed. The magnetic structure of samples with x = 0 and x = 1 is mainly due to effective local moments of iron and copper. In Pr-rich samples, Fe ions occupy two non-equivalent positions, making it substantially plausible that two or more magnetic subsets might coexist in the system. This contribution presents magnetization studies on five samples of the Pr x La 1-x BaCuO 5 Fe system (x = 0.0, 0.2, 0.5, 0.7 and 1.0). All samples exhibit a strong irreversible behavior between zero-field-cooled and field-cooled procedures below a certain irreversibility temperature T i . Above T i , both branches are coincident and well described by a Curie-Weiss fitting. Decreasing the temperature below T i , the zero-field-cooled response increases less than the field-cooled curve, indicating some degree of frustrated antiferromagnetic couplings. (orig.)
Magnetic properties of the HoMn6-xFe xSn6 compounds
International Nuclear Information System (INIS)
Cakir, O.; Dincer, I.; Duman, E.; Krenke, T.; Elmali, A.; Elerman, Y.
2007-01-01
Intermetallic compounds of HoMn 6-x Fe x Sn 6 (0 ≤ x ≤ 1.2) were studied by means of field-cooled (FC) and zero-field-cooled (ZFC) magnetization measurements in the temperature range 5 K ≤ T ≤ 600 K. The unit cell parameters decrease with the increasing of Fe content. The compounds with x = 0 and 0.3 behave ferrimagnetically in the whole temperature range and spin reorientation transition is observed at 200 and 185 K, respectively. The x = 0.5 and 0.6 compounds show ferrimagnetic-helimagnetic-ferrimagnetic phase transitions with decreasing temperature while the compounds with x = 0.9 and 1.2 only show helimagnetic-ferrimagnetic phase transitions. Additionally, for the x = 0.6 compound the metamagnetic phase transition from helimagnetism to ferrimagnetism is induced by an applied field 20 kOe
Feng, Nan; Mi, Wenbo; Cheng, Yingchun; Guo, Zaibing; Schwingenschlö gl, Udo; Bai, Haili
2014-01-01
Using first-principles calculations, we have investigated the electronic structure and magnetic properties of Fe-X 6 clusters (X = S, C, N, O, and F) incorporated in 4 4 monolayer MoS 2, where a Mo atom is substituted by Fe and its nearest S atoms are substituted by C, N, O, and F. Single Fe and Fe-F 6 substituions make the system display half-metallic properties, Fe-C 6 and Fe-N 6 substitutions lead to a spin gapless semiconducting behavior, and Fe-O 6 doped monolayer MoS 2 is semiconducting. Magnetic moments of 1.93, 1.45, 3.18, 2.08, and 2.21...? B are obtained for X = S, C, N, O, and F, respectively. The different electronic and magnetic characters originate from hybridization between the X and Fe/Mo atoms. Our results suggest that cluster doping can be an efficient strategy for exploring two-dimensional diluted magnetic semiconductors.
Feng, Nan
2014-02-05
Using first-principles calculations, we have investigated the electronic structure and magnetic properties of Fe-X 6 clusters (X = S, C, N, O, and F) incorporated in 4 4 monolayer MoS 2, where a Mo atom is substituted by Fe and its nearest S atoms are substituted by C, N, O, and F. Single Fe and Fe-F 6 substituions make the system display half-metallic properties, Fe-C 6 and Fe-N 6 substitutions lead to a spin gapless semiconducting behavior, and Fe-O 6 doped monolayer MoS 2 is semiconducting. Magnetic moments of 1.93, 1.45, 3.18, 2.08, and 2.21...? B are obtained for X = S, C, N, O, and F, respectively. The different electronic and magnetic characters originate from hybridization between the X and Fe/Mo atoms. Our results suggest that cluster doping can be an efficient strategy for exploring two-dimensional diluted magnetic semiconductors.
International Nuclear Information System (INIS)
Hearne, G.R.; Diguet, G.; Baudelet, F.; Itié, J.-P.; Manyala, N.
2015-01-01
Both Fe and Co K-edge x-ray magnetic circular dichroism (XMCD) have been employed as element-specific probes of the magnetic moments in the composition series of the disordered ferromagnet Fe 1−x Co x Si (for x=0.2, 0.3, 0.4, 0.5). A definitive single peaked XMCD profile occurs for all compositions at both Fe and Co K-edges. The Fe 4p orbital moment, deduced from the integral of the XMCD signal, has a steep dependence on x at low doping levels and evolves to a different (weaker) dependence at x≥0.3, similar to the behavior of the magnetization in the Co composition range studied here. It is systematically higher, by at least a factor of two, than the corresponding Co orbital moment for most of the composition series. Fine structure beyond the K-edge absorption (limited range EXAFS) suggests that the local order (atomic environment) is very similar across the series, from the perspective of both the Fe and Co absorbing atom. The variation in the XMCD integral across the Co composition range has two regimes, that which occurs below x=0.3 and then evolves to different behavior at higher doping levels. This is more conspicuously present in the Fe contribution. This is rationalized as the evolution from a half-metallic ferromagnet at low Co doping to that of a strong ferromagnet at x>0.3 and as such, spin polarization crossover occurs. The Fermi level is tuned from the majority spin band for x<0.3 where a strongly polarized majority spin electron gas prevails, to a regime where minority spin carriers dominate at higher doping. The evolution of the Fe-derived spin polarized (3d) bands, indirectly probed here via the 4p states, is the primary determinant of the doping dependence of the magnetism in this alloy series. - Highlights: • Element-specific probing of the electronic structure of the Fe 1−x Co x Si series. • XMCD at the level of 10 −4 at the K-edge in such low-moment systems. • Element-specific probing of magnetic contributions from both Fe and Co
1s2p resonant inelastic x-ray scattering in a-Fe2O3
Caliebe, W.A.; Kao, C.-C.; Hastings, J.B.; Taguchi, M.; Kotani, A.; Uozumi, T.; Groot, F.M.F. de
1998-01-01
We report experimental and theoretical results on the Fe K edge x-ray absorption spectrum and 1s2p resonant inelastic x-ray scattering (RIXS) spectra in a-Fe2O3 . The results are interpreted using an FeO6^9- cluster model with intra-atomic multiplet coupling and interatomic covalency
Ferromagnetic resonance on oxideless magnetic Fe and FeRh nanoparticles
International Nuclear Information System (INIS)
Trunova, Anastasia
2009-01-01
This work is dedicated to investigations of structural and magnetic properties of the colloidal Fe/Fe x O y nanocubes (13 nm) and the Fe x Rh 100-x core/shell nanoparticles (2 nm). As compared with other works, where the measurements on oxidized nanoparticles were carried out, we additionally performed investigations on nanoparticles in an oxide free state. In order to make the measurements on oxide free particles possible, oxygen- and hydrogenplasma was used to remove the ligands and reduce the oxide shell of the Fe nanocubes. The oxide free Fe nanocubes were covered with a Ag/Pt protective coating to prevent them from new oxidation. This method allowed carrying out the magnetic measurements on oxide free Fe nanocubes. Micromagnetic simulations as well as simulations of the high frequency susceptibility were used for the data analysing. It was found that both the g-factor g=2.09±0.01 and the anisotropy constant K 4 =(4.8±0.5).10 4 J/m 3 coincide with that of bulk iron. However, the saturation magnetization M S (5 K)=(1.2±0.12).10 6 A/m differs from the bulk value by 30%. The reduction by 30% compared to the bulk value in the case of nanoparticles may be caused by the following possible reasons: a) the presence of inner oxide layer (approx. 10 at.%) that cannot be reduced; b) the anti-parallel order between magnetic moments of iron core and magnetic moments of antiferomagnetic iron oxide; c) some structural changes of the surface after plasma treatment. The obtained damping parameter α=0.03±0.005 is ten times larger than that of the Fe layers as it is known for nanoparticles systems in general. The core/shell Fe x Rh 100-x nanoparticles (x=80,50) were produced under Ar-atmosphere and were sealed into a quartz tube to prevent oxidation. The analysis of g-factors shows that the value for the FePh nanoparticles with Fe-rich core is larger (g=2.08±0.01) than that for the nanoparticles with Rh-rich core and coincides within error bars with the g-factor of bulk
Magnetic and hyperfine interactions in HoFe{sub 1−x}Cr{sub x}O{sub 3} (0≤x≤1) compounds
Energy Technology Data Exchange (ETDEWEB)
Kotnana, Ganesh [Magnetic Materials and Device Physics Laboratory, Department of Physics, Indian Institute of Technology Hyderabad, Hyderabad 502285 (India); Reddy, V. Raghavendra [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001 (India); Jammalamadaka, S. Narayana, E-mail: surya@iith.ac.in [Magnetic Materials and Device Physics Laboratory, Department of Physics, Indian Institute of Technology Hyderabad, Hyderabad 502285 (India)
2017-05-01
We report on the magnetic and Mössbauer properties of polycrystalline HoFe{sub 1-x}Cr{sub x}O{sub 3} (0≤x≤1) compounds. Magnetization data reveals the continuous tailoring of magnetic transition due to weakening of Ho{sup 3+}-Fe{sup 3+} and Fe{sup 3+}-Fe{sup 3+} interactions in the entire temperature range by replacing the Fe{sup 3+} ions with Cr{sup 3+} ions. The observed decrease in Néel temperature (T{sub N}) and increase in spin re-orientation transition temperature (T{sub SR}) with the replacement of Fe{sup 3+} with Cr{sup 3+} is ascribed to the weakening of Fe(Cr)-O-Fe(Cr) antiferromagnetic exchange interaction. In addition, we also attribute such a change in T{sub N} to the enhancement of ferromagnetic interaction of adjacent Cr{sup 3+} moments through t-e hybridization as a result of the structural distortion. The decrease in isomer shift (IS) suggests enhancement of the interaction between nuclear charge with the 3s electrons as a result of decrease in radial part of 3d wave function with Cr addition. In this paper we also discuss about the variation of quadrupole splitting (QS) and hyperfine fields (H{sub hf}) with Cr addition in HoFe{sub 1-x}Cr{sub x}O{sub 3} (0≤x≤1) compounds. - Highlights: • Magnetic and Mössbauer properties of HoFe{sub 1-x}Cr{sub x}O{sub 3} (0≤x≤1) compounds. • T{sub N} changes due to weakening of Ho{sup 3+}-Fe{sup 3+} and Fe{sup 3+}-Fe{sup 3+} interactions with Cr. • The decrease in isomer shift (IS) is due to decrease in radial part of 3d wavefunction. • Octahedral distortion leads to increase in quadrupole splitting.
Asakura, Daisuke; Nanba, Yusuke; Makinose, Yuki; Matsuda, Hirofumi; Glans, Per-Anders; Guo, Jinghua; Hosono, Eiji
2018-04-17
We analyzed the Fe 3d electronic structure in LiFePO 4 /FePO 4 (LFP/FP) nanowire with a high cyclability by using soft X-ray emission spectroscopy (XES) combined with configuration-interaction full-multiplet (CIFM) calculation. The ex situ Fe L 2,3 -edge resonant XES (RXES) spectra for LFP and FP are ascribed to oxidation states of Fe 2+ and Fe 3+ , respectively. CIFM calculations for Fe 2+ and Fe 3+ states reproduced the Fe L 3 RXES spectra for LFP and FP, respectively. In the calculations for both states, the charge-transfer energy was considerably larger than those for typical iron oxides, indicating very little electron transfer from the O 2p to Fe 3d orbitals and a weak hybridization on the Fe-O bond during the charge-discharge reactions. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Magnetic exchange coupling in amorphous Fe80-xDy xB20 alloys
International Nuclear Information System (INIS)
Annouar, F.; Lassri, H.; Ayadi, M.; Omri, M.; Lassri, M.; Krishnan, R.
2005-01-01
Amorphous Fe 80-x Dy x B 20 alloys have been prepared by melt spinning and their magnetic properties have been studied. The mean field theory has been used to explain the temperature dependence of the magnetization. The exchange interactions between Co-Co and Dy-Co atom pairs have been evaluated. High-field magnetization studies on samples with stoichiometry close to that of a compensated ferrimagnet show a magnetic behavior that is characteristic of a non-collinear magnetic structure of the Dy and Fe sublattices. The region of the canted moments can be described by a phase diagram in the H-T plane
Synthesis and magnetic properties of PrFe11V1-xTix and their nitrides
International Nuclear Information System (INIS)
Tang, S.L.; Wang, B.W.; Zhang, C.; Jin, X.M.; Zhang, S.Y.; Du, Y.W.
1997-01-01
We have succeeded in synthesizing PrFe 11 V 1-x Ti x (x=0.2 1) compound and their nitrides with the ThMn 12 -type structure. The phase formation and magnetic properties have been investigated by x-ray diffraction, differential thermometric analysis, and magnetic measurement. The stable temperature range of the 1-12 phase for PrFe 11 V 1-x Ti x alloys has been determined as a function of Ti content. PrFe 11 V compounds with the ThMn 12 -type structure do not exist and PrFe 11 Ti compounds with the TnMn 12 -type structure are obtained by annealing in a narrow temperature range between 1303 and 1383 K. Furthermore, 1-12 phase with the ThMn 12 -type structure can be obtained at lower temperature and wider temperature range with decreasing Ti content x (0.2≤x≤1). PrFe 11 V 1-x Ti x N y with x=0.2 1 has a T c of about 730 785 K, B a larger than 8 T and M s in the range 144 148 emu/g. These intrinsic magnetic properties are highly favorable for permanent magnet applications. As a preliminary, an intrinsic coercivity of 5.4 kOe is obtained for PrFe 11 V 0.5 Ti 0.5 N y at room temperature by using mechanical alloying technique. copyright 1997 American Institute of Physics
Directory of Open Access Journals (Sweden)
Kosuke Takiguchi
2017-10-01
Full Text Available Group-IV-based ferromagnetic semiconductor Ge1−xFex (GeFe is one of the most promising materials for spin injection/detection in Si and Ge. In this paper, we demonstrate a systematic study of tunneling magnetoresistance (TMR in magnetic tunnel junctions (MTJs composed of Fe/MgO/Ge1−xFex with various Fe concentrations (x = 0.065, 0.105, 0.140, and 0.175. With increasing x, the TMR ratio increases up to 1.5% when x≤ 0.105, and it decreases when x> 0.105. This is the first observation of the TMR ratio over 1% in MTJs containing a group-IV ferromagnetic semiconductor. With increasing x, while the Curie temperature of GeFe increases, the MgO surface becomes rougher, which is thought to be the cause of the upper limit of the TMR ratio. The quality of the MgO layer on GeFe is an important factor for further improvement of TMR in Fe/MgO/GeFe MTJs.
Magnetic properties of PrMn2-xFexGe2-57Fe Moessbauer spectroscopy
International Nuclear Information System (INIS)
Wang, J L; Campbell, S J; Cadogan, J M; Tegus, O; Studer, A J; Hofmann, M
2006-01-01
We have investigated the magnetic behaviour of PrMn 2-x Fe x Ge 2 compounds with x = 0.4, 0.6 and 0.8 over the temperature range 4.2-350 K using ac magnetic susceptibility, dc magnetization and 57 Fe Moessbauer effect spectroscopy, as well as neutron diffraction for the PrMn 1.2 Fe 0.8 Ge 2 compound. Replacement of Mn with Fe leads to contraction of the unit cell and a shortening of the Mn-Mn spacing, resulting in modification of the magnetic structure. PrMn 1.6 Fe 0.4 Ge 2 is an intralayer antiferromagnet at room temperature and ferromagnetic below T C inter ∼230 K with additional ferromagnetic ordering of the Pr sublattice detected below T C Pr ∼30 K. Re-entrant ferromagnetism has been observed in PrMn 1.4 Fe 0.6 Ge 2 with four magnetic transitions (T N intra ∼333 K, T C inter ∼168 K, T N inter ∼152 K and T C Pr ∼40 K). Moreover, it was found that T C inter and T C Pr increase with applied field while T N inter decreases. PrMn 1.2 Fe 0.8 Ge 2 is antiferromagnetic with T N intra ∼242 K and T N inter ∼154 K. The magnetic transition temperatures for all compounds are also marked by changes in the 57 Fe magnetic hyperfine field and the electric quadrupole interaction parameters. The 57 Fe transferred hyperfine field at 4.5 K in PrMn 1.6 Fe 0.4 Ge 2 and PrMn 1.4 Fe 0.6 Ge 2 is reduced (below the ordering temperature of the Pr sublattice) compared with that at 80 K (above T C Pr ), indicating that the transferred hyperfine field from Pr acts in the opposite direction to that from the Mn atoms. The neutron data for PrMn 1.2 Fe 0.8 Ge 2 demonstrate that an anisotropic thermal expansion occurs within the interplanar antiferromagnetic range
A study on electrodeposited NixFe1−x alloy films
Indian Academy of Sciences (India)
Several techniques such as X-ray diffraction [9], VSM. [10], Mössbauer spectroscopy [11], four-point probe [12] etc. are used to investigate the crystallographic, magnetic and magnetotransport properties of NiFe systems. In this study our aim is to prepare NiFe alloy films relatively thicker (in µm scale) than those reported in ...
Fabry-Perot observations of [FeX] in the Cygnus Loop and IC443
International Nuclear Information System (INIS)
Ballet, J.; Rothenflug, R.; Soutoul, A.; Caplan, J.
1988-01-01
The authors present the first results of an observational program of SNRs in the coronal lines of [FeX] and [FeXIV] using Fabry--Perot spectrophotometer. These support previously published brightnesses
Structure and magnetic properties of GdxY1−xFeO3 obtained by mechanosynthesis
International Nuclear Information System (INIS)
Bolarín-Miró, A.M.; Sánchez-De Jesús, F.; Cortés-Escobedo, C.A.; Valenzuela, R.; Ammar, S.
2014-01-01
Highlights: • Orthohombic GDxY1-xFeO3 was obtained by mechanosynthesis after 5 h of milling. • Mechanosynthesized GdxY1-xFeO3 show weak ferromagnetic behavior. • Mechanosynthesis promotes unexpected magnetic properties in GdxY1-xFeO3. • The maximum magnetization that was reached 7.7 emu/g for Gdo.75Y0.25FeO3. • For Gd0.5Y0.5FeO3, the magnetization decreases down to 2.1 emu/g. -- Abstract: Solid solutions of yttrium–gadolinium orthoferrites Gd x Y 1−x FeO 3 (0 ⩽ x ⩽ 1) were prepared by high-energy ball milling. The aim of this work was to study the influence of the synthesis parameters on the crystal structure and the magnetic behavior of these solid solutions. The precursors, Fe 2 O 3 , Y 2 O 3 and Gd 2 O 3 , mixed in a stoichiometric ratio to obtain these orthoferrites, were milled for different times (up to 5 h). X-ray diffraction and Rietveld refinement were used to elucidate the phase transformation as a function of the milling time. Results showed the complete formation of orthoferrite with an orthorhombic structure (S.G. Pbnm) without any annealing after 5 h of milling for all of the compositions. The effect of the synthesis process and the x value on the crystal structure and the magnetic properties were also studied. All of the synthesized powders demonstrated weak ferromagnetic behavior. In particular, an increase in the maximum magnetization for all the compositions was found, with a maximum that reached 7.7 emu/g for Gd 0.75 Y 0.25 FeO 3 . For Gd 0.5 Y 0.5 FeO 3 , the magnetization decreases down to 2.1 emu/g. A small contamination of metallic Fe was confirmed through electron spin resonance experiments
Synthesis and magneto-structural study of CoxFe3-xO4 nanoparticles
International Nuclear Information System (INIS)
Betancourt-Galindo, R.; Ayala-Valenzuela, O.; Garcia-Cerda, L.A.; Rodriguez Fernandez, O.; Matutes-Aquino, J.; Ramos, G.; Yee-Madeira, H.
2005-01-01
The Co 2+ ion in an octahedral site of the cubic spinel structure has a highly anisotropic character. The electric crystal field produces a degenerate ground state with a orbital magnetic momentum fixed parallel to a trigonal axis, and the spin-orbit interaction tends to align the spin magnetic moment parallel to this trigonal axis giving high anisotropy. Then, the use of Co x Fe 3-x O 4 system allows the tailoring of the magnetic properties by changing the cobalt content, which can be very useful in magnetic fluids, magnetic latex and free rotors applications. In this work Co x Fe 3-x O 4 nanoparticles over a compositional range 0.0 x Fe 3-x O 4 powders shows that an increase of the cobalt contain yields a steadily decrease in the maximum magnetization
Low-temperature specific heat measurements on the NdCoxFe1-xO3 system
International Nuclear Information System (INIS)
Bartolome, F.; Kuz'min, M.D.; Bartolome, J.; Blasco, J.; Garcia, J.
1995-01-01
Low-temperature specific heat measurements have been carried out on the NdCo x Fe 1-x O 3 perovskite system (x=0, 0.25, 0.5, 0.9, 1). Magnetic ordering of Nd 3+ ions have been observed in NdCoO 3 (at 1.20 K) and NdFeO 3 (at 1.05 K). The studied dilutions, unlike the pure Fe or Co compounds, do not show a magnetic order of the Nd ions due to the stronger molecular field caused by decompensation of the internal field upon the introduction of the (Co 3+ ) magnetic vacancies in the antiferromagnetically ordered Fe subsystem. The specific heat curve of the system at x=0.9 resembles spin-glass behaviour. ((orig.))
Morphology and composition tailoring of Co x Fe3 - x O4 nanoparticles
Fernandes de Medeiros, I. A.; Madigou, V.; Lopes-Moriyama, A. L.; Pereira de Souza, C.; Leroux, Ch.
2018-01-01
Nano-octahedra of cobalt ferrite Co x Fe3 - x O4 (1 ≤ x hydrothermal method using nitrates as precursors. For the first time, single-phased nano-octahedra of cobalt-rich ferrite Co x Fe3 - x O4 ( x = 1.5) were synthesized. The nano-octahedra are crystallized in a normal spinel structure, with tetrahedral sites occupied by Co2+. This specific octahedral shape was obtained with anionic, cationic, and nonionic surfactants. The nature of the surfactant influenced the chemical composition of the powder and the size of the nano-octahedra. The {100} truncation of the octahedra is more pronounced for the small particles. For the first time, single-phased nanoparticles with as much as x = 1.8 cobalt were synthesized with ethylene glycol as solvent. These nanoparticles, around 8 nm in size, have no specific shape and possess a lacunar spinel structure similar to maghemite. The samples were characterized by X-ray diffraction, transmission electron microscopy, and energy-dispersive spectroscopy.
Texturing for bulk α-Fe/Nd2Fe14B nanocomposites with enhanced magnetic properties
International Nuclear Information System (INIS)
Lou, L.; Hou, F.C.; Wang, Y.N.; Cheng, Y.; Li, H.L.; Li, W.; Guo, D.F.; Li, X.H.; Zhang, X.Y.
2014-01-01
In the present study, the texturing of bulk α-Fe/Nd 2 Fe 14 B nanocomposites produced from Nd-lean amorphous Nd x Fe 92.5−x Cu 1.5 B 6 (x=9 to 11.5 at%) via a hot deformation under a uniaxial stress of ∼350 MPa at 973 K has been studied. An enhanced (00l) texture of the hard phase is observed with increasing Nd content, which results in an increase in the magnetic anisotropy of the nanocomposite magnets. As a result, both the coercivity and the remanence of the magnets increase simultaneously with increasing Nd content from x=9–11.5 at%, yielding a significant enhancement of the maximum energy product from (BH) max =13.2 to 17.5 MGOe in the direction parallel to stress axis. - Highlights: • Textured bulk α-Fe/Nd 2 Fe 14 B nanocomposites have been produced from Nd-lean alloys. • Nd content has an effect on the texturing of α-Fe/Nd 2 Fe 14 B nanocomposite magnets. • An enhanced (00l) texture of hard phase is observed with increasing Nd content. • Both the coercivity and remanence increase simultaneously with Nd content
Wang, Wei-Cheng; Chen, Shih-Yun; Glans, Per-Anders; Guo, Jinghua; Chen, Ren-Jie; Fong, Kang-Wei; Chen, Chi-Liang; Gloter, Alexandre; Chang, Ching-Lin; Chan, Ting-Shan; Chen, Jin-Ming; Lee, Jyh-Fu; Dong, Chung-Li
2013-09-21
This study reports on the electronic structure of Fe-doped CeO2 nanoparticles (NPs), determined by coupled X-ray absorption spectroscopy and X-ray emission spectroscopy. A comparison of the local electronic structure around the Ce site with that around the Fe site indicates that the Fe substitutes for the Ce. The oxygen K-edge spectra that originated from the hybridization between cerium 4f and oxygen 2p states are sensitive to the oxidation state and depend strongly on the concentration of Fe doping. The Ce M(4,5)-edges and the Fe L(2,3)-edges reveal the variations of the charge states of Ce and Fe upon doping, respectively. The band gap is further obtained from the combined absorption-emission spectrum and decreased upon Fe doping, implying Fe doping introduces vacancies. The oxygen vacancies are induced by Fe doping and the spectrum reveals the charge transfer between Fe and Ce. Fe(3+) doping has two major effects on the formation of ferromagnetism in CeO2 nanoparticles. The first, at an Fe content of below 5%, is that the formation of Fe(3+)-Vo-Ce(3+) introduces oxygen deficiencies favoring ferromagnetism. The other, at an Fe content of over 5%, is the formation of Fe(3+)-Vo-Fe(3+), which favors antiferromagnetism, reducing the Ms. The defect structures Fe(3+)-Vo-Ce(3+) and Fe(3+)-Vo-Fe(3+) are crucial to the magnetism in these NPs and the change in Ms can be described as the effect of competitive interactions of magnetic polarons and paired ions.
Iron 1s X-ray photoemission of Fe2O3
Miedema, P. S.; Borgatti, F.; Offi, F.; Panaccione, G.; de Groot, F. M. F.
We present the Is X-ray photoemission spectrum of alpha-Fe2O3 in comparison with its 2p photoemission spectrum. We show that in case of transition metal oxides, because the 1s core hole is not affected by core hole spin-orbit coupling and almost not affected by core-valence multiplet effects, the Fe
Energy Technology Data Exchange (ETDEWEB)
Corkett, Alex J.; Free, David G. [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom); Cassidy, Simon J. [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom); Diamond Light Source Limited, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom); Ramos, Silvia [Diamond Light Source Limited, Harwell Science and Innovation Campus, Didcot, OX11 0DE (United Kingdom); Clarke, Simon J., E-mail: simon.clarke@chem.ox.ac.uk [Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (United Kingdom)
2014-08-15
The effect of the isovalent substitution of Sr{sup 2+} by Ca{sup 2+} on the structure and superconducting properties of Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs is described in the compositional range 0≤x≤0.5. SQUID magnetometry measurements reveal that after an initial increase in T{sub c}, which is maximised at 29.5 K in Sr{sub 1.95}Ca{sub 0.05}VO{sub 3}FeAs, a rapid suppression of superconductivity is observed with increasing x. XANES spectra of Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs collected on the Fe and V absorption K-edges show that the position of both edges are invariant with composition within the experimental uncertainty. A combination of synchrotron X-ray powder diffraction and neutron powder diffraction techniques is used to rationalise the observed changes in T{sub c} with x, in terms of changes to the structure of the FeAs layer upon partial Ca substitution. These findings demonstrate that superconductivity in the Fe-based superconductors is extremely sensitive to the crystal structure with T{sub c} maximised in samples with regular FeAs{sub 4}-tetrahedra. - Graphical abstract: Superconducting transition temperature is controlled by structural parameters in Sr{sub 2−x}Ca{sub x}VO{sub 3}FeAs. - Highlights: • Substitution of Sr by Ca in the superconductor Sr{sub 2}VO{sub 3}FeAs is isovalent. • Relationship between superconducting T{sub c} and structural parameters is demonstrated. • Linear dependence of T{sub c} on structural parameters rather than composition.
International Nuclear Information System (INIS)
Kim, J.; Shvydko, Y.
2011-01-01
Momentum-resolved resonant inelastic x-ray scattering (RIXS) spectroscopy has been carried out successfully at the Fe K-edge for the first time. The RIXS spectra of a FeBO 3 single crystal reveal a wealth of information on ∼ 1-10 eV electronic excitations. The IXS signal resonates when the incident photon energy approaches the pre-edge (1s - -3d) and the main-edge (1s - -4p) of the Fe K-edge absorption spectrum. The RIXS spectra measured at the pre-edge and the main-edge show quantitatively different dependences on the incident photon energy, momentum transfer, photon polarization, and temperature. We present a multielectron analysis of the Mott-Hubbard (MH) and charge transfer (CT) excitations, and calculate their energies. Electronic excitations observed in the pre-edge and main-edge RIXS spectra are interpreted as MH and CT excitations, respectively. We propose the electronic structure around the chemical potential in FeBO 3 based on the experimental data.
Experimental phases diagram Zr-Fe and Zr-Sn-Fe of the Fe rich zone at a temperature of 1100oC
International Nuclear Information System (INIS)
Nieva, N.; Jimenez, J.; Gomez, A; Granovsky, M.S
2010-01-01
Zr-based alloys are frequently used in the nuclear energy industry; among these are the Zr-based Zircaloys whose main alloys are Sn and Fe. In order to experimentally evaluate part of the diagram of the binary Zr-Fe phases and the ternary Zr-Sn-Fe in the Fe-rich zone, different binary alloys in the area closest to the composition of the ZrFe 2 and Zr 6 Fe 23 compounds were designed as well as a ternary alloy of Zr-Sn-Fe in the Fe-rich region of the ternary system. All the alloys underwent a two month heat treatment at a temperature of 1100 o C. Later the phases that were present were identified using different complementary techniques (mainly X-ray diffraction and microanalysis). The clear presence of the Zr 6 Fe 23 phase was not observed in any of the alloys. A new ternary phase consisting approximately of Zr 2 0Sn 14 Fe 66 was verified in the ternary alloy
Energy Technology Data Exchange (ETDEWEB)
Liu, Xinzhi, E-mail: liuxinzhi1984.cn@163.com [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Hao, Lijie; Ma, Xiaobai [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Wang, Chin-Wei [Neutron Group, National Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan (China); Klose, Frank [Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Department of Physics and Materials Science, The City University of Hong Kong, Hong Kong Special Administrative Region (Hong Kong); Liu, Yuntao, E-mail: ytliu@ciae.ac.cn [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Sun, Kai; Li, Yuqing [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Chen, Dongfeng, E-mail: dongfeng@ciae.ac.cn [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China)
2017-07-01
Highlights: • The temperature dependent magnetism of HoCr{sub 1-x}Fe{sub x}O{sub 3} (x = 0, 0.2) were investigated by neutron diffraction. • Cr{sup 3+} moment follows a mean field theory while Ho{sup 3+} follows a spin 1/2 model. • An magneto-elastic strain was observed accompanying with the ordering of Cr{sup 3+}. - Abstract: The temperature dependent magnetism of Fe-doped rare earth orthochromite HoCr{sub 1-x}Fe{sub x}O{sub 3}(x = 0, 0.2) was investigated by neutron powder diffraction. It is found that the magnetism of Cr(Fe){sup 3+} can be well understood within mean field theory, while the ordering of Ho{sup 3+} was induced by the Cr(Fe){sup 3+} sublattice and can be satisfyingly described by an effective S = 1/2 model. The absences of both the most common G{sub x}F{sub z} configuration of Cr{sup 3+} and the ordering of Ho{sup 3+} caused by Ho-Ho interaction evidence a strong Ho{sup 3+}-Cr{sup 3+} interaction which dominates this system. On the other hand, a remarkable magnetoelastic strain was observed accompanying the Cr(Fe){sup 3+} ordering. An analysis based on the equation of state with a Grüneisen approximation was performed and revealed magnetic origin of this strain.
May, M. J.; Beiersdorfer, P.; Dunn, J.; Jordan, N.; Hansen, S. B.; Osterheld, A. L.; Faenov, A. Ya.; Pikuz, T. A.; Skobelev, I. Yu.; Flora, F.; Bollanti, S.; Di Lazzaro, P.; Murra, D.; Reale, A.; Reale, L.; Tomassetti, G.; Ritucci, A.; Francucci, M.; Martellucci, S.; Petrocelli, G.
2005-06-01
Iron spectra have been recorded from plasmas created at three different laser plasma facilities: the Tor Vergata University laser in Rome (Italy), the Hercules laser at ENEA in Frascati (Italy), and the Compact Multipulse Terawatt (COMET) laser at LLNL in California (USA). The measurements provide a means of identifying dielectronic satellite lines from Fe XVI and Fe XV in the vicinity of the strong 2p-->3d transitions of Fe XVII. About 80 Δn>=1 lines of Fe XV (Mg-like) to Fe XIX (O-like) were recorded between 13.8 and 17.1 Å with a high spectral resolution (λ/Δλ~4000) about 30 of these lines are from Fe XVI and Fe XV. The laser-produced plasmas had electron temperatures between 100 and 500 eV and electron densities between 1020 and 1022 cm-3. The Hebrew University Lawrence Livermore Atomic Code (HULLAC) was used to calculate the atomic structure and atomic rates for Fe XV-XIX. HULLAC was used to calculate synthetic line intensities at Te=200 eV and ne=1021 cm-3 for three different conditions to illustrate the role of opacity: optically thin plasmas with no excitation-autoionization/dielectronic recombination (EA/DR) contributions to the line intensities, optically thin plasmas that included EA/DR contributions to the line intensities, and optically thick plasmas (optical depth ~200 μm) that included EA/DR contributions to the line intensities. The optically thick simulation best reproduced the recorded spectrum from the Hercules laser. However, some discrepancies between the modeling and the recorded spectra remain.
Magnetocaloric effects in Mn1.35Fe0.65P1−xSix compounds
International Nuclear Information System (INIS)
Geng Yao-Xiang; Tegus O; Bi Li-Ge
2012-01-01
The structural and magnetocaloric properties of Mn 1.35 Fe 0.65 P 1−x Si x compounds are investigated. The Si-substituted compounds, Mn 1.35 Fe 0.65 P 1−x Si x with x = 0.52, 0.54, 0.55, 0.56, and 0.57, are prepared by high-energy ball milling and the solid-state reaction. The X-ray diffraction shows that the compounds crystallize into the Fe 2 P-type hexagonal structure with space group P6-bar2m. The magnetic measurements show that the Curie temperature of the compound increases from 253 K for x = 0.52 to 296 K for x = 0.56. The isothermal magnetic-entropy change of the Mn 1.35 Fe 0.65 P 1−x Si x compound decreases with the Si content increasing. The maximal value of the magnetic-entropy change is about 7.0 J/kg·K in the Mn 1.35 Fe 0.65 P 0.48 Si 0.52 compound with a field change of 1.5 T. The compound quenched in water possesses a larger magnetic entropy change and a smaller thermal hysteresis than the non-quenched samples. The thermal hysteresis of the compound is less than 3.5 K. The maximum adiabatic temperature change is about 1.4 K in the Mn 1.35 Fe 0.65 P 0.45 Si 0.55 compound with a field change of 1.48 T. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Moessbauer spectroscopy on amorphous Fe/sub x/Ni/sub 80-x/B/sub 20/ after neutron irradiation
Energy Technology Data Exchange (ETDEWEB)
Sitek, J.; Miglierini, M. (Slovenska Vysoka Skola Technicka, Bratislava (Czechoslovakia))
1985-05-16
Amorphous Fe/sub x/Ni/sub 80-x/B/sub 20/ glassy alloys (x = 40, 50, 60, and 70) irradiated with fast neutrons in a fluence range of 10/sup 14/ to 10/sup 19/ cm/sup -2/ were investigated by Moessbauer spectroscopy. There were some significant changes in the Moessbauer spectrum parameters of the 10/sup 19/ cm/sup -2/ irradiated samples except Fe/sub 40/Ni/sub 40/B/sub 20/. This corresponds to a change in the direction of the easy axis of magnetization. The measurements show that the resistance of the Fe-Ni-B system against neutron irradiation improves with increasing Ni content up to a certain point.
Modification of interlayer exchange coupling in Fe/V/Fe trilayers using hydrogen
Energy Technology Data Exchange (ETDEWEB)
Skoryna, J., E-mail: jskoryna@ifmpan.poznan.pl [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17 St., 60-179 Poznań (Poland); Marczyńska, A. [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17 St., 60-179 Poznań (Poland); Lewandowski, M. [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85 St., 61-614 Poznań (Poland); Smardz, L. [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17 St., 60-179 Poznań (Poland)
2015-10-05
Highlights: • Magnetic films and multilayers. • Thin films. • Hydrogen absorbing materials. • Magnetic measurements. • Exchange coupling. - Abstract: Fe/V/Fe trilayers with constant-thickness Fe and step-like wedged V sublayers were prepared at room temperature using UHV magnetron sputtering. The bottom Fe layer grows onto oxidised Si(1 0 0) substrate and shows relatively high coercivity. The top Fe layer grows on vanadium spacer and shows considerably lower coercivity. The planar growth of the Fe and V sublayers was confirmed in-situ by X-ray photoelectron spectroscopy. Results show that the Fe sublayers are weakly exchange coupled for d{sub V} > 1.4 nm. Results on the coercivity studies as a function of the V interlayer thickness show near d{sub V} ∼ 1.95 nm (∼2.45 nm) weak antiferromagnetic (ferromagnetic) coupling, respectively. The hydrogenation of the Fe/V/Fe trilayers leads to increase of the strength of the ferromagnetic interlayer exchange coupling.
Mechanical alloying of the FeNi-Ag system
International Nuclear Information System (INIS)
Gonzalez, G.; Ibarra, D.; Ochoa, J.; Villalba, R.; Sagarzazu, A.
2007-01-01
The Fe-Ni-Ag system is of particular interest for its potential applications as soft magnetic granular material with small magnetic grains embedded in a non-magnetic metal matrix. Under equilibrium conditions: Fe-Ag and Ni-Ag are immiscible and Fe-Ni shows complete solubility. These materials are particularly important for magnetoresistivity properties. The properties of these alloys are closely related to their microstructure; therefore, a detailed study of the transformations occurring during milling was undertaken using pre-alloyed Fe x Ni 100-x (x = 30, 50 and 70) further milled with different Ag content to give the following alloys compositions (Fe x -Ni 100-x ) 100-y Ag y (y = 5, 20, 60). Consolidation of the mechanically alloyed powders by sintering at 950 o C was performed. Morphological and structural characterization of the sintered powders was carried out by scanning and transmission electron microscopy and X-ray diffraction. Fe 30 Ni 70 and Fe 50 Ni 50 formed ordered FeNi 3 compound. Fe 70 Ni 30 showed the formation of a mixture of γ-(Fe,Ni) and α-Fe(Ni) solid solutions. The mixture of these systems with Ag showed the metal solid solutions surrounded by Ag islands of Fe x Ni y -Ag, There was also evidence of Ag diffusing into the γ-(Fe,Ni). High Ag content (60%) shows formation of islands of FeNi surrounded by Ag. Sintering is always improved with the Ag content
Energy Technology Data Exchange (ETDEWEB)
Fardi-Ilkhchy, Ali [Faculty of Materials Engineering, Sahand University of Technology, Tabriz 51335-1996 (Iran, Islamic Republic of); Nasirpouri, Farzad, E-mail: Nasirpouri@sut.ac.ir [Faculty of Materials Engineering, Sahand University of Technology, Tabriz 51335-1996 (Iran, Islamic Republic of); Bran, Cristina; Vázquez, Manuel [Institute of Materials Science of Madrid, CSIC, 28049 Madrid (Spain)
2016-12-15
Fe{sub (1−x)}-Pt{sub (x)} (0<x<1) compositionally graded nanowires (50 nm in diameter and 1 µm in length) were fabricated by alternating current (AC) electrodeposition into nanoporous aluminum oxide templates through a systematic approach. The effect of AC electrodeposition parameters such as frequency, voltage and electrolyte concentration on morphology and chemical composition of Fe-Pt alloy nanowires was studied. Based on experimental data, AC sine wave deposition at an intermediate voltage of 12 V{sub rms} and a frequency of 50 Hz, produces nanowires with nearly stoichiometric composition (Fe{sub 42}Pt{sub 58}) and a reasonably good uniformity of pore filling. However, there is a gradual change of composition in Fe-Pt alloy nanowires along the length under certain AC parameters. The observed dependency of alloy composition on the deposition voltage and frequency of AC electrodeposition is explained by an interplay between reduction potentials and diffusion coefficients of Fe and Pt ions which makes FePt system able to access compositionally graded nanowires. Magnetic measurements of nanowires of as-deposited nanowires confirm that maximum coercivity of 1.55 kOe is observed for nearly stoichiometric composition which increases up to 1.81 kOe after thermal annealing at 550 °C. - Graphical abstract: Evaluation of synthesizing extrinsic parameters (such as deposition voltages and frequency) and intrinsic parameters (diffusion coefficient and reduction potential of ion species) in compositionally graded Fe{sub (1−x)}-Pt{sub (x)} nanowires prepared by alternating current electrodeposition into alumina templates.
Magnetic Properties of Nanocrystalline Fe{sub x}Cu{sub 1-x} Alloys Prepared by Ball Milling
Energy Technology Data Exchange (ETDEWEB)
Yousif, A.; Bouziane, K., E-mail: bouzi@squ.edu.om; Elzain, M. E. [Sultan Qaboos University, Physics Department, College of Science (Oman); Ren, X.; Berry, F. J. [The Open University, Department of Chemistry (United Kingdom); Widatallah, H. M. [Sudan Atomic Energy Commission, Institute of Nuclear Research (Sudan); Al Rawas, A.; Gismelseed, A.; Al-Omari, I. A. [Sultan Qaboos University, Physics Department, College of Science (Oman)
2004-12-15
X-ray diffraction, Moessbauer and magnetization measurements were used to study Fe{sub x}Cu{sub 1-x} alloys prepared by ball-milling. The X-ray data show the formation of a nanocrystalline Fe-Cu solid solution. The samples with x{>=}0.8 and x{<=}0.5 exhibit bcc or fcc phase, respectively. Both the bcc and fcc phases are principally ferromagnetic for x{>=}0.2, but the sample with x=0.1 remains paramagnetic down to 78 K. The influence of the local environment on the hyperfine parameters and the local magnetic moment are discussed using calculations based on the discrete-variational method in the local density approximation.
Electronic Properties of LiFePO4 and Li doped LiFePO4
International Nuclear Information System (INIS)
Zhuang, G.V.; Allen, J.L.; Ross, P.N.; Guo, J.-H.; Jow, T.R.
2005-01-01
The potential use of different iron phosphates as cathode materials in lithium-ion batteries has recently been investigated.1 One of the promising candidates is LiFePO4. This compound has several advantages in comparison to the state-of-the-art cathode material in commercial rechargeable lithium batteries. Firstly, it has a high theoretical capacity (170 mAh/g). Secondly, it occurs as mineral triphylite in nature and is inexpensive, thermally stable, non-toxic and non-hygroscopic. However, its low electronic conductivity (∼10-9 S/cm) results in low power capability. There has been intense worldwide research activity to find methods to increase the electronic conductivity of LiFePO4, including supervalent ion doping,2 introducing non-carbonaceous network conduction3 and carbon coating, and the optimization of the carbon coating on LiFePO4 particle surfaces.4 Recently, the Li doped LiFePO4 (Li1+xFe1-xPO4) synthesized at ARL has yield electronic conductivity increase up to 106.5 We studied electronic structure of LiFePO4 and Li doped LiFePO4 by synchrotron based soft X-ray emission (XES) and X-ray absorption (XAS) spectroscopies. XAS probes the unoccupied partial density of states, while XES the occupied partial density of states. By combining XAS and XES measurements, we obtained information on band gap and orbital character of both LiFePO4 and Li doped LiFePO4. The occupied and unoccupied oxygen partial density of states (DOS) of LiFePO4 and 5 percent Li doped LiFePO4 are presented in Fig. 1. Our experimental results clearly indicate that LiFePO4 has wideband gap (∼ 4 eV). This value is much larger than what is predicted by DFT calculation. For 5 percent Li doped LiFePO4, a new doping state was created closer to the Fermi level, imparting p-type conductivity, consistent with thermopower measurement. Such observation substantiates the suggestion that high electronic conductivity in Li1.05Fe0.95 PO4 is due to available number of charge carriers in the material
Structural study of U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 at high pressure
Sikolenko, V V; Pomjakushina, E V; Pomjakushin, V Y; Balagurov, A M; Keller, L; Glazkov, V P; Gribanov, A V; Goncharenko, I N; Savenko, B N
2003-01-01
The crystal structure of the U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 compounds with Fe content x = 0- 0.03 and the crystal and magnetic structure of U(Pd sub 0 sub . sub 9 sub 8 Fe sub 0 sub . sub 0 sub 2) sub 2 Ge sub 2 at high external pressures up to 4.5 GPa were studied by means of powder neutron diffraction in the temperature range 1.5-300 K. With increasing Fe content the values of the lattice parameters and interatomic distances change only slightly, but it is known from previous experiments that the magnetic structure changes drastically for x >= 0.015. In contrast to this, high external pressure modifies the crystal structure more significantly while the magnetic structure remains unchanged. The results obtained allow one to infer that drastic changes in the magnetic structure of the U(Pd sub 1 sub - sub x Fe sub x) sub 2 Ge sub 2 compounds with increasing Fe content are a consequence of modification of the RKKY-type (RKKY standing for Ruderman, Kittel, Kasuya and Yosida) indirect exchange in...
Scaling of the L2,3 circular magnetic x-ray dichroism of Fe nitrides
International Nuclear Information System (INIS)
Alouani, M.; Wills, J.M.; Wilkins, J.W.
1998-01-01
We have implemented the calculation of the x-ray-absorption cross section for left- and right-circularly polarized x-ray beams within the local-density approximation by means of our all-electron full-relativistic and spin-polarized full-potential linear muffin-tin orbital method. We show that the L 2,3 circular magnetic x-ray dichroism of Fe, Fe 3 N, and Fe 4 N compounds scales to a single curve when divided by the local magnetic moment. Sum rules determine the spin and orbital magnetic moment of iron atoms in these ordered iron nitrides. copyright 1998 The American Physical Society
Triton X-100 functionalized Fe3O4 nanoparticles for biomedical applications
Gawali, Santosh L.; Madan, Devendra P.; Barick, K. C.; Somani, R.; Hassan, P. A.
2018-04-01
We report the preparation of Triton X-100 functionalized Fe3O4 nanoparticles (TXMNPs) and investigated their potential application in hyperthermia therapy. The formation of highly crystalline, spinel-structured Fe3O4 nanoparticles of average size of about 10 nm was evident from X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), UV-visible spectroscopy and zeta-potential measurements suggest the successful functionalization of nanoparticles with TX-100. These TXMNPs exhibit good colloidal stabilization in aqueous medium and show protein resistance characteristic in physiological medium. They showed excellent heating efficacy under AC magnetic field (AMF) with specific absorption rate (SAR) values of 146 and 260 W/g of Fe for 1.25 and 0.625 mg/ml of Fe, respectively at an applied AMF of 507 Oe and frequency of 300 kHz. Thus, these nanoparticles can be used as effective thermoseed for hyperthermia treatment of cancer.
Energy Technology Data Exchange (ETDEWEB)
Hu, Guo-rong, E-mail: hgrhsj@263.net; Liu, Ji-jun; Du, Ke; Peng, Zhong-dong; Cao, Yan-bing; Wang, Wei-gang; Duan, Jian-guo
2014-08-01
To separate ferrum from chromium in the leaching sulfate solution of ferrochrome alloy, the oxalic acid was employed to precipitate the ferrum as the form of FeC{sub 2}O{sub 4} and Cr was left in the solution. In this route, small amount of nickel, cobalt and manganese exited in ferrochrome alloy were also precipitated simultaneously together with ferrous oxalate. Analysis from ICP shows that the molar percent of Fe in oxalic precipitate is 97.9% and the main doped elements are Ni (1.1%) and Mn (0.4%).The mixed metal oxalate Fe{sub (1−x)}M{sub x}C{sub 2}O{sub 4} was used as a raw material to prepare doped LiFePO{sub 4} cathode material of lithium ion batteries. The obtained LiFe{sub (1−x)}M{sub x}PO{sub 4}/C was a single olivine-type phase with higher crystallinity and presents the well-distributed fine particles. It shows an outstanding electrochemical performance with a discharge capacity of 162 mAh/g at the rate of 0.1 C, 136 mAh/g at 1 C and 103 mAh/g at 5 C. When cycled at 1 C for 50 times, the capacity retention is 98.2%.
NMR evidence for spin fluctuations in underdoped LaO{sub 1-x}F{sub x}FeAs
Energy Technology Data Exchange (ETDEWEB)
Hammerath, Franziska; Grafe, Hans-Joachim; Lang, Guillaume; Behr, Guenter; Werner, Jochen; Buechner, Bernd [Leibniz-Institut fuer Festkoerper- und Werkstoffforschung, Dresden (Germany); Paar, Dalibor [Department of Physics, Faculty of Science, University of Zagreb (Croatia)
2012-07-01
We present {sup 75}As Nuclear Magnetic Resonance (NMR) measurements on the iron-based superconductor LaO{sub 1-x}F{sub x}FeAs with 0 {<=} x {<=} 0.1, covering a broad range of the phase diagram from magnetically-ordered to optimally-doped superconducting samples. For underdoped samples (x=0.05,x=0.075) the {sup 75}As NMR spin-lattice relaxation rate (T{sub 1}T){sup -1} shows a Curie-Weiss-like increase at intermediate temperatures, indicating the slowing down of spin fluctuations. However, a simple Curie-Weiss fit fails to describe (T{sub 1}T){sup -1}(T) above 250 K and the occurrence of a peak in (T{sub 1}T){sup -1} slightly above T{sub c}. Instead, the data can be well described by considering a BPP-model for fluctuating magnetic fields in combination with a doping-independent linear temperature dependence at high temperature. At optimal doping (x=0.1) spin fluctuations are suppressed and only the linear contribution to (T{sub 1}T){sup -1} is left. This stands in contrast to other pnictides, such as Ba(Fe{sub 1-x}Co{sub x}As){sub 2} and Ba(FeAs{sub 1-x}P{sub x}){sub 2}. Our analysis is consistent with charge carrier localization in underdoped LaO{sub 1-x}F{sub x}FeAs as seen by means of resistivity measurements.
Structural and electrochemical properties of La 0.8Sr 0.2Ga 1-xFe xO 3
Mori, Kazuhiro; Onodera, Yohei; Kiyanagi, Ryoji; Richardson, James W.; Itoh, Keiji; Sugiyama, Masaaki; Kamiyama, Takashi; Fukunaga, Toshiharu
2009-02-01
Mixed ionic-electronic conductor of Fe doped lanthanum gallate, La 0.8Sr 0.2Ga 1-xFe xO 3, has been studied by the dc four-probe method and the neutron powder diffraction. In the electrical conductivity measurement at RT, insulator-metal transition-like phenomenon was observed at around x˜0.35; this suggests an existence of the percolation limit for the electronic conductivity. Simultaneously, a bond length between O atoms, lO-O, in a MO 6 octahedron (M dbnd Ga 1-xFe x) drastically expands over x˜0.4, according to the result of crystal structure refinement based on the hexagonal phase. Such a drastic expansion in the lO-O would induce the decrease in the oxygen ionic conductivity.
Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3−δ} (Me = Fe, Mn)
Energy Technology Data Exchange (ETDEWEB)
Niwa, Eiki, E-mail: e-niwa@phys.chs.nihon-u.ac.jp [Department of Physics, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550 (Japan); Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550 (Japan); Maeda, Hiroki; Uematsu, Chie [Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550 (Japan); Hashimoto, Takuya [Department of Physics, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550 (Japan); Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, Setagaya-ku, Tokyo 156-8550 (Japan)
2015-10-15
Graphical abstract: Compositional dependence of (a) electrical conductivity and (b) E{sub a} for hopping conduction of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn). - Highlights: • Electrical conduction mechanism of LaNi{sub x}Me{sub 1−x}O{sub 3} (Me = Fe, Mn) was investigated. • Hopping conduction model could be applied for conductivity of both specimens. • The difference of E{sub a} due to that of energy level of Fe and Mn was observed. • Hole concentration estimated by iodimetry increases with increasing Ni content. - Abstract: Electrical conduction mechanism of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} expected as Sr-free new cathode material for solid oxide fuel cells was analyzed. Electrical conduction behaviors of both specimens could be well fitted by small polaron hopping conduction model. The electrical conductivity of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} increased with increasing Ni content, showing agreement with decrease of activation energy for hopping conduction. The decrease of electrical conductivity and increase of activation energy of LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} were observed with increasing Ni content for 0.0 ≤ x ≤ 0.4. Further Ni substitution increased electrical conductivity and decreased activation energy for 0.4 ≤ x ≤ 0.6. It was revealed using iodometry that the difference of hole carrier density between LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1−x}O{sub 3+δ} was small. It was suspected that the origin of the difference of electrical conduction behavior of LaNi{sub x}Fe{sub 1−x}O{sub 3−δ} and LaNi{sub x}Mn{sub 1-x}O{sub 3+δ} was difference of energy level of e{sub g} band composed of Fe 3d or Mn 3d orbitals and their overlapping quantity with O 2p and Ni 3d band.
Hard magnetic off-stoichiometric (Fe,Sb){sub 2+x}Hf{sub 1-x} intermetallic phase
Energy Technology Data Exchange (ETDEWEB)
Goll, D.; Gross, T.; Loeffler, R.; Pflanz, U.; Vogel, T.; Kopp, A.; Grubesa, T.; Schneider, G. [Aalen University, Materials Research Institute (Germany)
2017-09-15
By high-throughput screening the ternary Fe-Hf-Sb system, off-stoichiometric (Fe,Sb){sub 2+x}Hf{sub 1-x} with a composition of Fe60.0-Hf26.5-Sb13.5 with high potential as hard magnetic phase is discovered. By quantitative domain structure analysis, promising intrinsic properties of J{sub s} ∝ 1 T, K{sub 1} ∝ 1.5 MJ m{sup -3} are found at room temperature. By magnetometry, bulk intrinsic properties of J{sub s} ∝ 0.7 T, K{sub 1} ∝ 1.4 MJ m{sup -3} are found. Alloying elements like Co or Mn turns out to be an effective adjusting screw on the crystal structure and ferromagnetic behavior. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
International Nuclear Information System (INIS)
Dote, Haruka; Yasuhara, Hiroki; Nakashima, Satoru
2013-01-01
New mixed crystals, Fe(NCS) x (NCBH 3 ) (2-x) (bpp) 2 were synthesized. 57 Fe Mössbauer spectroscopy showed that the ratio of low-spin state in the Fe(NCBH 3 ) 2 unit changed with the change of x. The results revealed that the high spin site of Fe(NCS) 2 unit affects the spin state of Fe(NCBH 3 ) 2 unit. (author)
X-Ray Absorption Spectroscopy of Fe-Substituted Allophane and Imogolite
Baker, L. L.; Strawn, D. G.; Nickerson, R. D.; McDaniel, P.
2011-12-01
Martian rocks and sediments contain weathering products including clay minerals formed as a result of interaction between rocks and water, and these materials can act as important indicators of past surface conditions on Mars. Weathering of terrestrial volcanic rocks similar to those on Mars produces nano-sized, variably hydrated aluminosilicate and iron oxide minerals, including allophane, imogolite, halloysite, hisingerite, and ferrihydrite. The nanoaluminosilicates can contain isomorphically substituted Fe, which may affect their spectral and physical properties as well as their eventual recrystallization products. Detection and quantification of such minerals in natural environments on Earth is difficult due to their variable chemical composition and lack of long-range crystalline order. Their accurate detection and quantification on Mars requires a better understanding of how composition affects their spectral properties and evolution to more crystalline phases. Aluminosilicate nanoparticles of varying composition were synthesized with isomorphically substituted Fe at Fe:Al ratios of 1:100. Allophanes were synthesized with Al:Si ratios of 2:1, 1:1, and 1:3. The substituted Fe was probed using Fe K-edge X-ray absorption fine structure spectroscopy (XAFS). The XAFS spectrum contains information about the molecular environment surrounding the target atom, and is an ideal technique for studying poorly crystalline materials that are difficult to characterize using bulk methods such as XRD. The near-edge (XANES) and extended (EXAFS) portions of the XAFS spectrum were examined, and allophane backscattering paths were fit using coordinates for a modified nanoball model (1). XANES spectra rule out ferrihydrite in the synthetic samples, suggesting all Fe was incorporated into the aluminosilicate structure. The XAFS results suggest that Fe substituted into the allophane structure is present as Fe(III) in octahedral coordination in a well-ordered sheet. Some Fe
Preparation and properties of [(NdFeB)x/(Nb)z]n multi-layer films
International Nuclear Information System (INIS)
Tsai, J.-L.; Chin, T.-S.; Yao, Y.-D.; Melsheimer, A.; Fisher, S.; Drogen, T.; Kelsch, M.; Kronmueller, H.
2003-01-01
Multi-layer [(NdFeB) x /(Nb) z ] n films with 200 nm≥x≥10 nm, 10 nm≥z≥0, 40≥n≥2, prepared by ion beam sputtering and subsequent annealing, show significantly enhanced coercivity due to the reduced grain size that enhances the anisotropy of individual grains. After annealing at 630 deg. C, some Nd 2 Fe 14 B grains were enriched with Nb and isolated as the thickness of the Nb spacer layer increases. For multi-layer (NdFeB x /Nb z ) n films with 100 nm ≥x≥25 nm, 5 nm≥z≥2 nm, their coercivity and remanence ratio are better than that of a single NdFeB film. Up to 17.8 kOe room temperature coercivity has been obtained for a sample with x=25 nm, z=5 nm and n=16
Conductivity and electrochemical characterization of PrFe1-xNixO3-δ at high temperature
DEFF Research Database (Denmark)
Hashimoto, Shin-Ichi; Kammer Hansen, Kent; Poulsen, Finn Willy
2007-01-01
PrFe(1-x)NixO(3)- (x=0.4-0.6) compounds were synthesized and characterized by powder XRD, electrical conductivity and electrochemical impedance spectroscopy on point electrodes on a Ce0.9Gd0.1O2-delta (CGO10) electrolyte. As a reference, the electrochemical performance of LaFe(0.4)AM(0.6)O(3-delta......) was also measured. The main phase in the PrFe1-xNixO3-delta series was perovskite-type structure and belonged to the orthorhombic crystal system. The conductivities are fairly high, e.g. around 220 S cm(-1) at 873 K for the x = 0.4 compound. The electrochemical performance of the PrFe(1-x)NixO(3-delta...
A structural, magnetic, and Mössbauer study of the Dy{sub 2}Fe{sub 17−x}Nb{sub x} solid solutions
Energy Technology Data Exchange (ETDEWEB)
Rai, B.K. [Department of Physics, The University of Memphis, Memphis, TN 38152 (United States); Syed Ali, K.S. [Department of Science, Estill High school, Estill, SC 29918 (United States); Mishra, S.R., E-mail: srmishra@memphis.edu [Department of Physics, The University of Memphis, Memphis, TN 38152 (United States); Khanra, S.; Ghosh, K. [Department of Physics, Astronomy, and Materials Science, The Missouri State University, Springfield, MO 65897 (United States)
2014-03-15
The single-phase intermetallic compounds of refractory metal Nb doped Dy{sub 2}Fe{sub 17−x}Nb{sub x} were prepared by arc melting. The substitution of Nb in the Dy{sub 2}Fe{sub 17} compound was found to have an important effect on their structure and magnetic properties. The Rietveld analysis of X-ray diffraction data shows that Dy{sub 2}Fe{sub 17−x}Nb{sub x} (x=0–1.5) solid solutions crystallize with the Th{sub 2}Ni{sub 17} structure. The lattice parameters obtained from Rietveld refinement show that the unit cell volume of Dy{sub 2}Fe{sub 17−x}Nb{sub x} increases linearly with increasing Nb concentration up to x=1. The solubility of Nb was found to be limited to x∼1. The substitutional Nb atoms occupied all four sites in the order 12j>12k>6g>4f of a Th{sub 2}Ni{sub 17} structure. The Curie temperature (T{sub c}) was found to be Nb content dependent. The T{sub c} first increased and then decreased with increasing Nb content x, attaining a maximum value of 460 K at around x=1, which is 78 K higher than that of Dy{sub 2}Fe{sub 17}. The saturation magnetization decreased linearly with increasing Nb content from 69 emu/g for x=0 to 38 emu/g for x=1.5. {sup 57}Fe Mössbauer spectra show the presence of DyFe{sub 3} and NbFe{sub 2} phases at a higher Nb content x≥1. The hyperfine field values of 4f site first increased up to x=1 and then decreased at higher Nb content. - Highlights: • Nb is used to suppress the free alpha iron in 2:17 intermediates. At higher concentration x>1, Nb forms paramagnetic phase with alpha iron, NbFe{sub 2}. • The low level of Nb doping (x<1) in Dy{sub 2}Fe{sub 17−x}Nb{sub x} brings in ∼21% increase in the Curie temperature. • In Al, Si or Ga doped 2:17 intermatallics, similar improvement is observed in T{sub c} at a much higher doping concentration at the cost of reduction in net magnetization. • The maximum Curie temperature, 460 K, is observed for x∼1 Nb doping.
Adhesive and Cohesive Strength in FeB/Fe2B Systems
Meneses-Amador, A.; Blancas-Pérez, D.; Corpus-Mejía, R.; Rodríguez-Castro, G. A.; Martínez-Trinidad, J.; Jiménez-Tinoco, L. F.
2018-05-01
In this work, FeB/Fe2B systems were evaluated by the scratch test. The powder-pack boriding process was performed on the surface of AISI M2 steel. The mechanical parameters, such as yield stress and Young's modulus of the boride layer, were obtained by the instrumented indentation technique. Residual stresses produced on the boride layer were estimated by using the x-ray diffraction (XRD) technique. The scratch test was performed in order to evaluate the cohesive/adhesive strength of the FeB/Fe2B coating. In addition, a numerical evaluation of the scratch test on boride layers was performed by the finite element method. Maximum principal stresses were related to the failure mechanisms observed by the experimental scratch test. Shear stresses at the interfaces of the FeB/Fe2B/substrate system were also evaluated. Finally, the results obtained provide essential information about the effect of the layer thickness, the residual stresses, and the resilience modulus on the cohesive/adhesive strength in FeB/Fe2B systems.
Energy Technology Data Exchange (ETDEWEB)
Bochenek, D., E-mail: dariusz.bochenek@us.edu.pl [University of Silesia, Faculty of Computer Science and Material Science, Institute of Technology and Mechatronics, 12, Żytnia St., 41–200, Sosnowiec (Poland); Niemiec, P. [University of Silesia, Faculty of Computer Science and Material Science, Institute of Technology and Mechatronics, 12, Żytnia St., 41–200, Sosnowiec (Poland); Guzdek, P. [Institute of Electron Technology Cracow Division, 39, Zabłocie St., Cracow, 30-701 (Poland); Wzorek, M. [Institute of Electron Technology, Al. Lotników 32/46, 02-668, Warsaw (Poland)
2017-07-01
In the paper ferro–electro–magnetic (1-x)BiFeO{sub 3}-(x)Pb(Fe{sub 1/2}Nb{sub 1/2})O{sub 3} (BF-PFN) solid solutions were obtained (containing the percentage BF/PFN: 60/40 and 70/30). Individual components of the solid solution were prepared by follows methods: synthesizing a powder BF was performed by calcining the simple oxides (Bi{sub 2}O{sub 3}, Fe{sub 2}O{sub 3}), and synthesizing a powder PFN was carried out by calcining a mixture of complex oxides (FeNbO{sub 4}, PbO). Compaction of synthesized and mixed BiFeO{sub 3}, PbFe{sub 1/2}Nb{sub 1/2}O{sub 3} powders was carried out by free sintering methods. X–ray, microstructure, dielectric, magnetic and magnetoelectric studies, DC electrical conductivity and electrical hysteresis loop were carried out. Magnetoelectric effect measurements performed at room temperature showed coupling between electric and magnetic subsystem of the BF–PFN solid solutions. - Highlights: • BF-PFN samples have a densely packed microstructure, with well crystallized grains. • Bi atoms possibly migrate from BF toward PFN component during sintering. • BF-PFN have a diffuse character of the ferroelectric–paraelectric phase transition. • Magnetoelectric coefficient (α{sub ME}) for BF-PFN is higher, than for pure BF. • The α{sub ME} for BF-PFN is about three times higher than for 0.75BiFeO{sub 3}–0.25BaTiO{sub 3}.
Crystal structure and electrical resistivity studies of Gd(Fe1-x Cox)2 intermetallics
International Nuclear Information System (INIS)
Onak, M.; Guzdek, P.; Stoch, P.; Chmist, J.; Bednarski, M.; Panta, A.; Pszczola, J.
2007-01-01
From X-ray analysis (295 K) it was found that the cubic, MgCu 2 -type, Fd3m crystal structure appears across the Gd(Fe 1-x Co x ) 2 series. Electrical resistivity measurements for the Gd(Fe 1-x Co x ) 2 intermetallics were performed in a wide temperature region and the parameters characterizing the resistivity dependence on temperature and composition were determined. The differential of the electrical resistivity against temperature was used to estimate Curie temperatures. The Curie temperature versus x, high and moderately increasing in the iron-rich area, rapidly drops in the cobalt-rich region. The obtained results are compared with the data known for the Dy(Fe 1-x Co x ) 2 series. The Curie temperature is related to both the number of 3d electrons and the de Gennes factor
Energy Technology Data Exchange (ETDEWEB)
Srivastava, Yogesh, E-mail: 123209001_yogesh@manit.ac.in [Department of Materials Science & Metallurgical Engineering, Ceramic & Powder Metallurgy Laboratory, Maulana Azad National Institute of Technology, Bhopal, Madhya Pradesh 462003 (India); Vajpai, Sanjay Kumar, E-mail: vajpaisk@gmail.com [Department of Materials Science & Metallurgical Engineering, Maulana Azad National Institute of Technology, Bhopal, Madhya Pradesh 462003 (India); Srivastava, Sanjay, E-mail: s.srivastava.msme@gmail.com [Department of Materials Science & Metallurgical Engineering, Maulana Azad National Institute of Technology, Bhopal, Madhya Pradesh 462003 (India)
2017-07-01
Highlights: • A series of nanocrystalline Co{sub 2}(Cr{sub 1−x}Fe{sub x})Al Heusler alloy by powder metallurgy. • Effect of substitution of Fe for Cr on the microstructure and magnetic properties. • Increasing amounts of B2 type disordered structure with increasing Fe content. • Enhanced Ms, Mr, Hc, and Tc with increasing Fe content. • Relative magnetic anisotropy decreased with increasing Fe content. - Abstract: In the present study, a series of nanocrystalline Co{sub 2}(Cr{sub 1−x}Fe{sub x})Al Heusler alloy powders were successfully prepared by high energy ball milling and the effect of substitution of Fe for Cr on the microstructure and magnetic properties was investigated in detail. The Co{sub 2}CrAl alloy powder consisted of only A2 type disordered structure whereas the substitution of Cr by Fe led to the appearance of increasing amounts of B2 type disordered structure along with A2 type structure. All the Co{sub 2}(Cr{sub 1−x}Fe{sub x})Al Heusler alloy powders demonstrated high spontaneous magnetization together with a very small hysteresis losses. The saturation magnetization, remanence, coercivity, and Curie temperature increased with increasing Fe content. The increasing magnetization with increasing Fe content was attributed to the replacement of antiferromagnetic Cr by strongly ferromagnetic Fe and an increasing amounts of relatively more ordered, atomically as well as ferromagnetically, B2 structure as compared to that of A2 phase. The increment in remanence and coercivity with increasing Fe content were associated with the variation in microstructural characteristics, such as grain size, lattice defects, and the presence of small amounts of magnetic/nonmagnetic secondary phases. The increment in Curie temperature with increasing Fe content was attributed to the enhancement of d-d exchange interaction due to the possible occupancy of vacant sites by Fe atoms. All the Heusler alloys indicated extremely low magnetic anisotropy and the
Energy Technology Data Exchange (ETDEWEB)
Nascimento, V.P., E-mail: valberpn@yahoo.com.br [Departamento de Física, Universidade Federal do Espírito Santo, 29075-910 Vitória (Brazil); Merino, I.L.C.; Passamani, E.C. [Departamento de Física, Universidade Federal do Espírito Santo, 29075-910 Vitória (Brazil); Alayo, W. [Departamento de Física, Universidade de Pelotas, 96010-610 Pelotas (Brazil); Tafur, M. [Instituto de Ciências Exatas, Universidade Federal de Itajubá, 37500-903 Itajubá (Brazil); Pelegrini, F. [Instituto de Física, Universidade Federal de Goiás, 74001-970 Goiânia (Brazil); Magalhães-Paniago, R. [Universidade Federal de Minas Gerais, Belo Horizonte (Brazil); Alvarenga, A.D. [Instituto Nacional de Metrologia, 25250-020 Xerém (Brazil); Saitovitch, E.B. [Coordenação de Física Experimental e Baixas Energias, Centro Brasileiro de Pesquisas Físicas, 22290-180 Rio de Janeiro (Brazil)
2013-09-02
NiFe(30 nm)/FeMn(13 nm)/NiFe(10 nm) heterostructures prepared by magnetron sputtering at different argon working pressures (0.27, 0.67 and 1.33 Pa) were systematically investigated by using specular and off-specular diffuse X-ray scattering experiments, combined with ferromagnetic resonance technique, in order to distinguish the contribution from roughness and atomic diffusion to the total structural disorder at NiFe/FeMn interfaces. It was shown that an increase in the working gas pressure from 0.27 to 1.33 Pa causes an enhancement of the atomic diffusion at the NiFe/FeMn interfaces, an effect more pronounced at the top FeMn/NiFe interface. In particular, this atomic diffusion provokes a formation of non-uniform magnetic dead-layers at the NiFe/FeMn interfaces (NiFeMn regions with paramagnetic or weak antiferromagnetic properties); that are responsible for the substantial reduction of the exchange bias field in the NiFe/FeMn system. Thus, this work generically helps to understand the discrepancies found in the literature regarding the influence of the interface broadening on the exchange bias properties (e.g., exchange bias field) of the NiFe/FeMn system. - Highlights: • Roughness and atomic diffusion contributions to the interface broadening • Clarification of the exchange bias field dependence on the interface disorder • Ferromagnetic, paramagnetic and antiferromagnetic phases at the magnetic interface • Magnetic dead layers formed by increasing the argon work pressure • Atomic diffusion in heterostructures prepared at higher argon pressure.
Magnetic structure and phase formation of magnetocaloric Mn-Fe-P-X compounds
Ou, Z.Q.
2013-01-01
This thesis presents a study of the crystal and magnetic structure, the magnetocaloric effect and related physical properties in Mn-Fe-P-X compounds. The influences of boron addition in (Mn,Fe)2(P,As) compounds have been studied. It is found that boron atoms occupy interstitial sites within the
Temperature dependence of diffuse satellites in Ti–(50 − x)Pd–xFe (14 ⩽ x ⩽ 20 (at.%)) alloys
International Nuclear Information System (INIS)
Todai, Mitsuharu; Fukuda, Takashi; Kakeshita, Tomoyuki
2014-01-01
Highlights: • Diffuse satellites of Ti–(50 − x)Pd–xFe alloys have been investigated. • Diffuse satellites appear at g B2 + 〈ζζ ¯ 0〉 * below T min . • The peak position of diffuse satellites at T min agree with the length of the nesting vector. • The present result implies that the nesting effect of Fermi surface originates diffuse satellites in Ti–(50 − x)Pd–xFe alloys. - Abstract: Diffuse satellites appearing in electron diffraction pattern of shape memory Ti–(50 − x)Pd–xFe (14, 16, 18, 19 and 20, in at.%) alloys have been investigated. The satellites appear in each alloy below T min , where its electrical resistivity shows a local minimum. The positions of satellites are g B2 + 〈ζ ζ ¯ 0〉 * , where g B2 is a reciprocal lattice vector of the B2-phase. The value of ζ is smaller than 1/5 at T min for all the alloys; it increases with decreasing temperature and decreases with increasing iron content. The value of ζ at T min agrees with the length of the nesting vector previously calculated by the present authors. This result implies that Fermi surface nesting is the origin of diffuse satellites in Ti–(50 − x)Pd–xFe alloys
Energy Technology Data Exchange (ETDEWEB)
Goltz, Til
2015-10-28
In this thesis, I study the electronic and structural phase diagrams of the superconducting 122 iron pnictides systems Ba{sub 1-x}K{sub x}(Fe{sub 1-y}Co{sub y}){sub 2}As{sub 2} and EuFe{sub 2}(As{sub 1-x}P{sub x}){sub 2} by means of the local probe techniques {sup 57}Fe Moessbauer spectroscopy (MS) and muon spin relaxation (μSR). For both isovalent substitution strategies - Co/K for Fe/Ba and P for As, respectively - the antiferromagnetic Fe ordering and orthorhombic distortion of the parent compounds BaFe{sub 2}As{sub 2} and EuFe{sub 2}As{sub 2} are subsequently suppressed with increasing chemical substitution and superconductivity arises, once long-range and coherent Fe magnetic order is sufficiently but not entirely suppressed. For Ba{sub 1-x}K{sub x}(Fe{sub 1-y}Co{sub y}){sub 2}As{sub 2} in the charge compensated state (x/2 ∼ y), a remarkably similar suppression of both, the orthorhombic distortion and Fe magnetic ordering, as a function of increasing substitution is observed and a linear relationship between the structural and the magnetic order parameter is found. Superconductivity is evidenced at intermediate substitution with a maximum T{sub SC} of 15 K coexisting with static magnetic order on a microscopic length scale. The appearance of superconductivity within the antiferromagnetic state can by explained by the introduction of disorder due to nonmagnetic impurities to a system with a constant charge carrier density. Within this model, the experimental findings are compatible with the predicted s{sup ±} pairing symmetry. For EuFe{sub 2}(As{sub 1-x}P{sub x}){sub 2}, the results from {sup 57}Fe MS and ZF-μSR reveal an intriguing interplay of the local Eu{sup 2+} magnetic moments and the itinerant magnetic Fe moments due to the competing structures of the iron and europium magnetic subsystems. For the investigated single crystals with x = 0.19 and 0.28, {sup 57}Fe MS evidences the interplay of Fe and Eu magnetism by the observation of a transferred
Ion-irradiation induced chemical ordering of FePt and FePtAu nanoparticles
Energy Technology Data Exchange (ETDEWEB)
Seetala, Naidu V. [Department of Physics, Grambling State University, RWE Jones Drive, Carver Hall 81, Grambling, LA 71245 (United States)]. E-mail: naidusv@gram.edu; Harrell, J.W. [MINT Center, University of Alabama, Tuscaloosa, AL 35487 (United States); Lawson, Jeremy [MINT Center, University of Alabama, Tuscaloosa, AL 35487 (United States); Nikles, David E. [MINT Center, University of Alabama, Tuscaloosa, AL 35487 (United States); Williams, John R. [Department of Physics, Auburn University, Auburn, AL 36849 (United States); Isaacs-Smith, Tamara [Department of Physics, Auburn University, Auburn, AL 36849 (United States)
2005-12-15
We have studied the effect of ion-beam irradiation on reducing the ordering temperature of FePt and FePtAu nanoparticles. FePt and FePt(Au14%) 4 nm particles dispersed on a Si-substrate were irradiated by 300 keV Al-ions with a dose of 1 x 10{sup 16} ions/cm{sup 2} at 43 {sup o}C using a water-cooled flange in order to minimize the vacancy migration and voids formation within the collision cascades. Partial chemical ordering has been observed in as-irradiated particles with coercivity of 60-130 Oe. Post-irradiation annealing at 220 {sup o}C enhanced chemical ordering in FePt nanoparticles with coercivity of 3500 Oe, magnetic anisotropy of 1.5 x 10{sup 7} erg/cc, and thermal stability factor of 130. A much higher 375 {sup o}C post-irradiation annealing was required in FePtAu, presumably because Au atoms were trapped at Fe/Pt lattice sites at lower temperatures. As the annealing temperature increased, anomalous features in the magnetization reversal curves were observed that disappeared at higher annealing temperatures.
Electron microscopy and diffraction of barium-lanthanum ferrites: Ba/sub x/La/sub 1-x/FeO/sub 3-y/
Energy Technology Data Exchange (ETDEWEB)
Parras, M.; Vallet-Regi, M.; Gonzalez-Calbet, J.M.; Alario-Franco, M.; Grenier, J.C.
1988-05-01
The system formed by Ba/sub 2/Fe/sub 2/O/sub 5/ and LaFeO/sub 3/ has been studied at the microstructural level. Four different phases, which are metrical multiples of the perovskite cubic cell, appear as a function of the Ba/La ratio. Their microstructure ranges from three-dimensional multitwinning, as in LaFeO/sub 3/, to an apparently stoichiometric line phase of Ba/sub 2/Fe/sub 2/O/sub 5/ composition with parameters a = 23.40(1) A, b = 11.71(1) A, c = 7.05(1) A, and ..beta.. = 98/sup 0/3(1)'. For 0 < x < 0.25, cubic regions appear within a LaFeO/sub 3/ matrix. When x = 0.33, a double perovskite cell is intergrown with a single one. Such a single cubic perovskite is the only phase obtained in the 0.33 < x < 0.66 range.
Crystal growth and characterization of CeFe{sub 1-x}Ru{sub x} PO
Energy Technology Data Exchange (ETDEWEB)
Balle, Tanita; Kliemt, Kristin; Krellner, Cornelius [Goethe Universitaet Frankfurt, Kristall- und Materiallabor (Germany)
2016-07-01
CeRuPO is a one of the few heavy fermion systems, which order ferromagnetically at low temperatures (T{sub C} = 15 K), because of dominant RKKY-interaction. CeFePO on the other hand shows no long-range magnetic order even at low temperatures because of dominant Kondo effect (T{sub K} = 10 K). By substituting CeFePO with ruthenium we can reach a quantum critical point, at which the RKKY-interaction and the Kondo effect are equally strong. To study the quantum critical point, and to enlighten the question if the order stays ferromagnetically down to lowest temperatures, high quality crystals are needed. Here, the growth and characterization of the single crystals will be discussed. We obtained mm-sized single crystals of the unsubstituted CeRuPO and CeFePO by a modified Bridgeman method using tin as a flux. The quality of the crystals was verified by Powder-X-Ray-Diffraction, energy dispersive X-ray spectroscopy and Laue backscattering.
Properties of half metallic (Ba0.8Sr0.2)2-x La2x/3x/3FeMoO6 double perovskites
International Nuclear Information System (INIS)
Serrate, D.; De Teresa, J.M.; Blasco, J.; Morellon, L.; Ibarra, M.R.
2005-01-01
Previous work in (Ba 0.8 Sr 0.2 ) 2- x La x FeMoO 6 and Ba 1+ x Sr 1-3 x La 2 x FeMoO 6 have stated electron doping as the most important parameter in terms of T c enhancement. Here we report complementary structural, magnetic and transport properties, say a series where there is no doping and only structural parameters are changed: (Ba 0.8 Sr 0.2 ) 2- x La 2 x /3 x /3 FeMoO 6 . We propose a complete phase diagram where structural and bandfilling impact on the Curie temperature is clearly evidenced
Magnetic-entropy change in Mn1.1Fe0.9P0.7As0.3-xGe x
International Nuclear Information System (INIS)
Tegus, O.; Fuquan, B.; Dagula, W.; Zhang, L.; Brueck, E.; Si, P.Z.; Boer, F.R. de; Buschow, K.H.J.
2005-01-01
We have studied the magnetic properties and magnetic-entropy changes of Mn 1.1 Fe 0.9 P 0.7 As 0.3-x Ge x compounds with x = 0, 0.05, 0.1, 0.15 and 0.3. X-ray diffraction (XRD) study shows all the compounds crystallize in the Fe 2 P-type structure. Magnetic measurements show that the Curie temperature increases from 150 K for Mn 1.1 Fe 0.9 P 0.7 As 0.3 to 380 K for Mn 1.1 Fe 0.9 P 0.7 Ge 0.3 . A field-induced first-order magnetic phase transition is observed above the Curie temperature for the compounds with x up to 0.15. There exists an optimal composition in which the first-order phase transition is the sharpest. The optimal composition for this system is x = 0.1. The maximal magnetic-entropy change derived from the magnetization data is about 40 J/(kg K) for a field change from 0 to 3 T
Structure and electrical conduction of the system La sub(1-x)Ca sub(x)FeO sub(3-α)
International Nuclear Information System (INIS)
Hombo, Jukichi; Urabe, Noriake; Hiroshige, Gota; Hamada, Kotaro.
1982-01-01
Perovskite phases in the system, La sub(1-x)Ca sub(x)FeO sub(3-α) were prepared with La 2 O 3 , CaCO 3 , and Fe 2 O 3 by firing in air and in vacuo. The compositions of samples fired in vacuo and in air are represented as La sub(1-x)Ca sub(x)FeO sub(3-x 2) and La sub(1-x)Ca sub(x)Fe sub(1-y)sup(3+)Fe sub(y)sup(4+)O sub(3-x/2+y/2), respectively. That is, samples fired in vacuo contain some oxygen vacancies and no tetravalent iron; in contrast, samples fired in air contain both oxygen vacancies and tetravalent iron in the structures. The electrical conductivities of these synthesized oxides depended extensively upon the content of tetravalent iron. For instance, the conductivity of the sample x = 0.6 fired in air was larger by 10 6 than that of the sample fired in vacuo. In this system, except for the two terminal compositions of x = 0 and x = 1.0, the values of activation energy for conduction are considerably small, and from the results of thermo-electromotive force measurement, the charge carrier was positive. Furthermore, the conductivity increased somewhat with time during the conductivity measurement by the direct-current method. These facts suggest that the electrical conducted would not be ionic but electronic. The electrical conduction would then be carried out by the so-called hopping mechanism by which the positive charge is transferred. (author)
Superconductivity induced by doping Rh in CaFe2-xRhxAs2
International Nuclear Information System (INIS)
Qi Yanpeng; Wang Lei; Gao Zhaoshun; Wang Dongliang; Zhang Xianping; Wang Chunlei; Yao Chao; Ma Yanwei
2011-01-01
In this paper, we report the synthesis of iron-based superconductors CaFe 2-x Rh x As 2 using a one-step solid state reaction method that crystallizes in the ThCr 2 Si 2 -type structure with a space group I4/mmm. The systematic evolution of the lattice constants demonstrates that the Fe ions are successfully replaced by the Rh. By increasing the doping content of Rh, the spin-density-wave (SDW) transition in the parent compound is suppressed and superconductivity emerges. The maximum superconducting transition temperature is found at 18.5 K with a doping level of x=0.15. The temperature dependence of dc magnetization confirms superconducting transitions at around 15 K. The general phase diagram was obtained and found to be similar to the case of the Rh-doping Sr122 system. Our results explicitly demonstrate the feasibility of inducing superconductivity in Ca122 compounds by higher d-orbital electron doping; however, different Rh-doping effects between FeAs122 compounds and FeAs1111 systems still remains an open question.
Differential effects of x-rays and high-energy 56Fe ions on human mesenchymal stem cells.
Kurpinski, Kyle; Jang, Deok-Jin; Bhattacharya, Sanchita; Rydberg, Bjorn; Chu, Julia; So, Joanna; Wyrobek, Andy; Li, Song; Wang, Daojing
2009-03-01
Stem cells hold great potential for regenerative medicine, but they have also been implicated in cancer and aging. How different kinds of ionizing radiation affect stem cell biology remains unexplored. This study was designed to compare the biological effects of X-rays and of high-linear energy transfer (LET) (56)Fe ions on human mesenchymal stem cells (hMSC). A multi-functional comparison was carried out to investigate the differential effects of X-rays and (56)Fe ions on hMSC. The end points included modulation of key markers such as p53, cell cycle progression, osteogenic differentiation, and pathway and networks through transcriptomic profiling and bioinformatics analysis. X-rays and (56)Fe ions differentially inhibited the cell cycle progression of hMSC in a p53-dependent manner without impairing their in vitro osteogenic differentiation process. Pathway and network analyses revealed that cytoskeleton and receptor signaling were uniquely enriched for low-dose (0.1 Gy) X-rays. In contrast, DNA/RNA metabolism and cell cycle regulation were enriched for high-dose (1 Gy) X-rays and (56)Fe ions, with more significant effects from (56)Fe ions. Specifically, DNA replication, DNA strand elongation, and DNA binding/transferase activity were perturbed more severely by 1 Gy (56)Fe ions than by 1 Gy X-rays, consistent with the significant G2/M arrest for the former while not for the latter. (56)Fe ions exert more significant effects on hMSC than X-rays. Since hMSC are the progenitors of osteoblasts in vivo, this study provides new mechanistic understandings of the relative health risks associated with low- and high-dose X-rays and high-LET space radiation.
Epitaxial Fe{sub 3-x}Ti{sub x}O{sub 4} films from magnetite to ulvöspinel by pulsed laser deposition
Energy Technology Data Exchange (ETDEWEB)
Droubay, T.C.; Pearce, C.I.; Ilton, E.S.; Engelhard, M.H.; Engelhard, M.H.; Heald, S.M.; Arenholz, E.; Rosso, K.M.
2011-07-21
Epitaxial films along the Fe{sub 3-x}Ti{sub x}O{sub 4} (titanomagnetite) compositional series from pure end-members magnetite (Fe{sub 3}O{sub 4}) to ulvöspinel (Fe{sub 2}TiO{sub 4}) were successfully grown by pulsed laser deposition on MgO(100) substrates. Spectroscopic characterization including high resolution x-ray diffraction, x-ray photoelectron spectroscopy, and synchrotron-based x-ray absorption and magnetic circular dichroism consistently shows that Ti(IV) substitutes for Fe(III) in the inverse spinel lattice with a proportional increase in lattice Fe(II) concentration. No evidence of Ti interstitials, spinodal decomposition, or secondary phases was found in the bulk of the grown films. At the uppermost few nanometers of the Ti-bearing film surfaces, evidence suggests that Fe(II) is susceptible to facile oxidation, and that an associated lower Fe/Ti ratio in this region is consistent with surface compositional incompleteness or alteration to a titanomaghemite-like composition and structure. The surface of these films nonetheless appear to remain highly ordered and commensurate with the underlying structure despite facile oxidation, a surface condition that is found to be reversible to some extent by heating in low oxygen environments.
Preparation of nanocrystalline Ce1-xSmx(Fe,Co)11Ti by melt spinning and mechanical alloying
Wuest, H.; Bommer, L.; Huber, A. M.; Goll, D.; Weissgaerber, T.; Kieback, B.
2017-04-01
Permanent magnetic materials based on Ce(Fe, Co)12-xTix with the ThMn12 structure are promising candidates for replacing NdFeB magnets. Its intrinsic magnetic properties are not far below the values of Nd2Fe14B, and the high amount of Fe and the fact that Ce is much more abundant and less expensive than Nd encourages the reasonable interest in these compounds. Nanocrystalline magnetic material of the composition Ce1-xSmxFe11-yCoyTi (x=0-1 and y=0; 1.95) has been produced by both melt spinning and mechanical alloying. Alloys containing only Ce as rare earth element (x=0) show coercivities below 77 kA/m, while for x=1 Hc,J values up to 392 kA/m are reached. Coercivity shows rather an exponential than a linear dependence on the gradual substitution of Ce by Sm.
Energy Technology Data Exchange (ETDEWEB)
Ponzoni, C. [Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Modena 42025 (Italy); Cannio, M., E-mail: maria.cannio@unimore.it [Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Modena 42025 (Italy); Boccaccini, D.N.; Bahl, C.R.H.; Agersted, K. [Department of Energy Conversion and Storage, Technical University of Denmark Frederiksborgvej, 4000 Roskilde (Denmark); Leonelli, C. [Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Modena 42025 (Italy)
2015-07-15
In this work a microwave assisted hydrothermal method is applied to successfully synthesize lanthanum doped bismuth ferrites (BLFO, Bi{sub 1−x}La{sub x}FeO{sub 3} where x = 0, 0.15, 0.30 and 0.45). The growth mechanism of the Bi{sub 1−x}La{sub x}FeO{sub 3} crystallites is discussed in detail. The existence of the single-phase perovskite structure for all the doped samples is confirmed by the X-ray powder diffraction patterns. A peak shift, observed at lower angle with increasing La doping concentration, indicates that the BiFeO{sub 3} lattice is doped. The results of TG/DTA show a shift in the transition temperature from 805 °C to 815 °C as function of the La-doping for all the doped powders. At higher levels of La doping, i.e. x = 0.30 and 0.45, significant weight losses occur above 860 °C suggesting a change in the physical and chemical properties. Finally, magnetic measurements are carried out at room temperature for pure BiFeO{sub 3} and Bi{sub 0.85}La{sub 0.15}FeO{sub 3}. The results indicate that the materials are both weakly ferromagnetic, with no significant hysteresis in the curves. - Graphical abstract: Display Omitted - Highlights: • MW hydrothermal method applied to synthesize Bi{sub 1−x}La{sub x}FeO{sub 3}, x = 0, 0.15, 0.30, 0.45. • A single-phase perovskite structure for all the samples was confirmed by XRD. • A T{sub c} shift in La doped BiFeO{sub 3} DTA was observed as function of the La-doping. • Magnetic measurements indicate that the materials are weakly ferromagnetic.
Fe/Rh (100) multilayer magnetism probed by x-ray magnetic circular dichroism
Tomaz, M. A.; Ingram, D. C.; Harp, G. R.; Lederman, D.; Mayo, E.; O'brien, W. L.
1997-09-01
We report the layer-averaged magnetic moments of both Fe and Rh in sputtered Fe/Rh (100) multilayer thin films as measured by x-ray magnetic circular dichroism. We observe two distinct regimes in these films. The first is characterized by Rh moments of at least 1μB, Fe moments enhanced as much as 30% above bulk, and a bct crystal structure. The second regime is distinguished by sharp declines of both Fe and Rh moments accompanied by a transition to an fct crystal lattice. The demarcation between the two regions is identified as the layer thickness for which both bct and fct phases first coexist, which we term the critical thickness tcrit. We attribute the change in magnetic behavior to the structural transformation.
Energy Technology Data Exchange (ETDEWEB)
Volkov, N.V. [Kirensky Institute of Physics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036 (Russian Federation); Eremin, E.V., E-mail: eev@iph.krasn.ru [Kirensky Institute of Physics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036 (Russian Federation); Bayukov, O.A.; Sablina, K.A. [Kirensky Institute of Physics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036 (Russian Federation); Solov’ev, L.A. [Institute of Chemistry and Chemical Technology, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660049 (Russian Federation); Velikanov, D.A.; Mikhashenok, N.V.; Osetrov, E.I. [Kirensky Institute of Physics, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk 660036 (Russian Federation); Schefer, J.; Keller, L. [Laboratory for Neutron Scattering, ETH Zurich and Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Boehm, M. [Institut Laue-Langevin, 6 rue Jules Horowitz, BP 156, 38042 Grenoble, Cedex 9 (France)
2013-09-15
Structure and magnetic properties of Pb{sub 3}(Mn{sub 1−x}Fe{sub x}){sub 7}O{sub 15} single crystals with x=0–0.2 grown by spontaneous crystallization from solution in melt have been investigated. All the crystals belong to the hexagonal space group P6{sub 3}/mcm. The magnetic properties appeared to be strongly dependent on the iron doping level. At small (x=0.05) dopant concentrations, the value of magnetization and Neel temperature T{sub N} decrease insignificantly (T{sub N}=70 K). With increasing x, the three-dimensional magnetic ordering does not occur and temperature dependences of magnetization at x≥0.1 exhibit spin-glass-like features in the low-temperature region. - Highlights: • In the first time the single crystals of Pb{sub 3}(Mn{sub 1−x}Fe{sub x}){sub 7}O{sub 15} were grown. • The valence and locations of iron ions in crystal were determined. • Suppression of the long-range magnetic order in Pb{sub 3}(Mn{sub 1−x}Fe{sub x}){sub 7}O{sub 15} was discovered.
Investigations on the parent compounds of Fe-chalcogenide superconductors
International Nuclear Information System (INIS)
Koz, Cevriye
2015-01-01
This work is focused on the parent compounds of the Fe-chalcogenide superconductors. For this purpose poly- and single-crystalline forms of tetragonal β-Fe x Se, Fe 1+y Te, Fe 1+y Te 1-x Se x and Fe (1+y)-x M x Te (M = Ni, Co) have been prepared. Second focal points of this study are the low-temperature structural phase transitions and physical property changes in tetragonal Fe 1+y Te which are induced by composition, external pressure, and cationic substitution.
Electrochemical vs X-ray Spectroscopic Measurements of NiFe(CN)6 Crystals
Peecher, Benjamin; Hampton, Jennifer
Pseudocapacitive materials like hexacyanoferrate have greater energy storage capabilities than standard capacitors while maintaining an ability to charge and discharge quickly. We modify the surface of an electrodeposited Ni thin film with a layer of hexacyanoferrate. Charging and discharging these modified films using cyclic voltammetry (CV) allows us to measure the electrochemically active Fe in the film. To determine how closely this resembles the full amount of Fe in the film, we measure the films' composition using particle-induced x-ray emission (PIXE). We also vary the amount of Ni deposited, both to compare the electrolysis value of charge deposited to the PIXE measurement of Ni in the film, and also to measure how varying the thickness of the Ni surface affects the presence of Fe in the film. Comparisons of the CV and PIXE measurements show agreement in Ni levels but disagreement in Fe levels. PIXE measurements of Fe in the film have positive correlation with Ni in the film. This correlation between PIXE measurements of Ni and Fe suggests that PIXE provides a reliable measure of Fe in the film. This implies that a variable proportion of total Fe in a given film is electrochemically active. This research was made possible by the Hope College Department of Physics Frissel Research Fund and the National Science Foundation under Grants RUI-DMR-1104725, MRI-CHE-0959282, and MRI/RUI-PHY-0319523.
Short-range order in Fe-based metallic glasses: Wide-angle X-ray scattering studies
International Nuclear Information System (INIS)
Babilas, Rafał; Hawełek, Łukasz; Burian, Andrzej
2014-01-01
The local atomic structure of the Fe 80 B 20 , Fe 70 Nb 10 B 20 and Fe 62 Nb 8 B 30 glasses prepared in the form of ribbons has been studied by wide-angle X-ray scattering. Structural information about the amorphous ribbons has been derived from analysis of the radial distribution functions using the least-squares curve-fitting method. The obtained structural parameters indicate that Fe–Fe, Fe–B, Fe–Nb and Nb–B contributions are involved in the near-neighbor coordination spheres. The possible similarities of the local atomic arrangement in the investigated glasses and the crystalline Fe 3 B, Fe 23 B 6 and bcc Fe structures are also discussed. - Graphical abstract: Pair distribution functions (a) and best-fit model and experimental radial distribution functions for Fe 80 B 20 (b), Fe 70 Nb 10 B 20 (c) and Fe 62 Nb 8 B 30 (d) metallic glasses. - Highlights: • The short-range ordering in the Fe-based metallic glasses is presented. • The results of RDF function have been analyzed using the least-squares method. • The Fe–Fe, Fe–B, Fe–Nb or Nb–B contributions are involved in coordination spheres. • The structural unit is distorted triangular prism containing B, Fe or Nb atoms. • Similarities of atomic arrangement in glassy and crystalline structures are discussed
Energy Technology Data Exchange (ETDEWEB)
Zhang, Jin Na [College of Chemistry and Materials Science, Liaoning University of Petroleum and Chemical Technology, Fushun 113001 (China); State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Lu, Hui, E-mail: huilu@dicp.ac.cn [Greenhouse Gas Research Center, Climate Change Technology Research Division, Korea Institute of Energy Research, Daejeon 305-343 (Korea, Republic of); State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China); Gui, Jian Zhou [College of Chemistry and Materials Science, Liaoning University of Petroleum and Chemical Technology, Fushun 113001 (China); Kim, Jong Pyo; Son, Sou Hwan [Greenhouse Gas Research Center, Climate Change Technology Research Division, Korea Institute of Energy Research, Daejeon 305-343 (Korea, Republic of); Park, Jung Hoon, E-mail: pjhoon@kier.re.kr [Greenhouse Gas Research Center, Climate Change Technology Research Division, Korea Institute of Energy Research, Daejeon 305-343 (Korea, Republic of)
2013-04-20
Highlights: ► The novel Fe/Nb co-substituted SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.05, 0.10) oxides were characterized by the XRD, DSC, TG and SEM–EDS. ► The high structural stability of the co-substituted SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.05, 0.10) oxides. ► The excellent oxygen permeation performance of the co-substituted SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.10) membrane. -- Abstract: The novel Fe/Nb co-substituted SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.05, 0.10) oxides have been synthesized and characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TG), and scanning electron microscopy (SEM). The XRD and DSC results demonstrate that the structural stability of the Fe/Nb co-substituted samples x = 0.05, 0.10 is improved greatly compared to the sample x = 0.00. The Fe/Nb co-doping in the SrCoO{sub 3−δ} oxide results in the improved structural stability of the SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.05, 0.10) oxides. The nonstoichiometric and sintering properties were investigated by TG and SEM, and the oxygen permeation fluxes were measured at 800–950 °C for the sample x = 0.10. The improved oxygen permeability of the ceramic SrCo{sub 1−2x}(Fe,Nb){sub x}O{sub 3−δ} (x = 0.10) membrane compared to the (Ba{sub 0.5}Sr{sub 0.5})(Co{sub 0.8}Fe{sub 0.2})O{sub 3−δ} and SrCo{sub 0.8}Fe{sub 0.2}O{sub 3–δ} membranes, was observed under an air/He oxygen partial pressure gradient at 800–950 °C.
Energy Technology Data Exchange (ETDEWEB)
Falcao, R.B.; Dammann, E.D.C.C.; Rocha, C.J.; Leal Neto, R.M., E-mail: railson.falcao@usp.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Ciencias e Tecnologia de Materiais. Lab. de Intermetalicos
2010-07-01
In this work TiFe compound was obtained by two process routes involving high-energy ball milling: mechanical alloying from Ti and Fe powders (route 1) and mechanical milling from TiH{sub 2} and Fe powders, both followed by an annealing heat treatment. Shaker and planetary ball mills were utilized for times varying from 1-25 hours. Milled and annealed powders were characterized by SEM and X-ray diffraction analyses. TiFe compound was formed in both routes. A strong powder adherence in the milling vial and balls occurred with route 1 in both mills. Powder adherence was significantly reduced by using TiH{sub 2} (route 2) mainly in the planetary mill, in spite of TiFe formation has only occurred after the annealing treatment. (author)
Magnetic properties and magnetocaloric effects in Mn1.2Fe0.8P1-xGex compounds
International Nuclear Information System (INIS)
Ou, Z Q; Wang, G F; Lin Song; Tegus, O; Brueck, E; Buschow, K H J
2006-01-01
We have studied the magnetic properties and magnetocaloric effects in the Mn 1.2 Fe 0.8 P 1-x Ge x compounds with x = 0.2, 0.22, 0.3, 0.4 and 0.5. X-ray diffraction patterns show that the Mn 1.2 Fe 0.8 P 1-x Ge x compounds crystallize in the hexagonal Fe 2 P-type crystal structure. The magnetic moments of the Mn 1.2 Fe 0.8 P 1-x Ge x compounds measured at 5 K and 5 T increase with increasing Ge content. The Curie temperature increases strongly and the magnetic entropy change has a maximum around 233 K for the compound with x = 0.22, which is about 19 and 31 J kg -1 K -1 for a field change of 2 and 5 T, respectively
A study of nitrogenation of a NdFe12-xMox compound by in situ neutron powder diffraction
International Nuclear Information System (INIS)
Loong, C.; Short, S.M.; Lin, J.; Ding, Y.
1998-01-01
The effects on the crystal lattice of a NdFe 12-x Mo x (x congruent 1.7) during controlled nitrogenation over the 25 endash 600 degree C temperature range were studied by neutron powder diffraction. Prior to nitrogenation the sample contained a major phase of NdFe 10.3 Mo 1.7 and a minor phase (∼12vol%) of bcc-Fe. The sample inside the furnace was connected to a closed volume of ultrapure nitrogen gas while neutron data were collected over regular time intervals during sequential heating. Substantial nitrogen absorption occurred between 500 and 600 degree C. During the nitrogenation process the NdFe 12-x Mo x N y lattice expanded while the bcc-Fe lattice contracted. An increasing decomposition of the compound into bcc-Fe at 600 degree C was observed. The average size of the NdFe 12-x Mo x N y crystalline grains decreased starting at ∼300 degree C, reaching a minimum at ∼500 degree C and then increased markedly at higher temperatures. The development of lattice strains, on the other hand, showed an opposite trend, i.e., a maximum at 500 degree C. copyright 1998 American Institute of Physics
What is the correct Fe L{sub 23} X-ray absorption spectrum of magnetite?
Energy Technology Data Exchange (ETDEWEB)
Zhu, Xiaohui; Kalirai, Samanbir S. [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON L8S 4M1 (Canada); Hitchcock, Adam P., E-mail: aph@mcmaster.ca [Department of Chemistry and Chemical Biology, McMaster University, Hamilton, ON L8S 4M1 (Canada); Bazylinski, Dennis A. [School of Life Sciences, University of Nevada at Las Vegas, Las Vegas, NV 89154-4004 (United States)
2015-02-15
Highlights: • Fe L{sub 3} X-ray absorption spectra of biological (MV-1 magnetotactic bacteria) and abiotic (Sigma–Aldrich) nano-magnetite are reported. • An inconsistency in the literature for this spectrum is documented. • Powder diffraction shows the abiotic sample is partly oxidized, toward maghemite. • H{sub 2} thermal reduction converts the Fe L{sub 3} spectrum of the abiotic sample to that of the biotic. • Strong oxidation (air, 600 °C) is needed to convert the spectrum of the biotic magnetite to that of maghemite; magnetosome chains are protected by an air-impervious membrane. - Abstract: Various groups have reported Fe L{sub 23} X-ray absorption spectra (XAS) of magnetite (Fe{sub 3}O{sub 4}), each claiming to be that of magnetite, but which contradict each other. Here we report an XAS study of two kinds of magnetite: one is biogenic magnetite nanocrystals extracted from the magnetotactic bacterium Magnetovibrio blakemorei strain MV-1; the other is synthetic, abiogenically produced nano-magnetite. We see significantly different XAS spectra of these two materials. Only when the abiogenic magnetite was reduced under H{sub 2} did it give the same spectrum as the biogenic sample. Extensive heating of the biogenic magnetite in air produced spectra similar to that of the abiogenic magnetite. These two spectra are typical of the range of published Fe L{sub 23} spectra of magnetite. X-ray diffraction confirmed that the biogenic material is stoichiometric Fe{sub 3}O{sub 4}, and showed that the as-received or partly reduced abiogenic material is a non-stoichiometric oxide, intermediate between magnetite and maghemite (γ-Fe{sub 2}O{sub 3}). When the membrane which surrounds magnetosome chains was intact, the biotic magnetite single crystals were surprisingly resistant to oxidation. This study clarifies a significant confusion existing in the literature as to the correct Fe L{sub 23} X-ray absorption spectra of magnetite and maghemite.
Microstructure and Room-Temperature Mechanical Properties of FeCrMoVTi x High-Entropy Alloys
Guo, Jun; Huang, Xuefei; Huang, Weigang
2017-07-01
FeCrMoVTi x ( x values represent the molar ratio, where x = 0, 0.5, 1.0, 1.5, and 2.0) high-entropy alloys were prepared by a vacuum arc melting method. The effects of Ti element on the microstructure and room-temperature mechanical properties of the as-cast FeCrMoVTi x alloys were investigated. The results show that the prepared alloys exhibited typical dendritic microstructure and the size of the microstructure became fine with increasing Ti content. The FeCrMoV alloy exhibited a single body-centered cubic structure (BCC1) and the alloys prepared with Ti element exhibited BCC1 + BCC2 mixed structure. The new BCC2 phase is considered as (Fe, Ti)-rich phase and was distributed in the dendrite region. With the increase of Ti content, the volume fraction of the BCC2 phase increased and its shape changed from a long strip to a network. For the FeCrMoV alloy, the fracture strength, plastic strain, and hardness reached as high as 2231 MPa, 28.2%, and 720 HV, respectively. The maximum hardness of 887 HV was obtained in the FeCrMoVTi alloy. However, the fracture strength, yield stress, and plastic strain of the alloys decreased continuously as Ti content increased. In the room-temperature compressive test, the alloys showed typical brittle fracture characteristics.
Síntesis de nanocomposites NTC-13%ZrO2 – (87-xAl2O3-xFe
Directory of Open Access Journals (Sweden)
Legorreta García, F.
2014-04-01
Full Text Available Carbon nanotubes (CNT in a ceramic matrix – Fe, NTC-13%ZrO2 – (87-xAl2O3-xFe, (x = 1.9, 4.6 y 6.4%, were obtained using a combustion synthesis urea-nitrate, calcination treatment and chemical vapor deposition (CCVD in H2-CH4 atmosphere. The effect of the addition of Fe ions on the ceramic matrix was studied and presented. The ceramic powder obtained was calcined at 1200 °C for 2 h to modify the phases present in the solid solution. Subsequently it was introduced in a H2-CH4 reducing atmosphere at 1000 °C in order to promote the formation of CNT in the matrix. Both, the solid solution obtained and the composite materials were characterized by X-ray diffraction (XRD and high resolution scanning electron microscopy (HRSEM. Carbon content and specific surface also were determined. The quality and quantity of CNT present in the nanocomposite powder were related to the concentration of Fe, which significantly modifies their carbon content and specific surface.Mediante una síntesis por combustión ureica-nitratos, calcinación y la aplicación de un tratamiento de deposición química catalítica de vapor (CCVD en una atmósfera H2-CH4, se obtuvieron polvos nanocomposites: nanotubos de carbono (NTC en una matriz cerámica –Fe, NTC-13%ZrO2 – (87-xAl2O3-xFe, (x = 1.9, 4.6 y 6.4 %. El efecto de la adición de iones Fe sobre la matriz cerámica es estudiado y presentado. El polvo cerámico obtenido es calcinado a 1200 °C durante 2 h para modificar las fases presentes del composite. Posteriormente es sometido a una atmósfera reductora H2-CH4 a 1000 °C con la finalidad de promover la formación de NTC in situ en la matriz. Tanto el composite obtenido, como el material nanocomposite fueron caracterizados por difracción de rayos X (DRX y microscopía electrónica de barrido de alta resolución (MEB. También se determinó el contenido de carbono y la superficie específica. Se observó que la calidad y cantidad de NTC presentes en los polvos
Structural, Raman, and dielectric studies on multiferroic Mn-doped Bi 1-xLax FeO 3 ceramics
Xing, Zhibiao
2014-04-03
Multiferroic Bi1-xLaxFeO3 [BLFO (x)] ceramics with x = 0.10-0.50 and Mn-doped BLFO (x = 0.30) ceramics with different doping contents (0.1-1.0 mol%) were prepared by solid-state reaction method. They were crystallized in a perovskite phase with rhombohedral symmetry. In the BLFO (x) system, a composition (x)-driven structural transformation (R3c→C222) was observed at x = 0.30. The formation of Bi2Fe 4O9 impure phase was effectively suppressed with increasing the x value, and the rhombohedral distortion in the BLFO ceramics was decreased, leading to some Raman active modes disappeared. A significant red frequency shift (~13 cm-1) of the Raman mode of 232 cm-1 in the BLFO ceramics was observed, which strongly perceived a significant destabilization in the octahedral oxygen chains, and in turn affected the local FeO6 octahedral environment. In the Mn-doped BLFO (x = 0.30) ceramics, the intensity of the Raman mode near 628 cm-1 was increased with increasing the Mn-doping content, which was resulted from an enhanced local Jahn-Teller distortions of the (Mn,Fe)O6 octahedra. Electron microscopy images revealed some changes in the ceramic grain sizes and their morphologies in the Mn-doped samples at different contents. Wedge-shaped 71° ferroelectric domains with domain walls lying on the {110} planes were observed in the BLFO (x = 0.30) ceramics, whereas in the 1.0 mol% Mn-doped BLFO (x = 0.30) samples, 71° ferroelectric domains exhibited a parallel band-shaped morphology with average domain width of 95 nm. Dielectric studies revealed that high dielectric loss of the BLFO (x = 0.30) ceramics was drastically reduced from 0.8 to 0.01 (measured @ 104 Hz) via 1.0 mol% Mn-doping. The underlying mechanisms can be understood by a charge disproportion between the Mn4+ and Fe2+ in the Mn-doped samples, where a reaction of Mn4+ + Fe2+→Mn3+ + Fe3+ is taken place, resulting in the reduction in the oxygen vacancies and a suppression of the electron hopping from Fe3+ to Fe2+ ions
Structural, Raman, and dielectric studies on multiferroic Mn-doped Bi 1-xLax FeO 3 ceramics
Xing, Zhibiao; Zhu, Xinhua; Zhu, Jianmin; Liu, Zhiguo; Al-Kassab, Talaat
2014-01-01
Multiferroic Bi1-xLaxFeO3 [BLFO (x)] ceramics with x = 0.10-0.50 and Mn-doped BLFO (x = 0.30) ceramics with different doping contents (0.1-1.0 mol%) were prepared by solid-state reaction method. They were crystallized in a perovskite phase with rhombohedral symmetry. In the BLFO (x) system, a composition (x)-driven structural transformation (R3c→C222) was observed at x = 0.30. The formation of Bi2Fe 4O9 impure phase was effectively suppressed with increasing the x value, and the rhombohedral distortion in the BLFO ceramics was decreased, leading to some Raman active modes disappeared. A significant red frequency shift (~13 cm-1) of the Raman mode of 232 cm-1 in the BLFO ceramics was observed, which strongly perceived a significant destabilization in the octahedral oxygen chains, and in turn affected the local FeO6 octahedral environment. In the Mn-doped BLFO (x = 0.30) ceramics, the intensity of the Raman mode near 628 cm-1 was increased with increasing the Mn-doping content, which was resulted from an enhanced local Jahn-Teller distortions of the (Mn,Fe)O6 octahedra. Electron microscopy images revealed some changes in the ceramic grain sizes and their morphologies in the Mn-doped samples at different contents. Wedge-shaped 71° ferroelectric domains with domain walls lying on the {110} planes were observed in the BLFO (x = 0.30) ceramics, whereas in the 1.0 mol% Mn-doped BLFO (x = 0.30) samples, 71° ferroelectric domains exhibited a parallel band-shaped morphology with average domain width of 95 nm. Dielectric studies revealed that high dielectric loss of the BLFO (x = 0.30) ceramics was drastically reduced from 0.8 to 0.01 (measured @ 104 Hz) via 1.0 mol% Mn-doping. The underlying mechanisms can be understood by a charge disproportion between the Mn4+ and Fe2+ in the Mn-doped samples, where a reaction of Mn4+ + Fe2+→Mn3+ + Fe3+ is taken place, resulting in the reduction in the oxygen vacancies and a suppression of the electron hopping from Fe3+ to Fe2+ ions
Gabay, A. M.; Hadjipanayis, G. C.
2018-05-01
Recently, Fe-based rare-earth-free compounds with non-cubic crystal structures were proposed as a base for permanent magnets which would not rely on critical elements. In this work, two series of alloys, Zr27Fe73-wSiw (0 ≤ w ≤ 15) and Zr33-xFe52+xSi15 (0 ≤ x ≤ 11), were prepared and characterized after annealing at 1538 K in order to determine the fundamental magnetic properties of the C36 and C14 hexagonal Laves phase compounds. A mixture of the cubic C15 and Zr6Fe23 structures was observed instead of the expected C36 structure. The hexagonal C14 was found in all Zr33-xFe52+xSi15 alloys with its lattice parameters linearly decreasing as the Fe(Si) atoms occupy the Zr sites in the Laves phase crystal structure. The solubility limit of Fe in the C14 structure at 1538 K corresponds to x = 9.5. The Curie temperature of the C14 compounds increases with deviation from the Laves phase stoichiometry from 290 K to 530 K. The room-temperature spontaneous magnetization also increases reaching, after correcting for the non-magnetic impurities, a value of 6.7 kG. The magnetocrystalline anisotropy of the off-stoichiometric C14 Laves phase was found to be uniaxial with the easy magnetization direction parallel to the hexagonal axis. Unfortunately, the anisotropy field, which does not exceed 10 kOe, is not sufficiently high to make the compounds interesting as permanent magnet materials.
Fe site occupancy and superconductivity in Y1-zCazBaz(Cu1-xFex)3O6+y
International Nuclear Information System (INIS)
Smith, M.G.; Taylor, R.D.; Oesterreicher, H.
1990-01-01
X-ray diffraction and 57 Fe Moessbauer spectroscopy studies show that partial substitution of Ca for Y in Y 1-z Ca z Ba 2 (Cu 1-x Fe x ) 3 O 6+y (0.05 ≤ z ≤ 0.15,0.003 ≤ x ≤ 0.20) result in increased Fe solubility and a larger percentage of Fe occupancy of the Cu(2) plane site (prepared conventionally). Materials with z > 0.00 have a slightly depressed superconducting transition onset temperature T c relative to the z = 0.00 compounds. It is also shown that Fe occupancy of the Cu(2) site in Y 1-z Ca z Ba 2 (Cu 1-x Fe x ) 3 O 6+y can be substantially increased when these materials are treated at high temperatures in inert atmospheres followed by oxygenation at low temperatures. T c decreases more rapidly in these latter materials compared to the conventionally prepared ones. Implications concerning ordered Fe cluster formation and superconducting pair breaking in the Cu(2) site are drawn. 7 refs., 4 tabs
Energy Technology Data Exchange (ETDEWEB)
Nowacki, J. [Wydzial Inzynierii Materialowej, Politechnika Szczecinska, Szczecin (Poland); Klimek, L. [Instytut Inzynierii Materialowej i Technik Bezwiorowych, Politechnika Lodzka, Lodz (Poland)
1998-12-31
The process of multiphase sintering of iron in the vacuum has been analysed. As a result of the process iron-iron boride cermets have been produced. Fe-Fe{sub 2}B cermets were obtained as a result of sintering of the Fe and B pure elements in the vacuum. Attemps at sintering in the solid phase and with the participation of the liquid phase, the Fe-Fe{sub 2}B eutectic, have been made. Metallographic qualitative and quantitative studies, X-ray structural qualitative and qauantitative analysis allowed to determine the structure of Fe{sub 2}B cermets, as well as a description of the kinetics of quantitative changes in phase proportions in the course of sintering. It has been found that their structure varies widely depending on sintering parameters and the composition of the sinters. Measurements of the Fe-Fe{sub 2}B cermets hardness and measurements on wear during dry friction by the pin-on-disc method have shown distinct advantages of the cermets as a modern constructional materials. The hardness of Fe-Fe{sub 2}B cermets, depending on their chemical composition and sintering parameters, ranges widely from 150 to 1500 HV, and their resistance to wear is comparable to that of diffusively boronized steels. FeFe{sub 2}B cermets are a composite material in which iron boride, Fe{sub 2}B, with a hardness of about 1800 HV plays the role of the reinforcement,while iron-iron boride, Fe-Fe{sub 2}B, with a hardness of about 500 HV plays the role of matrix. The eutectic in the spaces between iron boride grains is composed of boron solid solution plates in iron with a hardness of arround 250 HV, and iron boride, Fe{sub 2}B, plates with a hardness of approximaly 1800 HV. The combination of such different materials, a hard reinforcement and a relatively plastic matrix produces favourable properties of the cermet thus produced high hardness (1500 HV) constant over whole cross section of the material, resistance of abrasive wear and acceptable ductility. The properties mentioned above
Study of the conduction phenomenon in the system Zn(1-x)FeCrO4Nix
International Nuclear Information System (INIS)
Zhou Yuan; Xia Yuanfu; Zhang Shiyuan; Chen Kunji
1993-01-01
In order to explore an 'anomalous' conduction phenomenon in the system Zn (1-x) FeCrO 4 Ni x which was investigated with Moessbauer spectra, X-rays diffraction, infrared spectra and other methods. The results show that the conductivity anomaly is not an intrinsic behavior but arises from the moisture-adsorption. Their native conduction is similar to that of semiconductors, obeying the relationship σ = σ ∝ exp (E a /KT). All samples crystallize in cubic symmetry and their lattice parameters increase with x. The cation distribution is (Zn (1-x) Fe x ) [Fe ( -1 -x) Ni x Cr]O 4 . No phase change occurs in the temperature range from 283 to 423 K
Differential Effects of X-Rays and High-Energy 56Fe Ions on Human Mesenchymal Stem Cells
International Nuclear Information System (INIS)
Kurpinski, Kyle; Jang, Deok-Jin; Bhattacharya, Sanchita; Rydberg, Bjorn; Chu, Julia; So, Joanna; Wyrobek, Andy; Li Song; Wang Daojing
2009-01-01
Purpose: Stem cells hold great potential for regenerative medicine, but they have also been implicated in cancer and aging. How different kinds of ionizing radiation affect stem cell biology remains unexplored. This study was designed to compare the biological effects of X-rays and of high-linear energy transfer (LET) 56 Fe ions on human mesenchymal stem cells (hMSC). Methods and Materials: A multi-functional comparison was carried out to investigate the differential effects of X-rays and 56 Fe ions on hMSC. The end points included modulation of key markers such as p53, cell cycle progression, osteogenic differentiation, and pathway and networks through transcriptomic profiling and bioinformatics analysis. Results: X-rays and 56 Fe ions differentially inhibited the cell cycle progression of hMSC in a p53-dependent manner without impairing their in vitro osteogenic differentiation process. Pathway and network analyses revealed that cytoskeleton and receptor signaling were uniquely enriched for low-dose (0.1 Gy) X-rays. In contrast, DNA/RNA metabolism and cell cycle regulation were enriched for high-dose (1 Gy) X-rays and 56 Fe ions, with more significant effects from 56 Fe ions. Specifically, DNA replication, DNA strand elongation, and DNA binding/transferase activity were perturbed more severely by 1 Gy 56 Fe ions than by 1 Gy X-rays, consistent with the significant G2/M arrest for the former while not for the latter. Conclusions: 56 Fe ions exert more significant effects on hMSC than X-rays. Since hMSC are the progenitors of osteoblasts in vivo, this study provides new mechanistic understandings of the relative health risks associated with low- and high-dose X-rays and high-LET space radiation
Directory of Open Access Journals (Sweden)
K. Kamala Bharathi
2012-03-01
Full Text Available The structure and electrical characteristics of Gd doped Ni ferrite materials, namely NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4, are reported to demonstrate their improved electrical properties compared to that of pure NiFe2O4. NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds crystallize in the cubic inverse spinel phase with a very small amount of GdFeO3 additional phase while pure NiFe2O4 crystallize in inverse spinel phase without any impurity phase. The back scattered electron imaging analysis indicate the primary and secondary formation in NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds. Atomic force microscopy measurements indicate that the bulk grains are ∼2-5 micron size while the grain boundaries are thin compared to bulk grains. Impedance spectroscopic analysis at different temperature indicates the different relaxation mechanisms and their variation with temperature, bulk grain and grain-boundary contributions to the electrical conductivity (Rg and capacitance (Cg of these materials. The conductivity in pure NiFeO4 is found to be predominantly due to intrinsic bulk contribution (Rg=213 kΩ and Cg=4.5 x 10-8 F. In the case of NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds, grain and grain-boundary contributions to the conductivity are clearly observed. The DC conductivity values (at 300 K of NiFe2O4, NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds are found to be 1.06 x 10-7 Ω-1 cm-1, 5.73 x 10-8 Ω-1 cm-1 and 1.28 x 10-8 Ω-1 cm-1 respectively.
Energy Technology Data Exchange (ETDEWEB)
Bufaiçal, L., E-mail: lbufaical@ufg.br [Instituto de Física, Universidade Federal de Goiás, 74001-970 Goiânia, GO (Brazil); Adriano, C. [Instituto de Física “Gleb Wataghin”, UNICAMP, 13083-859 Campinas, SP (Brazil); Lora-Serrano, R. [Instituto de Física, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG (Brazil); Duque, J.G.S. [Núcleo de Física, Universidade Federal de Sergipe, Campus Itabaiana, 49500-000 Itabaiana, SE (Brazil); Mendonça-Ferreira, L. [Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-170 Santo André, SP (Brazil); Rojas-Ayala, C.; Baggio-Saitovitch, E.; Bittar, E.M. [Centro Brasileiro de Pesquisas Físicas, 22290-180 Rio de Janeiro, RJ (Brazil); Pagliuso, P.G. [Instituto de Física “Gleb Wataghin”, UNICAMP, 13083-859 Campinas, SP (Brazil)
2014-04-01
Polycrystalline samples of the series of double perovskites Sr{sub 2−x}La{sub x}FeIrO{sub 6} were synthesized. Their structural, electronic and magnetic properties were investigated by X-ray powder diffraction, Mössbauer spectroscopy, magnetic susceptibility, heat capacity and electrical resistivity experiments. The compounds crystallize in a monoclinic structure and were fitted in space group P2{sub 1}/n, with a significant degree of Fe/Ir cationic disorder. As in Ca{sub 2−x}La{sub x}FeIrO{sub 6} the Sr-based system seems to evolve from an antiferromagnetic ground state for the end members (x=0.0 and x=2.0) to a ferrimagnetic order in the intermediate regions (x∼1). Since Mössbauer spectra indicate that Fe valence remains 3+ with doping, this tendency of change in the nature of the microscopic interaction could be attributed to Ir valence changes, induced by La{sup 3+} electrical doping. Upon comparing both Ca and Sr series, Sr{sub 2−x}La{sub x}FeIrO{sub 6} is more structurally homogenous and presents higher magnetization and transition temperatures. Magnetic susceptibility measurements at high temperatures on Sr{sub 1.2}La{sub 0.8}FeIrO{sub 6} indicate a very high ferrimagnetic Curie temperature T{sub C}∼700K. For the Sr{sub 2}FeIrO{sub 6} compound, electrical resistivity experiments under applied pressure suggest that this material might be a Mott insulator. - Graphical abstract: The Weiss constant as a function of La doping for the (Ca,Sr){sub 2−x}La{sub x}FeIrO{sub 6} series, indicating changes in Fe–Ir magnetic coupling on both families. - Highlights: • The double perovskite series (Ca,Sr){sub 2−x}La{sub x}FeIrO{sub 6} were synthesized. • Changes in the Fe-Ir magnetic coupling due to La doping on both series. • Evidence of high T{sub C} on Sr{sub 1.2}La{sub 0.8}FeIrO{sub 6}. • Indication of Mott insulator behavior on Sr{sub 2}FeIrO{sub 6}.
Ionic configuration of copper ferrimanganites Cu 0.5Mn xFe 2.5- xO 4
Lenglet, M.; Kasperek, J.; Hannoyer, B.; Lopitaux, J.; d'Huysser, A.; Tellier, J. C.
1992-06-01
Mössbauer spectrometry, neutron diffraction, XANES, and XPS have led to the determination of the cation distributions of the system Cu 0.5Mn xFe 2.5- xO 4 (0≤ x≤1.5). The three cations are present in both tetrahedral and octahedral sites, and the relative number of Fe ions on A- and B-sites remains nearly constant in the whole range of x. It appears that for x≤0.5 manganese is divalent and copper is in its two oxidation states. For x>0.5 copper and iron are respectively divalent and trivalent; the manganese is in +2 and +3 oxydation states.
Ultrafast microwave hydrothermal synthesis and characterization of Bi1−xLaxFeO3 micronized particles
International Nuclear Information System (INIS)
Ponzoni, C.; Cannio, M.; Boccaccini, D.N.; Bahl, C.R.H.; Agersted, K.; Leonelli, C.
2015-01-01
In this work a microwave assisted hydrothermal method is applied to successfully synthesize lanthanum doped bismuth ferrites (BLFO, Bi 1−x La x FeO 3 where x = 0, 0.15, 0.30 and 0.45). The growth mechanism of the Bi 1−x La x FeO 3 crystallites is discussed in detail. The existence of the single-phase perovskite structure for all the doped samples is confirmed by the X-ray powder diffraction patterns. A peak shift, observed at lower angle with increasing La doping concentration, indicates that the BiFeO 3 lattice is doped. The results of TG/DTA show a shift in the transition temperature from 805 °C to 815 °C as function of the La-doping for all the doped powders. At higher levels of La doping, i.e. x = 0.30 and 0.45, significant weight losses occur above 860 °C suggesting a change in the physical and chemical properties. Finally, magnetic measurements are carried out at room temperature for pure BiFeO 3 and Bi 0.85 La 0.15 FeO 3 . The results indicate that the materials are both weakly ferromagnetic, with no significant hysteresis in the curves. - Graphical abstract: Display Omitted - Highlights: • MW hydrothermal method applied to synthesize Bi 1−x La x FeO 3 , x = 0, 0.15, 0.30, 0.45. • A single-phase perovskite structure for all the samples was confirmed by XRD. • A T c shift in La doped BiFeO 3 DTA was observed as function of the La-doping. • Magnetic measurements indicate that the materials are weakly ferromagnetic
Atomic Physics Measurements in Support of X-ray Astronomy
Beiersdorfer, Peter; Brown, G. V.; Kelley, R. E.; Kilbourne, C. A.; Leutenegger, M.; Porter, F. S.; Obst, M.; Lepson, J. K.; Desai, P.; Gu, M. F.
2010-10-01
X-ray astronomy has been a voracious consumer of atomic data, especially after the launch of the Chandra and XMM-Newton X-ray Observatories, which have produced very high-resolution grating spectra of point sources. One of the important issues has been to understand the physics underlying the Fe L-shell spectra, and the Fe XVII spectrum in particular. A lot of progress has been made, including measurements of the electron-impact and resonance excitation cross sections, which now provides a rather clear picture of the production mechanism of the Fe XVII spectrum. Recent measurements of the radiative rates provide additional information on the deexcitation channels, while investigations of dielectronic satellite transitions provide a measure of the electron temperature. Many questions, however, still remain. Work at LLNL was performed under the auspices of DOE under contract DE-AC53-07NA27344 and supported by NASA's APRA program under contracts NNH07AF81I and NNG06WF08I. Part of this work was supported by Chandra Cycle 10 Award AR9-0002X.
International Nuclear Information System (INIS)
Zhang Weifang; Zhang Xinghong; Wang Jianli; Hong Changqing
2004-01-01
Fully dense TiC-Fe cermets (x = 10, 20, 30, and 40 wt.%) were produced from Ti-C-Fe powder mixtures by combustion synthesis with quasi-isostatic pressing. The effect of Fe content on combustion temperature, combustion wave velocity, and final product density was investigated. The final product was characterized by XRD, SEM, and TEM. The combustion temperature and wave velocity decreased with increasing Fe content. Product density increased with increasing Fe content (96% at 30 wt.%). X-ray diffraction and transmission electron microscopy (TEM) revealed the final product to contain TiC, Fe phases, lath martensite, and Fe 2 Ti. The TiC particle size decreased with increasing Fe content. In addition, a low density of dislocations was observed in both the TiC particles and Fe binder, indicative of annealing and recrystallization, respectively
Epitaxial growth of bcc-Fe{sub x}Co{sub 100-x} thin films on MgO(1 1 0) single-crystal substrates
Energy Technology Data Exchange (ETDEWEB)
Ohtake, Mitsuru, E-mail: ohtake@futamoto.elect.chuo-u.ac.j [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Nishiyama, Tsutomu; Shikada, Kouhei [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan); Kirino, Fumiyoshi [Graduate School of Fine Arts, Tokyo National University of Fine Arts and Music, 12-8 Ueno-koen, Taito-ku, Tokyo 110-8714 (Japan); Futamoto, Masaaki [Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)
2010-07-15
Fe{sub x}Co{sub 100-x} (x=100, 65, 50 at%) epitaxial thin films were prepared on MgO(1 1 0) single-crystal substrates heated at 300 deg. C by ultra-high vacuum molecular beam epitaxy. The film structure and the growth mechanism are discussed. FeCo(2 1 1) films with bcc structure grow epitaxially on MgO(1 1 0) substrates with two types of variants whose orientations are rotated around the film normal by 180 deg. each other for all compositions. Fe{sub x}Co{sub 100-x} film growth follows the Volmer Weber mode. X-ray diffraction analysis indicates the out-of-plane and the in-plane lattice spacings are in agreement with the values of respective bulk Fe{sub x}Co{sub 100-x} crystals with very small errors less than +-0.4%, suggesting the strains in the films are very small. High-resolution cross-sectional transmission electron microscopy shows that periodical misfit dislocations are preferentially introduced in the film at the Fe{sub 50}Co{sub 50}/MgO interface along the MgO[1 1-bar 0] direction. The presence of such periodical dislocations decreases the large lattice mismatch of about -17% existing at the FeCo/MgO interface along the MgO[1 1-bar 0] direction.
Energy Technology Data Exchange (ETDEWEB)
Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Sidi bouzid, Safi (Morocco); LMPHE, Faculte des Sciences, Universite Mohamed V, Rabat (Morocco); Hamedoun, M. [Institute for Nanomaterials and Nanotechnologies, MaScIR, Rabat (Morocco); Academie Hassan II des Sciences et Techniques, Rabat (Morocco); Benyoussef, A. [LMPHE, Faculte des Sciences, Universite Mohamed V, Rabat (Morocco); Institute for Nanomaterials and Nanotechnologies, MaScIR, Rabat (Morocco); Academie Hassan II des Sciences et Techniques, Rabat (Morocco)
2012-04-01
The exchange interactions (J{sub BB} and J{sub AB} are the intra and the inter-sublattice exchange interactions between neighbouring spins, respectively) are obtained by using the general expressions of canting angle and critical temperature obtained by mean field theory of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4}. The expression of magnetic energy of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} is obtained for different spin configurations and dilution x. The saturation magnetisation of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} is obtained with different values of dilution x. The magnetic phase diagram of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} materials is obtained by high temperature series expansions (HTSEs). The critical exponent associated with the magnetic susceptibility of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} is deduced.
Mössbauer and magnetic studies of Mg{sub 1+2x}Sb{sub x}Fe{sub 2−3x}O{sub 4} spinel ferrites
Energy Technology Data Exchange (ETDEWEB)
Widatallah, H.M., E-mail: hishammw@squ.edu.om [Department of Physics, College of Science, Sultan Qaboos University, 123 Muscat (Oman); Al-Mamari, F.A.S.; Al-Saqri, N.A.M.; Gismelseed, A.M.; Al-Omari, I.A.; Al-Shahumi, T.M.H. [Department of Physics, College of Science, Sultan Qaboos University, 123 Muscat (Oman); Alhaj, A.F. [Department of Physics, Qasim University, Al-Qasim (Saudi Arabia); Abo El Ata, A.M. [Department of Physics, Faculty of Science, Tanta University, Tanta (Egypt); Elzain, M.E. [Department of Physics, College of Science, Sultan Qaboos University, 123 Muscat (Oman)
2013-06-15
Spinel-related Mg{sub 1+2x}Sb{sub x}Fe{sub 2−3x}O{sub 4} samples (x = 0.0, 0.05, 0.10, 0.15, 0.20, and 0.30) prepared using the conventional double sintering technique were investigated using {sup 57}Fe Mössbauer spectroscopy and magnetic measurements. Mössbauer spectra favor a cationic distribution of the form (Mg{sub δ}Fe{sub 1−δ}){sup A}[Mg{sub 1+2x−δ}Sb{sub x}Fe{sub 1+δ−3x}]{sup B}O{sub 4} among the tetrahedral-A and octahedral-B sites of the spinel structure. The cation distribution parameter (δ) was found to vary with the Sb{sup 5+} concentration (x). The Mössbauer hyperfine magnetic fields at both sites and the Curie temperatures of the ferrites decrease as x increases. This was attributed to gradual weakening in the magnetic exchange interaction as more Fe{sup 3+} ions are substituted by diamagnetic Sb{sup 5+} and Mg{sup 2+} ones. The sample with x = 0.30 exhibits short range magnetic order due to cationic clustering and/or superparamagnetism. The magnetization of all samples was found to be temperature-dependent implying that δ depends on temperature in addition to x. At low temperatures the substituted ferrites (x ≠ 0.0) unexpectedly exhibit higher magnetization values relative to that of the pure ferrite MgFe{sub 2}O{sub 4}. This behavior, while at variance with the Néel's model for ferrimagnetism, is explicable in terms of the spin canting mechanism proposed in the Yafet–Kittel model. - Highlights: ► A Mössbauer and magnetic study of Sb{sup 5+} and Mg{sup 2+} co-substituted ferrites of the composition Mg{sub 1+2x}Sb{sub x}Fe{sub 2−3x}O{sub 4} is reported. ► The cation distribution in Mg{sub 1+2x}Sb{sub x}Fe{sub 2−3x}O{sub 4} is shown to depend on both the Sb{sup 5+} ionic concentration and the temperature. ► The A–B magnetic exchange interaction and Mössbauer hyperfine fields weaken with increasing Sb{sup 5+} and Mg{sup 2+} concentrations. ► The magnetization of the substituted samples with x ≠ 0.00 increases
Pressure-induced magnetic transition in Fe sub 4 N probed by Fe K-edge XMCD measurement
Ishimatsu, N; Maruyama, H; Kawamura, N; Suzuki, M; Ohishi, Y; Ito, M; Nasu, S; Kawakami, T
2003-01-01
X-ray magnetic circular dichroism (XMCD) of gamma'-iron nitride (Fe sub 4 N) was recorded at Fe K-edge under high pressure up to 27 GPa. The XMCD intensity decreased remarkably with pressure, and vanished at 24 GPa. Compressibility was measured by the X-ray diffraction method. These results indicate that Fe sub 4 N undergoes a second-order phase transition from the ferromagnetic state to a paramagnetic state without any structural change. The pressure-induced demagnetizing process is discussed in terms of the Fe magnetic states in the local environment.
Acetone sensors based on microsheet-assembled hierarchical Fe2O3 with different Fe3+ concentrations
Wang, Han; Yan, Lei; Li, Shuo; Li, Yu; Liu, Li; Du, Liting; Duan, Haojie; Cheng, Yali
2018-02-01
Several different morphologies of microsheet-assembled Fe2O3 have been fabricated by hydrothermal method using diverse concentrations of Fe3+ precursor solutions (0.025, 0.020, 0.015, 0.010 mol/L Fe3+). The as-synthesized materials have been characterized by scanning electron microscope (SEM), X-ray powder diffraction (XRD), and energy-dispersive X-ray spectrometry (EDS). The SEM images reflect that the morphologies of as-synthesized materials are affected by the concentrations of Fe3+ in precursor solutions. The less concentration of Fe3+, the more porous of Fe2O3 microflowers, and thinner of slices distributed on the surface. Furthermore, gas sensors based on these Fe2O3 microflowers manufactured and tested to various common gases. The optimum response value to 100 ppm acetone is 52 at the working temperature of 220 °C. Meanwhile, the Fe2O3 microflower sensors possess ultrafast response-recovery speed, which are 8 and 19 s, respectively. The possible sensing mechanism was mainly attributed to the high surface area, three-dimensional porous structure.
Glassy behavior of the Nd sublattice induced by Fe doping in NdFexGa1-xO3
International Nuclear Information System (INIS)
Bartolome, F.; Parra-Borderias, M.; Blasco, J.; Bartolome, J.
2007-01-01
The evolution of the magnetic ordering of Nd with the Fe content in NdFe x Ga 1-x O 3 is studied by low-temperature specific-heat measurements for x= =0.2. Fe doping creates a distribution of internal fields on Nd, originating a Schottky contribution to the specific heat which is present for x>0. The power law followed by the low-temperature specific heat suggests a glassy behavior for x>=0.1
Magnetic and structural characterizations on nanoparticles of FePt, FeRh and their composites
International Nuclear Information System (INIS)
Ko, Hnin Yu Yu; Suzuki, Takao; Nam, Nguyen T.; Phuoc, Nguyen N.; Cao Jiangwei; Hirotsu, Yoshihiko
2008-01-01
The various compositions of FePt and FeRh nanoparticles, and their composite particles have been fabricated by the solution-phase chemical method and their magnetic properties characterized. High-resolution transmission electron microscopic observations indicate that mono-dispersed FeRh and FePt/FeRh nanoparticles are fabricated with the average size of 3-5 nm. However, larger size particles are distributed in the annealed state. From X-ray diffraction results, the as-deposited FeRh nanoparticles reveal a chemically disordered fcc structure which can be transformed into CsCl-type structure through thermal annealing. Similarly, the annealed FePt nanoparticles show the L1 0 -phase fct structure although the fcc structure is apparent in the as-deposited state. It is also found that the first time in the exchange bias effect in the composite of ferromagnetic (FePt) and anti-ferromagnetic (FeRh) nanoparticles; result in a shift of the hysteresis loop after field cooling process
Energy Technology Data Exchange (ETDEWEB)
Brueckner, Felix; Sarkar, Rajib; Kamusella, Sirko; Klauss, Hans-Henning [Institut fuer Festkoerperphysik, Technische Universitaet Dresden (Germany); Luetkens, Hubertus [Paul-Scherrer-Institut, Villigen (Switzerland); Pachmayr, Ursula; Nitsche, Fabian; Johrendt, Dirk [Department Chemie, Ludwig-Maximilians-Universitaet Muenchen (Germany)
2015-07-01
In the family of iron-based superconductors, where the superconducting dome is usually separated from the magnetic phase, only few compounds show ferromagnetism arising in the superconducting state. The so far discovered examples show ferromagnetic ordering of Eu{sup 2+} ions. In this context, the presented ordering of iron orbitals in (Li{sub 1-x}Fe{sub x}OH)(Fe{sub 1-y}Li{sub y}Se) is unique. We performed a wealth of experimental methods to characterize the physics in this system, including dc resistivity and magnetization. With use of local probes (μSR,NMR,Moessbauer), we are able to describe the emergence of bulk ferromagnetism and superconductivity in a microscopic scale. Both phenomena can coexist, though they compete with each other, due to a spatial separation in the multilayer system.
Structure and electrical conduction of the system La sub(1-x)Ca sub(x)FeO sub(3-. cap alpha. )
Energy Technology Data Exchange (ETDEWEB)
Hombo, Jukichi; Urabe, Noriake [Kumamoto Univ. (Japan). Faculty of Engineering; Hiroshige, Gota; Hamada, Kotaro
1982-08-01
Perovskite phases in the system, La sub(1-x)Ca sub(x)FeO sub(3-..cap alpha..) were prepared with La/sub 2/O/sub 3/, CaCO/sub 3/, and Fe/sub 2/O/sub 3/ by firing in air and in vacuo. The compositions of samples fired in vacuo and in air are represented as La sub(1-x)Ca sub(x)FeO sub(3-x 2) and La sub(1-x)Ca sub(x)Fe sub(1-y)sup(3+)Fe sub(y)sup(4+)O sub(3-x/2+y/2), respectively. That is, samples fired in vacuo contain some oxygen vacancies and no tetravalent iron; in contrast, samples fired in air contain both oxygen vacancies and tetravalent iron in the structures. The electrical conductivities of these synthesized oxides depended extensively upon the content of tetravalent iron. For instance, the conductivity of the sample x = 0.6 fired in air was larger by 10/sup 6/ than that of the sample fired in vacuo. In this system, except for the two terminal compositions of x = 0 and x = 1.0, the values of activation energy for conduction are considerably small, and from the results of thermo-electromotive force measurement, the charge carrier was positive. Furthermore, the conductivity increased somewhat with time during the conductivity measurement by the direct-current method. These facts suggest that the electric conduction would not be ionic but electronic. The electrical conduction would then be carried out by the so-called hopping mechanism by which the positive charge is transferred.
Energy Technology Data Exchange (ETDEWEB)
Nomura, Kiyoshi, E-mail: dqf10204@nifty.com [Tokyo University of Science, Photocatalysis International Research Center (Japan); Suzuki, Shigeyo; Koike, Yuya [Meiji University, Department of Science and Engineering (Japan); Li, Hongling [The University of Tokyo, Graduate School of Engineering (Japan); Okazawa, Atsushi [The University of Tokyo, Graduate School of Arts and Sciences (Japan); Kojima, Norimichi [Toyota Physical and Chemical Research Institute (Japan)
2016-12-15
The dilute magnetic properties of SrSn{sub 1−x}Fe{sub x}O{sub 3} (x = 0.01 − 0.15) prepared by sol-gel and thermal decomposition methods were investigated by {sup 57}Fe Mössbauer spectrometry, magnetometry, and X-ray diffractometry. It was found that SrSnO{sub 3} doped with 2–8 % Fe show weak ferromagnetism although only paramagnetic doublets are observed in {sup 57}Fe Mössbauer spectra at room temperature (RT), whereas SrSnO{sub 3} doped with 10–15 % Fe show relatively strong ferromagnetism, and the sextets are additionally observed in the {sup 57}Fe Mössbauer spectra at RT. The weak ferromagnetism by doping 2–8 % Fe is considered to be caused by the induced magnetic defects, and the ferromagnetism by doping 10–15 % Fe are considered mainly due to the magnetic coupling between dilute Fe {sup 3+} partially substituted at Sn {sup 4+} sites in the orthorhombic structure of SrSnO{sub 3−δ} accompanying the oxygen deficiencies. It is further remarkable that poor crystalline 8 % Fe doped SrSnO{sub 3−δ} obtained by annealing at 600 {sup ∘}C shows relatively high saturation magnetization and low coercivity.
International Nuclear Information System (INIS)
Yosef Sarwanto and Wisnu Ari Adi
2018-01-01
Crystallographic structure and magnetic properties of pseudobrookite Fe 2-x Ni x TiO 5 system (x=0, 0.1, 0.2, 0.3 ,0.5 and 1)have been performed through solid state reaction. Pseudobrookite Fe 2-x Ni x TiO 5 system was synthesized by mixing of Fe 2 O 3 , NiO, and TiO 2 with stoichiometry composition using wet mill. The mixture was milled for 5 hours and sintered in the electric chamber furnace at 1000 °C in the air at atmosphere pressure for 5 hours. The refinement against of X-ray diffraction data shows that the samples with composition of (x = 0) and (x = 0.1) have a single phase with Fe 2 TiO 5 structure. How ever the samples with composition of (x > 0.1) consist of multiple phases, namely Fe 2-x Ni x TiO 5 , FeTiO 3 , Fe 2 NiO 4 and NiO. Particle morphologies of the composition x = 0 and x =0.1 are homogenous and uniform on the sample surface with a polygonal particle shape and particle size varies. At room temperature, the sample with x =0 is paramagnetic and that with x =0.1 is ferromagnetic. Magnetic phase transformation of this study is the caused by the present of Ni substituted Fe in the system. Thus substitution Ni into Fe on the system pseudobrookite Fe 2 TiO 5 only capable of 0.1 at.% without changing the crystal structure of the material. It means that there is an interaction between the magnetic spin Fe 3+ on the 3d 5 configurations and Ni 2 + on the 3d 3 configurations through the mechanism of double exchange. Double exchange mechanism is a magnetic type of exchange that appears between the ions Fe 3+ and Ni 2+ adjacent in different oxidation states. (author)
Liu, Xin; Meng, Changgong; Han, Yu
2012-01-01
We investigated the electronic structure of Fe nanoparticle-graphene composites and the impact of the interfacial interaction on NH x (x = 0, 1, 2, 3) adsorption by first-principles based calculations. We found that Fe 13 nanoparticles can
Energy Technology Data Exchange (ETDEWEB)
Mani, Angom Devadatta, E-mail: angomdevadattamani@gmail.com; Soibam, Ibetombi
2017-02-15
BiFeO{sub 3} (BFO) and nickel zinc ferrite Ni{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} (NZFO) were prepared by sol gel and auto combustion route respectively. Stoichiometric proportions were mixed to obtain the multiferroic nanocomposites having the compositional formula (1−x)BiFeO{sub 3}-x Ni{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} (x=0.0, 0.2, 0.5, 0.8, 1.0). The phases were confirmed by XRD analyses. SEM micrographs showed the agglomerated nature of the particles with continuous grain growth in all directions. Elemental compositions were confirmed from EDAX studies. FTIR studies showed the stretching and bending vibrations of the various bonds present in the samples. The dielectric properties such as dielectric constant, ε′ and dielectric loss tangent, tanδ were studied for the spinel, perovskite and nanocomposite ferrites. Experimental result shows an increasing trend in the value of dielectric constant in going from spinel to perovskite phase. The frequency dependence of tanδ showed minimum loss for x=0.5 nanocomposite. Possible mechanisms explaining the above results were being discussed.
Magnetic properties of LaFe13-xAlxNy compounds
International Nuclear Information System (INIS)
Liu, J.P.; Tang, N.; Boer, F.R. de; Chatel, P.F. de; Buschow, K.H.J.
1995-01-01
Interstitial nitrides of the type LaFe 13-x Al x N y have been synthesized and their magnetic properties have been investigated. It is found that the magnetic properties are drastically modified by the introduction of interstitial nitrogen. The physical origin of the changes is discussed. ((orig.))
Phase diagram of (Li(1-x)Fe(x))OHFeSe: a bridge between iron selenide and arsenide superconductors.
Dong, Xiaoli; Zhou, Huaxue; Yang, Huaixin; Yuan, Jie; Jin, Kui; Zhou, Fang; Yuan, Dongna; Wei, Linlin; Li, Jianqi; Wang, Xinqiang; Zhang, Guangming; Zhao, Zhongxian
2015-01-14
Previous experimental results have shown important differences between iron selenide and arsenide superconductors which seem to suggest that the high-temperature superconductivity in these two subgroups of iron-based families may arise from different electronic ground states. Here we report the complete phase diagram of a newly synthesized superconducting (SC) system, (Li1-xFex)OHFeSe, with a structure similar to that of FeAs-based superconductors. In the non-SC samples, an antiferromagnetic (AFM) spin-density-wave (SDW) transition occurs at ∼127 K. This is the first example to demonstrate such an SDW phase in an FeSe-based superconductor system. Transmission electron microscopy shows that a well-known √5×√5 iron vacancy ordered state, resulting in an AFM order at ∼500 K in AyFe2-xSe2 (A = metal ions) superconductor systems, is absent in both non-SC and SC samples, but a unique superstructure with a modulation wave vector q = (1)/2(1,1,0), identical to that seen in the SC phase of KyFe2-xSe2, is dominant in the optimal SC sample (with an SC transition temperature Tc = 40 K). Hence, we conclude that the high-Tc superconductivity in (Li1-xFex)OHFeSe stems from the similarly weak AFM fluctuations as FeAs-based superconductors, suggesting a universal physical picture for both iron selenide and arsenide superconductors.
Reduction of the Curie temperature in the multiferroic Bi5Fe1+xTi3−xO15 solid solution
International Nuclear Information System (INIS)
Salazar-Kuri, U; Mendoza, M E; Silva, R; Siqueiros, J M; Gervacio-Arciniega, J J
2014-01-01
In this work, the phase diagram of the system Bi 4 Ti 3 O 12 -BiFeO 3 in the region of the solid solution Bi 5 Fe 1+x Ti 3−x O 15 was refined. The limit of solubility was determined to be at x = 0.1. The Curie temperature (T C ) of the ferroelectric phase transition was determined by dielectric permittivity measurements at 100 kHz for the phase Bi 5 FeTi 3 O 15 as well as for the solid solution. A decrease in T C from 750 °C to 742 °C (solid solution at x = 0.1) was found. These results can be explained in terms of the perturbation of the oxygen octahedral perovskite layers resulting from the substitution of Ti 4+ by Fe 3+ ions. (paper)
Interactions among magnetic moments in the double perovskites Sr2Fe1+xMo1−xO6
International Nuclear Information System (INIS)
Pilo, J.; Carvajal, E.; Oviedo-Roa, R.; Cruz-Irisson, M.; Navarro, O.
2014-01-01
It is well known that every double perovskite shows a characteristic magnetic behavior, as a consequence of the interactions among the magnetic moments associated with the atoms in their cells; at the same time, the electric and magnetic properties of the bulk double perovskite Sr 2 FeMoO 6 are well characterized. In this work we studied the iron rich compounds Sr 2 Fe 1+x Mo 1−x O 6 , using a supercell to model such concentrations that made Fe richer perovskites by ±66.6% and ±200%. Starting from the stoichiometric double perovskite, and modifying the Fe/Mo ratio in the compound, the study of these materials were based on the calculation of the magnetic moment at each atom, as well as the partial density of states
Metallic glasses of the type Fe80B17X3
International Nuclear Information System (INIS)
Riedel, M.; Gnaser, H.; Ruedenauer, F.G.
1981-08-01
Absolute and relative practical sensitivities for Osub2sup+ - bombardement of 14 elements, present as a 3% admixture in a Fe80B17X3 metallic glass matrix, were determined by SIMS. The variation of sensitivity data between elements is similar to that found for pure element samples. The 3% admixture causes a small but statistically significant matrix effect on the matrix elements Fe and B. Comparison with yield data of the same minor impurity elements in other matrices (stainless steel, silicon) shows, that sensitivities in different matrices are within 30% for most elements, indicating the possibility of transferring relative sensitivity factor data determined on metallic glasses to other Fe-based alloys and thereby obtaining a semi- quantitative analysis. (author)
Moessbauer and XRD study of pulse plated Fe-P and Fe-Ni thin layers
International Nuclear Information System (INIS)
Miko, Annamaria; Kuzmann, Erno; Lakatos-Varsanyi, Magda; Kakay, Attila; Nagy, Ferenc; Varga, Lajos Karoly
2005-01-01
57 Fe conversion electron Moessbauer spectroscopy, X-ray diffraction, electrochemical and magnetic measurements were used to study pulse electroplated Fe-P and Ni-Fe coatings. XRD and 57 Fe CEMS measurements revealed the amorphous character of the novel pulse plated Fe-P alloys. CEM spectra indicated significant differences in the short range order and in the magnetic anisotropy between the Fe-P deposits pulse plated at medium long deposition time (t on = 2 ms), with short relaxation time (t off = 9 ms) and low current density (I p = 0.05 Acm -2 ) or at short deposition time (t on = 1 ms) with long relaxation time (t off = 250 ms) and high current density (I p = 1.0 Acm -2 ). The broad peaks centred around the fcc reflections in XRD of the pulse plated Ni-22 wt.% Fe deposit reflected a microcrystalline Ni-Fe alloy with a very fine, 5-8 nm, grain size. The CEM spectrum of the pulse plated Ni-22 wt.% Fe coating corresponded to a highly disordered solid solution alloy containing a minute amount of ferrihydrite. Extreme favourable soft magnetic properties were observed with these Ni-Fe and Fe-P pulse plated thin layers.
Scaling of the anomalous Hall current in Fe100−x(SiO2)x films
Xu, W. J.
2011-05-20
To study the origin of the anomalous Hall effect, Fe100−x(SiO2)x granular films with a volume fraction of SiO2 (0 ⩽ x ⩽ 40.51) were fabricated using cosputtering. Hall and longitudinal resistivities were measured in the temperature range of 5–350 K with magnetic fields up to 5 T. As x increased from 0 to 40.51, the anomalous Hall resistivity and longitudinal resistivity increased by about four and three orders in magnitude, respectively. Analysis of the results revealed that the normalized anomalous Hall conductivity is a constant for all of the samples, which may suggest a scattering-independent anomalous Hall conductivity in Fe.
Crystal structure and thermal expansion of Mn(1-x)Fe(x)Ge.
Dyadkin, Vadim; Grigoriev, Sergey; Ovsyannikov, Sergey V; Bykova, Elena; Dubrovinsky, Leonid; Tsvyashchenko, Anatoly; Fomicheva, L N; Chernyshov, Dmitry
2014-08-01
A series of temperature-dependent single-crystal and powder diffraction experiments has been carried out using synchrotron radiation in order to characterize the monogermanides of Mn, Fe and their solid solutions. The MnGe single crystal is found to be enantiopure and we report the absolute structure determination. The thermal expansion, parametrized with the Debye model, is discussed from the temperature-dependent powder diffraction measurements for Mn(1-x)Fe(x)Ge (x = 0, 0.1, 0.2, 0.25, 0.3, 0.4, 0.5, 0.6, 0.7, 0.75, 0.8, 0.9). Whereas the unit-cell dimension and the Debye temperature follow a linear trend as a function of composition, the thermal expansion coefficient deviates from linear dependence with increasing Mn content. No structural phase transformations have been observed for any composition in the temperature range 80-500 K for both single-crystal and powder diffraction, indicating that the phase transition previously observed with neutron powder diffraction most probably has a magnetic origin.
Energy Technology Data Exchange (ETDEWEB)
Liu, Xinzhi [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Hao, Lijie, E-mail: haolijie@ciae.ac.cn [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Liu, Yuntao; Ma, Xiaobai; Meng, Siqin; Li, Yuqing; Gao, Jianbo; Guo, Hao; Han, Wenze; Sun, Kai; Wu, Meimei [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China); Chen, Xiping; Xie, Lei [Institute of Nuclear Physics and Chemistry, CAEP, Mianyang 621900 (China); Klose, Frank [Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales 2234 (Australia); Department of Physics and Materials Science, The City University of Hong Kong, Hong Kong (China); Chen, Dongfeng, E-mail: dongfeng@ciae.ac.cn [Department of Nuclear Physics, China Institute of Atomic Energy, Beijing 102413 (China)
2016-11-01
Orthoferrite solid solution HoFe{sub 1−x}Cr{sub x}O{sub 3} (x=0, 0.2,…,1.0) was synthesized via solid state reaction methods. The crystal structure, magnetism and spin reorientation properties of this system were investigated by X-ray diffraction, neutron powder diffraction and magnetic measurements. For compositions of x≤0.6, the system exhibits similar magnetic properties to HoFeO{sub 3}. With increasing Cr-doping, the system adopts a Γ{sub 4}(G{sub x}A{sub y}F{sub z}) magnetic configuration with a decreased Neel temperature from 640 K to 360 K. A Γ{sub 42} spin reorientation of Fe(Cr){sup 3+} was also observed in this system with an increase in transition temperature from 56 K to about 200 K due to competition between the Fe(Cr)–Fe(Cr) and Ho–Fe(Cr) interactions. For the x≥0.8, the system behaves more like HoCrO{sub 3} which adopts a Γ{sub 2}(F{sub x}C{sub y}G{sub z}) configuration with no spin reorientation below the Neel temperature T{sub N}. Throughout the whole substitution range, we found that the saturated moment of Fe(Cr) was less than the ideal value for a free ion, which implies the existence of spin fluctuation in this system. A systematic magnetic structure variation with Cr-substitution is revealed by Rietveld refinement. A phase diagram combining the results of the magnetic measurements and neutron powder diffraction results was obtained. - Highlights: • With Cr-substitution in the HoFe{sub 1−x}Cr{sub x}O{sub 3} system, A Γ{sub 42} spin reorientation of Fe(Cr){sup 3+} was observed with an increase in transition temperature from 56 K to about 200 K for x=0−0.6. • The saturated moment of Fe(Cr) position was found to be systematically less than the ideal value of free ion, and thus implies the presence of spin quantum fluctuation. • A composition–temperature phase diagram throughout x=0–1 for HoFe{sub 1−x}Cr{sub x}O{sub 3} system was established.
Synthesis of LaO1-xFxFeAs (x=0-0.15) via solid state metathesis reaction
Frankovsky, Rainer; Marchuk, Alexey; Pobel, Roman; Johrendt, Dirk
2012-04-01
LaOFeAs and superconducting LaO1-xFxFeAs have been synthesized via salt metathesis reactions and characterized by X-ray powder diffraction and magnetic susceptibility measurements. The process uses LaOCl and NaFeAs as precursors and yielded very pure samples. Superconductivity was confirmed in samples with x=0.05, 0.10 and 0.15 at critical temperatures of 11 K, 26 K and 9 K, respectively. According to temperature-dependent X-ray diffraction data, the reaction pathway is not topotactic in contrast to earlier suggestions.
Formation cross section of iron-60 with reactor neutrons in 59Fe(n, γ)60Fe reaction
International Nuclear Information System (INIS)
Sato, T.; Suzuki, T.
1993-01-01
Ingrowth of 60 Co radioactivity in an iron sample irradiated in a nuclear reactor has been measured for determination of formation cross section of 60 Fe in the 59 Fe(n, γ) 60 Fe reaction with reactor neutrons. After 5 years cooling, the irradiated iron was purified from 60 Co and other radioactive nuclides by an anion exchange separation method and isopropyl ether extraction in hydrochloric acid. The amount of 60 Co ingrowth was measured by γ-spectrometry using a Ge-detector coupled to a multichannel pulse height analyzer 4 years after the purification of iron. Neutron flux of the irradiation position was calculated from the amount of 55 Fe produced. The observed value of 12.5 ± 2.8 barn is slightly greater than reported value for burnup cross section of 59 Fe(n, x)X, where x refers γ, α, d, p and 2n, and X is any nuclide produced by the above reactions. (author) 8 refs.; 2 tabs
Microstructures of neutron-irradiated Fe-12Cr-XMn (X=15-30) ternary alloys
International Nuclear Information System (INIS)
Miyahara, K.; Hosoi, Y.; Garner, F.A.
1992-01-01
The objective of this effort is to determine the factors which control the stability of irradiated alloys proposed for reduced activation applications. The Fe-Cr-Mn alloy system is being studied as an alternative to the Fe-Cr-Ni system because of the need to reduce long-term radioactivation in fusion-power devices. In this study, four Fe-12Cr-XMn (X =15, 20, 25, 30 wt%) alloys were irradiated in the Fast Flux Test Facility to 20 dpa at 643K and 40 dpa at 679, 793, and 873K to investigate the influence of manganese content on void swelling and phase stability. The results confirm and expand the results of earlier studies that indicate that the Fe-Cr-Mn system is relatively unstable compared to that of the Fe-Cr-Ni system, with alpha and sigma phases forming as a consequence of thermal aging or high temperature irradiation
Studies on Kondo insulating FeSi
International Nuclear Information System (INIS)
Bharathi, A.; Mani, Awadhesh; Ravindran, Nithya; Mathi Jaya, S.; Sundar, C.S.; Hariharan, Y.
2000-01-01
Temperature dependent electrical resistivity measurements have been carried out in Fe (1-x) Ru x Si and FeSi (1-x) Ge x to examine the robustness of the Kondo Insulating gap to substitution in the Fe and Si sublattices. The gap is seen to decrease with Ge substitution, while for Ru substitution the gap shows an initial decrease followed by an increase at higher concentration. The results can be understood in terms of the shift in the mobility edge due to disorder and/or pressure effects in combination with changes in band structure
Low Temperature X-Ray Diffraction Study on CaFe2As2
Huyan, Shuyuan; Deng, Liangzi; Wu, Zheng; Zhao, Kui; Lv, Bing; Xue, Yiyu; Chu, Ching-Wu; B. Lv Collaboration; HPLT (Paul C. W. Chu) Team
For undoped CaFe2As2 single crystals, we observed that utilizing thermal treatments could stabilize two pure tetragonal phases PI and PII. Both phases are non-superconducting, while the superconductivity with a Tc up to 25 K can be induced through proper thermal treatment. Room temperature X-ray studies suggest that the origin of superconductivity arises from the interface of the mesoscopically stacked layers of PI and PII. To further investigate, a systematic low temperature X-ray study was conducted over a series of thermal treated CaFe2As2 single crystals. From which, we observed the phase aggregation of PI and PII upon cooling, more importantly, an ordered stacking structure exists at low temperature, which closely related to superconducting volume fraction and the ratio of PI and PII. These results further support the proposal of interface-enhanced superconductivity in undoped CaFe2As2. UT Dallas
Transport properties of dilute α -Fe (X ) solid solutions (X = C, N, O)
Schuler, Thomas; Nastar, Maylise
2016-06-01
We extend the self-consistent mean field (SCMF) method to the calculation of the Onsager matrix of Fe-based interstitial solid solutions. Both interstitial jumps and substitutional atom-vacancy exchanges are accounted for. A general procedure is introduced to split the Onsager matrix of a dilute solid solution into intrinsic cluster Onsager matrices, and extract from them flux-coupling ratios, mobilities, and association-dissociation rates for each cluster. The formalism is applied to vacancy-interstitial solute pairs in α -Fe (V X pairs, X = C, N, O), with ab initio based thermodynamic and kinetic parameters. Convergence of the cluster mobility contribution gives a controlled estimation of the cluster definition distance, taking into account both its thermodynamic and kinetic properties. Then, the flux-coupling behavior of each V X pair is discussed, and qualitative understanding is achieved from the comparison between various contributions to the Onsager matrix. Also, the effect of low-activation energy second-nearest-neighbor interstitial solute jumps around a vacancy on these results is addressed.
International Nuclear Information System (INIS)
Yan, Su-Yuan; Wang, Cheng-Yang; Gu, Rong-Min; Sun, Shuai; Li, Ming-Wei
2015-01-01
Highlights: • LiMn 0.6 Fe 0.4 PO 4 /C cathode material shows enhanced rate capability. • The Fe doped in the partial Mn sites could significantly facilitate the Li ions transfer. • The enhanced Li + ions diffusion contributes to the optimized rate capability of LiMn 0.6 Fe 0.4 PO 4 . • ACM carbonization forms well carbon coating and a 3D carbon network structure. - Abstract: To enhance the rate and cyclic performances of LiMnPO 4 cathode material for lithium-ion batteries, Mn is partially substituted with Fe, and LiMn 1−x Fe x PO 4 (x = 0.2, 0.3, 0.4, 0.5) solid solutions are synthesized and investigated. Amphiphilic carbonaceous material (ACM) forms well carbon coating and connects the LiMn 1−x Fe x PO 4 crystallites by a three-dimensional (3D) carbon network. The synergetic Fe substitution and carbon connection obviously improve the samples’ rate capacities and cyclic stability. The optimized LiMn 0.6 Fe 0.4 PO 4 /C sample delivers discharge capacities of 160 mA h g −1 at 0.05 C, 148 mA h g −1 at 1 C, and 115 mA h g −1 at 20 C. All samples have well capacity retention (>92%) after 50 charge/discharge cycles at 1 C. The enhanced electrochemical properties are mainly attributed to the improvement of Li ion and electron transport in the LiMn 1−x Fe x PO 4 /C samples, respectively mainly resulting from their modified crystal structures caused by Fe substitution and the 3D carbon coating/connection originating from ACM carbonization. LiMn 1−x Fe x PO 4 materials exhibit two discharge plateaus at ∼4.0 and ∼3.5 V (vs. Li + /Li), whose heights respectively reflect the redox potentials of Mn 3+ /Mn 2+ and Fe 3+ /Fe 2+ couples. The plateaus’ lengths correspond to the Mn/Fe ratio in LiMn 1−x Fe x PO 4 and are affected by the kinetic behavior of samples. Though the ∼4.0 V plateau shrinks with increasing discharge rate, the ∼3.5 V plateau may slightly elongate. Moreover, the Fe substituted in the partial Mn sites could significantly improve
International Nuclear Information System (INIS)
Li, J.; Jing, J.
1992-01-01
X-ray diffraction and Moessbauer measurements were performed on novelly synthesized La 1-x Ba x FeO 3-y (0≤x≤0.70). Two phases were found in the system. La 1-x Ba x FeO 3-y for 0≤x≤0.10 is an orthorhombic perovskite. La 1-x Ba x FeO 3-y for 0.54≤x≤0.70 is a cubic perovskite. La 1-x Ba x FeO 3-y for 0.10≤x≤0.54 consists of these two phases. (orig.)
Permeability and giant magnetoimpedance in Co69Fe4.5X1.5Si10B15 (X=Cr, Mn, Ni) amorphous ribbons
International Nuclear Information System (INIS)
Byon, Kwang Seok; Yu, Seong-Cho; Kim, Cheol Gi
2001-01-01
The magnetoimpedance (MI) has been measured in the amorphous ribbons of the soft ferromagnetic alloy Co 69 Fe 4.5 X 1.5 Si 10 B 15 (X=Cr, Mn, Ni) as functions of frequency (f). For all of the three samples, at low frequency, f≤5MHz, the MI ratio increases with increasing frequency, but the MI ratio decreases at high frequency, f≥5MHz. The MI profiles are not changed at low frequency regions of f≤1MHz in the amorphous ribbons. The MI ratio at high frequency of f=5MHz becomes 57% in Co 69 Fe 4.5 Cr 1.5 Si 10 B 15 , but the MI ratio becomes 30% in Co 69 Fe 4.5 Mn 1.5 Si 10 B 15 and Co 69 Fe 4.5 Ni 1.5 Si 10 B 15 . The MI ratio at f=10MHz becomes 45% in Co 69 Fe 4.5 Cr 1.5 Si 10 B 15 and the MI ratio becomes 23% in Co 69 Fe 4.5 Mn 1.5 Si 10 B 15 and Co 69 Fe 4.5 Ni 1.5 Si 10 B 15 , respectively. The maximum values of field sensitivity are 2.7(X=Cr), 2.5(X=Mn), 2.2(X=Ni)%/Oe for f=5MHz. [copyright] 2001 American Institute of Physics
Lu, Jinwen; Zhao, Yongqing; Niu, Hongzhi; Zhang, Yusheng; Du, Yuzhou; Zhang, Wei; Huo, Wangtu
2016-05-01
The present study is to investigate the microstructural characteristics, electrochemical corrosion behavior and elasticity properties of Ti-6Al-xFe alloys with Fe addition for biomedical application, and Ti-6Al-4V alloy with two-phase (α+β) microstructure is also studied as a comparison. Microstructural characterization reveals that the phase and crystal structure are sensitive to the Fe content. Ti-6Al alloy displays feather-like hexagonal α phase, and Ti-6Al-1Fe exhibits coarse lath structure of hexagonal α phase and a small amount of β phase. Ti-6Al-2Fe and Ti-6Al-4Fe alloys are dominated by elongated, equiaxed α phase and retained β phase, but the size of α phase particle in Ti-6Al-4Fe alloy is much smaller than that in Ti-6Al-2Fe alloy. The corrosion resistance of these alloys is determined in SBF solution at 37 °C. It is found that the alloys spontaneously form a passive oxide film on their surface after immersion for 500 s, and then they are stable for polarizations up to 0 VSCE. In comparison with Ti-6Al and Ti-6Al-4V alloys, Ti-6Al-xFe alloys exhibit better corrosion resistance with lower anodic current densities, larger polarization resistances and higher open-circuit potentials. The passive layers show stable characteristics, and the wide frequency ranges displaying capacitive characteristics occur for high iron contents. Elasticity experiments are performed to evaluate the elasticity property at room temperature. Ti-6Al-4Fe alloy has the lowest Young's modulus (112 GPa) and exhibits the highest strength/modulus ratios as large as 8.6, which is similar to that of c.p. Ti (8.5). These characteristics of Ti-6Al-xFe alloys form the basis of a great potential to be used as biomedical implantation materials. Copyright © 2016 Elsevier B.V. All rights reserved.
Synthesis and physical properties of the CuFe{sub 2−x}Mn{sub x}O{sub 4} (0 ≤ x ≤ 2) solid solution
Energy Technology Data Exchange (ETDEWEB)
Helaïli, N. [Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry, U.S.T.H.B., BP 32 El-Alia, 16111 Algiers (Algeria); Centre of Research in Physical and Chemical Analysis (CRAPC), BP 248, RP 16004 Algiers (Algeria); Bessekhouad, Y., E-mail: ybessekhouad@yahoo.fr [Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry, U.S.T.H.B., BP 32 El-Alia, 16111 Algiers (Algeria); National Veterinary High School, BP 161-El Harrach, Algiers (Algeria); Bachari, K. [Centre of Research in Physical and Chemical Analysis (CRAPC), BP 248, RP 16004 Algiers (Algeria); Trari, M. [Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry, U.S.T.H.B., BP 32 El-Alia, 16111 Algiers (Algeria)
2014-12-15
The CuFe{sub 2−x}Mn{sub x}O{sub 4} (0 ≤ x ≤ 2) solid solutions have been prepared by direct solid state reaction and the dependence of optical, electrical and electrochemical properties on the composition has been investigated. All samples exhibited the formation of a unique cubic phase irrespective of the composition with crystallite sizes on the order of 44 nm. Mn is localized in both octahedral and tetrahedral sites, and forms Mn{sup 3+}–O{sup 2−} complexes. The CuFe{sub 2−x}Mn{sub x}O{sub 4} system exhibits a p-type conductivity with indirect transition band gaps that decrease from 1.54 to 1.28 eV. Charge transport occurs either between Fe{sup 2+}/Fe{sup 3+} or Mn{sup 2+}/Mn{sup 3+} ions in B-sites according to the x value, and the conduction mechanism is controlled by small polaron hopping with a thermal activation of the mobility (μ), which is in the order of ∼10{sup −5} cm{sup 2} V{sup −1}s{sup −1} and does not depend on x. The conduction bands are particularly affected by the Mn introduction and the potentials can shift by as much as 0.5 eV. Finally, the CuFe{sub 2−x}Mn{sub x}O{sub 4} system was used as a bulk electrode in a photoelectrochemical cell and as a microphotoelectrode for H{sub 2}-production. CuFe{sub 1.6}Mn{sub 0.4}O{sub 4} demonstrates the best quantum conversion efficiency in terms of electricity (η = 0.21) and H{sub 2}-production (η{sup ∗} = 1.59). - Highlights: • The CuFe{sub 2−x}Mn{sub x}O{sub 4} (0 ≤ x ≤ 2) solid solutions have been prepared by solid state reaction. • CuFe{sub 2−x}Mn{sub x}O{sub 4} system exhibits p-type conductivity with indirect transition band gaps. • The charge transport occurs either between Fe{sup 2+}/Fe{sup 3+} or Mn{sup 2+}/Mn{sup 3+} ions in B-sites. • CuFe{sub 1.6}Mn{sub 0.4}O{sub 4} demonstrates the best quantum conversion efficiency {η"∗(H_2) = 1.59}.
International Nuclear Information System (INIS)
Liu, Xudong; Zhao, Yanming; Kuang, Quan; Li, Xiaoming; Dong, Youzhong; Jing, Zhenzhen; Hou, Shiyu
2016-01-01
Highlights: • Monoclinic structure Li_3V_2_−_xFe_x(PO_4)_3 (0≤ x≤2) solid solutions have been successfully fabricated via a two-step synthesis method. • Trace amounts of acetylene black would play a role of deoxidizer during the sintering process in an inert atmosphere. • V1-site is the preferred position when Fe"3"+ ions doped into Li_3V_2(PO_4)_3 from our structural analysis. - Abstract: Mixing transition-metal phosphates Li_3V_2_−_xFe_x(PO_4)_3 (0≤x≤2) were first designed to be a type of intercalated and deintercalated cathodes to obtain high specific capacity for safe Li-ion batteries. Since the residual oxygen in the quartz tube furnace and pellet would oxidize the V"3"+ to V"4"+ in the Ar ambience during the sintering process, trace amounts of acetylene black inside and outside the pellet could play a role of deoxidizer to protect V"3"+ meanwhile ensure Fe"3"+ not reducing to Fe"2"+. With the concerted effort of inside and outside acetylene black, monoclinic structure Li_3V_2_−_xFe_x(PO_4)_3 (0≤x≤2) solid solutions had been successfully fabricated via a two-step synthesis method. X-ray diffractions with Rietveld refinement revealed that V1-sites were the preferred position when Fe"3"+ ions doped into Li_3V_2(PO_4)_3, which means, every V1-site was occupied with the same probability by V"3"+ and Fe"3"+ when 0< x<1, and then for V2-site when 1< x<2. X-ray photoelectron spectroscopy result showed the presence of trace amounts of acetylene black had realized the coexist of V"3"+ and Fe"3"+ in the Li_3M_2(PO_4)_3 framework. When evaluated as cathodes for Li-ion batteries, the pure Li_3V_2(PO_4)_3 electrode displayed the highest charge (137.2 mAh g"−"1) and discharge (121.5 mAh g"−"1) capacities in the first cycle, with the increase of Fe"3"+ content, all the charge and discharge capacities reduced drastically. Furthermore, the EIS results showed that the incorporation of the sluggish Fe"3"+ ions reduced the electronic conductivity and
Adsorption of As(V) from water using Mg-Fe-based hydrotalcite (FeHT)
Energy Technology Data Exchange (ETDEWEB)
Tuerk, T. [Mineral Processing Division, Department of Mining Engineering, Karadeniz Technical University, 61080 Trabzon (Turkey); Alp, I., E-mail: ialp@ktu.edu.tr [Mineral Processing Division, Department of Mining Engineering, Karadeniz Technical University, 61080 Trabzon (Turkey); Deveci, H. [Mineral Processing Division, Department of Mining Engineering, Karadeniz Technical University, 61080 Trabzon (Turkey)
2009-11-15
This paper describes a study of the sorptive removal of arsenate (As(V)) from aqueous solutions by synthetically prepared Mg-Fe-based hydrotalcites (FeHT) as layered double hydroxide (LDH) adsorbents. The synthesis of Fe{sup 3+}-substituted hydrotalcites (FeHT) with the chemical formula [Mg(II){sub 6}Fe(III){sub 2}(OH){sub 16}]{sup 2+}[CO{sub 3} x yH{sub 2}O]{sup 2-} was achieved by a co-precipitation method. The reaction products were characterized by powder X-ray diffraction analysis. The influences of solution pH, initial arsenate (As(V)) concentration, and sorbent concentration were investigated in multiple kinetic runs. The adsorption rates and isotherms were investigated in batch experiments. The pseudo-first-order and second-order kinetic models were tested and the latter was found to fit better to the experimental data. Langmuir and Freundlich isotherms were used to describe the adsorption data from equilibrium experiments. The results have shown that FeHT has a high arsenate removal efficiency, with the ability to reduce the concentration of arsenate in the aqueous solution from an initial value of 330 {mu}g/l to <10 {mu}g/l (i.e. below the limit value specified by WHO).
Raman-spectroscopic (Fe/Fe+Mg, CO2) and Structural studies of Mg-Fe cordierites
International Nuclear Information System (INIS)
Haefeker, U.
2013-01-01
-determination in cordierite do not consider the effects of peak-broadening and peak-overlaps as a consequence of Fe-incorporation so far. The accuracy of the determination method, which is based on the relation between the intensity ratios of two Si-O stretching vibrations and the CO 2 -peak was increased and correction factors for Fe-bearing samples were obtained. This lead to a significant reduction of the overall error. Improved calibration diagrams which are based on the data of 10 natural Mg-Fe-cordierites with XFe = 0.044-0.76 and CO 2 -contents of 0.12-1.97 wt.%. were obtained using the excitation wavelengths of 488, 515 und 633 nm and these correlation diagrams were then successfully applied to natural cordierite grains in thin sections from a granulite from the Sauwald, Upper Austria. Fe-incorporation leads to various changes within the structure of cordierite. The hexagonal and the orthorhombic polymorph of Fe-cordierite were investigated with Raman-spectroscopy and XRD methods and a detailed structural description was provided. X-ray diffraction of both synthetic Fe-cordierite polymorphs yielded a, c (hex) = 9.8801(16) Å, 9.2852(5) Å and a, b, c (ortho) = 17.2306(2) 20 Å, 9.8239(1) Å, 9.2892(1) Å. The crystal structure was then refined using single crystal data and the obtained structural properties have been compared to the Mg-end-member by focussing on the changes on the octahedral positions. Raman data of the hexagonal Fe-cordierite have also been provided and various peaks could be assigned to certain lattice vibrations by comparing them with the results of quantum-mechanical calculations for cordierite. (author) [de
Magnetism mediated by a majority of [Fe³⁺ + VO²⁻] complexes in Fe-doped CeO₂ nanoparticles.
Paidi, V K; Ferreira, N S; Goltz, D; van Lierop, J
2015-08-26
We examine the role of Fe(3+) and vacancies (V(O)) on the magnetism of Fe-doped CeO2 nanoparticles. Magnetic nanoparticles of Ce(100-x)Fe(x)O2 (x = 0, 0.26, 1.82, 2.64, 5.26, 6.91, and 7.22) were prepared by a co-precipitation method, and their structural, compositional and magnetic properties were investigated. The CeO2 nanoparticles had a mixed valance of Ce(4+) and Ce(3+) ions, and doping introduced Fe(3+) ions. The decrease in Ce(3+) and increase in Fe(3+) concentrations indicated the presence of more [Fe(3+) + V(O)(2-)] complexes with Fe loading in the particles. Charge neutralization, Fe(3+) + V(O)(2-) + 2Ce(4+) ↔ 2Ce(3+) + Fe(3+), identified the impact of V(O) on the magnetism, where our results suggest that the Fe-doped CeO2 nanoparticle magnetism is mediated by a majority of [Fe(3+) + V(O)(2-)]-Ce(3+) -[Fe(3+) + V(O)(2-)] complexes.
Electronic structure of multiferroic BiFeO3 by resonant soft-x-ray emission spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Higuchi, Tohru; Higuchi, T.; Liu, Y.-S.; Yao, P.; Glans, P.-A.; Guo, Jinghua; Chang, C.; Wu, Z.; Sakamoto, W.; Itoh, N.; Shimura, T.; Yogo, T.; Hattori, T.
2008-07-11
The electronic structure of multiferroic BiFeO{sub 3} has been studied using soft-X-ray emission spectroscopy. The fluorescence spectra exhibit that the valence band is mainly composed of O 2p state hybridized with Fe 3d state. The band gap corresponding to the energy separation between the top of the O 2p valence band and the bottom of the Fe 3d conduction band is 1.3 eV. The soft-X-ray Raman scattering reflects the features due to charge transfer transition from O 2p valence band to Fe 3d conduction band. These findings are similar to the result of electronic structure calculation by density functional theory within the local spin-density approximation that included the effect of Coulomb repulsion between localized d states.
Structural and magnetic characterization of Nd-based Nd-Fe and Nd-Fe-Co-Al metastable alloys
International Nuclear Information System (INIS)
Kumar, G.
2005-01-01
The aim of the present work is to characterize a metastable hard magnetic phase referred to as ''A1'' in Nd-Fe alloys, which forms as a part of the fine eutectic depending on the composition and cooling rate. In order to define the range of composition for the formation of A1, Nd 100-x Fe x (x=20,25,40) alloys are cooled at about 150 K/s. The effect of cooling rate on the formation of hard magnetic A1 is studied by investigating the Nd 80 Fe 20 alloys cooled at different rates. The Nd-richer regions are identified as dhcp Nd and fcc Nd-Fe solid solution. However, the Fe-richer regions also referred to as A1, are diffuse and give an average composition of Nd 56 Fe 44 . HRTEM images of the Fe-richer regions reveal the presence of 5-10 nm crystallites embedded in an amorphous phase. The demagnetization curves the hard magnetic Nd80Fe20 measured at temperatures above 30 K are typical of a hard magnetic material. The measurements of initial magnetization, field dependence of coercivity, and temperature dependence of coercivity suggest the Stoner-Wohlfarth type magnetization reversal process for the hard magnetic A1. The values of anisotropy constant are estimated by fitting the magnetization data to the law-of-approach to saturation. The temperature dependence of anisotropy constant and the coercivity indicate that the origin of coercivity is magnetic anisotropy
Structural and magnetic properties and superconductivity in Ba(Fe1-xTMx)2As2
Energy Technology Data Exchange (ETDEWEB)
Thaler, Alexander [Iowa State Univ., Ames, IA (United States)
2012-01-01
We studied the effects on structural and magnetic phase transitions and the emergence of superconductivity in transition metal substituted BaFe2As2. We grew four series of Ba(Fe1-xTM2)2As2 (TM=Ru, Mn, Co+Cr and Co+Mn) and characterized them by crystallographic, magnetic and transport measurements. We also subjected Ba(Fe1-xCrx)2As2 and Ba(Fe1-xCox)2As2 to heat treatment to explore what changes might be induced.
Chen Zhi Gang; Yu Jun; Ibrahim, K; Dong Yu Hui; Wu Zi Yu; Wei Long; Wang Yu Tian
2002-01-01
LaFe sub 1 sub - sub x Cr sub x O sub 3 systematic compounds were prepared by Cr sup 3 sup + doping into the end component LaFeO sub 3. The crystal constants have been evaluated by using MarqX code. The analysis of the XRD data confirms that the perovskite compounds are in their single-phase state. The authors have also performed O 1s core-level photoemission experiments using photon energies above and below Fe 2p absorption edge, respectively, in order to investigate the crystal structure variation trend in terms of electronic structure. A preliminary conclusion has been drawn that the charge transfer amount from 0 2p to Cr 3d varies regularly with the doping level of Cr sup 3 sup + in LaFe sub 1 sub - sub x Cr sub x O sub 3
Resonant Ni and Fe KLL Auger spectra photoexcited from NiFe alloys
International Nuclear Information System (INIS)
Koever, L.; Cserny, I.; Berenyi, Z.; Egri, S.; Novak, M.
2005-01-01
Complete text of publication follows. KLL Auger spectra of 3d transition metal atoms in solid environment, measured using high energy resolution, give an insight into the details of the local electronic structure surrounding the particular atoms emitting the signal Auger electrons. Fine tuning the energy of the exciting monochromatic photons across the K-absorption edge, features characteristic to resonant phenomena can be identified in the spectra. The shapes of the resonantly photoexcited KLL Auger spectra induced from 3d transition metals and alloys are well interpreted by the single step model of the Auger process, based on the resonant scattering theory. The peak shapes are strongly influenced by the 4p partial density of unoccupied electronic states around the excited atom. High energy resolution studies of KLL Auger spectra of 3d transition metals using laboratory X-ray sources, however, request very demanding experiments and yield spectra of limited statistical quality making the evaluation of the fine details in the spectra difficult. The Tunable High Energy XPS (THE- XPS) instrument at BW2 offers optimum photon x and energy resolution for spectroscopy of deep core Auger transitions. For the present measurements high purity polycrystalline Ni and Fe sheets as well as NiFe alloy samples of different compositions (Ni 80 Fe 20 , Ni 50 Fe 50 , Ni 20 Fe 80 ) were used. The surfaces of the samples were cleaned by in-situ argon ion sputtering. The measurements of the Ni and Fe KL 23 L 23 Auger spectra of the metal and alloy samples were performed with the THE-XPS instrument using high electron energy resolution (0.2 eV). In Fig.1, the measured Fe KL 23 L 23 spectrum, photoexcited at the Fe K absorption edge from Fe metal, is compared with the respective spectrum excited from a Ni 50 Fe 50 alloy. A significant broadening of the 1 D 2 peak and an enhancement of the spectral intensity at the low energy loss part of this peak observed in the alloy sample, while the
Moessbauer and XRD study of pulse plated Fe-P and Fe-Ni thin layers
Energy Technology Data Exchange (ETDEWEB)
Miko, Annamaria [Bay Zoltan Institute for Material Science (Hungary); Kuzmann, Erno, E-mail: kuzmann@para.chem.elte.hu [Eoetvoes Lorand University, Research Group for Nuclear Methods in Structural Chemistry, Hungarian Academy of Sciences, Department of Nuclear Chemistry (Hungary); Lakatos-Varsanyi, Magda [Bay Zoltan Institute for Material Science (Hungary); Kakay, Attila [Research Institute for Solid State Physics and Optics (Hungary); Nagy, Ferenc [Eoetvoes Lorand University, Research Group for Nuclear Methods in Structural Chemistry, Hungarian Academy of Sciences, Department of Nuclear Chemistry (Hungary); Varga, Lajos Karoly [Research Institute for Solid State Physics and Optics (Hungary)
2005-09-15
{sup 57}Fe conversion electron Moessbauer spectroscopy, X-ray diffraction, electrochemical and magnetic measurements were used to study pulse electroplated Fe-P and Ni-Fe coatings. XRD and {sup 57}Fe CEMS measurements revealed the amorphous character of the novel pulse plated Fe-P alloys. CEM spectra indicated significant differences in the short range order and in the magnetic anisotropy between the Fe-P deposits pulse plated at medium long deposition time (t{sub on} = 2 ms), with short relaxation time (t{sub off} = 9 ms) and low current density (I{sub p} = 0.05 Acm{sup -2}) or at short deposition time (t{sub on} = 1 ms) with long relaxation time (t{sub off} = 250 ms) and high current density (I{sub p} = 1.0 Acm{sup -2}). The broad peaks centred around the fcc reflections in XRD of the pulse plated Ni-22 wt.% Fe deposit reflected a microcrystalline Ni-Fe alloy with a very fine, 5-8 nm, grain size. The CEM spectrum of the pulse plated Ni-22 wt.% Fe coating corresponded to a highly disordered solid solution alloy containing a minute amount of ferrihydrite. Extreme favourable soft magnetic properties were observed with these Ni-Fe and Fe-P pulse plated thin layers.
Experimental investigation and thermodynamic calculation of the Fe-Mg-Mn and Fe-Mg-Ni systems
Energy Technology Data Exchange (ETDEWEB)
Wang, Peisheng; Zhao, Jingrui; Xu, Honghui; Liu, Shuhong; Ouyang, Hongwu [Central South Univ., Hunan (China). State Key Lab. of Powder Metallurgy; Du, Yong [Central South Univ., Hunan (China). State Key Lab. of Powder Metallurgy; Harbin Institute of Technology (China). State Key Lab. of Advanced Welding Production Technology; Gang, Tie; Fen, Jicai [Harbin Institute of Technology (China). State Key Lab. of Advanced Welding Production Technology; Zhang, Lijun [Central South Univ., Hunan (China). State Key Lab. of Powder Metallurgy; Bochum Univ. (Germany). ICAMS Inst.; He, Cuiyun [Guangxi Univ. (China). College of Physical Science and Technology
2011-01-15
Based on the thermodynamic calculations extrapolated from the corresponding binary sub-systems, four decisive alloys in the Fe-Mg-Mn system and three in the Fe-Mg-Ni system were selected and prepared using a powder metallurgy method to measure the isothermal sections at 500 C in both systems. The prepared samples were annealed at 500 C, and then subjected to X-ray diffraction, optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectrometry as well as electron probe microanalysis. Taking into account the presently obtained experimental data and the experimental data available in the literature, thermodynamic modeling was performed for the above systems. It was found that a direct extrapolation from the corresponding three binary systems can well reproduce all the experimental data in the Fe-Mg-Mn system, while two thermodynamic parameters are needed in the Fe-Mg-Ni system to fit all the experimental data. The liquidus projections and reaction schemes for the Fe-Mg-Mn and Fe-Mg-Ni systems are also presented. (orig.)
Iodine as an oxidant in the topotactic deintercalation of interstitial iron in Fe(1+x)Te.
Rodriguez, Efrain E; Zavalij, Peter; Hsieh, Ping-Yen; Green, Mark A
2010-07-28
The layered telluride, Fe(1+x)Te, is a parent compound of the isostructural and superconducting phases, Fe(1+x)(Te, Se, S). Here we show that, through a simple reaction of I(2) vapor with both powder and single crystal samples, the interstitial iron can be removed from the FeTe framework topotactically. Neutron powder diffraction and X-ray single crystal diffraction confirm that the iron being extracted is the partially occupied site that lies between the 2-D blocks of edge-sharing FeTe(4) tetrahedra. The deintercalation process has consequences for both magnetic and crystallographic phase transitions in the compound at low temperatures. This technique could be of use for the tuning of stoichiometry of the superconducting phases and therefore enable more careful studies on how chemical composition affects magnetic and superconducting properties.
Energy Technology Data Exchange (ETDEWEB)
Stueble, Pirmin; Roehr, Caroline [Institut fuer Anorganische und Analytische Chemie, Universitaet Freiburg (Germany)
2017-11-17
The three cesium selenido ferrate title compounds with an Se:Fe ratio of 2:1 were synthesized from stoichiometric samples reacting elemental Cs either (A) with Fe and Se in a double-crucible setup (Cs[FeSe{sub 2}], Cs{sub 3}[FeSe{sub 2}]{sub 2}) or (B) with previously prepared FeSe{sub 2} (Cs{sub 3}[FeSe{sub 2}]{sub 2}, Cs{sub 7}[Fe{sub 4}S{sub 8}]) (T{sub max} = 800-1000 C). The pure Fe{sup III} ferrate Cs[FeSe{sub 2}] crystallizes in the Tl[FeSe{sub 2}] type [monoclinic, space group C2/m, a = 1392.95(10), b = 564.43(3), c = 737.44(6) pm, β = 119.163(5) , Z = 4, R{sub 1} = 0.0550]. It is thus not isotypic to all other alkali ferrates(III) A[FeS{sub 2}] and A[FeSe{sub 2}] containing chains of edge-sharing tetrahedra, but crystallizes in a t2 subgroup of the Immm structure of Cs[FeS{sub 2}]. The mixed-valent chain compound Cs{sub 3}[FeSe{sub 2}]{sub 2} is isotypic to its sulfido analogue [orthorhombic, space group Pnma, a = 777.88(6), b = 1151.02(6), c = 1341.61(7) pm, Z = 4, R{sub 1} = 0.0470]. In contrast to the isopunctal Na{sub 3}[FeSe{sub 2}]{sub 2} type K/Rb compounds the chains are only slightly corrugated. The monoclinic, likewise mixed-valent Fe{sup II/III} selenido ferrate Cs{sub 7}[Fe{sub 4}Se{sub 8}] [monoclinic, space group C2/c, a = 1953.79(10), b = 879.71(5), c = 1717.03(10) pm, β = 117.890(2) , Z = 4, R{sub 1} = 0.0816] is isostructural both to the cesium sulfido and tellurido compound. The structure contains oligomeric moieties of four edge sharing [FeSe{sub 4}] tetrahedra forming slightly distorted tetrahedral clusters [Fe{sub 4}Se{sub 8}]{sup 7-}, which are surrounded by a cube of 26 Cs cations. Based on a structure map, the crystal chemistry of the three title compounds is discussed together with all chain/cluster ferrates of the general series A{sub 1+x}[Fe{sup III}{sub 1-x}Fe{sup II}{sub x}Q{sub 2}] (x = 0-1; A = Na, K, Rb, Cs; Q = S, Se, Te). (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Atanda, Luqman A.
2011-04-01
A series of Mg3Fe0.5-xCoxAl0.5 (x = 0-0.5) catalysts were prepared from hydrotalcite precursors and their activities in the dehydrogenation of ethylbenzene were compared with those of a series of Mg3Fe0.5-yNiyAl0.5 (y = 0-0.5) catalysts also derived from hydrotalcite. The hydrotalcites prepared by co-precipitation were calcined at 550 °C to the mixed oxides with a high surface area of 150-240m2gcat-1; they were composed of Mg(Fe,Me,Al)O periclase and Mg(Me)(Fe,Al)2O4 spinel (Me = Co or Ni). Bimetallic Fe3+-Co2+ system showed a synergy, i.e., an increase in the activity, whereas Fe3+-Ni2+ bimetallic system showed no synergy. The high styrene yield was obtained on Mg 3Fe0.1Co0.4Al0.5; however, a large substitution of Fe3+ with Co2+ caused a decrease in styrene selectivity along with coking on the catalysts, due to an isolation of CoOx on the catalyst surface. The highest yield as well as the highest selectivity for styrene production was obtained at x = 0.25 at time on stream of 30 min. The coprecipitation at pH = 10.0 and the composition of Mg3Fe0.25Co0.25Al0.5 were the best for preparing the active catalyst. This is partly due to the formation of a good hydrotalcite structure. On this catalyst, the active Fe3+ species was reduced at a low temperature by the Fe3+-Co2+ bimetal formation, leading to a high activity. Simultaneously, the amount of reducible Fe3+ was the smallest, resulting in a high stability of the active Fe3+ species. It is likely that the dehydrogenation was catalyzed by the reduction-oxidation between Fe3+ and Fe2+ and that Co2+ assisted the reduction-oxidation by forming Fe 3+-Co2+ (1/1) bimetallic active species. © 2011 Elsevier B.V. All rights reserved.
X-ray studies of interface Fe-oxide in annealed MgO based magnetic tunneling junctions
Energy Technology Data Exchange (ETDEWEB)
Telesca, D., E-mail: donaldtelesca@gmail.com [Department of Physics, University of Connecticut, 2152 Hillside Road, Storrs, CT 06269 (United States); Space Vehicles Directorate, Air Force Research Lab (AFRL), Kirtland AFB, NM 87117 (United States); Sinkovic, B. [Space Vehicles Directorate, Air Force Research Lab (AFRL), Kirtland AFB, NM 87117 (United States); Yang, See-Hun; Parkin, S.S.P. [IBM Amaden Research Center, 650 Harry Road, San Jose, CA 95120 (United States)
2012-08-15
Highlights: Black-Right-Pointing-Pointer This work concludes the presence of oxide in MgO/transition-metal bi-layers. Black-Right-Pointing-Pointer Thermal annealing causes a possible structural transformation of the oxide. Black-Right-Pointing-Pointer This is first evidence for a possible structural change of the oxide. Black-Right-Pointing-Pointer First use of the O K-edge XAS signature of TM oxides to confirm presence of oxide. Black-Right-Pointing-Pointer We see a diffusion of oxygen and a decrease in interface roughness. -- Abstract: X-ray absorption spectroscopy and X-ray scattering have been used to determine the oxidation reactions at the buried MgO/Fe interface as a result of the deposition of MgO. We confirm that Fe-oxide is present at the MgO/Fe and MgO/CoFe interfaces and amounts to less than 1 mL in thickness. The Fe-oxide is a mixture of different iron oxide phases within the ultra-thin layer which can be reduced following annealing. We observe the transformation of the interfacial oxide from a more Fe{sub 2}O{sub 3}-like phase to a more FeO-like phase following annealing, and that this process is most noticeable between the 200 and 350 Degree-Sign C annealing steps. In addition, the formation of a more bulk like MgO electronic structure following annealing was observed.
International Nuclear Information System (INIS)
Miyake, Takashi; Nakamura, Kazuma; Arita, Ryotaro; Imada, Masatoshi
2010-01-01
Effective low-energy Hamiltonians for several different families of iron-based superconductors are compared after deriving them from the downfolding scheme based on first-principles calculations. Systematic dependences of the derived model parameters on the families are elucidated, many of which are understood from the systematic variation of the covalency between Fe-3d and pnictogen-/chalcogen-p orbitals. First, LaFePO, LaFeAsO (1111), BaFe 2 As 2 (122), LiFeAs (111), FeSe, and FeTe (11) have overall similar band structures near the Fermi level, where the total widths of 10-fold Fe-3d bands are mostly around 4.5 eV. However, the derived effective models of the 10-fold Fe-3d bands (d model) for FeSe and FeTe have substantially larger effective onsite Coulomb interactions U - 4.2 and 3.4 eV, respectively, after the screening by electrons on other bands and after averaging over orbitals, as compared to ∼2.5 eV for LaFeAsO. The difference is similar in the effective models containing p orbitals of As, Se or Te (dp or dpp model), where U ranges from ∼4 eV for the 1111 family to ∼7 eV for the 11 family. The exchange interaction J has a similar tendency. The family dependence of models indicates a wide variation ranging from weak correlation regime (LaFePO) to substantially strong correlation regime (FeSe). The origin of the larger effective interaction in the 11 family is ascribed to smaller spread of the Wannier orbitals generating larger bare interaction, and to fewer screening channels by the other bands. This variation is primarily derived from the distance h between the pnictogen/chalcogen position and the Fe layer: The longer h for the 11 family generates more ionic character of the bonding between iron and anion atoms, while the shorter h for the 1111 family leads to more covalent-bonding character, the larger spread of the Wannier orbitals, and more efficient screening by the anion p orbitals. The screened interaction of the d model is strongly orbital
Preparation and property of magnetic photocatalyst BiOCl/Mn{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4}
Energy Technology Data Exchange (ETDEWEB)
Feng, Shan; Xu, Longjun, E-mail: xulj@cqu.edu.cn; Liu, Chenglun [State Key Laboratory of Coal Mine Disaster Dynamics and Control (China); Du, Haigang [Liupanshui Normal University, Department of Mining Engineering (China); Xie, Taiping [State Key Laboratory of Coal Mine Disaster Dynamics and Control (China); Zhu, Qianqian [Chongqing University, College of Chemistry and Chemical Engineering (China)
2017-02-15
The magnetic photocatalyst BiOCl/Mn{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} was prepared by impregnation-calcination method. The structure and properties of the prepared photocatalyst were characterized by FTIR, XRD, SEM, TEM, UV–vis DRS, and VSM. Mn{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} inhibited the growth along (001) crystal face and promoted (110) crystal surface exposure of BiOCl. The as-prepared magnetic composite appeared flower-like microspheres assembled with nanosheets. The average crystallite size and the nanosheet thickness range of BiOCl/Mn{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} were 57.6 and 75.7–112.2 nm, respectively. The band gap energy (E{sub g}) of BiOCl/Mn{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} was 2.48 eV, which was lower than that of BiOCl. The saturation magnetization (Ms), coercive force (Hc), and remanent magnetization (Mr) of BiOCl/Mn{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} were respectively 4.64 emu g{sup −1}, 50.12 G and 0.09 emu g{sup −1}, indicating a good resistance to demagnetization and paramagnetism. The optimum synthesis condition of BiOCl/Mn{sub x}Zn{sub 1−x}Fe{sub 2}O{sub 4} was obtained by orthogonal experiments, and the degradation ratio of RhB with the photocatalyst was 99.6% at 30 min. After four cycles, the degradation ratio of RhB with the recovered photocatalyst was still above 83%.
Park, Shin Ae; Lee, Hee Jung; Cho, Yea Jin; Choi, Sora; Oh, Moonhyun
2014-05-05
A precise fabrication of nanobamboo structures made from hybrid coordination polymers of the type {Fex In1-x }-MIL-88B is demonstrated. The compositions of the hybrid coordination polymer nanobamboos of {Fex In1-x }-MIL-88B (x=0.06, 0.19, or 0.75) are regulated by altering the amount of metal ions used in the reactions. Interestingly, the formation of a virtual In-MIL-88B (precise structure, {Fe0.06 In0.94 }-MIL-88B), which cannot be created in a typical reaction, is induced by the assistance of a Fe-MIL-88B structure. The a and c cell parameters of {Fe0.06 In0.94 }-MIL-88B are calculated at 10.95 and 19.86 Å, respectively. These values of {Fe0.06 In0.94 }-MIL-88B are larger than those of pure Fe-MIL-88B owing to the large ionic size of In(3+) within the framework. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Liu, Xin
2012-01-01
We investigated the electronic structure of Fe nanoparticle-graphene composites and the impact of the interfacial interaction on NH x (x = 0, 1, 2, 3) adsorption by first-principles based calculations. We found that Fe 13 nanoparticles can be stabilized by the sp 2 dangling bonds on single vacancy graphene substrate with a binding energy up to -7.07 eV. This interaction not only deformed the carbon atoms around the defect and gave rise to the stability of the Fe nanoparticle against sintering, but also had significant impact on the adsorption of NH x that is related to the catalytic performance of these composites in NH 3 decomposition. Doping of the single vacancy graphene with N or B can finely tune the adsorption of NH x. Further analysis revealed that the calculated adsorption energies of NH x on these composites correlated well with the shift of the average d-band center of the Fe nanoparticles and they were around the peak of the activity-adsorption energy curve for NH 3 decomposition catalysts, especially when doped with B. The optimal adsorption of NH x on Fe nanoparticles deposited on boron-doped defective graphene suggests the possible high stability and superior catalytic performance of these composites in the low-temperature catalytic decomposition of NH 3. This journal is © 2012 the Owner Societies.
Thermodynamics of the (Sm{sub 2}Fe{sub 17-x}Ga{sub x}+H{sub 2}) system
Energy Technology Data Exchange (ETDEWEB)
Kubis, M.; Handstein, A.; Gebel, B.; Gutfleisch, O.; Mueller, K.H.; Schultz, L. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany). Inst. fuer Metallische Werkstoffe
2000-08-10
Sm{sub 2}Fe{sub 17-x}Ga{sub x} samples (with x=0, 0.5, 1, and 2) were disproportionated into SmH{sub 2} and {alpha}-(Fe,Ga) by heating the samples in 4 MPa hydrogen up to 650 C. It was possible to disproportionate even the more stable compounds with a higher Ga content under these conditions. The recombination into the original 2:17 phase was carried out by annealing in low hydrogen pressures of 2.5, 12 and 60 kPa. The values of the hydride formation enthalpy, {delta}H, and of the change of entropy, {delta}S, for the Sm{sub 2}Fe{sub 17-x}Ga{sub x} compounds were obtained by using the Van't Hoff relation. It was found that the negative {delta}H increases monotonically from 141 to 229 kJ/mol H{sub 2} and the negative {delta}S increases monotonically from 112 to 258 J/Kmol H{sub 2} for x=0 to x=2, respectively. These results show that the higher stability for the compounds with increasing Ga content is mainly attributed to the increasing negative change of entropy -{delta}S and not, as expected before, to a decrease of -{delta}H. (orig.)
Katayama, Tsukasa; Chikamatsu, Akira; Kamisaka, Hideyuki; Kumigashira, Hiroshi; Hasegawa, Tetsuya
2016-02-01
We investigated the electronic structure of perovskite SrFeO3-xFx (0.6 ≤ x ≤ 1) films by optical absorption, photoemission, and X-ray absorption spectroscopies, as well as density functional theory (DFT)-based calculations. The optical bandgap expanded with x, yielding a wider direct bandgap for the SrFeO2F film than for the LaFeO3 film. The DFT calculations suggested that the majority of FeO4F2 octahedra in the SrFeO2F film had cis configurations and that the enlarged bandgap mainly originated from bond bending in the O-Fe-O chains. We experimentally observed the valence and conduction bands of the SrFeO2F film, and found them to be qualitatively consistent with the results of DFT-based calculations.
Energy Technology Data Exchange (ETDEWEB)
Schuster, Ellen Ursula
2007-12-17
The research in this thesis is focused on the study of the Fe spin structure and interface magnetism of thin epitaxial Fe layers or epitaxial FePt alloy films with chemical L1{sub 0} order on GaAs(001) surfaces. The main method of investigation was isotope-specific conversion electron Moessbauer spectroscopy (CEMS) combined with the {sup 57}Fe probe-layer technique in the temperature range of 4.2-300 K. The film structure was studied using electron diffraction (RHEED) and X-ray diffraction (XRD). The chemical order parameter S determined by XRD was found to increase with rising growth temperature, T{sub S}, to a maximum value of 0.71, until long range order is destroyed at T{sub S}>350 C by alloying with the substrate. As an important result a linear correlation between short-range order (revealed by the relative spectral area of the L1{sub 0} phase) and long-range order S was observed. The observed perpendicular Fe spin texture, characterized by the mean tilting angle left angle {theta} right angle of the Fe spins (relative to the film normal direction), was found to correlate with the L1{sub 0} phase content and with S. Furthermore, epitaxial Fe(001) films on GaAs(001)-(4 x 6) and on GaAs(001)-LED surfaces were grown successfully. In the initial stage of Fe film growth non-monotonous behavior of the in-plane lattice parameter was observed by RHEED. The magnetic hyperfine field distributions P(B{sub hf}) at the Fe/GaAs interface extracted from CEMS spectra for T{sub S}=-140 C or room temperature (RT) were found to be very similar. The observed large mean hyperfine fields of left angle B{sub hf} right angle {approx}25-27 T at the interface indicate the presence of high average Fe moments of 1.7-1.8 {mu}{sub B}. Nonmagnetic interface layers either can be excluded (Fe/GaAs) or are very thin (0.5 ML,Fe/GaAs-LED). Owing to its island structure an ultrathin (1.9 ML thick) uncoated Fe(001) film on GaAs(001)-(4 x 6) shows superparamagnetism with a blocking temperature of
Energy Technology Data Exchange (ETDEWEB)
Gatimu, Alvin J.; Berthelot, Romain; Muir, Sean; Sleight, Arthur W. [Department of Chemistry, Oregon State University, Corvallis, OR 97331 (United States); Subramanian, M.A., E-mail: mas.subramanian@oregonstate.edu [Department of Chemistry, Oregon State University, Corvallis, OR 97331 (United States)
2012-06-15
The effects of Ti, Fe and Co substitutions for Ir on the structure and on the physical properties of Sr{sub 2}IrO{sub 4} are investigated. A complete solid solution Sr{sub 2}Ir{sub 1-x}Ti{sub x}O{sub 4} is obtained while both Fe and Co doping are relatively limited. In each case however, the c-axis cell parameter and the initial IrO{sub 6} octahedra tilting decreases with substitution. Doping with Ti, Fe and Co results in a decrease of the magnetic susceptibility and in an increase in the paramagnetic effective moment for Co and Fe doped samples and a suppression of the weak ferromagnetic ordering observed for Sr{sub 2}IrO{sub 4}. - Graphical abstract: Solid solutions of Sr{sub 2}Ir{sub 1-x}M{sub x}O{sub 4} (M=Ti, Fe, Co) have been synthesized and characterized by powder X-ray diffraction, magnetism and electrical measurements. Changes in the a parameter and decreases in both the c-axis cell parameters and the initial IrO{sub 6} octahedra tilting are found to be correlated. Highlights: Black-Right-Pointing-Pointer Solid Solutions of Sr{sub 2}Ir{sub 1-x}M{sub x}O{sub 4} (M=Ti, Fe, Co) are synthesized. Black-Right-Pointing-Pointer The Sr{sub 2}Ir{sub 1-x}Ti{sub x}O{sub 4} solid solution is complete while those of Fe and Co are relatively limited. Black-Right-Pointing-Pointer The change in a cell parameter with substitution is much less than that of the c parameter. Black-Right-Pointing-Pointer Decreased tilting and the smaller size of the M cation contrastingly affect the a parameter. Black-Right-Pointing-Pointer Doping results in a suppression of the weak ferromagnetic ordering in Sr{sub 2}IrO{sub 4}.
Magneto-optical imaging of iron-oxypnictide SmFeAsO1-xFx and SmFeAsO1-y
International Nuclear Information System (INIS)
Tamegai, T.; Nakajima, Y.; Tsuchiya, Y.; Iyo, A.; Miyazawa, K.; Shirage, P.M.; Kito, H.; Eisaki, H.
2009-01-01
We have prepared iron-oxypnictide SmFeAsO 1-x F x by ambient-pressure technique and SmFeAsO 1-y by high-pressure technique, and characterized their bulk and local magnetic properties by using SQUID magnetometer and magneto-optical imaging. While the high-pressure samples have densities close to the theoretical value, the ambient-pressure samples have several small voids. Despite these structural differences between the two kinds of samples, they both have superconducting transition temperature above 50 K. In addition, magneto-optical images for both samples show similar kinds of inhomogeneities with large current concentrated in several grains and with small intergranular current. The estimated intragranular currents for both samples are over 10 5 A/cm 2 at low temperatures and low fields.
Knyazev, Yu. V.; Kazak, N. V.; Bayukov, O. A.; Platunov, M. S.; Velikanov, D. A.; Bezmaternykh, L. N.; Ivanova, N. B.; Ovchinnikov, S. G.
2017-04-01
The investigation of mixed Co-Fe ludwigite single crystals shows that their magnetic properties are close to the magnetic properties of Fe3BO5 despite the predominance of cobalt ions. The magnetic properties of Co3 - x Fe x BO5 single crystals with x = 0.10 are studied in detail. Magnetometric measurements demonstrate a strong magnetic anisotropy with easy magnetization axis b, and the orbital magnetic moment of cobalt is in a frozen state. The detected temperature dependence of the absorption of Mössbauer spectra allowed us to determine the magnetic ordering temperature, which agrees with the results of magnetization measurements ( T C = 84 K).
International Nuclear Information System (INIS)
Kubis, M.; Cao, L.; Handstein, A.; Gebel, B.; Mueller, K.; Schultz, L.
1997-01-01
A hydrogenation-disproportionation-desorption-recombination process (HDDR) was applied to Sm 2 Fe 17-x Ga x (x=0.5, 1, and 2). The process was studied by means of temperature-pressure analysis, x-ray diffraction and scanning electron microscopy. It was shown that Ga not only stabilizes the interstitially modified compounds Sm 2 Fe 17-x Ga x C y (0 2 Fe 17-x Ga x against the disproportionation by hydrogen. Therefore, only for x=0.5 can a nearly complete HDDR be performed. The HDDR-treated and subsequently nitrogenated or carburized samples show coercivities μ 0J H C up to 3.1 T and 2.5 T, respectively. Hot compaction increases the density of the Sm 2 Fe 16.5 Ga 0.5 C y powder; however, it leads to a loss of coercivity due to decomposition into α-iron and samarium carbides. copyright 1997 American Institute of Physics
High-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga,Fe)Sb
International Nuclear Information System (INIS)
Tu, Nguyen Thanh; Hai, Pham Nam; Anh, Le Duc; Tanaka, Masaaki
2016-01-01
We show high-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga_1_−_x,Fe_x)Sb (x = 23% and 25%) thin films grown by low-temperature molecular beam epitaxy. Magnetic circular dichroism spectroscopy and anomalous Hall effect measurements indicate intrinsic ferromagnetism of these samples. The Curie temperature reaches 300 K and 340 K for x = 23% and 25%, respectively, which are the highest values reported so far in intrinsic III-V ferromagnetic semiconductors.
International Nuclear Information System (INIS)
Hancock, Cathryn A.; Herranz, Tirma; Marco, Jose F.; Berry, Frank J.; Slater, Peter R.
2012-01-01
Fluorination of the Ruddlesden Popper phase, Sr 3 Fe 2 O 7−x by heat treatment with polyvinylidine fluoride (PVDF) gives a range of novel oxide fluoride compounds. Fluorination with 1 mol equivalent PVDF leads to a filling of the normal Ruddlesden Popper structure anion sites and a material of composition Sr 3 Fe 2 O 5+x F 2−x (x≈0.28(4)) which contains both Fe 4+ and Fe 3+ . Increasing the amount of PVDF to 2 mol equivalent leads to an increase in anion content due to filling of half the interstitial sites within the structure, with iron being completely reduced to Fe 3+ leading to a composition Sr 3 Fe 2 O 4 F 4 . An increase in the amount of PVDF to ≈3 mol equivalent leads to a further increase in unit cell volume, attributed to complete filling of the interstitial sites and a composition Sr 3 Fe 2 O 3 F 6 . 57 Fe Mössbauer spectra in the temperature range 10–300 K demonstrated the complexity of the magnetic interactions in each of the three phases which reflect different local compositions of oxygen and fluorine around the iron ions thus influencing the superexchange pathways. - Graphical abstract: Low temperature (375 °C) fluorination of Sr 3 Fe 2 O 7−x with poly(vinylidene fluoride) leads to the production of three new Ruddlesden Popper oxide fluorides with progressive filling of the anion sites within the structure. Highlights: ► The fluorination of Sr 3 Fe 2 O 7−x using PVDF. ► The control of the fluorine content with amount of PVDF used. ► The synthesis of three new Fe based oxide fluorides. ► The identification of the structures of these oxide fluorides.
Senko, John M.; Dewers , Thomas A.; Krumholz, Lee R.
2005-01-01
A nitrate-dependent Fe(II)-oxidizing bacterium was isolated and used to evaluate whether Fe(II) chemical form or oxidation rate had an effect on the mineralogy of biogenic Fe(III) (hydr)oxides resulting from nitrate-dependent Fe(II) oxidation. The isolate (designated FW33AN) had 99% 16S rRNA sequence similarity to Klebsiella oxytoca. FW33AN produced Fe(III) (hydr)oxides by oxidation of soluble Fe(II) [Fe(II)sol] or FeS under nitrate-reducing conditions. Based on X-ray diffraction (XRD) analysis, Fe(III) (hydr)oxide produced by oxidation of FeS was shown to be amorphous, while oxidation of Fe(II)sol yielded goethite. The rate of Fe(II) oxidation was then manipulated by incubating various cell concentrations of FW33AN with Fe(II)sol and nitrate. Characterization of products revealed that as Fe(II) oxidation rates slowed, a stronger goethite signal was observed by XRD and a larger proportion of Fe(III) was in the crystalline fraction. Since the mineralogy of Fe(III) (hydr)oxides may control the extent of subsequent Fe(III) reduction, the variables we identify here may have an effect on the biogeochemical cycling of Fe in anoxic ecosystems.
Energy Technology Data Exchange (ETDEWEB)
Guezlane, M. [Department of Physics, Faculty of Science, University of Batna, 05000 Batna (Algeria); Baaziz, H., E-mail: baaziz_hakim@yahoo.fr [Physics Department, Faculty of Science, University of M' sila, 28000 M' sila (Algeria); El Haj Hassan, F., E-mail: hassan.f@ul.edu.lb [Université Libanaise, Faculté des Sciences (I), Laboratoire de Physique et d’Electronique (LPE), Elhadath, Beirut (Lebanon); Charifi, Z. [Physics Department, Faculty of Science, University of M' sila, 28000 M' sila (Algeria); Djaballah, Y. [Laboratoire d’étude Physico-Chimique des Matériaux, Département de Physique, Faculté des Sciences, Université de Batna, Rue Chahid Boukhlouf, 05000 Batna (Algeria)
2016-09-15
Density functional theory (DFT) based on the full-potential linearized augmented plane wave (FP-LAPW) method is used to investigate the structural, electronic, magnetic and thermal properties of Co{sub 2}Cr{sub x}Fe{sub 1−x}X (X=Al, Si) full Heusler alloys, with L2{sub 1} structure. The structural properties and spin magnetic moments are investigated by the generalized gradient approximations (GGA) minimizing the total energy. For band structure calculations, GGA, the Engel–Vosko generalized gradient approximation (EVGGA) and modified Becke–Johnson (mBJ) schemes are used. Results of density of states (DOS) and band structures show that these alloys are half-metallic ferromagnets (HMFS). A regular-solution model has been used to investigate the thermodynamic stability of the compounds Co{sub 2}Cr{sub x}Fe{sub 1−x}X that indicates a phase miscibility gap. The thermal effects using the quasi-harmonic Debye model are investigated within the lattice vibrations. The temperature and pressure effects on the heat capacities, Debye temperatures and entropy are determined from the non-equilibrium Gibbs functions. - Highlights: • We present electronic, magnetic and thermal properties of Co{sub 2}Cr{sub x}Fe{sub 1−x}X (X=Al, Si) Heusler alloys. • The calculated phase diagram indicates a significant phase miscibility gap. • The computed band structures of ternary compounds using GGA, EVGGA and mBJ schemes indicate an indirect band gap (Γ-X) for the ternary compounds Co{sub 2}FeAl, Co{sub 2}CrAl, Co{sub 2}FeSi and Co{sub 2}CrSi while both alloys have a direct band gap. • The quasi-harmonic Debye model is successfully applied to determine the thermal properties.
Analyais of solar X-ray emission line profiles
International Nuclear Information System (INIS)
Burek, A.J.; Marrus, D.M.; Blake, R.L.; Fenimore, E.E.
1981-01-01
We report results of the analysis of the X-ray emission line profiles for the Ne X La and Fe XVII 4d 1 P 1 lines produced in an active region that was undergoing a radio and X-ray gradual rise and fall (GRF) in intensity. The spectra were obtained with collimated Bragg spectrometers launched on a rocket from White Sands Missile Range on 1976 March 26. Using a crystal of ammonium acid phthalate, we have fully resolved the Ne X La and Fe XVII 4d 1 P 1 lines, permitting an accurate determinination of the Ne X La intensity and allowing Doppler broadened profiles for lines formed from ions having greatly different atomic mass and charge to be measured. An isothermal model derived from the Ne IX/Ne X resonance line intensity ratio gives an electron temperature of 3.4 x 10 6 K. An isothermal model, however, fails to account for the intensities of all lines and continuum observed. All multitemperature models that do reproduce the observed relative line intensities require the presence of a hot plasma component with an electron temperature in excess of 5 x 10 6 K. The presence of a high temperature component is also suggested by the measured line to continuum ratio of 3.6 in the 12--15 A wavelength interval. Interpretation of the line profiles in terms of a multitemperature model requires an rms turbulence velocity of 48 +- 15 km s -1 for Fe XVII 1 P 1 and 74 +- 54 km s - 2exclamation for Ne X La at the 95% confidence level. Collimated scans across the active region show the presence of a compact source of intense X-ray emission close to the magnetic neutral line, which is very probably the GRF plasma
Tagawa, S.; Ohta, K.; Hirose, K.
2014-12-01
The light elements in the Earth's core have not been fully identified yet, but hydrogen is now collecting more attention in part because recent planet formation theory suggests that large amount of water should have been brought to the Earth during its formation (giant-impact stage). Nevertheless, the effect of hydrogen on the property of iron alloys is little known so far. The earlier experimental study by Hirao et al. [2004 GRL] examined the compression behavior of dhcp FeHx (x ≈ 1) and found that it becomes much stiffer than pure iron above 50 GPa, where magnetization disappears. Here we examined the solubility of hydrogen into iron-rich Fe-Si alloys and the compression behavior of dhcp Fe-Si-H alloy at room temperature. Fe+6.5wt.%Si or Fe+9wt.%Si foil was loaded into a diamond-anvil cell (DAC), and then liquid hydrogen was introduced at temperatures below 20 K. X-ray diffraction measurements at SPring-8 revealed the formation of a dhcp phase with or without thermal annealing by laser above 8.4 GPa. The concentration of hydrogen in such dhcp lattice was calculated following the formula reported by Fukai [1992]; y = 0.5 and 0.2 for Fe-6.5wt.%Si-H or Fe-9wt.%Si-H alloys, respectively when y is defined as Fe(1-x)SixHy. Unlike Fe-H alloy, hydrogen didn't fully occupy the octahedral sites even under hydrogen-saturated conditions in the case of Fe-Si-H system. Anomaly was observed in obtained pressure-volume curve around 44 Å3 of unit-cell volume for both Fe-6.5wt.%Si-H and Fe-9wt.%Si-H alloys, which may be related to the spin transition in the dhcp phase. They became slightly stiffer at higher pressures, but their compressibility was still similar to that of pure iron.
High saturation magnetization FeB(C) nanocapsules
International Nuclear Information System (INIS)
Ma, S.; Si, P.Z.; Zhang, Y.; Wu, B.; Li, Y.B.; Liu, J.J.; Feng, W.J.; Ma, X.L.; Zhang, Z.D.
2007-01-01
FeB(C) nanocapsules were prepared by arc-discharging Fe 80 B 20 alloy in Ar and CH 4 . X-ray diffraction and transmission electron microscopy analyses showed that the FeB(C) nanocapsules had a core-shell structure with α-Fe and Fe 3 B as cores and graphite as shells. The formation mechanism of the FeB(C) nanocapsules is discussed. The graphite shells display a strong anti-acid effect. The saturation magnetization at room temperature of the FeB(C) nanocapsules is much higher than that of Fe(B) nanocapsules. The blocking temperature of FeB(C) nanocapsules is above 300 K
Preparation and thermoelectric properties of p-Type PrzFe4-xCoxSb12 skutterudites
International Nuclear Information System (INIS)
Shin, Dong-Kil; Kim, Il-Ho
2014-01-01
p-Type Pr z Fe 4-x Co x Sb 12 (z = 0.8, 1.0 and x = 0, 0.5, 1.0) skutterudites were synthesized by encapsulated melting and annealing and were consolidated with hot pressing. The effects of Pr filling and Co substitution for Fe (charge compensation) on the transport and the thermoelectric properties were examined. A few secondary phases, such as Sb and FeSb 2 , were formed together with the skutterudite phase, but the formation was suppressed with increasing Pr and Co contents. We confirmed that Pr filled in the voids and that Co was substituted for Fe in all specimens because the lattice constant increased with increasing Pr content and decreased with increasing Co content. The electrical conductivity decreased slightly with increasing temperature, showing degenerate semiconductor characteristics. The Hall and the Seebeck coefficients showed positive signs, indicating that the major carriers were holes (p-type conduction). The electrical conductivity and the thermal conductivity were decreased due to a decrease in the carrier concentration with increasing Pr and Co contents. As a result, the dimensionless figure of merit, ZT, was improved by Pr filling and Co substitution, and a maximum ZT = 0.89 was obtained at 723 K for Pr 0.8 Fe 3 CoSb 12 .
Energy Technology Data Exchange (ETDEWEB)
Carneiro, J.F.; Sabioni, A.C.S. [Universidade Federal de Ouro Preto (LDM/DF/UFOP), MG (Brazil). Dept. de Fisica. Lab. de Difusao em Materiais; Trindade, V.B. [Universidade Federal de Ouro Preto (DEMM/UFOP), MG (Brazil). Dept. de Engenharia Metalurgica e de Materiais; Ji, V. [Laboratoire d' Etude des Materiaux Hors-Equilibre (LEMHE), Orsay (France)
2010-07-01
The high temperature oxidation behavior of Fe-1.5%Cr, Fe-5.0%Cr, Fe-10%Cr and Fe- 15%Cr model alloys were investigated from 700 to 850 deg C, in air atmosphere. The oxidation treatments were performed in a thermobalance with a sensitivity of 1{mu}g. The oxide films grown by oxidation of the alloys were characterized by scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The oxide films are Fe-Cr spinels with variable composition depending on the alloy composition. For all conditions studied, the oxidation kinetics of these alloys follow a parabolic law. The comparison of the oxidation rates of the four alloys, at 700 deg C, shows that the parabolic oxidation constants decrease from 1.96x10{sup -9}g{sup 2}.cm{sup -4}.s{sup -1}, for the alloy Fe-1.5% Cr, to 1.18 x 10-14g{sup 2}.cm{sup -4}.s{sup -1} for the alloy Fe-15% Cr. Comparative analysis of the oxidation behavior of the Fe-10%Cr and Fe-15%Cr alloys, between 700 and 850 deg C, shows that the oxidation rates of these alloys are comparable to 800 deg C, above this temperature the Fe-10%Cr alloy shows lower resistance to oxidation. (author)
Isothermal section of the Er-Fe-Al ternary system at 800 oC
International Nuclear Information System (INIS)
Jemmali, M.; Walha, S.; Pasturel, M.; Tougait, O.; Ben Hassen, R.; Noel, H.
2010-01-01
Physico-chemical analysis techniques, including X-ray diffraction and Scanning Electron Microscope-Energy Dispersive X-ray Spectroscopy, were employed to construct the isothermal section of the Er-Fe-Al system at 800 o C. At this temperature, the phase diagram is characterized by the formation of five intermediate phases, ErFe 12-x Al x with 5 ≤ x ≤ 8 (ThMn 12 -type), ErFe 1+x Al 1-x with -0.2 ≤ x ≤ 0.75 (MgZn 2 -type), ErFe 3-x Al x with 0.5 2 Al-type), Er 2 Fe 17-x Al x with 4.74 ≤ x ≤ 5.7 (TbCu 7 -type) and Er 2 Fe 17-x Al x with 5.7 2 Zn 17 -type), seven extensions of binaries into the ternary system; ErFe x Al 3-x with x 3 Cu-type), ErFe x Al 2-x with x ≤ 0.68 (MgCu 2 -type), Er 2 Fe x Al 1-x with x ≤ 0.25 (Co 2 Si-type), ErFe 2-x Al x with x ≤ 0.5 (MgCu 2 -type), ErFe 3-x Al x with x ≤ 0.5 (Be 3 Nb-type), Er 6 Fe 23-x Al x with x ≤ 8 (Th 6 Mn 23 -type), and Er 2 Fe 17-x Al x with x ≤ 4.75 (Th 2 Ni 17 -type) and one intermetallic compound; the ErFe 2 Al 10 (YbFe 2 Al 10 -type).
International Nuclear Information System (INIS)
Rahimi, Hamed; Ghasemi, Ali; Mozaffarinia, Reza; Tavoosi, Majid
2017-01-01
In current work, Nd2Fe14B nanoparticles was synthesized by sol-gel method. Dysprosium powders were added into Nd2Fe14B nanoparticles by mechanical alloying process in order to enhancement of coercivity. The phase analysis, structure, and magnetic properties of annealed (Nd_1_−_xDy_x)_2Fe_1_4B nanoparticles with different Dy-content (x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6) were investigated by employing X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive spectroscopy, field emission scanning electron microscope, transmission electron microscope and vibrating sample magnetometer techniques. The results showed that with an increase in Dy amounts, the coercivity of particles increased from 2.9 kOe to 13.4 kOe and then decreased to 5.6 kOe. By adding an optimum amount of Dy (x=0.4), the coercivity was significantly increased from 2.9 kOe to 13.4 kOe. The average particle size of annealed (Nd_1_−_xDy_x)_2Fe_1_4B nanoparticles was below 10 nm. Magnetization reversal studies indicate that the coercivity of milled and annealed (Nd_1_−_xDy_x)_2Fe_1_4B nanoparticles is controlled by the nucleation of reversed magnetic domains. The experimental results in the angular dependence of coercivity for (Nd_1_−_xDy_x)_2Fe_1_4B permanent magnets showed that the normalized coercivity of the permanent magnets H_c(θ)/H_c(0) increases from 1 to about 1.2–1.5 with increasing θ from 0 to about π/3, for x=0.4–0.6. - Highlights: • Dy was added to Nd_2Fe_1_4B nanoparticles to improve the coercivity. • A maximum squareness ratio of 0.99 was obtained. • The average particle size decreased with an increase in Dy-content.
International Nuclear Information System (INIS)
Chaboy, J.; Marcelli, A.; Garcia, L.M.; Bartolome, J.; Kuz'min, M.D.; Maruyama, H.; Kobayashi, K.; Kawata, H.; Iwazumi, T.
1995-01-01
We present the first experimental observation of spin reorientation phase transitions (SRT) with the X-Ray circular magnetic dichroism (XCMD) technique. Both the first-order SRT in Er 2 Fe 14 B and the second-order one in Nd 2 Fe 14 B have been clearly detected, demonstrating the feasibility of this technique for studying SRTs. ((orig.))
Synthesis and magnetic properties of ferrites spinels Mg{sub x}Cu{sub 1-x}Fe{sub 2}O{sub 4}
Energy Technology Data Exchange (ETDEWEB)
Mounkachi, O.; Hamedoun, M. [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); Belaiche, M. [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Laboratoire de Magnetisme, Materiaux Magnetiques, Microonde et Ceramique, Ecole Normale Superieure, Universite Mohammed V-Agdal, B.P. 9235, Ocean, Rabat (Morocco); Benyoussef, A. [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); LMPHE, (URAC 12), Faculte des Sciences, Universite Mohammed V-Agdal, Rabat (Morocco); Masrour, R. [Laboratory of Materials, Process, Environment and Quality, Cady Ayad University, National School of Applied Sciences, Safi (Morocco); El Moussaoui, H. [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); LMPHE, (URAC 12), Faculte des Sciences, Universite Mohammed V-Agdal, Rabat (Morocco); Sajieddine, M., E-mail: hamedoun@hotmail.com [Faculte des Sciences et Techniques, Universite Moulay Slimane, Beni Mellal (Morocco)
2012-01-01
Polycrystalline Mg{sub 0.6}Cu{sub 0.4}Fe{sub 2}O{sub 4} ferrites have been prepared using solid-state reaction technique. Their structural and magnetic properties have been studied, using X-ray diffraction and magnetic measurements. Using mean field theory and high-temperature series expansions (HTSE), extrapolated with the pade approximants method, the magnetic properties of Mg{sub 1-x}Cu{sub x}Fe{sub 2}O{sub 4} have been studied. The nearest neighbor super-exchange interactions for intra-site and inter-site of the Mg{sub 1-x}Cu{sub x}Fe{sub 2}O{sub 4} ferrites spinels, in the range 0{<=}x{<=}1, have been computed using the probability approach, based on Moessbauer data. The Curie temperature T{sub c} is calculated as a function of Mg concentration. The obtained theoretical results are in good agreement with experimental ones obtained by magnetic measurements.
Extended x-ray absorption fine structure study of MnFeP0.56Si0.44 compound
International Nuclear Information System (INIS)
Li Ying-Jie; Haschaolu W; Wurentuya; Song Zhi-Qiang; Ou Zhi-Qiang; Tegus O; Nakai Ikuo
2015-01-01
The MnFeP 0.56 Si 0.44 compound is investigated by x-ray diffraction, magnetic measurements, and x-ray absorption fine structure spectroscopy. It crystallizes in Fe 2 P-type structure with the lattice parameters a = b = 5.9823(0) Å and c = 3.4551(1) Å and undergoes a first-order phase transition at the Curie temperature of 255 K. The Fe K edge and Mn K edge x-ray absorption fine structure spectra show that Mn atoms mainly reside at 3g sites, while 3f sites are occupied by Fe atoms. The distances between the absorbing Fe atom and the first and second nearest neighbor Fe atoms in a 3f-layer shift from 2.65 Å and 4.01 Å in the ferromagnetic state to 2.61 Å and 3.96 Å in the paramagnetic phase. On the other hand, the distance between the 3g-layer and 3f-layer changes a little as 2.66 Å–2.73 Å below the Curie temperature and 2.68 Å–2.75 Å above it. (paper)
MFM study of NdFeB and NdFeB/Fe/NdFeB thin films
International Nuclear Information System (INIS)
Gouteff, P.C.; Folks, L.; Street, R.
1998-01-01
Domain structures of NdFeB thin films, ranging in thickness between 1500 and 29 nm, have been studied qualitatively by magnetic force microscopy (MFM). Samples were prepared using a range of sputtering conditions resulting in differences in properties such as texture, coercivity and magnetic saturation. MFM images of all the films showed extensive interaction domain structures, similar to those observed in nanocrystalline bulk NdFeB. An exchange-coupled NdFeB/Fe/NdFeB trilayer with layer thicknesses 18 nm/15 nm/18 nm, respectively, was also examined using MFM. (orig.)
Microstructure and properties of multiphase sintered cermets Fe-Fe2B
International Nuclear Information System (INIS)
Nowacki, J.; Klimek, L.
1998-01-01
The process of multiphase sintering of iron in the vacuum has been analysed. As a result of the process iron-iron boride cermets have been produced. Fe-Fe 2 B cermets were obtained as a result of sintering of the Fe and B pure elements in the vacuum. Attemps at sintering in the solid phase and with the participation of the liquid phase, the Fe-Fe 2 B eutectic, have been made. Metallographic qualitative and quantitative studies, X-ray structural qualitative and qauantitative analysis allowed to determine the structure of Fe 2 B cermets, as well as a description of the kinetics of quantitative changes in phase proportions in the course of sintering. It has been found that their structure varies widely depending on sintering parameters and the composition of the sinters. Measurements of the Fe-Fe 2 B cermets hardness and measurements on wear during dry friction by the pin-on-disc method have shown distinct advantages of the cermets as a modern constructional materials. The hardness of Fe-Fe 2 B cermets, depending on their chemical composition and sintering parameters, ranges widely from 150 to 1500 HV, and their resistance to wear is comparable to that of diffusively boronized steels. FeFe 2 B cermets are a composite material in which iron boride, Fe 2 B, with a hardness of about 1800 HV plays the role of the reinforcement,while iron-iron boride, Fe-Fe 2 B, with a hardness of about 500 HV plays the role of matrix. The eutectic in the spaces between iron boride grains is composed of boron solid solution plates in iron with a hardness of arround 250 HV, and iron boride, Fe 2 B, plates with a hardness of approximaly 1800 HV. The combination of such different materials, a hard reinforcement and a relatively plastic matrix produces favourable properties of the cermet thus produced high hardness (1500 HV) constant over whole cross section of the material, resistance of abrasive wear and acceptable ductility. The properties mentioned above, resulting from the cermet
Magnetic properties of NdMn{sub 1−x}Fe{sub x}O{sub 3+δ} (0≤x≤0.3) system
Energy Technology Data Exchange (ETDEWEB)
Mihalik, Matúš, E-mail: matmihalik@saske.sk [Institute of Experimental Physics SAS, Watsonova 47, 040 01 Košice (Slovakia); Mihalik, Marián [Institute of Experimental Physics SAS, Watsonova 47, 040 01 Košice (Slovakia); Fitta, M.; Bałanda, M. [Institute of Nuclear Physics Polish Academy of Sciences, Radzikowskiego 152, 31-342 Kraków (Poland); Vavra, M. [Institute of Experimental Physics SAS, Watsonova 47, 040 01 Košice (Slovakia); P.J. Šafárik University, Moyzesova 11, 041 54 Košice (Slovakia); Gabáni, S.; Zentková, M. [Institute of Experimental Physics SAS, Watsonova 47, 040 01 Košice (Slovakia); Briančin, J. [Institute of Geotechnics SAS, Watsonova 45, 043 53 Košice (Slovakia)
2013-11-15
We have studied the effect of Fe for Mn substitution on magnetic properties of NdMn{sub 1−x}Fe{sub x}O{sub 3+δ} compounds. Our heat capacity, AC susceptibility and magnetization measurements revealed that the transition from paramagnetic to magnetically ordered state of the Mn sublattice decreases linearly from T{sub N}=74.9 K to T{sub N}=49 K with doping up to x=0.25. The ordering temperature T{sub 1} of Nd sublattice varies in a non-monotonous way in the temperature range 11–16 K. For x=0.3, the ordering of the Mn/Fe sublattice is residual, while the magnetism in Nd sublattice seems to be intact. The broad maximum in heat capacity C(T) at about 10 K was ascribed by 2-level Schottky contribution (Δ=21(1) K) for x=0, but this description failed for Fe-doped samples. An upturn of C(T) at temperatures below 0.5 K was observed on NdMnO{sub 3} and can be accounted to nuclear contribution. A more detailed study of AC susceptibility performed on samples with x=0.1 and 0.2 revealed a shift of both peaks to higher temperature with increasing frequency. The compensation temperature and a large negative field-cooled magnetization was observed for concentrations x=0.2 and x=0.25. - Highlights: • Fe substitution into NdMnO{sub 3} compound decreases T{sub N} by 10 K for 10% of Fe. • In this compound: Nd and Mn ions both order magnetically. • “Butterfly-type” hysteresis loops in the ordered state.
Magnetoresistance Versus Oxygen Deficiency in Epi-stabilized SrRu1 - x Fe x O3 - δ Thin Films.
Dash, Umasankar; Acharya, Susant Kumar; Lee, Bo Wha; Jung, Chang Uk
2017-12-01
Oxygen vacancies have a profound effect on the magnetic, electronic, and transport properties of transition metal oxide materials. Here, we studied the influence of oxygen vacancies on the magnetoresistance (MR) properties of SrRu 1 - x Fe x O 3 - δ epitaxial thin films (x = 0.10, 0.20, and 0.30). For this purpose, we synthesized highly strained epitaxial SrRu 1 - x Fe x O 3 - δ thin films with atomically flat surfaces containing different amounts of oxygen vacancies using pulsed laser deposition. Without an applied magnetic field, the films with x = 0.10 and 0.20 showed a metal-insulator transition, while the x = 0.30 thin film showed insulating behavior over the entire temperature range of 2-300 K. Both Fe doping and the concentration of oxygen vacancies had large effects on the negative MR contributions. For the low Fe doping case of x = 0.10, in which both films exhibited metallic behavior, MR was more prominent in the film with fewer oxygen vacancies or equivalently a more metallic film. For semiconducting films, higher MR was observed for more semiconducting films having more oxygen vacancies. A relatively large negative MR (~36.4%) was observed for the x = 0.30 thin film with a high concentration of oxygen vacancies (δ = 0.12). The obtained results were compared with MR studies for a polycrystal of (Sr 1 - x La x )(Ru 1 - x Fe x )O 3 . These results highlight the crucial role of oxygen stoichiometry in determining the magneto-transport properties in SrRu 1 - x Fe x O 3 - δ thin films.
Uptake and Release of Cerium During Fe-Oxide Formation and Transformation in Fe(II) Solutions
DEFF Research Database (Denmark)
Nedel, Sorin; Dideriksen, Knud; Christiansen, Bo C.
2010-01-01
Fe-oxides are ubiquitous in soils and sediments and form during Fe(0) corrosion. Depending on redox conditions and solution composition, Fe-oxides such as ferrihydrite, goethite, magnetite, and green rust (GR) may form. These phases typically have high surface area and large affinity for adsorption......(III) release. X-ray photoelectron spectroscopy revealed Ce(III) adsorbed on magnetite. When Fe-oxides were synthesized by air oxidation of Fe(II) solutions at pH 7, GR(Na,SO4) played a catalytic role in the oxidation of Ce(III) to Ce(IV) by O-2, removing more than 90% of the dissolved Ce. Transmission electron...
Fe-induced enhancement of antiferromagnetic spin correlations in Mn2-xFexBO4
Kazak, N. V.; Platunov, M. S.; Knyazev, Yu. V.; Moshkina, E. M.; Gavrilkin, S. Yu.; Bayukov, O. A.; Gorev, M. V.; Pogoreltsev, E. I.; Zeer, G. M.; Zharkov, S. M.; Ovchinnikov, S. G.
2018-04-01
Fe substitution effect on the magnetic behavior of Mn2-xFexBO4 (x = 0.3, 0.5, 0.7) warwickites has been investigated combining Mössbauer spectroscopy, dc magnetization, ac magnetic susceptibility, and heat capacity measurements. The Fe3+ ions distribution over two crystallographic nonequivalent sites is studied. The Fe introduction breaks a long-range antiferromagnetic order and leads to onset of spin-glass ground state. The antiferromagnetic short-range-order spin correlations persist up to temperatures well above TSG reflecting in increasing deviations from the Curie-Weiss law, the reduced effective magnetic moment and "missing" entropy. The results are interpreted in the terms of the progressive increase of the frustration effect and the formation of spin-correlated regions.
Energy Technology Data Exchange (ETDEWEB)
Diop, L.V.B. [Univ. Grenoble Alpes, Inst NEEL, F-38042 Grenoble (France); CNRS, Inst NEEL, F-38042 Grenoble (France); Kastil, J. [Univ. Grenoble Alpes, Inst NEEL, F-38042 Grenoble (France); CNRS, Inst NEEL, F-38042 Grenoble (France); Institute of Physics AS CR v.v.i., Na Slovance 2, 182 21 Prague 8 (Czech Republic); Isnard, O. [Univ. Grenoble Alpes, Inst NEEL, F-38042 Grenoble (France); CNRS, Inst NEEL, F-38042 Grenoble (France); Arnold, Z.; Kamarad, J. [Institute of Physics AS CR v.v.i., Na Slovance 2, 182 21 Prague 8 (Czech Republic)
2015-04-05
Highlights: • First report of the direct measurement of ΔT{sub ad} in Hf{sub 1−x}Ta{sub x}Fe{sub 2} compounds. • ΔT{sub ad} reach values of 2.5 K under μ{sub 0}ΔH = 3 T for x = 0.175 compound. • A field induced metamagnetic phase transition has been observed. - Abstract: Intrinsic magnetic properties and magnetocaloric effect (MCE) have been investigated for Hf{sub 1−x}Ta{sub x}Fe{sub 2} (x = 0.125 and 0.175) itinerant-electron compounds which exhibit a temperature-induced transition from the ferromagnetic (FM) to the antiferromagnetic (AFM) state. Upon increasing Ta concentration, the ferromagnetic ordering temperature strongly decreases with decreasing the lattice parameters and both the isothermal magnetic entropy change ΔS{sub M} and the adiabatic temperature change ΔT{sub ad} are enhanced. An adiabatic temperature change of ΔT{sub ad} = 2 and 2.5 K was observed in Hf{sub 0.875}Ta{sub 0.125}Fe{sub 2} and Hf{sub 0.825}Ta{sub 0.175}Fe{sub 2}, respectively, for a magnetic field change of 3 T. Therefore, the partial substitution of Ta for Hf is highly effective in the enhancement of the magnetocaloric effect in Hf{sub 1−x}Ta{sub x}Fe{sub 2} systems. In addition substitution can be used to tune both the transition temperature but also the magnetic transition from first toward second order type.
Magnetic properties of Fe1-xMnx/Fe nanocomposites
DEFF Research Database (Denmark)
Anhøj, Thomas Aarøe; Jacobsen, Claus Schelde; Mørup, Steen
2004-01-01
of the two materials showed enhanced coercivity, but almost negligible exchange bias at room temperature after field cooling from 520 K. However, samples with higher content of gamma-Fe50Mn50 showed significant exchange bias. The mechanisms for exchange bias and enhanced coercivity in the system...
Microstructural features of the La1−xCaxFeO3−δ solid solutions prepared via Pechini route
International Nuclear Information System (INIS)
Gerasimov, E.Yu.; Isupova, L.A.; Tsybulya, S.V.
2015-01-01
Highlights: • La 1−x Ca x FeO (3−δ) (0 ≤ x ≤ 0.7) perovskite were prepared by Pechini method. • Planar defects in direction (1 0 1) were observed in the perovskite surface. • α-Fe 2 O 3 particles (1–10 nm) on the surface of perovskite were revealed. • Amount of α-Fe 2 O 3 particles on the perovskite surface grew with rising x values. - Abstract: Solid solutions with La 1−x Ca x FeO 3−δ (0 ≤ x ≤ 0.7) perovskite-like structure prepared via Pechini route have been investigated by using high resolution transmission electron microscopy and X-ray diffraction. Extended planar defects lying in (1 0 1) crystallographic planes and α-Fe 2 O 3 nanoparticles on the surface of perovskite microcrystals are characteristic of the samples under investigation. It was found that testing of the samples in catalytic deep CH 4 oxidation process results in partial destruction of solid solutions with formation of planar defects in the bulk and α-Fe 2 O 3 particles on the surface
Charge disproportionation in Fe/sup 4 + -/oxides with perovskite-type structures
Energy Technology Data Exchange (ETDEWEB)
Takano, M; Nakanishi, N [Konan Univ., Kobe (Japan). Faculty of Science; Takeda, Y; Naka, S [Nagoya Univ. (Japan)
1979-01-01
For a further examination and elaboration of our simple charge disproportionation model for Fe/sup 4 +/-oxides, 2Fe/sup 4 +/..-->..Fe/sup 3 +/ + Fe/sup 5 +/, two series of solid solutions Casub(1-x)Srsub(x)FeO/sub 3/ and Srsub(1-x)Lasub(x)FeO/sub 3/ with the perovskite structure have been studied. The Moessbauer spectrum of Srsub(0,5)Lasub(0.5)FeO/sub 3/ at 4 K clearly indicates the disproportionation. For both series of oxides, the disproportionation seems to set in at the Tsub(N).
Magnetic transitions in double perovskite Sr2FeRe1-xSbxO6 (0≤x≤0.9)
International Nuclear Information System (INIS)
Jung, Alexandra; Ksenofontov, Vadim; Reiman, Sergey; Therese, Helen Annal; Felser, Claudia; Tremel, Wolfgang; Kolb, Ute
2006-01-01
The double perovskites Sr 2 FeMO 6 (M=Re,Mo) belong to the important class of half-metallic magnetic materials. In this study we explore the effect of replacing the electronic 5d buffer element Re with variable valency by the main group element Sb with fixed valency. X-ray diffraction reveals Sr 2 FeRe 1-x Sb x O 6 (0 2 FeReO 6 changes to antiferromagnetic upon Sb substitution as was determined by magnetic susceptibility measurements. Samples up to a doping level of 0.3 are ferrimagnetic, while Sb contents higher than 0.6 result in an overall antiferromagnetic behavior. 57 Fe and 121 Sb Moessbauer spectroscopy specifies the valence state of Sb to be +5 within the whole range of substitution whereas the Fe valence state changes from +2.7 for the parent compound to +2.9 for Sr 2 FeRe 0.1 Sb 0.9 O 6 . Accordingly, Fe adopts the role of an electronic buffer element from Re upon heavy Sb doping. Additionally, 57 Fe Moessbauer results show a coexistence of ferri- and antiferromagnetic clusters within the same perovskite-type crystal structure in the Sb substitution range 0.3 2 FeReO 6 and Sr 2 FeRe 0.9 Sb 0.1 O 6 are ''purely'' ferrimagnetic and Sr 2 FeRe 0.1 Sb 0.9 O 6 contains antiferromagnetically ordered Fe sites only. Consequently, a replacement of the Re atoms by a nonmagnetic main group element such as Sb blocks the superexchange pathways -Fe-O-Re(Sb)-O-Fe- along the crystallographic axis of the perovskite unit cell and destroys the itinerant magnetism of the parent compound
An X- and Q-band Fe3+ EPR study of nanoparticles of magnetic semiconductor Zn1−xFexO
International Nuclear Information System (INIS)
Misra, Sushil K.; Andronenko, S.I.; Thurber, A.; Punnoose, A.; Nalepa, A.
2014-01-01
EPR studies on two types of nanoparticles of Fe 3+ doped, 0.1–10%, ZnO, NL and QJ, prepared using similar chemical hydrolysis methods, in diethylene glycol, and in denatured ethanol solutions, respectively, were carried out at X-band (∼9.5 GHz) at 77 K and at Q-band (∼34.0 GHz) at 10, 80, and 295 K. To interpret the experimental results, EPR spectra were simulated by exact diagonalization of the spin-Hamiltonian matrix to identify the Fe ions at different magnetically active sites in these samples. The simulation for NL samples revealed that they contained (i) Fe 3+ ions, which substituted for Zn ions, the zero-field splitting (ZFS) parameter which has a large distribution over the sample due to oxygen vacancies in the second coordination sphere; (ii) EPR signal from surface oxygen defects; and (iii) ferromagnetically (FM) coupled Fe ions with concentration of Fe more than 1%. The EPR spectra for QJ samples are very different from those for NL samples, exhibiting only rather intense FM EPR lines. The FM and EPR spectra in NL and/or QJ samples are found to vary strongly with differences in the surface morphology of nanoparticles. - Highlights: • X and Q band EPR studies on NL and QJ nanoparticles of Fe 3+ doped ZnO at 10, 80, and 295 K. • Fe ions are present at different magnetically active sites in these samples. • NL samples consist of paramagnetic Fe 3+ ions, and ferromagnetically coupled Fe ions. • QJ samples exhibit only intense ferromagnetic lines, different from QJ. • Spectra vary strongly with the surface morphology of nanoparticles
Evidence of Room Temperature Ferromagnetism Due to Oxygen Vacancies in (In1- x Fe x )2O3 Thin Films
Chakraborty, Deepannita; Munuswamy, Kuppan; Shaik, Kaleemulla; Nasina, Madhusudhana Rao; Dugasani, Sreekantha Reddy; Inturu, Omkaram
2018-03-01
Iron substituted indium oxide (In1- x Fe x )2O3 thin films at x = 0.00, 0.03, 0.05 and 0.07 were coated onto Corning 7059 glass substrates using the electron beam evaporation technique followed by annealing at different temperatures. The prepared thin films were subjected to different characterization techniques to study their structural, optical and magnetic properties. The structural properties of the thin films were studied using x-ray diffractometry (XRD). From the XRD results it was found that the films were crystallized in cubic structure, and no change in crystal structure was observed with annealing temperature. No secondary phases related to iron were observed from the XRD profiles. The chemical composition and surface morphology of the films were examined by field emission scanning electron microscope (FE-SEM) attached with energy dispersive analysis of x-ray (EDAX). The valence state of the elements were studied by x-ray photoelectron spectroscopy (XPS) and found that the indium, iron and oxygen were in In+3, Fe+3 and O-2 states. From the data, the band gap of the (In1- x Fe x )2O3 thin films were calculated and it increased with increase of annealing temperature. The magnetic properties of the films were studied at room temperature by vibrating sample magnetometer (VSM). The films exhibited ferromagnetism at room temperature.
Magnetic ground state of Ti{sub 1-x}Sc{sub x}Fe{sub 2} system
Energy Technology Data Exchange (ETDEWEB)
Saoudi, M.; Deportes, J.; Ouladdiaf, B. E-mail: ouladdiaf@ill.fr
2001-06-01
The magnetic ground states of the Laves phases Ti{sub 1-x}Sc{sub x}Fe{sub 2} system have been investigated by means of powder neutron diffraction and magnetisation techniques. For x=0.23, a transition is observed from a collinear ferromagnet along the c-axis to a canted one at T{sub f}=200 K. For x=0.27, 0.3, 0.33, an additional first-order transition is observed at T{sub t1}{approx}120 K accompanied by a large magnetovolume anomaly associated to a jump of the magnetic moment of the Fe atoms at the 2a site. The magnetic moment instability in a frustrated lattice should be considered to interpret this transition, although most of the other magnetic states can be discussed within Moriya's theory for itinerant electron systems with competing ferromagnetic and antiferromagnetic spin fluctuations.
Ni doped Fe3O4 magnetic nanoparticles.
Larumbe, S; Gómez-Polo, C; Pérez-Landazábal, J I; García-Prieto, A; Alonso, J; Fdez-Gubieda, M L; Cordero, D; Gómez, J
2012-03-01
In this work, the effect of nickel doping on the structural and magnetic properties of Fe3O4 nanoparticles is analysed. Ni(x)Fe(3-x)O4 nanoparticles (x = 0, 0.04, 0.06 and 0.11) were obtained by chemical co-precipitation method, starting from a mixture of FeCl2 x 4H2O and Ni(AcO)2 x 4H2O salts. The analysis of the structure and composition of the synthesized nanoparticles confirms their nanometer size (main sizes around 10 nm) and the inclusion of the Ni atoms in the characteristic spinel structure of the magnetite Fe3O4 phase. In order to characterize in detail the structure of the samples, X-ray absorption (XANES) measurements were performed on the Ni and Fe K-edges. The results indicate the oxidation of the Ni atoms to the 2+ state and the location of the Ni2+ cations in the Fe2+ octahedral sites. With respect to the magnetic properties, the samples display the characteristic superparamagnetic behaviour, with anhysteretic magnetic response at room temperature. The estimated magnetic moment confirms the partial substitution of the Fe2+ cations by Ni2+ atoms in the octahedral sites of the spinel structure.
International Nuclear Information System (INIS)
Manghnani, Murli H.; Balogh, John; Hong Xinguo; Newville, Matthew; Amulele, G.
2007-01-01
Iron-nickel (Fe-Ni) alloy is regarded as the most abundant constituent of Earth's core, with an amount of 5.5 wt% Ni in the core based on geochemical and cosmochemical models. The structural role of nickel in liquid Fe-Ni alloys with light elements such as S or Si is poorly understood, largely because of the experimental difficulties of high-temperature melts. Recently, we have succeeded in acquiring Ni K-edge fluorescence x-ray absorption fine structure (XAFS) spectra of Fe-Ni-S and Fe-Ni-Si melts and alloys. Different structural environment of Ni atoms in Fe-Ni-S and Fe-Ni-Si melts is observed, supporting the effect of light elements in Fe-Ni melts
International Nuclear Information System (INIS)
Mini, S.M.; Fullerton, E.E.; Sowers, C.H.; Fontaine, A.; Pizzini, S.; Bommannavar, A.S.; Traverse, A.; Baudelet, F.
1994-12-01
The results of magnetic circular x-ray dichroism (MCXD) measurements and extended x-ray absorption fine structure measurements (EXAFS) of the Fe K-edges of textured Fe(110)/Pd(111) multilayers are reported. The EXAFS results indicates that the iron in the system goes from bcc to a more densely packed system as the thickness of the iron layer is decreased. The magnetic properties were measured by SQUID magnetometry from 5-350 K. For all the samples, the saturation magnetization was significantly enhanced over the bulk values indicating the interface Pd atoms are polarized by the Fe layer. The enhancement corresponds to a moment of ∼2.5μ B per interface Pd atom
Magnetisation and AC susceptibility studies of La1-xSrxFe0.8Cr0.2O3-δ (0.0<x<1.0) perovskites
International Nuclear Information System (INIS)
Ferreira, L.P.; Cruz, M.M.; Ramos, T.; Sa, M.A.; Carvalho, M.D.; Godinho, M.
2007-01-01
Magnetisation and AC magnetic susceptibility measurements have been performed in the perovskite-type compounds La 1-x Sr x Fe 0.8 Cr 0.2 O 3-δ (x=0.2, 0.4, 0.6 and 0.8). All compounds show an overall antiferromagnetic behaviour mainly attributed to predominant Fe 3+ -O-Fe 3+ interactions. For 0.2 ord . The coexistence of AFM and FM interactions leads to reentrant magnetic behaviour for the x=0.4 compound and to spin-glass like behaviour for x=0.8. Between x=0.6 and 0.8, the similar magnetic moments found in the paramagnetic region indicate that the Fe/Cr valences do not change significantly, pointing towards an increased role for oxygen vacancy formation in the charge compensation mechanism
Energy Technology Data Exchange (ETDEWEB)
Handstein, A.; Kubis, M.; Gebel, B.; Mueller, K.-H.; Schultz, L. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany). Inst. fuer Metallische Werkstoffe; Gutfleisch, O.; Harris, I.R. [Institut fuer Festkoerper- und Werkstofforschung Dresden e.V. (Germany). Inst. fuer Metallische Werkstoffe]|[Birmingham Univ. (United Kingdom). School of Metallurgy and Materials
1998-07-01
The complete disproportionation of Sm{sub 2}Fe{sub 17-x}Ga{sub x} during annealing in hydrogen is hindered due to an increased stability of the compounds with a higher Ga content (x {>=} 1). Therefore the HD process as the first step of HDDR (hydrogenation-disproportionation-desorption-recombination) has to be carried out at a high hydrogen pressure for x {>=} 1. The hydrogen absorption behaviour of Sm{sub 2}Fe{sub 17-x}Ga{sub x} (x = 0, 0.5, 1 and 2) was investigated by means of hydrogen differential thermal analysis (HDTA) and high pressure differential scanning calorimetry (HPDSC) at hydrogen pressures up to 70 bar. A dependency of hydrogenation and disproportionation temperatures on hydrogen pressure and Ga content was found. The comparison with other substituents (M = Al and Si) instead of M = Ga showed an increased stability of Sm{sub 2}Fe{sub 17-x}M{sub x} compounds against disproportionation by hydrogen in the sequence Al, Ga and Si. The Curie temperatures of the interstitially hydrogenated Th{sub 2}Zn{sub 17}-type materials increase with the hydrogen pressure. In order to produce coercive and thermally stable Sm{sub 2}Fe{sub 15}Ga{sub 2}C{sub y} powder by means of the HDDR process, we recombined material disproportionated at different hydrogen pressures. Preliminary results of magnetic properties of this HDDR treated and gas-carburized Sm{sub 2}Fe{sub 15}Ga{sub 2}C{sub y} are discussed. (orig.)
High-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga,Fe)Sb
Energy Technology Data Exchange (ETDEWEB)
Tu, Nguyen Thanh [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Department of Physics, Ho Chi Minh City University of Pedagogy, 280, An Duong Vuong Street, District 5, Ho Chi Minh City 748242 (Viet Nam); Hai, Pham Nam [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-0033 (Japan); Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Anh, Le Duc [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Tanaka, Masaaki [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Center for Spintronics Research Network (CSRN), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)
2016-05-09
We show high-temperature ferromagnetism in heavily Fe-doped ferromagnetic semiconductor (Ga{sub 1−x},Fe{sub x})Sb (x = 23% and 25%) thin films grown by low-temperature molecular beam epitaxy. Magnetic circular dichroism spectroscopy and anomalous Hall effect measurements indicate intrinsic ferromagnetism of these samples. The Curie temperature reaches 300 K and 340 K for x = 23% and 25%, respectively, which are the highest values reported so far in intrinsic III-V ferromagnetic semiconductors.
International Nuclear Information System (INIS)
Gurkan, R.; Altunay, N.
2013-01-01
A new cloud point extraction (CPE) method for the preconcentration of trace iron speciation in natural waters prior to determination by flame atomic absorption spectrometry (FAAS) was developed in the present study. In this method, Fe(II) sensitively and selectively reacts with Calcon carboxylic acid (CCA) in presence of cetylpyridinium chloride (CPC) yielding a hydrophobic complex at pH 10.5, which is then entrapped in surfactant-rich phase. Total Fe was accurately and reliably determined after the reduction of Fe(III) to Fe(II) with sulfite. The amount of Fe(III) in samples was determined from the difference between total Fe and Fe(II). CPC was used not only as an auxiliary ligand in CPE, but also as sensitivity enhancement agent in FAAS. The nonionic surfactant, polyethylene glycol tert-octylphenyl ether (Triton X-114) was used as an extracting agent. The analytical variables affecting CPE efficiency were investigated in detail. The preconcentration/enhancement factors of 50 and 82 respectively, were obtained for the preconcentration of Fe(II) with 50 mL solution. Under the optimized conditions, the detection limit of Fe(II) in linear range of 0.2-60 μg L/sup -1/ was 0.06 μg L/sup -1/. The relative standard deviation was 2.7 percentage (20 μg L/sup -1/, N: 5), recoveries for Fe(II) were in range of 99.0-102.0 percentage for all water samples including certified reference materials (CRMs). In order to verify its accuracy, two CRMs were analyzed and the results obtained were statistically in good agreement with the certified values. (author)
Ferroelectric domains and phase evolution in (Fe:) KTa{sub 1−x}Nb{sub x}O{sub 3} crystals
Energy Technology Data Exchange (ETDEWEB)
Zhao, Hongyang; Cai, Kang; Fan, Ziran; Huang, Zhideng [Hubei Key Laboratory of Plasma Chemistry and Advanced Materials, Department of Materials Science and Engineering, Wuhan Institute of Technology, 693 Xiongchu Road, Wuhan 430073 (China); Ma, Zhibin, E-mail: mazb@wit.edu.cn [Hubei Key Laboratory of Plasma Chemistry and Advanced Materials, Department of Materials Science and Engineering, Wuhan Institute of Technology, 693 Xiongchu Road, Wuhan 430073 (China); Jia, Tingting; Kimura, Hideo [National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047 (Japan); Yang, Yuguo [New Materials Research Institute, Shandong Academy of Sciences, No. 19, Keyuan Road, Jinan 250014 (China); Matsumoto, Takao; Tohei, Tetsuya; Shibata, Naoya; Ikuhara, Yuichi [Institute of Engineering Innovation, School of Engineering, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo 113-8656 (Japan)
2017-08-15
Highlights: • Three phase transitions were observed: the R–O, O–T, T–C evolutions. • KTN ferroelectric domain switching is because of the nano-polar-regions. • The domain evolution showed KTN has triangle shape, but Fe: KTN has straight line. - Abstract: The domain structures and phase evolution in mixed ferroelectric (Fe): KTa{sub 1−x}Nb{sub x}O{sub 3} (KTN) crystals were investigated. Temperature dependent Raman spectra show that Curie temperatures of KTN and Fe: KTN are far below room temperature, but the ferroelectric domain switching was still visualized by scanning probe microscopy at room temperature. These observed domains origin from the nano-regions near the grain boundaries. In addition, the intrinsic domains (triangle for KTN and straight line/stripe for Fe: KTN) could only be observed at low temperature by transmission electron microscopy. Three phase transitions in Fe: KTN crystals were found by Raman spectroscopy and dielectric testing: 175 K for Rhombohedral-to-Orthorhombic (R–O), 210 K for Orthorhombic-to-Tetragonal (O–T) and 250 K for Tetragonal-to-Cubic (T–C), which is consistent with the domain behavior.
EXAFS study of short range order in Fe-Zr amorphous alloys
International Nuclear Information System (INIS)
Fernandez-Gubieda, M.L.; Gorria, P.; Barandiaran, J.M.; Barquin, L.F.
1995-01-01
Room temperature X-ray absorption spectra on Fe K-edge have been performed in Fe 100-x-y Zr x B y and Fe 86 Zr 7 Cu 1 B 6 alloys (x=7, 7.7, 9; y=0, 2, 4, 6). Fe-Fe coordination number and interatomic distances do not change in any sample. However, small changes in the Fe-Zr short range order, which could explain the evolution of the magnetic properties, have been observed. (orig.)
Preparation and Mechanical Properties of TiC-Fe Cermets and TiC-Fe/Fe Bilayer Composites
Zheng, Yong; Zhou, Yang; Li, Runfeng; Wang, Jiaqi; Chen, Lulu; Li, Shibo
2017-10-01
TiC-Fe cermets and TiC-Fe/Fe bilayer composites consisting of a pure Fe layer and a TiC-Fe cermets layer were fabricated by hot-pressing sintering. The pure Fe layer contributes to the toughness of composites, and the TiC-Fe cermets layer endows the composites with an improved tensile strength and hardness. The effect of TiC contents (30-60 vol.%) on the mechanical properties of TiC-Fe cermets and TiC-Fe/Fe bilayer composites was investigated. Among the TiC-Fe cermets, the 40 vol.% TiC-Fe cermets possessed the highest tensile strength of 581 MPa and Vickers hardness of 5.1 GPa. The maximum fracture toughness of 17.0 MPa m1/2 was achieved for the TiC-Fe cermets with 30 vol.% TiC. For the TiC-Fe/Fe bilayer composites, the 40 vol.% TiC-Fe/Fe bilayer composite owns the maximum tensile strength of 588 MPa, which is higher than that of 40 vol.% TiC-Fe cermets. In addition, the 33.5% increment of tensile strength of 30 vol.% TiC-Fe/Fe bilayer composite comparing with the 30 vol.% TiC-Fe cermets, which is attributed to the 30 vol.% TiC-Fe/Fe bilayer composite exhibited the largest interlaminar shear strength of 335 MPa. The bilayer composites are expected to be used as wear resistance components in some heavy wear conditions.
International Nuclear Information System (INIS)
Xu, S.C.; Yang, C.; Liu, M.; Jiang, S.Z.; Ma, Y.Y.; Chen, C.S.; Gao, X.G.; Sun, Z.C.; Hu, B.; Wang, C.C.; Man, B.Y.
2012-01-01
High quality β-FeSi 2 thin films have been fabricated on silicon (100) substrate by the pulsed laser deposition (PLD) technique with the Fe and sintered FeSi 2 targets. The crystalline quality and surface morphology of the samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. These results indicate that the samples prepared with a Fe target can acquire a better crystalline quality and a smoother surface than those with a sintered FeSi 2 target. The reasons were discussed with subsurface superheating mechanism. The intrinsic PL spectrum attributed to the interband transition of β-FeSi 2 for all the samples was compared, showing that the film prepared with Fe target can acquire a good PL property by optimizing experimental parameters. It is suggested that sputtering Fe on Si substrate by the pulsed laser offers a cheap and convenient way to prepare the β-FeSi 2 thin films. -- Highlights: ► β-FeSi 2 films were fabricated by PLD technique with the Fe and FeSi 2 targets. ► The films prepared with Fe target have good crystalline quality and smooth surface. ► The Fe target prepared film acquired a high PL intensity. ► Sputtering Fe on Si substrate offers a convenient way to prepare the β-FeSi 2 films.
Giant Faraday rotation in Bi(x)Ce(3-x)Fe5O12 epitaxial garnet films.
Chandra Sekhar, M; Singh, Mahi R; Basu, Shantanu; Pinnepalli, Sai
2012-04-23
Thin films of Bi(x)Ce(3-x)Fe(5)O(12) with x = 0.7 and 0.8 compositions were prepared by using pulsed laser deposition. We investigated the effects of processing parameters used to fabricate these films by measuring various physical properties such as X-ray diffraction, transmittance, magnetization and Faraday rotation. In this study, we propose a phase diagram which provides a suitable window for the deposition of Bi(x)Ce(3-x)Fe(5)O(12) epitaxial films. We have also observed a giant Faraday rotation of 1-1.10 degree/µm in our optimized films. The measured Faraday rotation value is 1.6 and 50 times larger than that of CeYIG and YIG respectively. A theoretical model has been proposed for Faraday rotation based on density matrix method and an excellent agreement between experiment and theory is found. © 2012 Optical Society of America
International Nuclear Information System (INIS)
Yang, L.; Zhen, L.; Xu, C.Y.; Sun, X.Y.; Shao, W.Z.
2011-01-01
The effects of proton irradiation on the structure of NdFeB permanent magnet were investigated by X-ray diffraction and X-ray absorption fine structure (XAFS). The results reveal that proton irradiation has no effect on the long-range structure, but significantly affects the atomic local structure of the NdFeB magnet. The alignment degree of the magnet decreases and the internal stress of the lattice increases after proton irradiation. XAFS results show that the coordination number of Fe-Nd in the first neighboring coordination shell of the Fe atoms decreases and the disorder degree increases.
Energy Technology Data Exchange (ETDEWEB)
Yang, L. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Zhen, L., E-mail: lzhen@hit.edu.c [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Xu, C.Y.; Sun, X.Y.; Shao, W.Z. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)
2011-01-15
The effects of proton irradiation on the structure of NdFeB permanent magnet were investigated by X-ray diffraction and X-ray absorption fine structure (XAFS). The results reveal that proton irradiation has no effect on the long-range structure, but significantly affects the atomic local structure of the NdFeB magnet. The alignment degree of the magnet decreases and the internal stress of the lattice increases after proton irradiation. XAFS results show that the coordination number of Fe-Nd in the first neighboring coordination shell of the Fe atoms decreases and the disorder degree increases.
Study of hydrogenation of Sm2Fe17-yGay by means of X-ray diffraction
International Nuclear Information System (INIS)
Teresiak, A.; Uhlemann, M.; Kubis, M.; Gebel, B.; Mattern, N.; Mueller, K.-H.
2000-01-01
The hydrogenation process of Sm 2 Fe 17-y Ga y (y=0-2) was studied. X-ray investigations show a decreasing hydrogen solubility in the intermetallic alloy with increasing Ga-content from 4.0±0.3 atoms per formula unit for Sm 2 Fe 17 to 2.85±0.05 for Sm 2 Fe 15 Ga 2 . The larger Ga atoms reduce the size of the interstitial sites and thereby the maximum hydrogen concentration is decreased. The behaviour of the lattice parameters a and c with increasing Ga content points to a changed hydrogen distribution on the interstitial sites, becoming more statistical. In situ observations by means of high temperature X-ray diffraction show that the hydrogen absorption process is diffusion controlled. The hydrogen absorption starts at an annealing temperature of 120-140 C in all cases. The solubility of hydrogen decreases with increasing temperature. The hydrogen is completely desorbed above 350 C in all cases. The absorption/desorption process is reversible between room temperature and 400 C. Annealing at temperatures above 400 C leads to the decomposition of the Sm 2 Fe 17 phase, indicated by emerging of α-Fe. The formation of SmH x is established at 600 C. The decomposition temperature increases with increasing Ga-content. Up to 750 C, only Sm 2 Fe 17 is completely decomposed. (orig.)
Microstructure, tensile deformation mode and crevice corrosion resistance in Ti-10Mo-xFe alloys
International Nuclear Information System (INIS)
Min, X.H.; Emura, S.; Nishimura, T.; Tsuchiya, K.; Tsuzaki, K.
2010-01-01
The microstructure, the tensile deformation mode at ambient temperature and the crevice corrosion resistance at a high temperature of 373 K were investigated in the Ti-10Mo-xFe (x = 0, 1, 3, 5) alloys. The stability of the β phase increased, and the formation of the α'' martensite and the athermal ω phase was suppressed by the increase in the Fe content. EPMA examinations indicated that the existence of the α'' martensite in the Ti-10Mo alloy was caused by the solidification segregation of Mo atoms. EBSD observations showed that the deformation mode changed from a {3 3 2} twinning to a slip by an increase in the Fe content, which coincided with the prediction by the electron/atom (e/a) ratio. The Ti-10Mo-3Fe alloy showed the highest yield strength of 935 MPa among all the alloys, while the Ti-10Mo-1Fe alloy showed the lowest value of 563 MPa due to the change in the deformation mode. On the other hand, all the alloys exhibited a high crevice corrosion resistance in a high chloride and high acidic solution at the high temperature, although the corrosion resistance decreased with an increase in the Fe content. The decrease in the corrosion resistance can be explained by the bond order (Bo). A good combination of tensile properties and crevice corrosion resistance may be obtainable through a further optimization of the Fe content by the e/a ratio and the Bo.
Impurity band effects on transport and thermoelectric properties of Fe2 -xNixVAl
Knapp, I.; Budinska, B.; Milosavljevic, D.; Heinrich, P.; Khmelevskyi, S.; Moser, R.; Podloucky, R.; Prenninger, P.; Bauer, E.
2017-07-01
Full Heusler alloys of the series Fe2 -xNixVAl ,0 ≤x ≤0.2 , were prepared and characterized, and their physical properties, relevant to the thermoelectric performance of such materials, were studied in a wide temperature range. The starting material Fe2VAl is characterized by a pseudogap of the electronic density of states near the Fermi energy, with a gap width of the order of 1 eV. Density functional theory calculations were performed by application of two approaches. In the framework of the local-spin-density approximation and coherent potential approximation, the electronic densities of states of substitutional alloys were calculated, revealing that with increasing Ni content the Fermi energy moves toward the conduction band, and consequently, the nature of electronic transport changes from p type to n type. It appears that Ni, due to its extra electrons, provides a narrow impurity band near the Fermi level. These states can be made responsible for the experimentally observed evolution of transport properties. Furthermore, the Vienna ab initio Simulation package (vasp) was utilized for deriving electronic, structural, and vibrational properties of ordered Fe2VAl and Fe1.75Ni0.25VAl . In particular, it is found that due to Ni substitution there is a general shift to lower phonon frequencies by about 2 THz as compared to the undoped case. Associated to these modifications, the electrical resistivity, ρ (T ) , changes from a semiconducting-like behavior to a nonsimple metallic behavior, while the Seebeck coefficient reaches values of the order of -80 μ V /K around room temperature for the sample x =0.2 . The increase of the Ni content, in addition, goes along with a substantial reduction of the lattice part of the thermal conductivity. This change is analyzed in detail in terms of a disorder parameter Γ , characterizing the derangement of the crystalline lattice due to the substitution of Fe by Ni. Ab initio calculations of the phonon dynamics carried out
Structural and superconducting properties of epitaxial Fe{sub 1+y}Se{sub 1-x}Te{sub x} thin films
Energy Technology Data Exchange (ETDEWEB)
Richter, Stefan; Yuan, Feifei; Grinenko, Vadim; Huehne, Ruben [Institute for Metallic Materials, IFW Dresden (Germany); Sala, Alberto; Putti, Marina [Dipartimento di Fisica, Universita di Genova (Italy)
2015-07-01
The iron based superconductor Fe(Se,Te) is in the center of much ongoing research. The reason for this is on the one hand its simple crystal structure, that consists only of stacked Fe(Se,Te) layers so that structural and superconducting properties can be connected more easily, on the other hand FeSe itself shows a high sensibility for strain and changes in stoichiometry and can have potentially very high critical temperatures under hydrostatic pressure or in monolayers. We investigate epitaxial thin films of Fe{sub 1+y}Se{sub 1-x}Te{sub x} grown by pulsed laser deposition on different single crystalline substrates. A high crystalline quality and a superconducting transition of up to about 20 K can be achieved using optimized deposition parameters. The influence of growth conditions, Te-doping, film thickness and post growth oxygen treatment on the structural and superconducting properties on these films will be presented in detail.
International Nuclear Information System (INIS)
Sayouty, E.H.; Annouar, F.; Lassri, H.; Randrianantoandro, N.; Greneche, J.M.
2005-01-01
We have carried out magnetic and Moessbauer studies of amorphous Fe 80-x Tm x B 20 alloys (0 ≤ x ≤ 16). With an increasing Tm content, both the Curie temperature T C and the magnetic moment of Fe atom μ Fe decrease. We have extracted the value of exchange constant A from T C and that of the local magnetic anisotropy constant K L from the coercivity. Moessbauer studies were performed in a transmission geometry and also using the conversion electron spectroscopy. Both Moessbauer spectrometry techniques show that the average hyperfine field decreases linearly with the addition of rare-earth
High-Temperature Superconductivity in Doped BaFe2As2
International Nuclear Information System (INIS)
Martin, Marianne
2011-01-01
This thesis provides a detailed look on the synthesis, structural features and physical properties of iron arsenides. Especially the properties of BaFe 2 As 2 and the solid solutions (Ba 1-x K x )Fe 2 As 2 , (Ba 1-x Sr x )Fe 2 As 2 and BaFe 2 (As 1-x P x ) 2 which were all synthesized by solid state reactions by heating mixtures of the elements, were intensively investigated.
International Nuclear Information System (INIS)
Konishi, Hiroyuki; Mizuki, Jun'ichiro; Yamashita, Masato; Uchida, Hitoshi
2005-01-01
Chloride in atmosphere considerably reduces the corrosion resistance of conventional weathering steel containing a small amount of Cr. Ni is an effective anticorrosive element for improving the corrosion resistance of steel in a Cl-rich environment. In order to clarify the structure of the protective rust layer of weathering steel, Cl and Fe K-edge X-ray absorption near edge structure (XANES) spectra of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich atmosphere were measured. The Fe K-XANES measurements enable the characterization of mixture of iron oxides such as rust. The chemical composition of the rust was determined by performing pattern fitting of the measured spectra. All the rust is composed mainly of goethite, akaganeite, lepidocrocite and magnetite. Among these iron oxides, akaganeite in particular is the major component in the rust. Additionally, the amount of akaganeite in the rust of Fe-Ni alloy is much greater than that in rust of Fe-Cr alloy. Akaganeite is generally considered to facilitate the corrosion of steel, but our results indicate that akaganeite in the rust of Fe-Ni alloy is quantitatively different from that in rust of Fe-Cr alloy and does not facilitate the corrosion of steel. The shoulder peak observed in Cl K-XANES spectra reveals that the rust contains a chloride other than akaganeite. The energy of the shoulder peak does not correspond to that of any well-known chlorides. In the measured spectra, there is no proof that Cl, by combining with the alloying element, inhibits the alloying element from acting in corrosion resistance. The shoulder peak appears only when the content of the alloying element is lower than a certain value. This suggests that the generation of the unidentified chloride is related to the corrosion rate of steel. (author)
Sulfide phase in the Fe-Ti-S and Fe-C-Ti-S alloys
International Nuclear Information System (INIS)
Malinochka, Ya.N.; Balakina, N.A.; Shmelev, Yu.S.
1976-01-01
The nature of the sulfide phases in Fe-Ti-S and Fe-C-Ti-S alloys was studied. The carbide and the sulfide phase were identified the aid of X-ray spectral microanalysis. It was established that for a small content of titanium and sulfur in ternary Fe-Ti-S alloys the solidification of the γ-solution on the boundaries of dendritic branches is accompanied, along with the precipitation of a sulfide rich in iron of the (Fe, Ti) S type where a small quantity of titanium is dissolved, by the formation of a titanium-bearing sulfide eutectic γ + TiS. The amount of the sulfide eutectic increases with the contents of titanium and sulfur until a purely eutectic alloy is formed. Both carbides and sulfides may be formed in the solidification of quaternary alloys Fe-C-Ti-S
Composition controlled spin polarization in Co{sub 1-x}Fe{sub x}S{sub 2} alloys
Energy Technology Data Exchange (ETDEWEB)
Leighton, C [Department of Chemical Engineering and Materials Science, University of Minnesota (United States); Manno, M [Department of Chemical Engineering and Materials Science, University of Minnesota (United States); Cady, A [Advanced Photon Source, Argonne National Laboratory (United States); Freeland, J W [Advanced Photon Source, Argonne National Laboratory (United States); Wang, L [Department of Chemical Engineering and Materials Science, University of Minnesota (United States); Umemoto, K [Department of Chemical Engineering and Materials Science, University of Minnesota (United States); Wentzcovitch, R M [Department of Chemical Engineering and Materials Science, University of Minnesota (United States); Chen, T Y [Department of Physics and Astronomy, Johns Hopkins University (United States); Chien, C L [Department of Physics and Astronomy, Johns Hopkins University (United States); Kuhns, P L [National High Magnetic Field Laboratory, Florida State University (United States); Hoch, M J R [National High Magnetic Field Laboratory, Florida State University (United States); Reyes, A P [National High Magnetic Field Laboratory, Florida State University (United States); Moulton, W G [National High Magnetic Field Laboratory, Florida State University (United States); Dahlberg, E D [School of Physics and Astronomy, University of Minnesota (United States); Checkelsky, J [Physics Department, Harvey Mudd College (United States); Eckert, J [Physics Department, Harvey Mudd College (United States)
2007-08-08
The transition metal (TM) chalcogenides of the form TMX{sub 2} (X = S or Se) have been studied for decades due to their interesting electronic and magnetic properties such as metamagnetism and metal-insulator transitions. In particular, the Co{sub 1-x}Fe{sub x}S{sub 2} alloys were the subject of investigation in the 1970s due to general interest in itinerant ferromagnetism. In recent years (2000-present) it has been shown, both by electronic structure calculations and detailed experimental investigations, that Co{sub 1-x}Fe{sub x}S{sub 2} is a model system for the investigation of highly spin polarized ferromagnetism. The radically different electronic properties of the two endpoint compounds (CoS{sub 2} is a narrow bandwidth ferromagnetic metal, while FeS{sub 2} is a diamagnetic semiconductor), in a system forming a substitutional solid solution allows for composition control of the Fermi level relative to the spin split bands, and therefore composition-controlled conduction electron spin polarization. In essence, the recent work has shown that the concept of 'band engineering' can be applied to half-metallic ferromagnets and that high spin polarization can be deliberately engineered. Experiments reveal tunability in both sign and magnitude of the spin polarization at the Fermi level, with maximum values obtained to date of 85% at low temperatures. In this paper we review the properties of Co{sub 1-x}Fe{sub x}S{sub 2} alloys, with an emphasis on properties of relevance to half-metallicity. Crystal structure, electronic structure, synthesis, magnetic properties, transport properties, direct probes of the spin polarization, and measurements of the total density of states at the Fermi level are all discussed. We conclude with a discussion of the factors that influence, or even limit, the spin polarization, along with a discussion of opportunities and problems for future investigation, particularly with regard to fundamental studies of spintronic devices.
Energy Technology Data Exchange (ETDEWEB)
Legarra, E., E-mail: estibaliz.legarra@ehu.es [Dpto. Electricidad y Electronica, Universidad del Pais Vasco (UPV/EHU), CP. 644, 48080 Bilbao (Spain); Apiñaniz, E. [Dpto. Fisica Aplicada I, Universidad del Pais Vasco, Alameda de Urquijo s/n, 48013 Bilbao (Spain); Plazaola, F. [Dpto. Electricidad y Electronica, Universidad del Pais Vasco (UPV/EHU), CP. 644, 48080 Bilbao (Spain); Jimenez, J.A. [Centro Nacional de Investigaciones Metalurgicas (CENIM), Avda. Gregorio del amo 8, 28040 Madrid (Spain)
2014-02-15
Highlights: • Fe{sub 60}Al{sub 40−x}Si{sub x} alloys were disordered by means of planetary ball milling technique. • Paramagnetic to ferromagnetic transition is observed with disordering. • Si addition hinders the disordering process and the increase of the lattice parameter. • Si addition promotes the paramagnetic to ferromagnetic transition. -- Abstract: We have used Mössbauer spectroscopy and X-ray diffraction to study the influence of different Al/Si ratios on the structural and magnetic properties of the mechanically deformed Fe{sub 60}Al{sub 40−x}Si{sub x} alloys. The results indicate that ternary alloys also present the magnetic transition with disordering observed in binary Fe{sub 60}Al{sub 40} alloys. Besides, Si introduction has two opposite contributions. From a structural point of view, hinders the disordering process, but, from a magnetic point of view promotes the magnetic transition.
A pulse synthesis of beta-FeSi sub 2 layers on silicon implanted with Fe sup + ions
Batalov, R I; Terukov, E I; Kudoyarova, V K; Weiser, G; Kuehne, H
2001-01-01
The synthesis of thin beta-FeSi sub 2 films was performed by means of the Fe sup + ion implantation into Si (100) and the following nanosecond pulsed ion treatment of implanted layer. Using the beta-FeSi sub 2 beta-FeSi sub 2 e X-ray diffraction it is shown that the pulsed ion treatment results in the generation of the mixture of two phases: FeSi and beta-FeSi sub 2 with stressed crystal lattices. The following short-time annealing leads to the total transformation of the FeSi phase into the beta-FeSi sub 2 one. The Raman scattering data prove the generation of the beta-FeSi sub 2 at the high degree of the silicon crystallinity. The experimental results of the optical absorption testify to the formation of beta-FeSi sub 2 layers and precipitates with the straight-band structure. The photoluminescence signal at lambda approx = 1.56 mu m observes up to 210 K
Heller, Maija I.; Lam, Phoebe J.; Moffett, James W.; Till, Claire P.; Lee, Jong-Mi; Toner, Brandy M.; Marcus, Matthew A.
2017-08-01
Oxygen minimum zones (OMZs) have been proposed to be an important source of dissolved iron (Fe) into the interior ocean. However, previous studies in OMZs have shown a sharp decrease in total dissolved Fe (dFe) and/or dissolved Fe(II) (dFe(II)) concentrations at the shelf-break, despite constant temperature, salinity and continued lack of oxygen across the shelf-break. The loss of both total dFe and dFe(II) suggests a conversion of the dFe to particulate form, but studies that have coupled the reduction-oxidation (redox) speciation of both dissolved and particulate phases have not previously been done. Here we have measured the redox speciation and concentrations of both dissolved and particulate forms of Fe in samples collected during the U.S. GEOTRACES Eastern tropical Pacific Zonal Transect (EPZT) cruise in 2013 (GP16). This complete data set allows us to assess possible mechanisms for loss of dFe. We observed an offshore loss of dFe(II) within the oxygen deficient zone (ODZ), where dissolved oxygen is undetectable, accompanied by an increase in total particulate Fe (pFe). Total pFe concentrations were highest in the upper ODZ. X-ray absorption spectroscopy revealed that the pFe maximum was primarily in the Fe(III) form as Fe(III) oxyhydroxides. The remarkable similarity in the distributions of total particulate iron and nitrite suggests a role for nitrite in the oxidation of dFe(II) to pFe(III). We present a conceptual model for the rapid redox cycling of Fe that occurs in ODZs, despite the absence of oxygen.
Energy Technology Data Exchange (ETDEWEB)
Ben Hassine, R.; Cherif, W. [Sfax University, Faculty of Sciences, B. P. 1171, 3000 (Tunisia); Alonso, J.A., E-mail: ja.alonso@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, E-28049 Madrid (Spain); Mompean, F. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, Cantoblanco, E-28049 Madrid (Spain); Fernández-Díaz, M.T. [Institut Laue-Langevin, B.P. 156, F-38042 Grenoble Cedex 9 (France); Elhalouani, F. [Sfax University, National School of Engineers, B. P. W 3038 (Tunisia)
2015-11-15
We present the structural and magnetic properties of a novel series of La{sub 0.67}Sr{sub 0.22}Ba{sub 0.11}Mn{sub 1-x}Fe{sub x}O{sub 3} (0 ≤ x ≤ 0.3) perovskites prepared by the sol–gel method. These oxides were characterized by x-ray (XRD), neutron powder diffraction (NDP) at room temperature and magnetization measurements versus temperature and various applied magnetic fields. The NPD data, very sensitive to the octahedral tilting, show a crystallographic phase transition from an orthorhombic structure (Pnma) for x = 0 to a rhombohedral structure (R-3c) for Fe-doped samples. Magnetic data show that x = 0 and x = 0.1 perovskites exhibit a paramagnetic–ferromagnetic transition at low temperature, while for 0.2 ≤ x ≤ 0.3 a strong divergence between ZFC and FC curves suggest the presence of antagonistic antiferromagnetic and ferromagnetic interactions. The magnetic entropy change (|ΔSmax|) takes values of 2.46 J kg{sup −1} K{sup −1}, 2.43 J kg{sup −1} K{sup −1} and 0.91 J kg{sup −1} for x = 0, x = 0.1 and 0.2, respectively at 5 T. The relative cooling power (RCP) amounts 169 J Kg{sup −1}, 241 J Kg{sup −1} and 70 J Kg{sup −1} at 5 T for x = 0, 0.1, 0.2 respectively. These values are compared favorably with those of some others reported manganites, making La{sub 0.67}Sr{sub 0.22}Ba{sub 0.11}Mn{sub 0.9}Fe{sub 0.1}O{sub 3} a promising candidate for magnetic refrigeration. - Graphical abstract: The title perovskites present a crystallographic phase transition from an orthorhombic structure (Pnma) for x = 0 to a rhombohedral structure (R-3c) for Fe-doped samples, as shown in a neutron study. Magnetic data show that x = 0 and x = 0.1 perovskites exhibit sharp paramagnetic–ferromagnetic transitions. The relative cooling power (RCP) is as high as 241 J Kg{sup −1} for x = 0.1, being a promising candidate for magnetic refrigeration. - Highlights: • Novel Fe-doped manganite oxides prepared by a sol–gel procedure. • Neutron diffraction shows
Effect of Fe substitution on multiferroic hexagonal YMnO3
International Nuclear Information System (INIS)
Zaghrioui, M.; Greneche, J.M.; Autret-Lambert, C.; Gervais, M.
2011-01-01
Polycrystalline YMn 1-x Fe x O 3 (x=0.02-0.20) powders were synthesized by means of modified citrate method. Powder X-ray diffraction gives evidence that all the samples are single phase and exhibit hexagonal structure with P6 3 cm space group as observed for YMnO 3 . The solubility limit of Fe was determined as about 6 wt.%. Cell parameter values were found to increase with Fe content, since Fe 3+ and Mn 3+ have the same ionic radii. This can be attributed to the increase of the tilting of MnO 5 bipyramid and the buckling of Y atoms. In addition, 57 Fe Moessbauer spectrometry provides evidence of two Fe 3+ sites attributed to two different nearest atomic neighbours. Magnetic properties reveal a paramagnetic-to-antiferromagnetic transition, a possible increase of the magnetic anisotropy, and a competition between ferromagnetic and antiferromagnetic interactions. - Research highlights: → The increase of the tilting of MnO 5 bipyramid and the buckling of Y atoms leads to the increase of cell parameter in YMn 1-x Fe x O 3 . → 57 Fe Moessbauer spectrometry provides evidence of two Fe 3+ sites.
Magnetism and electronic structure of CoFeCrX (X = Si, Ge) Heusler alloys
International Nuclear Information System (INIS)
Jin, Y.; O'Connell, A.; Kharel, P.; Lukashev, P.; Staten, B.; Tutic, I.; Valloppilly, S.; Herran, J.; Mitrakumar, M.; Bhusal, B.; Huh, Y.; Yang, K.; Skomski, R.; Sellmyer, D. J.
2016-01-01
The structural, electronic, and magnetic properties of CoFeCrX (X = Si, Ge) Heusler alloys have been investigated. Experimentally, the alloys were synthesized in the cubic L2 1 structure with small disorder. The cubic phase of CoFeCrSi was found to be highly stable against heat treatment, but CoFeCrGe disintegrated into other new compounds when the temperature reached 402 °C (675 K). Although the first-principle calculation predicted the possibility of tetragonal phase in CoFeCrGe, the tetragonal phase could not be stabilized experimentally. Both CoFeCrSi and CoFeCrGe compounds showed ferrimagnetic spin order at room temperature and have Curie temperatures (T C ) significantly above room temperature. The measured T C for CoFeCrSi is 790 K but that of CoFeCrGe could not be measured due to its dissociation into new compounds at 675 K. The saturation magnetizations of CoFeCrSi and CoFeCrGe are 2.82 μ B /f.u. and 2.78 μ B /f.u., respectively, which are close to the theoretically predicted value of 3 μ B /f.u. for their half-metallic phases. The calculated band gaps for CoFeCrSi and CoFeCrGe are, respectively, 1 eV and 0.5 eV. These materials have potential for spintronic device applications, as they exhibit half-metallic electronic structures with large band gaps, and Curie temperatures significantly above room temperature.
Synthesis and characterization of Sr2Ir1−xMxO4 (M=Ti, Fe, Co) solid solutions
International Nuclear Information System (INIS)
Gatimu, Alvin J.; Berthelot, Romain; Muir, Sean; Sleight, Arthur W.; Subramanian, M.A.
2012-01-01
The effects of Ti, Fe and Co substitutions for Ir on the structure and on the physical properties of Sr 2 IrO 4 are investigated. A complete solid solution Sr 2 Ir 1−x Ti x O 4 is obtained while both Fe and Co doping are relatively limited. In each case however, the c-axis cell parameter and the initial IrO 6 octahedra tilting decreases with substitution. Doping with Ti, Fe and Co results in a decrease of the magnetic susceptibility and in an increase in the paramagnetic effective moment for Co and Fe doped samples and a suppression of the weak ferromagnetic ordering observed for Sr 2 IrO 4 . - Graphical abstract: Solid solutions of Sr 2 Ir 1−x M x O 4 (M=Ti, Fe, Co) have been synthesized and characterized by powder X-ray diffraction, magnetism and electrical measurements. Changes in the a parameter and decreases in both the c-axis cell parameters and the initial IrO 6 octahedra tilting are found to be correlated. Highlights: ► Solid Solutions of Sr 2 Ir 1−x M x O 4 (M=Ti, Fe, Co) are synthesized. ► The Sr 2 Ir 1−x Ti x O 4 solid solution is complete while those of Fe and Co are relatively limited. ► The change in a cell parameter with substitution is much less than that of the c parameter. ► Decreased tilting and the smaller size of the M cation contrastingly affect the a parameter. ► Doping results in a suppression of the weak ferromagnetic ordering in Sr 2 IrO 4 .
Moessbauer study of Fe-Co nanowires
Energy Technology Data Exchange (ETDEWEB)
Chen Ziyu [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou (China)]. E-mail: chenzy@lzu.edu.cn; Zhan Qingfeng; Xue Desheng; Li Fashen [Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou (China); Zhou Xuezhi; Kunkel, Henry; Williams, Gwyn [Department of Physics and Astronomy, the University of Manitoba (Canada)
2002-01-28
Arrays of Fe{sub 1-x}Co{sub x} (0.0{<=}x{<=}0.92) nanowires have been prepared by an electrochemical process, co-depositing Fe and Co atoms into the pores of anodic aluminium; their compositions were determined by atomic absorption spectroscopy. Transmission electron microscope results show that the nanowires are regularly spaced and uniform in shape with lengths of about 7.5 {mu}m and diameters of 20 nm. The x-ray diffraction indicates a texture in the deposited nanowires. For the composition below 82 at.% cobalt, the nanowires had a body-centred-cubic structure with a [110] preferred orientation. For the 92 at.% cobalt sample, the alloy exhibited a mixture of bcc and face-centred-cubic structure. The room temperature {sup 57}Fe Moessbauer spectra of the arrays of Fe{sub 1-x}Co{sub x} nanowires have second and fifth absorption lines of the six-line pattern with almost zero intensity, indicating that the internal magnetic field in the nanowires lies along the long axis of the nanowire. The maximum values of the hyperfine field (B{sub hf} 36.6{+-}0.1 T) and isomer shift (IS=0.06{+-}0.01 mm s-1) occur for 44 at.% cobalt. The variations of the isomer shift and the linewidths with composition indicate that the Fe{sub 1-x}Co{sub x} alloy nanowires around the equiatomic composition are in an atomistic disordered state. (author)
Energy Technology Data Exchange (ETDEWEB)
Kadomtseva, A M [Moskovskij Gosudarstvennyj Univ. (USSR); Moskvin, A S; Bostrem, I G [Ural' skij Gosudarstvennyj Univ., Sverdlovsk (USSR)
1977-06-01
The theoretical results of an analysis of the Fe/sup 3 +/-Fe/sup 3 +/,Cr/sup 3 +/ -Cr/sup 3 +/nd Fe/sup 3 +/-Cr/sup 3 +/ exchange interactions are successfully employed to explain the anomalous magnetic properties of yttrium ferrite-chromite single crystals YFesub(1-x)Crsub(x)Osub(3) (where x=0; 0.05; 0.15; 0.2; 0.5; 0.65; 0.85; 0.95; 1). It is shown that these compounds are weak ferrimagnets with the mixed Dzyaloshinsky interaction. A qualitative explanation of the complex concentration and temperature dependences of the weak-ferrimagnetic moment is presented. The nature of the spin reorientation phenomenon is discussed.
Anomalous Hall effect in the van der Waals bonded ferromagnet Fe3 -xGeTe2
Liu, Yu; Stavitski, Eli; Attenkofer, Klaus; Petrovic, C.
2018-04-01
We report the anomalous Hall effect (AHE) in single crystals of a quasi-two-dimensional Fe3 -xGeTe2 (x ≈0.36 ) ferromagnet grown by the flux method which induces defects on the Fe site and bad metallic resistivity. Fe K-edge x-ray absorption spectroscopy was measured to provide information on the local atomic environment in such crystals. The dc and ac magnetic susceptibility measurements indicate a second-stage transition below 119 K in addition to the paramagnetic to ferromagnetic transition at 153 K. A linear scaling behavior between the modified anomalous Hall resistivity ρx y/μ0Heff and longitudinal resistivity ρxx 2M /μ0Heff implies that the AHE in Fe3 -xGeTe2 should be dominated by the intrinsic Karplus-Luttinger mechanism rather than the extrinsic skew-scattering and side-jump mechanisms. The observed deviation in the linear-M Hall conductivity σxy A below 30 K is in line with its transport characteristic at low temperatures, implying the scattering of conduction electrons due to magnetic disorder and the evolution of the Fermi surface induced by a possible spin-reorientation transition.
Exchange interactions and the state of iron atoms in Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ}
Energy Technology Data Exchange (ETDEWEB)
Chezhina, N.V., E-mail: chezhina@nc2490.spb.edu [St. Petersburg State University, 7/9 Universitetskaya Nab., 199034 (Russian Federation); Korolev, D.A. [St. Petersburg State University, 7/9 Universitetskaya Nab., 199034 (Russian Federation); Zhuk, N.A. [Syktyvkar State University (Russian Federation); Lutoev, V.P.; Makeev, B.A. [Institute of Geology Komi Scientific Center of Ural branch of Russian Academy of Sciences, Syktyvkar (Russian Federation)
2017-03-15
On the basis of the results of magnetic susceptibility and ESR studies of the Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ} solid solutions iron atoms in the solid solutions of cubic modification of bismuth niobate were found to exist as Fe(III) monomers and exchange bound Fe(III)-O-Fe(III) dimers with antiferro- and ferromagnetic type of superexchange. The exchange parameters and the distribution of monomers and dimers in the solid solutions were calculated as a function of paramagnetic atom content. - Graphical abstract: The study of the Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ} solid solutions showed that the introduction of iron atoms into the structure of Bi{sub 3}NbO{sub 7} stabilizes the cubic structure of bismuth niobate making the phase transition tetragonal ↔ cubic structure irreversible. In the Bi{sub 3}Nb{sub 1−x}Fe{sub x}O{sub 7−δ} solid solutions we observe the formation of dimers with antiferro- and ferromagnetic exchange. Such clusters are partially retained even at the infinite dilution of the solid solution, which testifies for their rigidity. A sufficiently high parameter of ferromagnetic exchange in a dimer (+53 cm{sup −1}) seems to result from iron atoms being located in the vicinity of oxygen vacancy. - Highlights: • The reversible transition cubic – tetragonal modifications in Bi{sub 3}NbO{sub 7} becomes irreversible. • Only cubic modification of Bi{sub 3}Nb{sub 1-x}Fe{sub x}O{sub 7-δ} is stable due to clusters of Fe atoms. • These clusters are sufficiently strong and retained even at the infinite dilution. • The calculations of magnetic susceptibility give the distribution of the clusters and single atoms.
Electromagnetic and microwave absorption properties of BaMg{sub x}Co{sub 1−x}TiFe{sub 10}O{sub 19}
Energy Technology Data Exchange (ETDEWEB)
Chen, Jing [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010 (China); Meng, Pingyuan [Huzhou Innovation Center of Advanced Materials, Shanghai Institute of Ceramics Chinese Academy of Sciences, Huzhou 215100 (China); Wang, Meiling [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010 (China); Zhou, Guanchen [School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010 (China); Wang, Xinqing [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang 621010 (China); School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010 (China); Xu, Guangliang, E-mail: xuguangliang@swust.edu.cn [School of Materials Science and Engineering, Southwest University of Science and Technology, Mianyang 621010 (China)
2016-09-15
To improve the impedance matching and then achieve a better microwave absorption performance in electromagnetic absorber, the Mg{sup 2+} was added to occupy the sites of Co{sup 2+} in hexagonal-type ferrite BaCoTiFe{sub 10}O{sub 19}. BaMg{sub x}Co{sub 1−x}TiFe{sub 10}O{sub 19} were synthesized by a simple sol-gel combustion technique and the phase of BaMg{sub x}Co{sub 1−x}TiFe{sub 10}O{sub 19} was confirmed by X-ray diffraction analysis (XRD). The grain size of BaMg{sub x}Co{sub 1−x}TiFe{sub 10}O{sub 19} was in the range of 100–400 nm and crystal particles were refined with the augment of doped Mg{sup 2+}. Based on the static magnetic measurement, the coercivity (H{sub c}) increased and the saturation magnetization (M{sub s}) decreased as the x increased. Moreover, it was found that BaMg{sub 0.4}Co{sub 0.6}TiFe{sub 10}O{sub 19} possessed a maximum reflection loss of −33.7 dB with a matching thickness of 2.0 mm measured by the vector net-analyzer in the frequency of 0.5–18 GHz, which also had a bandwidth below −20 dB ranging from 11.5 GHz to 17.2 GHz. Meanwhile, the permeability of the prepared ferrites could be adjusted and a proper match was provided between dielectric and magnetic properties by controlling the doped content of Mg{sup 2+}, which would be significant to the application of BaMg{sub x}Co{sub 1−x}TiFe{sub 10}O{sub 19} in the field of the microwave absorbing materials. - Highlights: • The Mg{sup 2+} ions were first employed to occupy the place of Co{sup 2+} ions in BaCoTiFe{sub 10}O{sub 19}. • The grains were refined as Co substitution by Mg in ferrite. • The peaks of complex permeability shift to high frequency with Mg{sup 2+} substituted. • The coercivity increased and saturation magnetization slightly decreased. • Substitution of Mg{sup 2+} enhanced microwave absorption and broadened bandwidth.
Effect of Mn Substitution for Multiferroic BiFeO3 Probed by High-Resolution Soft-X-Ray Spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Higuchi, Tohru; Higuchi, T.; Hattori, T.; Sakamoto, W.; Itoh, N.; Shimura, T.; Yogo, T.; Yao, P.; Liu, Y.; Glans, P.; Chang, C.; Wu, Z.; Guo, Jinghua
2008-07-11
The electronic structures of BiFeO{sub 3} (BF) and Mn-doped BiFeO{sub 3} (BF(Mn)) have been studied by X-ray absorption spectroscopy (XAS) and soft-X-ray emission spectroscopy (SXES). The BF and BF(Mn) have the mixed valence state of Fe{sup 2+} and Fe{sup 3+}. The valence band is mainly composed of O 2p state hybridized with the majority-spin t{sub 2g} and e{sub g} orbitals of Fe 3d state. The conduction band is composed of the minority-spin t{sub 2g} and e{sub g} orbitals of Fe 3d. The band gaps of BF and BF(Mn) are estimated to be 1.3 eV and 2.7 eV, respectively. The increase of band gap with Mn substitution contributes to the change of bandwidth of valence band.
Energy Technology Data Exchange (ETDEWEB)
Adil, Murtaza; Yang, Sen, E-mail: yang.sen@mail.xjtu.edu.cn; Mi, Meng; Zhou, Chao, E-mail: zhouch1982@gmail.com; Wang, Jieqiong; Zhang, Rui; Liao, Xiaoqi; Wang, Yu; Ren, Xiaobing; Song, Xiaoping, E-mail: xpsong@mail.xjtu.edu.cn [School of Sciences, Frontier Institute of Science and Technology, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Ren, Yang [X-Ray Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
2015-03-30
Morphotropic phase boundary (MPB), separating two ferroic phases of different crystal symmetries, has been studied extensively for its extraordinary enhancement of piezoelectricity in ferroelectrics. Based on the same mechanism, we have designed a magnetic MPB in the pseudobinary ferromagnetic system of Tb{sub 1−x}Gd{sub x}Fe{sub 2} and the corresponding crystal structure, magnetic properties, and magnetostriction are explored. With the synchrotron x-ray diffractometry, the structure symmetry of TbFe{sub 2}-rich compositions is detected to be rhombohedral (R) and that of GdFe{sub 2}-rich compositions is tetragonal (T) below T{sub c}. With the change of concentration, the value of magnetostriction of the samples changes monotonously, while the MPB composition Tb{sub 0.1}Gd{sub 0.9}Fe{sub 2}, which corresponds to the coexistence of R and T phases, exhibits the maximum magnetization among all available compositions and superposition of magnetostriction behaviour of R and T phases. Our result of MPB phenomena in ferromagnets may provide an effective route to design functional magnetic materials with exotic properties.
International Nuclear Information System (INIS)
Handstein, A.; Kubis, M.; Gebel, B.; Mueller, K.-H.; Schultz, L.; Gutfleisch, O.; Harris, I.R.; Birmingham Univ.
1998-01-01
The complete disproportionation of Sm 2 Fe 17-x Ga x during annealing in hydrogen is hindered due to an increased stability of the compounds with a higher Ga content (x ≥ 1). Therefore the HD process as the first step of HDDR (hydrogenation-disproportionation-desorption-recombination) has to be carried out at a high hydrogen pressure for x ≥ 1. The hydrogen absorption behaviour of Sm 2 Fe 17-x Ga x (x = 0, 0.5, 1 and 2) was investigated by means of hydrogen differential thermal analysis (HDTA) and high pressure differential scanning calorimetry (HPDSC) at hydrogen pressures up to 70 bar. A dependency of hydrogenation and disproportionation temperatures on hydrogen pressure and Ga content was found. The comparison with other substituents (M = Al and Si) instead of M = Ga showed an increased stability of Sm 2 Fe 17-x M x compounds against disproportionation by hydrogen in the sequence Al, Ga and Si. The Curie temperatures of the interstitially hydrogenated Th 2 Zn 17 -type materials increase with the hydrogen pressure. In order to produce coercive and thermally stable Sm 2 Fe 15 Ga 2 C y powder by means of the HDDR process, we recombined material disproportionated at different hydrogen pressures. Preliminary results of magnetic properties of this HDDR treated and gas-carburized Sm 2 Fe 15 Ga 2 C y are discussed. (orig.)
International Nuclear Information System (INIS)
Saydam, M.; Aksoy, C.; Cengiz, E.; Alaşalvar, C.; Tıraşoğlu, E.; Apaydın, G.
2012-01-01
The fluorescence cross-sections (σ Ki ) and the intensity ratios K β /K α for pure Fe, Se, Te elements and FeSe, FeTe, TeSe complexes have been investigated. The samples were excited by 59.5 keV γ-rays from 241 Am annular radioactive source and emitted X-rays. They were counted by an Ultra-LEGe detector with resolution of 150 eV at 5.9 keV. For pure elements results have been compared with the theoretical calculated values. According to our results band length and mutual interaction of atoms affected the results. We claimed that these effects would help researchers who study on superconductors, especially determining which compound can be show the superconductor properties. - Highlights: ► TeSe, FeSe and FeTe complexes have affected each other in terms of charge transfer. ► Fe excitement and enhancement have been made by Se and Te. ► Attractive interactions between electrons can help to becoming superconductivity.
Crystal Structure Analysis of Electromagnetic Wave Absorber Material BaFe12-xTix/2Znx/2O19Based
Delina, M.; Nenni, N.; Adi, W. A.
2018-04-01
The optimization of BaFe12-xTix/2Znx/2O19 (x=2.2; 2.4; 2.6; 2.8)single phase composition have been performed. The materials were synthesized by solid state reaction method through mechanical milling technique.The materials were made from the mixture of oxide materials, which are BaCO3, Fe2O3, TiO2 and ZnO. The mixture was milled for five hours using a High Energy Milling (HEM), was dried at 100°C in the Oven and then was sintered at 1000°C for five hours in the Furnace. The phase identification of BaFe12-xTix/2Znx/2O19 (x=2.2; 2.4; 2.6; 2.8) were carried out by using a Match Program while the crystal structure analysis were investigated by using a General Structure Analysis System (GSAS) program. The refinement results of x-ray diffraction pattern showed that the sample of x ≤ 2.4 have a BaFe12O19 single phase while the sample of x> 2.4 have two phases, which are BaFe12O19 and ZnFe2O4 phases. The surface morphology of sample and the element of sample were identified through an analysis of Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS) data.
Synthesis of LiNixFe1−xPO4 solid solution as cathode materials for lithium ion batteries
International Nuclear Information System (INIS)
Qing, Rui; Yang, Ming-Che; Meng, Ying Shirley; Sigmund, Wolfgang
2013-01-01
Highlights: • Phase pure LiNi x Fe 1−x PO 4 and LiNi x Fe 1−x PO 4 /C nanocomposites were obtained via a solid state reaction method. • Crystallite sizes were around 50 nm. Linear relationship was observed between lattice parameters and chemical composition. • Synthesized materials displayed electronic conductivity similar to reported value of LiFePO 4 . Carbon coating increased the conductivity to ∼10 −3 S/cm. • Chemical delithiation via NO 2 BF 4 extracted more than 90% of lithium from the nanocomposites, proving that Ni 2+ /Ni 3+ redox couple was activated. -- Abstract: Nanosize LiNi x Fe 1−x PO 4 solid solution and LiNi x Fe 1−x PO 4 /C nanocomposites were prepared via a solid state reaction method under argon atmosphere. A single phase olivine-type structure with Pnma space group was determined by X-ray diffraction. Crystallite sizes were found to be around 50 nm. A linear relationship was observed between lattice parameters and chemical composition which follows Vegard's law. Synthesized materials displayed electronic conductivity similar to previous reported values of LiFePO 4 . Carbon coating further increased the overall conductivity of nanocomposites to the order of 10 −3 S/cm. Chemical delithiation via NO 2 BF 4 oxidant extracted more than 95% of lithium from the solid solution material accompanied by a decrease in lattice parameters
International Nuclear Information System (INIS)
Li Jinpo; Ai Zhihui; Zhang Lizhi
2009-01-01
The narrow pH range limits the wide application of Fenton reaction in the wastewater treatment. It is of great importance to widen working pH range of Fenton reaction from strong acidic condition to neutral, even basic ones. In this study, for the first time nanostructured Fe-Fe 2 O 3 was loaded on active carbon fiber (ACF) as an oxygen diffusion cathode to be used in a heterogeneous electro-Fenton (E-Fenton) oxidation system. This novel Fe-Fe 2 O 3 /ACF composite cathode was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), and element mapping. On the degradation of dye pollutant rhodamine B in water, this heterogeneous E-Fenton system with the Fe-Fe 2 O 3 /ACF cathode showed much higher activity than other E-Fenton systems with commercial zero valent iron powders (Fe 0 ) and ferrous ions (Fe 2+ ) under neutral pH. On the basis of experimental results, we proposed a possible pathway of rhodamine B degradation in this heterogeneous Fe-Fe 2 O 3 /ACF E-Fenton process. This heterogeneous E-Fenton system is very promising to remove organic pollutants in water at neutral pH
Magnetism and superconductivity in CeFe2-xTxAs2 (T = Co and Ni) single crystals
International Nuclear Information System (INIS)
Thamizhavel, A.
2010-01-01
Single crystals of pure and transition metal doped CaFe 2- x T x As 2 (T = Co and Ni) have been grown by flux method using molten Sn as solvent. The magnetic and superconducting properties of the grown crystals were studied by measuring the electrical resistivity, magnetic susceptibility and neutron diffraction measurements. A spin density wave (SDW)/structural transition is observed at 170 K for the pure CaFe 2 As 2 single crystal and it gets suppressed with T (Co and Ni) doping. For an optimum dopant concentration of x = 0.06, the sample becomes superconducting. From the detailed studies on CaFe 2- x Ni x As 2 single crystals we have constructed a magnetic phase diagram. (author)
Giannetta, B.; Plaza, C.; Zaccone, C.; Siebecker, M. G.; Rovira, P.; Vischetti, C.; Sparks, D. L.
2017-12-01
Soil organic matter (SOM) protection and long-term accumulation are controlled by adsorption to mineral surfaces in different ways, depending on its molecular structure and pedo-climatic conditions. Iron (Fe) oxides are known to be key regulators of the soil carbon (C) cycle, and Fe speciation in soils is highly dependent on environmental conditions and chemical interactions with SOM. However, the molecular structure and hydrolysis of Fe species formed in association with SOM is still poorly described. We hypothesize the existence of two pools of Fe which interact with SOM: mononuclear Fe(III)-SOM complexes and precipitated Fe(III) hydroxides. To verify our hypothesis, we investigated the interactions between Fe(III) and physically isolated soil fractions by means of batch experiments at pH 7. Specifically, we examined the fine silt plus clay (FSi+C) fraction, obtained by ultrasonic dispersion and wet sieving. The soil samples spanned several land uses, including coniferous forest (CFS), grassland (GS), technosols (TS) and agricultural (AS) soils. Solid phase products and supernatants were analyzed for C and Fe content. X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis were also performed. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was used to assess the main C functional groups involved in C complexation and desorption experiments. Preliminary linear combination fitting (LCF) of Fe K-edge extended X-ray absorption fine structure (EXAFS) spectra suggested the formation of ferrihydrite-like polymeric Fe(III) oxides in reacted CFS and GS samples, with higher C and Fe concentration. Conversely, mononuclear Fe(III) OM complexes dominated the speciation for TS and AS samples, characterized by lower C and Fe concentration, inhibiting the hydrolysis and polymerization of Fe (III). This approach will help revealing the mechanisms by which SOM pools can control Fe(III) speciation, and will elucidate how both Fe
Fe atom exchange between aqueous Fe2+ and magnetite.
Gorski, Christopher A; Handler, Robert M; Beard, Brian L; Pasakarnis, Timothy; Johnson, Clark M; Scherer, Michelle M
2012-11-20
The reaction between magnetite and aqueous Fe(2+) has been extensively studied due to its role in contaminant reduction, trace-metal sequestration, and microbial respiration. Previous work has demonstrated that the reaction of Fe(2+) with magnetite (Fe(3)O(4)) results in the structural incorporation of Fe(2+) and an increase in the bulk Fe(2+) content of magnetite. It is unclear, however, whether significant Fe atom exchange occurs between magnetite and aqueous Fe(2+), as has been observed for other Fe oxides. Here, we measured the extent of Fe atom exchange between aqueous Fe(2+) and magnetite by reacting isotopically "normal" magnetite with (57)Fe-enriched aqueous Fe(2+). The extent of Fe atom exchange between magnetite and aqueous Fe(2+) was significant (54-71%), and went well beyond the amount of Fe atoms found at the near surface. Mössbauer spectroscopy of magnetite reacted with (56)Fe(2+) indicate that no preferential exchange of octahedral or tetrahedral sites occurred. Exchange experiments conducted with Co-ferrite (Co(2+)Fe(2)(3+)O(4)) showed little impact of Co substitution on the rate or extent of atom exchange. Bulk electron conduction, as previously invoked to explain Fe atom exchange in goethite, is a possible mechanism, but if it is occurring, conduction does not appear to be the rate-limiting step. The lack of significant impact of Co substitution on the kinetics of Fe atom exchange, and the relatively high diffusion coefficients reported for magnetite suggest that for magnetite, unlike goethite, Fe atom diffusion is a plausible mechanism to explain the rapid rates of Fe atom exchange in magnetite.
Reactions between monolayer Fe and Si(001) surfaces
Energy Technology Data Exchange (ETDEWEB)
Hasegawa, M; Kobayashi, N; Hayashi, N [Electrotechnical Lab., Tsukuba, Ibaraki (Japan)
1997-03-01
Reactions between 1.5 monolayer(ML) Fe deposited on Si(001)-2x1 and -dihydride surfaces were studied in situ by reflection high-energy electron diffraction and time-of-flight ion scattering spectrometry with the use of 25 keV H ions. The reactions between Fe and Si which were successively deposited on Si(001)-dihydride surface were also studied. After the room temperature deposition Fe reacted with Si(001)-2x1 substrate resulting in the formation of polycrystalline Fe5Si3. By annealing to 560-650degC composite heteroepitaxial layer of both type A and type B {beta}-FeSi2 was formed. On the dihydride surface polycrystalline Fe was observed after 1.5ML Fe deposition at room temperature, and reaction between Fe and Si(001)-dihydride surface is not likely at room temperature. We observed 3D rough surface when we deposited only Fe layer on the dihydride surface and annealed above 700degC. The hydrogen termination of Si(001) surface prevents the deposited Fe from diffusing into the substrate below 500degC, however the annealing above 710degC leads to the diffusion. We obtained 2D ordered surface, which showed 3x3 RHEED pattern as referenced to the primitive unreconstructed Si(001) surface net, when we deposited 2.5ML Fe and 5.8ML Si successively onto Si(001)-dihydride surface and annealed to 470degC. (author)
Jing, Z.; Chantel, J.; Yu, T.; Sakamaki, T.; Wang, Y.
2015-12-01
Liquid iron is likely the dominant constituent in the cores of terrestrial planets and icy satellites such as Earth, Mars, Mercury, the Moon, Ganymede, and Io. Suggested by geophysical and geochemical observations, light elements such as S, C, Si, etc., are likely present in planetary cores. These light elements can significantly reduce the density and melting temperature of the Fe cores, and hence their abundances are crucial to our understanding of the structure and thermal history of planetary cores, as well as the generation of intrinsic magnetic fields. Knowledge on the density of Fe-light element alloying liquids at high pressures is critical to place constraints on the composition of planetary cores. However, density data on liquid Fe-light element alloys at core pressures are very limited in pressure and composition and are sometimes controversial. In this study, we extend the density dataset for Fe-rich liquids by measuring the density of Fe, Fe-10wt%S, Fe-20wt%S, Fe-27wt%S, and FeS liquids using the X-ray absorption technique in a DIA-type multianvil apparatus up to 7 GPa and 2173 K. An ion chamber (1D-detector) and a CCD camera (2D-detector) were used to measure intensities of transmitted monochromatic X-rays through molten samples, with the photon energy optimized at 40 keV. The densities were then determined from the Beer-Lambert law using the mass absorption coefficients, calibrated by solid standards using X-ray diffraction. At each pressure, density measurements were conducted at a range of temperatures above the liquidus of the samples, enabling the determination of thermal expansion. Combined with our previous results on the sound velocity of Fe and Fe-S liquids at high pressures (Jing et al., 2014, Earth Planet. Sci. Lett. 396, 78-87), these data provide tight constraints on the equation of state and thermodynamic properties such as the adiabatic temperature gradient for Fe-S liquids. We will discuss these results with implications to planetary
Energy Technology Data Exchange (ETDEWEB)
Mujamilah,; Ridwan, [Materials Science Research Center, National Atomic Energy Agency of Indonesia, Jakarta (Indonesia)
1998-10-01
The crystallographic and magnetic structure of R{sub 2}Fe{sub 17-x}M{sub x} intermetallic compounds system were refined by Rietveld analyses of the high resolution neutron powder diffraction data. The analyses results show that the substituent atoms were not distributed randomly over the Fe sites, but preferentially occupied some Fe sites. More further, it was also found that the substituent atoms which atomic radius smaller than Fe tend to avoid the 6c site at low concentration while the larger substituent atom tend to replace the Fe atom at this 6c site corresponding to their concentration. From these crystallographic data, it was suggested that the change of magnetic ordering temperature Tc, is not mainly determined by the change of short bond distance between this `dumb-bell` atoms, but it was also influenced by the nearest coordinated atoms to this site. (author)
The solubility and site preference of Fe3+ in Li7−3xFexLa3Zr2O12 garnets
International Nuclear Information System (INIS)
Rettenwander, D.; Geiger, C.A.; Tribus, M.; Tropper, P.; Wagner, R.; Tippelt, G.; Lottermoser, W.; Amthauer, G.
2015-01-01
A series of Fe 3+ -bearing Li 7 La 3 Zr 2 O 12 (LLZO) garnets was synthesized using solid-state synthesis methods. The synthetic products were characterized compositionally using electron microprobe analysis and inductively coupled plasma optical emission spectroscopy (ICP-OES) and structurally using X-ray powder diffraction and 57 Fe Mössbauer spectroscopy. A maximum of about 0.25 Fe 3+ pfu could be incorporated in Li 7−3x Fe x La 3 Zr 2 O 12 garnet solid solutions. At Fe 3+ concentrations lower than about 0.16 pfu, both tetragonal and cubic garnets were obtained in the synthesis experiments. X-ray powder diffraction analysis showed only a garnet phase for syntheses with starting materials having intended Fe 3+ contents lower than 0.52 Fe 3+ pfu. Back-scattered electron images made with an electron microprobe also showed no phase other than garnet for these compositions. The lattice parameter, a 0 , for all solid-solution garnets is similar with a value of a 0 ≈12.98 Å regardless of the amount of Fe 3+ . 57 Fe Mössbauer spectroscopic measurements indicate the presence of poorly- or nano-crystalline FeLaO 3 in syntheses with Fe 3+ contents greater than 0.16 Fe 3+ pfu. The composition of different phase pure Li 7−3x Fe x La 3 Zr 2 O 12 garnets, as determined by electron microprobe (Fe, La, Zr) and ICP-OES (Li) measurements, give Li 6.89 Fe 0.03 La 3.05 Zr 2.01 O 12 , Li 6.66 Fe 0.06 La 3.06 Zr 2.01 O 12 , Li 6.54 Fe 0.12 La 3.01 Zr 1.98 O 12 , and Li 6.19 Fe 0.19 La 3.02 Zr 2.04 O 12 . The 57 Fe Mössbauer spectrum of cubic Li 6.54 Fe 0.12 La 3.01 Zr 1.98 O 12 garnet indicates that most Fe 3+ occurs at the special crystallographic 24d position, which is the standard tetrahedrally coordinated site in garnet. Fe 3+ in smaller amounts occurs at a general 96h site, which is only present for certain Li-oxide garnets, and in Li 6.54 Fe 0.12 La 3.01 Zr 1.98 O 12 this Fe 3+ has a distorted 4-fold coordination. - Graphical abstract: Cubic nominally Li 7 La 3 Zr 2 O
The initial oxidation of e-Fe2N1-x: an XPS investigation
DEFF Research Database (Denmark)
Graat, Peter C.J.; Somers, Marcel A. J.; Mittemeijer, Eric J.
1998-01-01
. Analysis of the N Is spectra provided information on the electric charge on nitrogen atoms and the depth distribution of nitrogen. A linear relation was found between the N Is electron binding energy and the nitrogen concentration in the substrate. Upon oxidation of the iron nitride, nitrogen atoms...... accumulated underneath the oxide film. If the nitrogen concentration at that location exceeded the maximum solubility of nitrogen in epsilon-Fe2N1-x an additional N peak appeared in the N Is spectrum, which indicated the formation of a nitrogen containing phase other than epsilon-Fe2N1-x at the nitride...
Fe induced optical limiting properties of Zn1-xFexS nanospheres
Vineeshkumar, T. V.; Raj, D. Rithesh; Prasanth, S.; Unnikrishnan, N. V.; Mahadevan Pillai, V. P.; Sudarasanakumar, C.
2018-02-01
Zn1-xFexS (x = 0.00, 0.01, 0.03, 0.05) nanospheres were synthesized by polyethylene glycol assisted hydrothermal method. XRD studies revealed that samples of all concentrations exhibited cubic structure with crystallite grain size 7-9 nm. TEM and SEM show the formation of nanospheres by dense aggregation of smaller particles. Increasing Zn/Fe ratio tune the band gap from 3.4 to 3.2 eV and also quenches the green luminescence. FTIR spectra reveal the presence of capping agent, intensity variation and shifting of LO and TO phonon modes confirm the presence of Fe ions. Nonlinear optical properties were measured using open and closed aperture z-scan techniques, employing frequency doubled 532 nm pumping sources which indicated reverse saturable absorption (RSA) process. The nonlinear optical coefficients are obtained by two photon absorption (2PA). Composition dependent nonlinear optical coefficients ;β;, nonlinear refractive index, third order susceptibility and optical limiting threshold were estimated. The sample shows good nonlinear absorption and enhancement of optical limiting behavior with increasing Fe volume fraction. Contribution of RSA on optical nonlinearity of Zn1-xFexS nanospheres are also investigated using three different input energies. Zn1-xFexS with comparatively small limiting threshold value is a promising candidate for optical power limiting applications.
Energy Technology Data Exchange (ETDEWEB)
Blessington Selvadurai, A. Paul; Pazhanivelu, V.; Jagadeeshwaran, C.; Murugaraj, R. [Anna University, Department of Physics, Chennai (India); Gazzali, P.M. Mohammed; Chandrasekaran, G. [Pondicherry University, Department of Physics, Pudhucherry (India)
2017-01-15
La{sub 1-x}RE{sub x}FeO{sub 3} (x = 0.0 and 0.5, RE = Nd, Sm and Gd) is synthesised by sol-gel citrate combustion method. X-ray diffraction (XRD) and Raman spectra show orthorhombic phase with Pbnm symmetry, confirmed by profile fitting and Raman modes analysis for La{sub 1-x}R{sub x}FeO{sub 3} samples. The estimated crystallite size and the orthorhombic strain of La{sub 1-x}RE{sub x}FeO{sub 3} (x = 0.0 and 0.5, RE = Nd, Sm and Gd) from XRD data illustrate the role of ionic size substitution. The temperature- and field-dependent magnetisation M(T) and M(H) were measured using vibrating sample magnetometer. The M(H) curve parameters of La{sub 1-x}RE{sub x}FeO{sub 3}(x = 0.5, RE = Nd and Gd) exhibit a relation of M{sub r} ∝ (1)/(H{sub c}) and H{sub ex} ∝ H{sub C} at 20, 150 and 300 K. The M (T) curve of La{sub 0.5}Nd{sub 0.5}FeO{sub 3} and La{sub 0.5}Gd{sub 0.5}FeO{sub 3} indicates the paramagnetic-like behaviour, whereas the M (H) curve reveals the antiferromagnetic signature in them. The M (H) curve of La{sub 0.5}Sm{sub 0.5}FeO{sub 3} shows a strong AFM pinned ferromagnetism and ferromagnetism (FM) at 150 and 20 K, respectively. Further, field-cooled (FC) and zero-field-cooled (ZFC) measurement of La{sub 0.5}Sm{sub 0.5}FeO{sub 3} indicates a competitive interaction of AFM-FM, which is emphasised by a broad blocking temperature at ∝117 K in ZFC curve. The FM-like ordering of Sm{sup 3+} ions are observed below at ∝150 K in FC curve of La{sub 0.5}Sm{sub 0.5}FeO{sub 3}. In addition, the electron paramagnetic resonance spectra at room temperature show a high g value and a strong non-homogenous broadening for La{sub 0.5}Sm{sub 0.5}FeO{sub 3}. (orig.)
Directory of Open Access Journals (Sweden)
Akkouche K.
2012-06-01
Full Text Available Nanocrystalline Fe100-xAlx powders (x= 25, 30, 34 and 40 at % were prepared by the mechanical alloying process using a vario-planetary high-energy ball mill for a milling time of 35 h. The formation and physical properties of the alloys were investigated as a function of Al content by means of X-ray diffraction, scanning electron microscopy (SEM, energy dispersive X-ray and Mössbauer spectroscopy. For all Fe100-xAlx samples, the complete formation of bcc phase was observed after 35 h of milling. As Al content increases, the lattice parameter increases, whereas the grain size decreases from 106 to 12 nm. The powder particle morphology for different compositions was observed by SEM. The Mössbauer spectra were adjusted with a singlet line and a sextet containing two components. The singlet was attributed to the formation of paramagnetic A2 disordered structure rich with Al. About the sextet, the first component indicated the formation of Fe clusters/ Fe-rich phases; however, the second component is characteristic of disordered ferromagnetic phase.
Sonocatalytic degradation of diclofenac with FeCeOx particles in water.
Chong, Shan; Zhang, Guangming; Wei, Zhongheng; Zhang, Nan; Huang, Ting; Liu, Yucan
2017-01-01
This paper studies the sonocatalytic degradation of diclofenac in water using FeCeO x -catalyzed ultrasound. The effects of pre-adsorption and gas addition were investigated. Nitrogen adsorption/desorption, SEM, XRD, Raman and XPS analyses of FeCeO x before and after sonication were characterized. The proposed mechanism was based on the microstructure changes of FeCeO x and reactive-species-scavenging performances. The results show that FeCeO x has excellent performance in catalyzing an ultrasonic system in water, and 80% of diclofenac was removed in 30min ([Diclofenac]=20mg/L, FeCeO x amount=0.5g/L, pH=6, ultrasonic density=3.0W/cm 3 , ultrasonic frequency=20kHz, temperature=298K). The Fe, Ce, and O elements remained highly dispersed in the structure of FeCeO x , and the solid solution structure of FeCeO x remained stable after the reaction. Ce (III) was gradually oxidized to Ce (IV) and Fe (III) was gradually reduced to Fe (II) after the reaction, which indicates that Fe and Ce ions with different valences coexisted in dynamic equilibrium. The amount of oxygen vacancies in FeCeO x significantly decreased after the reaction, which indicates that oxygen vacancy participated in the ultrasonic process. Singlet oxygen 1 O 2 was the primary reactive species in the degradation process, and the hydroxyl radicals OH and superoxide radical anion O 2 - also participated in the reaction. FeCeO x had excellent chemical stability with negligible leaching ions in the ultrasonic process. Copyright © 2016 Elsevier B.V. All rights reserved.
The solubility and site preference of Fe3+ in Li7-3xFexLa3Zr2O12 garnets
Rettenwander, D.; Geiger, C. A.; Tribus, M.; Tropper, P.; Wagner, R.; Tippelt, G.; Lottermoser, W.; Amthauer, G.
2015-10-01
A series of Fe3+-bearing Li7La3Zr2O12 (LLZO) garnets was synthesized using solid-state synthesis methods. The synthetic products were characterized compositionally using electron microprobe analysis and inductively coupled plasma optical emission spectroscopy (ICP-OES) and structurally using X-ray powder diffraction and 57Fe Mössbauer spectroscopy. A maximum of about 0.25 Fe3+ pfu could be incorporated in Li7-3xFexLa3Zr2O12 garnet solid solutions. At Fe3+ concentrations lower than about 0.16 pfu, both tetragonal and cubic garnets were obtained in the synthesis experiments. X-ray powder diffraction analysis showed only a garnet phase for syntheses with starting materials having intended Fe3+ contents lower than 0.52 Fe3+ pfu. Back-scattered electron images made with an electron microprobe also showed no phase other than garnet for these compositions. The lattice parameter, a0, for all solid-solution garnets is similar with a value of a0≈12.98 Å regardless of the amount of Fe3+. 57Fe Mössbauer spectroscopic measurements indicate the presence of poorly- or nano-crystalline FeLaO3 in syntheses with Fe3+ contents greater than 0.16 Fe3+ pfu. The composition of different phase pure Li7-3xFexLa3Zr2O12 garnets, as determined by electron microprobe (Fe, La, Zr) and ICP-OES (Li) measurements, give Li6.89Fe0.03La3.05Zr2.01O12, Li6.66Fe0.06La3.06Zr2.01O12, Li6.54Fe0.12La3.01Zr1.98O12, and Li6.19Fe0.19La3.02Zr2.04O12. The 57Fe Mössbauer spectrum of cubic Li6.54Fe0.12La3.01Zr1.98O12 garnet indicates that most Fe3+ occurs at the special crystallographic 24d position, which is the standard tetrahedrally coordinated site in garnet. Fe3+ in smaller amounts occurs at a general 96h site, which is only present for certain Li-oxide garnets, and in Li6.54Fe0.12La3.01Zr1.98O12 this Fe3+ has a distorted 4-fold coordination.
Theoretical calculations of valence states in Fe-Mo compounds
International Nuclear Information System (INIS)
Estrada, F; Navarro, O; Noverola, H; Suárez, J R; Avignon, M
2014-01-01
The half-metallic ferromagnetic double perovskite compound Sr 2 FeMoO 6 is considered as an important material for spintronic applications. It appears to be fundamental to understand the role of electronic parameters controlling the half-metallic ground state. Fe-Mo double perovskites usually present some degree of Fe/Mo disorder which generally increases with doping. In this work, we study the valence states of Fe-Mo cations in the off-stoichiometric system Sr 2 Fe 1+x Mo 1−x O 6 (−1 ≤ x ≤ 1/3) with disorder. Our results for Fe and Mo valence states are obtained using the Green functions and the renormalization perturbation expansion method. The model is based on a correlated electron picture with localized Fe-spins and conduction Mo-electrons interacting with the local spins via a double-exchange-type mechanism
Generation and evolution of nanoscale AlP and Al{sub 13}Fe{sub 4} particles in Al-Fe-P system
Energy Technology Data Exchange (ETDEWEB)
Qiao, Huan; Gao, Tong; Zhu, Xiangzhen; Wu, Yuying; Qian, Zhao; Liu, Xiangfa, E-mail: xfliu@sdu.edu.cn
2015-02-15
Highlights: • Diffusion and gradual solid reactions between Al and Fe{sub x}P phases in Al-Fe-P alloy were investigated. • Nanoscale AlP clusters are in-situ generated and evolve during the whole process. • This novel Al-Fe-P alloy has an excellent low-temperature refining performance on hypereutectic Al-Si alloy. - Abstract: In this paper, the gradual solid reactions between Al and Fe{sub x}P phases in Al-Fe-P alloy were investigated. The results show that the whole reaction process undergoes four main stages: the diffusion of Al atom, the generation of (Al, Fe, P) intermediate compound, the precipitation of nano AlP and Al{sub 13}Fe{sub 4} clusters and their growth to submicron particles. The microstructure of Fe-P particles evolves from the “egg-type”, the “sponge-type” to the “sesame-cake” structure. AlP and Al{sub 13}Fe{sub 4} nano phases have in-situ generated and evolved during the whole process. The gradual reaction mechanism has been discussed. Furthermore, a novel Al-Fe-P alloy which contains (Al, Fe, P) intermediate compounds and nano AlP particles has been synthesized and its low-temperature refining performance on A390 alloy has also been investigated.
Pandey, Rabichandra; Pradhan, Lagen Kumar; Kar, Manoranjan
2018-04-01
In this study, the tartaric acid modified sol-gel method was used to synthesize (1-x)Bi0.85La0.15FeO3-(x)CoFe2O4 (BLFO-CFO) composites where x = 0.00, 0.10, 0.20, 0.30, 0.40, and 0.50. The X-ray diffraction (XRD) patterns indicated the formation of composites with both BLFO and CFO crystal symmetry, i.e., perovskite and spinel structures, respectively. Rietveld refinement of the XRD patterns was performed for all of the samples in order to analyze the crystal phases and obtain the structural parameters. There were decreases in the lattice parameters of the perovskite phase as the CFO spinel phase increased in the composites, which may be explained by the strain at the interface of the BLFO and CFO phases. Electrical polarization and dielectric constant enhancements were observed in the BLFO-CFO composites compared with BLFO. The saturation magnetization increased as the CFO phase increased in the composites. The theoretical saturation magnetization (calculated using Vegard's law) was less than the experimentally observed value, possibly due to the spin interaction at the interface of BLFO and CFO.
Energy Technology Data Exchange (ETDEWEB)
Jayakumar, O.D. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Gopalakrishnan, I.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)], E-mail: ikgopal@barc.gov.in; Vinu, A. [Nano-Ionics Materials Group, Fuel Cell Materials Center, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Asthana, A. [Advanced Electron Microscopy Group, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Tyagi, A.K. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)
2008-08-11
Nanocrystalline (Th{sub 1-x}Fe{sub x})O{sub 2-{delta}} particles with different Fe concentrations (x = 0.0, 0.05, 0.10, 0.15, 0.20 and 0.25) have been prepared by a gel combustion method. Rietveld refinement analyses of X-ray diffraction data revealed the formation of an impurity free cubic type Th{sub 1-x}Fe{sub x}O{sub 2-{delta}} structure up to x = 0.20. This observation is further confirmed from the detailed studies conducted on 10 at.% Fe doped ThO{sub 2} using high-resolution transmission electron microscopy (HRTEM) imaging and indexing of the selected-area electron diffraction (SAED) patterns. DC magnetization studies as a function field indicate that they are ferromagnetic with Curie temperature (T{sub c}) well above room temperature.
Energy Technology Data Exchange (ETDEWEB)
Li Jun [School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China); Liu Ying, E-mail: Liuying5536@163.com [School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China) and Key Laboratory of Advanced Special Material and Technology, Ministry of Education, Chengdu 610065 (China); Ma Yilong [School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China)
2012-07-15
Bulk anisotropic NdFeB/{alpha}-Fe nano-composites were obtained directly from alloys of Nd{sub 11}Dy{sub 0.5}Fe{sub 82.4-x}Nb{sub x}B{sub 6.1} (x=0,0.5,1.0,1.5). High resolution transmission electron microscopy images showed the existence of Nb-rich amorphous grain boundary phase in the alloys with Nb doped. Field emission scanning electron microscope morphologies and X-ray diffraction patterns revealed the grain size and grain alignment of hot pressed and hot deformed nanocomposites. It was found that Nb could refine the grain size and grain texture in hot worked ribbons. Vibrating sample magnetometer results showed that the magnetic properties of the anisotropic nanocomposites were improved with increased Nb doping. The remanence, coercivity and maximum energy product of the bulk anisotropic Nd{sub 11}Dy{sub 0.5}Fe{sub 80.4}Nb{sub 2}B{sub 6.1} nanocomposites were 1.04 T, 563 kA/m and 146 kJ/m{sup 3}, respectively. - Highlights: Black-Right-Pointing-Pointer Nb has great influence on the microstructure and magnetic properties of (NdDy){sub 11.5}Fe{sub 82.4-x}Nb{sub x}B{sub 6.1} (x=0-2.0) nanocomposites. Black-Right-Pointing-Pointer Most of Nb atoms gather in the grain boundary to form Nb-rich amorphous intergranular phase, not NbFeB boride. Black-Right-Pointing-Pointer Furthermore, grain alignment can be prompt by the Nb-rich solid intergranular phase during deform. Black-Right-Pointing-Pointer Remanence, coercivity and (BH){sub m} of deformed (NdDy){sub 11.5}Fe{sub 80.4}Nb{sub 2}B{sub 6.1} nanocomposite is 1.04T, 563 kA/m and 146 kJ/m{sup 3} respectively. Black-Right-Pointing-Pointer This study provides an alternative method for prepare anisotropic nanocomposite direct from Nd-lean alloys with low cost.
Energy Technology Data Exchange (ETDEWEB)
Han, D.-D. [Research Center for Materials Science and Engineering, Jilin Institute of Chemical Technology, Jilin 132022 (China); College of Chemistry, Northeast Normal University, Changchun 130024 (China); Lu, D.-Y., E-mail: cninjp11232000@yahoo.com [Research Center for Materials Science and Engineering, Jilin Institute of Chemical Technology, Jilin 132022 (China); Sun, X.-Y. [Research Center for Materials Science and Engineering, Jilin Institute of Chemical Technology, Jilin 132022 (China)
2013-11-05
Highlights: •Structural evolution and dielectric properties of (Ba{sub 1−x}Nd{sub x})(Ti{sub 1−y}Fe{sub y})O{sub 3} were studied. •A cubic ceramic with x = y = 0.05 exhibits a high-k Y5V behavior (ε{sub RT}{sup ′} = 6790). •The T{sub m} in BNTF with x = 0.05 decreased linearly at a rate of −5 °C/mol% Fe ions. •Evolution in the 840 cm{sup −1} Raman band gives evidence for Nd{sup 3+}–Fe{sup 3+} complex formation. •Defect chemistry associated with structure evolution is discussed. -- Abstract: The influence of donor and acceptor co-doping on structure and dielectric properties of (Ba{sub 1−x}Nd{sub x})(Ti{sub 1−y}Fe{sub y})O{sub 3} (BNTF) (x = 0.05, y = 0.01–0.07; and x = 0–0.08, y = 0.05) ceramics was investigated with X-ray diffraction (XRD), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), Raman spectroscopy, and dielectric measurements. When x < y, two types of Nd{sup 3+}–Fe{sup 3+} and Fe{sup 3+}–V{sub O}–Fe{sup 3+} defect complexes formed and could not coexist, leading to the mixed phases of cubic and hexagonal. A single-phase ceramic with a cubic or tetragonal structure formed for x ⩾ y and the dielectric-peak temperature (T{sub m}) in BNTF with x = 0.05 decreased linearly with increasing y at a rate of −5 °C/mol% Fe ions. A high-k Y5V behavior can be realized at x = y = 0.05 (i.e., C-N5F5). The same concentrations of Nd{sup 3+} and Fe{sup 3+} formed Nd{sup 3+}–Fe{sup 3+} complexes, which could effectively suppress the dielectric loss and silence the 840 cm{sup −1} band called “Raman charge effect” associated with Nd{sup 3+} donors. C-N5F5 exhibited a cubic structure, medium-sized grains (3.3 μm), low dielectric loss (<0.06), and high-k Y5V behavior (ε{sub RT}{sup ′} = 6790). Defect chemistry associated with structure evolution is discussed.
EPR spectroscopic investigations in 15BaO-25Li2O-(60-x) B2O3-xFe2O3 glass system
Bhogi, Ashok; Kumar, R. Vijaya; Kistaiah, P.
2018-05-01
Glasses with composition 15BaO-25Li2O-(60-x) B2O3 -xFe2O3 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1 mol %) were prepared by the conventional melt quenching technique. These glasses were characterized using X-ray diffraction (XRD). Electron paramagnetic resonance (EPR) investigations have been carried out as a function of iron ion concentration. The observed EPR spectra of Fe3+ ion exhibits resonance signals at g= 2.0, 4.3 and 8.0. The resonance signal at g= 4.3 is due to isolated Fe3+ ions in site with rhombic symmetry where as the g= 2.0 resonance signal is attributed to the Fe3+ ions coupled by exchange interaction in a distorted octahedral environment and the signal at g= 8.0 arises from axially distorted sites. The number of spins participating in resonance (N) and its paramagnetic susceptibilities (χ) have also been evaluated. The peak-to-peak line width ΔB for the resonance lines at g ≈ 4.3 and at g ≈ 2.0 is increasing as function of the iron ion content. The line intensity of the resonance centered at g ≈ 4.3 and at g ≈ 2.0 increases up to 0.8 mol% of Fe2O3 and for 1 mol% of Fe2O3 its value is found to decrease. The analysis of these results indicated that the conversion some of Fe3+ cations to Fe2+ ions beyond 0.8 mol%.
Energy Technology Data Exchange (ETDEWEB)
Chen, Xiang, E-mail: gxucx@163.com [School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China); Department of Physics and Electronic Informational Engineering, Neijiang Teachers College, Neijiang 641002 (China); Chen, Yungui, E-mail: ygchen60@yahoo.com.cn [School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China); Tang, Yongbo; Xiao, Dingquan [School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China)
2014-11-15
The effects of Co on the formation of NaZn{sub 13}-type phase in as-cast and annealed LaFe{sub 16−x}Co{sub x}Si{sub 1.4} and LaFe{sub 11.6}Si{sub 1.4−x}Co{sub x} alloys have been investigated systematically by XRD, SEM, and EDS, respectively. In LaFe{sub 11.6}Si{sub 1.4−x}Co{sub x} alloys, the introduction of Co will hamper the formation of 1:13 and LaFeSi phases, and help the formation of αof (Co, Si) solid solution, so there is almost only α-Fe(Co, Si) solid solution when x reaches 0.7 in as-cast and annealed LaFe{sub 11.6}Si{sub 1.4−x}Co{sub x} alloys. Although the amounts of 1:13 phase increases when x reaches 0.7 in as-cast LaFe{sub 16−x}Co{sub x}Si{sub 1.4} alloys, there is a small amount of α-Fe in LaFe{sub 11.6−x}Co{sub x}Si{sub 1.4} alloys annealed at 1523 K (5 h), which indicates that the annealing time for obtaining a 1:13 single-phase cannot be shortened in our high-temperature and short-time annealing. The studies on the magnetic properties show that the Curie temperature T{sub C} goes up from 207 K to 285 K with increase of Co content from x=0.1 to 0.8. The introduction of Co element weakens the first order magnetic phase transition, which results in the change of magnetic transition type from first to second order at about x=0.3–0.5. At the same time, it has effects on the phase transition temperature interval and magnetic filed interval, and the changing rate of magnetic entropy change dependence on the Co content in LaFe{sub 16−x}Co{sub x}Si{sub 1.4} alloys. The maximum entropy values of LaFe{sub 11.6−x}Co{sub x}Si{sub 1.4} alloys decrease with the increase of Co content, but the relative cooling power does not decrease, the reason of which is that the phase transition temperature interval increases and the first order phase transition character decreases, and the effective refrigeration temperature range becomes big, which is useful to the application of magnetic refrigeration material. - Highlights: • The introduction of Co
Nilmoung, Sukanya; Sonsupap, Somchai; Sawangphruk, Montree; Maensiri, Santi
2018-06-01
This work reports the fabrication and electrochemical properties of activated carbon nanofibers composited with copper manganese ferrite (ACNF/Cu x Mn1- x Fe2O4: x = 0.0, 0.2, 0.4, 0.6, 0.8) nanostructures. The obtained samples were characterized by means of X-ray diffraction, field emission scanning electron microscopy, Brunauer-Emmett-Teller analyzer, thermal gravimetric analysis, X-ray photoemission spectroscopy, and X-ray absorption spectroscopy. The supercapacitive behavior of the electrodes is tested using cyclic voltammetery, galvanostatic charge-discharge and electrochemical impedance spectroscopy. By varying ` x', the highest specific capacitance of 384 F/g at 2 mV/s using CV and 314 F/g at 2 A/g using GCD are obtained for the x = 0.2 electrode. The second one of 235 F/g at 2 mV/s using CV and 172 F/g at 2 A/g using GCD are observed for x = 0.8 electrode. The corresponding energy densities are 74 and 41 Wh/kg, respectively. It is observed that the cyclic stability of the prepared samples strongly depend on the amount of carbon, while the specific capacitance was enhanced by the sample with nearly proportional amount between carbon and CuMnFe2O4. Such results may arise from the synergetic effect between CuMnFe2O4 and ACNF.
Structure evolution upon chemical and physical pressure in (Sr{sub 1−x}Ba{sub x}){sub 2}FeSbO{sub 6}
Energy Technology Data Exchange (ETDEWEB)
Tiittanen, T.; Karppinen, M., E-mail: maarit.karppinen@aalto.fi
2017-02-15
Here we demonstrate the gradual structural transformation from the monoclinic I2/m to tetragonal I4/m, cubic Fm-3m and hexagonal P6{sub 3}/mmc structure upon the isovalent larger-for-smaller A-site cation substitution in the B-site ordered double-perovskite system (Sr{sub 1−x}Ba{sub x}){sub 2}FeSbO{sub 6}. This is the same transformation sequence previously observed up to Fm-3m upon heating the parent Sr{sub 2}FeSbO{sub 6} phase to high temperatures. High-pressure treatment, on the other hand, transforms the hexagonal P6{sub 3}/mmc structure of the other end member Ba{sub 2}FeSbO{sub 6} back to the cubic Fm-3m structure. Hence we may conclude that chemical pressure, physical pressure and decreasing temperature all work towards the same direction in the (Sr{sub 1−x}Ba{sub x}){sub 2}FeSbO{sub 6} system. Also shown is that with increasing Ba-for-Sr substitution level, i.e. with decreasing chemical pressure effect, the degree-of-order among the B-site cations, Fe and Sb, decreases. - Graphical abstract: In the (Sr{sub 1−x}Ba{sub x}){sub 2}FeSbO{sub 6} double-perovskite system the gradual structural transformation from the monoclinic I2/m to tetragonal I4/m, cubic Fm-3m and hexagonal P6{sub 3}/mmc structure is seen upon the isovalent larger-for-smaller A-site cation substitution. High-pressure treatment under 4 GPa extends stability of the cubic Fm-3m structure within a wider substitution range of x. - Highlights: • Gradual structural transitions upon A-cation substitution in (Sr{sub 1−x}Ba{sub x}){sub 2}FeSbO{sub 6.} • With increasing x structure changes from I2/m to I4/m, Fm-3m and P6{sub 3}/mmc. • Degree of B-site order decreases with increasing x and A-site cation radius. • High-pressure treatment extends cubic Fm-3m phase stability for wider x range. • High-pressure treatment affects bond lengths mostly around the A-cation.
Energy Technology Data Exchange (ETDEWEB)
Wei, Zhi-Xian, E-mail: zx_wei@126.com [Beijing Institute of Protective Materials and Technology, Beijing 100081 (China); School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Department of Chemistry, Science Institute, North University of China, Taiyuan, Shanxi 030051 (China); Wang, Yan [Department of Chemistry, Chengde Teachers College for Nationalities, Chengde, Hebei 067000 (China); Liu, Ji-Ping, E-mail: liujp@bit.edu.cn [Beijing Institute of Protective Materials and Technology, Beijing 100081 (China); School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Xiao, Cai-Mei; Zeng, Wei-Wei [Department of Chemistry, Science Institute, North University of China, Taiyuan, Shanxi 030051 (China)
2012-10-15
Perovskite LaFe{sub 0.5}Mn{sub 0.5}O{sub 3-{delta}} and LaFeO{sub 3} were synthesized by stearic acid solution combustion method. The obtained powders were characterized by X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), Vibrating sample magnetometer (VSM), XPS techniques and UV-vis absorption spectra techniques. The magnetic properties of the LaFeO{sub 3} and LaFe{sub 0.5}Mn{sub 0.5}O{sub 3-{delta}} were measured, and they were also evaluated for their photocatalytic activity towards the degradation of methyl orange (MO) under the sunlight irradiation. The experimental results show that the catalytic activities of the LaFe{sub 0.5}Mn{sub 0.5}O{sub 3-{delta}} were much higher than those of LaFeO{sub 3} due to its higher oxygen vacancies, variable valency Mn ions and the strong absorption in visible light. The optimum conditions for photocatalytic degradation MO using LaFe{sub 0.5}Mn{sub 0.5}O{sub 3-{delta}} were achieved. The ferromagnetism of the LaFe{sub 0.5}Mn{sub 0.5}O{sub 3-{delta}} could be caused by the Mn{sup 3+}/Fe{sup 3+} and Mn{sup 3+}/Mn{sup 4+}double exchange interaction, Mn{sup 3+}/Mn{sup 3+} superexchange interactions as well as the defective state in LaFe{sub 0.5}Mn{sub 0.5}O{sub 3-{delta}}. The LaFe{sub 0.5}Mn{sub 0.5}O{sub 3-{delta}} is applicable to the magnetic separation process for its lower coercivity (Hc) and remanent magnetization (Mr), and it can be reusable and maintain relatively high activity. -- Highlights: Black-Right-Pointing-Pointer The LaFe{sub 0.5}Mn{sub 0.5}O{sub 3-{delta}} is a bifunctional photocatalyst. Black-Right-Pointing-Pointer The origin of the ferromagnetism of the LaFe{sub 0.5}Mn{sub 0.5}O{sub 3-{delta}} is discussed. Black-Right-Pointing-Pointer LaFe{sub 0.5}Mn{sub 0.5}O{sub 3-{delta}} shows much higher photocatalytic activity than that of LaFeO{sub 3.} Black-Right-Pointing-Pointer LaFe{sub 0.5}Mn{sub 0.5}O{sub 3-{delta}} can be recycled by an external magnetic
Ab initio study of C14 laves phases in Fe-based systems
Directory of Open Access Journals (Sweden)
Pavlu J.
2012-01-01
Full Text Available Structural properties and energetics of Fe-based C14 Laves phases at various compositions (i.e. Fe2Fe, Fe2X, X2Fe, X2X, where X stands for Si, Cr, Mo, W, Ta were investigated using the pseudopotential VASP (Vienna Ab initio Simulation Package code employing the PAW-PBE (Projector Augmented Wave - Perdew Burke-Ernzerhof pseudopotentials. Full relaxation was performed for all structures studied including the reference states of elemental constituents and the equilibrium structure parameters as well as bulk moduli were found. The structure parameters of experimentally found structures were very well reproduced by our calculations. It was also found that the lattice parameters and volumes of the unit cell decrease with increasing molar fraction of iron. Thermodynamic analysis shows that the Fe2X configurations of Laves phases are more stable than the X2Fe ones. Some of the X2Fe configurations are even unstable with respect to the weighted average of the Laves phases of elemental constituents. Our calculations predict the stability of Fe2Ta. On the other hand, Fe2Mo and Fe2W are slightly unstable (3.19 and 0.68 kJ.mol-1, respectively and hypothetical structures Fe2Cr and Fe2Si are found unstable as well.
Synthesizing single-phase β-FeSi2 via ion beam irradiations of Fe/Si bilayers
International Nuclear Information System (INIS)
Milosavljevic, M.; Dhar, S.; Schaaf, P.; Bibic, N.; Lieb, K.P.
2001-01-01
This paper presents results on the direct synthesis of the β-FeSi 2 phase by ion beam mixing of Fe/Si bilayers with Xe ions. The influence of the substrate temperature, ion fluence and energy on the growth of this phase was investigated using Rutherford backscattering (RBS), X-ray diffraction (XRD) and conversion electron Moessbauer spectroscopy (CEMS). Complete growth of single-phase β-FeSi 2 was achieved by 205 keV Xe ion irradiation to a fluence of 2x10 16 ions/cm 2 at 600 deg. C. We propose a two-step reaction mechanism involving thermal and ion beam energy deposition
Magnetic properties of Sc{sub x}Ti{sub 1-x}Fe{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Kessler, M. [Lab. de Cristallographie, CNRS, 38 - Grenoble (France); Deportes, J. [Lab. Louis Neel, CNRS, 38 - Grenoble (France); Ouladdiaf, B. [Institut Laue-Langevin, 38 - Grenoble (France); Sayetat, F. [Lab. de Cristallographie, CNRS, 38 - Grenoble (France)
1995-02-09
The magnetic properties and their thermal dependences of Sc{sub 0.1}Ti{sub 0.9}Fe{sub 1.96}, Sc{sub 0.1}Ti{sub 0.9}Fe{sub 2} and Sc{sub 0.1}Ti{sub 0.9}Fe{sub 2.04} are compared with those of TiFe{sub 2}. The substitution changes the iron-iron distances. Consequently, the Fe atoms on the 6h site show in addition to the antiferromagnetic component a small ferromagnetic one, and a weak magnetic moment appears on the 2a site. ((orig.)).
Energy Technology Data Exchange (ETDEWEB)
Chauhan, Samta; Singh, Amit Kumar; Srivastava, Saurabh Kumar; Chandra, Ramesh, E-mail: ramesfic@iitr.ac.in
2016-09-15
We have studied the magnetic behavior of YMn{sub 1−x}Fe{sub x}O{sub 3} (x=0 and 0.2) nanoparticles synthesized by conventional solid state reaction method. The as-synthesized nanoparticles were found to have hexagonal phase with P6{sub 3cm} space group confirmed by X-Ray diffraction. The particle size was found to be ~70 nm as confirmed by both X-Ray diffraction and Transmission Electron Microscopy. DC magnetization and memory effect measurements imply that the h-YMnO{sub 3} nanoparticles bear a resemblance to super spin-glass state following de Almeida–Thouless like behavior which is being suppressed by Fe-doping. The Fe-doping in YMnO{sub 3} enhances the antiferromagnetic (AFM) transition temperature T{sub N} to ~79 K and induces a new magnetic state due to the surface spins which is realized as diluted antiferromagnet in a field (DAFF) as explored by the thermoremanent and isothermoremanent magnetization measured with different applied magnetic field. - Highlights: • Magnetic behavior of h-YMn{sub 1−x}Fe{sub x}O{sub 3} (x=0 and 0.2) nanoparticles have been studied. • The nanoparticles (~70 nm) were synthesized by solid state reaction method. • Magnetic data reveal spin-glass behavior in YMnO{sub 3} which was suppressed in YMn{sub 0.8}Fe{sub 0.2}O{sub 3}. • The h-YMnO{sub 3} nanoparticles show memory effect and obey de-Almeida Thouless line. • TRM and IRM suggest spin glass nature for YMnO{sub 3}, while the YMn{sub 0.8}Fe{sub 0.2}O{sub 3} resembles DAFF.
Nematic fluctuations in iron arsenides NaFeAs and LiFeAs probed by 75As NMR
Toyoda, Masayuki; Kobayashi, Yoshiaki; Itoh, Masayuki
2018-03-01
75As NMR measurements have been made on single crystals to study the nematic state in the iron arsenides NaFeAs, which undergoes a structural transition from a high-temperature (high-T ) tetragonal phase to a low-T orthorhombic phase at Ts=57 K and an antiferromagnetic transition at TN=42 K, and LiFeAs having a superconducting transition at Tc=18 K. We observe the in-plane anisotropy of the electric field gradient η even in the tetragonal phase of NaFeAs and LiFeAs, showing the local breaking of tetragonal C4 symmetry. Then, η is found to obey the Curie-Weiss (CW) law as well as in Ba (Fe1-xCox) 2As2 . The good agreement between η and the nematic susceptibility obtained by electronic Raman spectroscopy indicates that η is governed by the nematic susceptibility. From comparing η in NaFeAs and LiFeAs with η in Ba (Fe1-xCox) 2As2 , we discuss the carrier-doping dependence of the nematic susceptibility. The spin contribution to nematic susceptibility is also discussed from comparing the CW terms in η with the nuclear spin-lattice relaxation rate divided by temperature 1 /T1T . Finally, we discuss the nematic transition in the paramagnetic orthorhombic phase of NaFeAs from the in-plane anisotropy of 1 /T1T .
Mg1-xZnxFe2O4 nanoparticles: Interplay between cation distribution and magnetic properties
Directory of Open Access Journals (Sweden)
S. Raghuvanshi
2018-04-01
Full Text Available Correlation between cationic distribution, magnetic properties of Mg1-xZnxFe2O4 (0.0 ≤ x ≤ 1.0 ferrite is demonstrated, hardly shown in literature. X-ray diffraction (XRD confirms the formation of cubic spinel nano ferrites with grain diameter between 40.8 to 55.4 nm. Energy dispersive spectroscopy (EDS confirms close agreement of Mg/Fe, Zn/Fe molar ratio, presence of all elements (Mg, Zn, Fe, O, formation of estimated ferrite composition. Zn addition (for Mg shows: i linear increase of lattice parameter aexp, accounted for replacement of an ion with higher ionic radius (Zn > Mg; ii presence of higher population of Fe3+ ions on B site, and unusual occurrence of Zn, Mg on A and B site leads to non-equilibrium cation distribution where we observe inverse to mixed structure, and is in contrast to reported literature where inverse to normal transition is reported; iii effect on A-A, A-B, B-B exchange interactions, affecting coercivity Hc, Ms. A new empirical relation is also obtained showing linear relation between saturation magnetization Ms – inversion parameter δ, oxygen parameter u4¯3m. Non-zero Y-K angle (αYK values implies Y-K type magnetic ordering in the studied samples.
Effectiveness of FeEDDHA, FeEDDHMA, and FeHBED in Preventing Iron-Deficiency Chlorosis in Soybean.
Bin, Levi M; Weng, Liping; Bugter, Marcel H J
2016-11-09
The performance of FeHBED in preventing Fe deficiency chlorosis in soybean (Glycine max (L.) Merr.) in comparison to FeEDDHA and FeEDDHMA was studied, as well as the importance of the ortho-ortho and ortho-para/rest isomers in defining the performance. To this end, chlorophyll production (SPAD), plant dry matter yield, and the mass fractions of important mineral elements in the plant were quantified in a greenhouse pot experiment. All three Fe chelates increased SPAD index and dry matter yield compared to the control. The effect of FeHBED on chlorophyll production was visible over a longer time span than that of FeEDDHA and FeEDDHMA. Additionally, FeHBED did not suppress Mn uptake as much as the other Fe chelates. Compared to the other Fe chelates, total Fe content in the young leaves was lower in the FeHBED treatment; however, total Fe content was not directly related to chlorophyll production and biomass yield. For each chelate, the ortho-ortho isomer was found to be more effective than the other isomers evaluated.
Band structure and magnetic properties of DO3-type Fe3-xVxAl alloys. Super-cell approach
International Nuclear Information System (INIS)
Deniszczyk, J.; Borgiel, W.
2000-01-01
The electronic structure of Fe 3-x V x Al alloys can be calculated using the super-cell methodology of alloy modeling. The concentration range of x 0.0-1.0 was investigated. For a concentration of x = 0.0625 the energy based analysis reveals that vanadium prefers to replace the Fe atom at sites with the octahedral coordination. It was found that the iron atoms coordinated by the eight nearest-neighbour Fe atoms preserve their high magnetic moment up to a concentration of x = 0.9375 even through the average total magnetic moment goes to zero. The relatively high (∼ -1.0 μ B ) negative magnetic moment of V remains constant up to x ∼ 0.5. In the concentration range of x = 0.75-0.9375 the gap at ε F of the minority density of states is observed while the majority density of states displays a sharp peak structure at the Fermi energy. This feature suggests the heavy-fermion behaviour of the Fe 2 VAl compound. (author)
Cama, Christina A; Pelliccione, Christopher J; Brady, Alexander B; Li, Jing; Stach, Eric A; Wang, Jiajun; Wang, Jun; Takeuchi, Esther S; Takeuchi, Kenneth J; Marschilok, Amy C
2016-06-22
Copper ferrite, CuFe2O4, is a promising candidate for application as a high energy electrode material in lithium based batteries. Mechanistic insight on the electrochemical reduction and oxidation processes was gained through the first X-ray absorption spectroscopic study of lithiation and delithiation of CuFe2O4. A phase pure tetragonal CuFe2O4 material was prepared and characterized using laboratory and synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. Ex situ X-ray absorption spectroscopy (XAS) measurements were used to study the battery redox processes at the Fe and Cu K-edges, using X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and transmission X-ray microscopy (TXM) spectroscopies. EXAFS analysis showed upon discharge, an initial conversion of 50% of the copper(ii) to copper metal positioned outside of the spinel structure, followed by a migration of tetrahedral iron(iii) cations to octahedral positions previously occupied by copper(ii). Upon charging to 3.5 V, the copper metal remained in the metallic state, while iron metal oxidation to iron(iii) was achieved. The results provide new mechanistic insight regarding the evolution of the local coordination environments at the iron and copper centers upon discharging and charging.
International Nuclear Information System (INIS)
Chiu, Kuo-Feng; Su, Shih-Hsuan; Leu, Hoang-Jyh; Huang, Wei-Chieh
2015-01-01
LiFePO_4_−_xN_y thin films were sputter-deposited on micron carbon fibers (MCFs) under a gas mixture of N_2/Ar/H_2 as electrode materials in pseudocapacitors. The MCFs were fabricated by thermal chemical vapor deposition on stainless steel substrates as current collectors. Various amounts of N_2 were introduced by controlling the flow ratios of N_2 to Ar/H_2. The LiFePO_4_−_xN_y thin films coated on the surfaces of MCFs were observed by field emission scanning electron microscopy. The electrochemical properties of the LiFePO_4_−_xN_y thin films were characterized using cyclic voltammetry and charge–discharge processes. The LiFePO_4_−_xN_y thin-film electrode deposited under the optimal N_2 contents exhibited a high specific capacitance of 722 F/g at 1 A/g. Even at a current of 20 A/g, the electrode delivered a capacitance of 298 F/g. The pseudocapacitors using LiFePO_4_−_xN_y thin-film electrodes showed no significant capacitance fading after 1000 cycles at 1 A/g. The results indicated that nitrogen doping improved the electrochemical performances of LiFePO_4, demonstrating the potential of LiFePO_4_−_xN_y as an active material in pseudocapacitors. - Highlights: • LiFePO_4_−_xN_y thin films were sputter-deposited on micron carbon fibers (MCFs). • MCFs only act as a three-dimensional current collector in this system. • The pseudocapacitor exhibits a high specific capacitance.
Study on magnetic properties of (Nd0.8Ce0.2)2-xFe12Co2B (x = 0-0.6) alloys
Tan, G. S.; Xu, H.; Yu, L. Y.; Tan, X. H.; Zhang, Q.; Gu, Y.; Hou, X. L.
2017-09-01
In the present work, (Nd0.8Ce0.2)2-xFe12Co2B (x = 0-0.6) permanent alloys are prepared by melt-spinning method. The hard magnetic properties of (Nd0.8Ce0.2)2-xFe12Co2B (x = 0-0.6) alloys annealed at optimum temperatures have been investigated systematically. Depending on the Nd, Ce concentration, the maximum energy product ((BH)max) and remanence (Br) increase gradually with x in the range of 0 ≤ x ≤ 0.4, whereas decrease gradually in the alloys with 0.4 plays a certain role in the magnetization reversal behavior and can improve the microstructure of (Nd0.8Ce0.2)1.6Fe12Co2B alloy.
Energy Technology Data Exchange (ETDEWEB)
Ballot, N.; Schoenstein, F.; Mercone, S.; Chauveau, T.; Brinza, O. [Laboratoire des Sciences des Procedes et des Materiaux, CNRS, LSPM - UPR 3407, Universite Paris 13, PRES Sorbonne-Paris-Cite, 99 Avenue J.-B. Clement, 93430 Villetaneuse (France); Jouini, N., E-mail: jouini@univ-paris13.fr [Laboratoire des Sciences des Procedes et des Materiaux, CNRS, LSPM - UPR 3407, Universite Paris 13, PRES Sorbonne-Paris-Cite, 99 Avenue J.-B. Clement, 93430 Villetaneuse (France)
2012-09-25
Highlights: Black-Right-Pointing-Pointer Spinels nano-particles MFe{sub 2}O{sub 4} (M: Co, Fe or Ni) are obtained by hydrolysis in polyol medium. Black-Right-Pointing-Pointer Gentle reduction under hydrogen flow of spinel nano-particles yields metal and alloy nanoparticles. Black-Right-Pointing-Pointer TEM and X-ray analysis show that CoFe{sub 2}, Fe and Ni{sub 3}Fe nano-particles are monocrystalline particles with size less than 160 nm. Black-Right-Pointing-Pointer Iron with size of 150 nm presents ferromagnetic behavior. Black-Right-Pointing-Pointer CoFe{sub 2} alloy with size of 55 nm could be considered as a superparamagnetic material. - Abstract: A novel method to process metal and various alloy particles of nanometric size is described. The first step consists in the elaboration of MFe{sub 2}O{sub 4} (M: Fe, Ni or Co) spinel nanoparticles in polyol medium via hydrolysis and the second one in gently reducing these latter under hydrogen at 300 Degree-Sign C. X-ray diffraction analysis shows that pure Fe and CoFe{sub 2} alloy are well obtained by reducing Fe{sub 3}O{sub 4} and CoFe{sub 2}O{sub 4}, respectively. This is not the case when we try to reduce NiFe{sub 2}O{sub 4}. A mixture of Fe and Ni{sub 3}Fe is observed. TEM analysis reveals that the size of metal particles stays within the range of a few tenths of nm up to 150 nm, while the precursors (MFe{sub 2}O{sub 4}) never exceed 5 nm. Our results show that the formation of metal particles occurs via two main steps: (i) reduction of the spinel oxide nanoparticles into metal ones and (ii) aggregation of the latter, leading to larger metal nanoparticles. Magnetic measurements indicate that the as-obtained metallic materials have good magnetic properties mainly affected by the sizes of the nanoparticles and the purity of the reduced phases.
Energy Technology Data Exchange (ETDEWEB)
Zakaria, A.K.M., E-mail: zakaria6403@yahoo.com [Institute of Nuclear Science & Technology, Bangladesh Atomic Energy Commission, Dhaka (Bangladesh); Nesa, Faizun [Department of Natural Science, Daffodil International University, Dhaka (Bangladesh); Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh); Saeed Khan, M.A. [Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh); Datta, T.K.; Aktar, Sanjida; Liba, Samia Islam; Hossain, Shahzad; Das, A.K.; Kamal, I.; Yunus, S.M. [Institute of Nuclear Science & Technology, Bangladesh Atomic Energy Commission, Dhaka (Bangladesh); Eriksson, S.-G. [Department of Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg (Sweden)
2015-06-05
Highlights: • MgCr{sub x}Fe{sub 2−x}O{sub 4} ferrites crystallize at 1300 °C and possess cubic symmetry. • Cation distribution and crystallographic parameters have been determined precisely. • Cell parameter decreases with increasing Cr content in the system. • Ferrimagnetic ordering was found at room temperature for all the samples. - Abstract: The spinel system MgCr{sub x}Fe{sub 2−x}O{sub 4} (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) has been prepared by solid state sintering method in air at 1573 K. X-ray and neutron powder diffraction experiments have been performed on the samples at room temperature for structural characterization. Rietveld refinement of the neutron diffraction data reveals that all the samples of the series possess cubic symmetry corresponding to the space group F d-3m. The distribution of the three cations Mg, Fe and Cr over the two sublattices and other crystallographic parameters has been determined precisely. The results reveal that Cr has been substituted for Fe selectively. Cr ions invariably occupy the octahedral (B) site for all values of x. Mg and Fe ions are distributed over both A and B sites for all x values. With increasing x the occupation of Mg increases in the A site and decreases in the B site for all the samples, while the Fe ions gradually decreases in both the sites for all values of x. The lattice constant decreases with increasing Cr content in the system. The magnetic structure at room temperature was ferrimagnetic for all the samples.
Energy Technology Data Exchange (ETDEWEB)
Takeuchi, A., E-mail: takeuchi@imr.tohoku.ac.jp; Zhang, Y.; Takenaka, K.; Makino, A. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)
2015-05-07
Fe-based Fe{sub 85}B{sub 15}, Fe{sub 84}B{sub 15}Cu{sub 1}, Fe{sub 82}Si{sub 2}B{sub 15}Cu{sub 1}, Fe{sub 85}Si{sub 2}B{sub 12}Cu{sub 1}, and Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} (NANOMET{sup ®}) alloys were experimental and computational analyzed to clarify the features of NANOMET that exhibits high saturation magnetic flux density (B{sub s}) nearly 1.9 T and low core loss than conventional nanocrystalline soft magnetic alloys. The X-ray diffraction analysis for ribbon specimens produced experimentally by melt spinning from melts revealed that the samples were almost formed into an amorphous single phase. Then, the as-quenched samples were analyzed with differential scanning calorimeter (DSC) experimentally for exothermic enthalpies of the primary and secondary crystallizations (ΔH{sub x1} and ΔH{sub x2}) and their crystallization temperatures (T{sub x1} and T{sub x2}), respectively. The ratio ΔH{sub x1}/ΔH{sub x2} measured by DSC experimentally tended to be extremely high for the Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} alloy, and this tendency was reproduced by the analysis with commercial software, Thermo-Calc, with database for Fe-based alloys, TCFE7 for Gibbs free energy (G) assessments. The calculations exhibit that a volume fraction (V{sub f}) of α-Fe tends to increase from 0.56 for the Fe{sub 85}B{sub 15} to 0.75 for the Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} alloy. The computational analysis of the alloys for G of α-Fe and amorphous phases (G{sub α-Fe} and G{sub amor}) shows that a relationship G{sub α-Fe} ∼ G{sub amor} holds for the Fe{sub 85}Si{sub 2}B{sub 12}Cu{sub 1}, whereas G{sub α-Fe} < G{sub amor} for the Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} alloy at T{sub x1} and that an extremely high V{sub f} = 0.75 was achieved for the Fe{sub 85}Si{sub 2}B{sub 8}P{sub 4}Cu{sub 1} alloy by including 2.8 at. % Si and 4.5 at. % P into α-Fe. These computational results indicate that the Fe{sub 85}Si{sub 2}B
Fe distribution and speciation in human nails
Energy Technology Data Exchange (ETDEWEB)
Katsikini, M., E-mail: katsiki@auth.g [Aristotle University of Thessaloniki, School of Physics, 54124 Thessaloniki (Greece); Pinakidou, F.; Mavromati, E.; Paloura, E.C. [Aristotle University of Thessaloniki, School of Physics, 54124 Thessaloniki (Greece); Gioulekas, D. [Aristotle University of Thessaloniki, Medical School, 54124 Thessaloniki (Greece); Grolimund, D. [Swiss Light Source, Paul Scherer Institut, 5232 Villigen (Switzerland)
2010-02-15
Micro-X-ray Fluorescence (mu-XRF) and Fe-K edge micro-X-ray Absorption Near Edge Structure (mu-XANES) spectroscopies are applied for the study of the distribution and the spatially-resolved bonding environment of Fe in human nails. The mu-XRF maps reveal that Fe forms islands where its concentration is up to six times higher than in the rest of the sample. Comparison of the map characteristics of two nails that belong to healthy and ill donors (affected by lung cancer), reveals that there is no significant variation in the size distribution of the Fe-rich inclusions contrary to their spatial density which is found higher in the nail of the ill donor. However, a relation between the variations of the spatial density and the illness can not be established due to the small number of the studied samples. The analysis of the Fe-K mu-XANES spectra reveals that the bonding environment of Fe varies between the samples and between different spots of the same sample with different Fe concentration. The characteristics of the pre-edge peak in the Fe-K XANES spectra indicate the presence of both Fe{sup +3} and Fe{sup +2} that participate in the formation of distorted octahedra. Finally, the area under the pre-edge peak depends linearly on the position of the absorption edge indicating variation of the Fe ligation between the samples and/or between different spots in the same sample.
International Nuclear Information System (INIS)
Luo, Liqiang; Zhang, Yuting; Li, Fang; Si, Xiaojing; Ding, Yaping; Deng, Dongmei; Wang, Tianlin
2013-01-01
Graphical abstract: -- Highlights: •Spinel-type Co x Ni 1−x Fe 2 O 4 (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) were synthesized. •Co x Ni 1−x Fe 2 O 4 were first employed as novel enzyme mimic sensing materials of H 2 O 2 . •Co 0.5 Ni 0.5 Fe 2 O 4 /CPE showed excellent electrocatalytic activity to H 2 O 2 . •Co 0.5 Ni 0.5 Fe 2 O 4 /CPE was successfully applied to determine H 2 O 2 in toothpastes. -- Abstract: A series of spinel-type Co x Ni 1−x Fe 2 O 4 (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) magnetic nanomaterials were solvothermally synthesized as enzyme mimics for the eletroctrocatalytic oxidation of H 2 O 2 . X-ray diffraction and scanning electron microscope were employed to characterize the composition, structure and morphology of the material. The electrochemical properties of spinel-type Co x Ni 1−x Fe 2 O 4 with different (Co/Ni) molar ratio toward H 2 O 2 oxidation were investigated, and the results demonstrated that Co 0.5 Ni 0.5 Fe 2 O 4 modified carbon paste electrode (Co 0.5 Ni 0.5 Fe 2 O 4 /CPE) possessed the best electrocatalytic activity for H 2 O 2 oxidation. Under optimum conditions, the calibration curve for H 2 O 2 determination on Co 0.5 Ni 0.5 Fe 2 O 4 /CPE was linear in a wide range of 1.0 × 10 −8 –1.0 × 10 −3 M with low detection limit of 3.0 × 10 −9 M (S/N = 3). The proposed Co 0.5 Ni 0.5 Fe 2 O 4 /CPE was also applied to the determination of H 2 O 2 in commercial toothpastes with satisfactory results, indicating that Co x Ni 1−x Fe 2 O 4 is a promising hydrogen peroxidase mimics for the detection of H 2 O 2
Composition-driven magnetic and structural phase transitions in Bi1-xPrxFe1-xMnxO3 multiferroics
Khomchenko, V. A.; Ivanov, M. S.; Karpinsky, D. V.; Paixão, J. A.
2017-09-01
Magnetic ferroelectrics continue to attract much attention as promising multifunctional materials. Among them, BiFeO3 is distinguished by exceptionally high transition temperatures and, thus, is considered as a prototype room-temperature multiferroic. Since its properties are known to be strongly affected by chemical substitution, recognition of the doping-related factors determining the multiferroic behavior of the material would pave the way towards designing the structures with enhanced magnetoelectric functionality. In this paper, we report on the crystal structure and magnetic and local ferroelectric properties of the Bi1-xPrxFe1-xMnxO3 (x ≤ 0.3) compounds prepared by a solid state reaction method. The polar R3c structure specific to the parent BiFeO3 has been found to be unstable with respect to doping for x ≳ 0.1. Depending on the Pr/Mn concentration, either the antipolar PbZrO3-like or nonpolar PrMnO3-type structure can be observed. It has been shown that the non-ferroelectric compounds are weak ferromagnetic with the remanent/spontaneous magnetization linearly decreasing with an increase in x. The samples containing the polar R3c phase exhibit a mixed antiferromagnetic/weak ferromagnetic behavior. The origin of the magnetic phase separation taking place in the ferroelectric phase is discussed as related to the local, doping-introduced structural heterogeneity contributing to the suppression of the cycloidal antiferromagnetic ordering characteristic of the pure BiFeO3.
Muehe, E. M.; Adaktylou, I. J.; Obst, M.; Schröder, C.; Behrens, S.; Hitchcock, A. P.; Tylsizczak, T.; Michel, F. M.; Krämer, U.; Kappler, A.
2014-12-01
Agricultural soils are increasingly burdened with heavy metals such as Cd from industrial sources and impure fertilizers. Metal contaminants enter the food chain via plant uptake from soil and negatively affect human and environmental health. New remediation approaches are needed to lower soil metal contents. To apply these remediation techniques successfully, it is necessary to understand how soil microbes and minerals interact with toxic metals. Here we show that microbial Fe(III) reduction initially mobilizes Cd before its immobilization under anoxic conditions. To study how microbial Fe(III) reduction influences Cd mobility, we isolated a new Cd-tolerant, Fe(III)-reducing Geobacter sp. from a heavily Cd-contaminated soil. In lab experiments, this Geobacter strain first mobilized Cd from Cd-loaded Fe(III) hydroxides followed by precipitation of Cd-bearing mineral phases. Using Mössbauer spectroscopy and scanning electron microscopy, the original and newly formed Cd-containing Fe(II) and Fe(III) mineral phases, including Cd-Fe-carbonates, Fe-phosphates and Fe-(oxyhydr)oxides, were identified and characterized. Using energy-dispersive X-ray spectroscopy and synchrotron-based scanning transmission X-ray microscopy, Cd was mapped in the Fe(II) mineral aggregates formed during microbial Fe(III) reduction. Microbial Fe(III) reduction mobilizes Cd prior to its precipitation in Cd-bearing mineral phases. The mobilized Cd could be taken up by phytoremediating plants, resulting in a net removal of Cd from contaminated sites. Alternatively, Cd precipitation could reduce Cd bioavailability in the environment, causing less toxic effects to crops and soil microbiota. However, the stability and thus bioavailability of these newly formed Fe-Cd mineral phases needs to be assessed thoroughly. Whether phytoremediation or immobilization of Cd in a mineral with reduced Cd bioavailability are feasible mechanisms to reduce toxic effects of Cd in the environment remains to be
Hyperfine properties of La(V{sub 1−x}Fe{sub x})O{sub 3} compounds
Energy Technology Data Exchange (ETDEWEB)
Tupan, L. F. S.; Ivashita, F. F.; Barco, R. [Universidade Estadual de Maringá (Brazil); Hallouche, B. [Universidade de Santa Cruz do Sul (Brazil); Paesano, A., E-mail: paesano@wnet.com.br [Universidade Estadual de Maringá (Brazil)
2017-11-15
LaV{sub 1−x}Fe{sub x}O{sub 3} perovskites were synthesized in the vanadium-rich concentration range (i.e., x < 0.5) and characterized structurally and for the hyperfine properties of the iron nuclear probe. The aim of this investigation was to better understand the physical transformations that take place in the undoped compound (LaVO{sub 3}) at low temperatures. For that, X-ray diffraction analysis and, more extensively, {sup 57}Fe Mössbauer spectroscopy were applied. The results revealed that the LaV{sub 1}-xFexO{sub 3} vanadium-rich perovskites are orthorhombic at RT, and their lattice parameters decrease with increasing vanadium concentration. Lowering the temperature, the system becomes magnetic, with the iron moment freezing progressively. The presence of two magnetic subspectral components obtained at the lowest measurement temperatures suggests that the vanadium-rich samples, including LaVO{sub 3}, undergo a phase transition from an orthorhombic to a monoclinic structure at low temperatures.
International Nuclear Information System (INIS)
Gómez, J A Mejía; Palacio, C A; García, G I Supelano; Vargas, C A Parra
2015-01-01
The production and the structural and magnetic characterization of the Bi 1-x Y x FeO 3 (x= 0, 0.25 and 0.3) system is reported in this work. The system was produced through the solid-state reaction technique. The morphological characterization obtained by scanning electron microscopy technique evidences the granular behavior. The structural properties were studied by means of X-ray diffraction technique. Magnetization measurements in function of temperature of the Bi 1-x Y x FeO 3 (x= 0, 0.25 and 0.3) system were performed with the magnetometer VSM by means of the Zero Field Cooled-Field Cooled method. The results obtained from all the techniques evidence the effect of yttrium on the physical properties of BiFeO 3 . (paper)
Magnetic and Structural Properties of the Mechanically Alloyed Nd2(Fe100-xNbx)14B System
International Nuclear Information System (INIS)
Lozano, D. Oyola; Zamora, L. E.; Perez Alcazar, G. A.; Rojas, Y. A.; Bustos, H.; Greneche, J. M.
2005-01-01
In this work we report the magnetic and structural properties obtained by Moessbauer spectrometry, Vibrating Sample Magnetometer and X-ray diffraction of milled powders with initial composition Nd 2 (Fe 100-x Nb x ) 14 B with x = 0 and x = 4. The mixtures were ball milled for different times up to 240 h. Structural and microstructural parameters were derived from high statistics X-ray patterns and discussed as a function of milling time. The Moessbauer spectra of the samples were fitted by means of a sextet and an hyperfine field distribution, associated to a pure iron phase (α-Fe) and a disordered iron-based phase, respectively. The α-Fe grain size decreases from 50 nm for 6 h up to 5 nm for 240 h milling time. The Vibrating Sample Magnetometer results allow to conclude that these samples behave as soft ferromagnets.
Nano-sized magnetic instabilities in Fe/NiO/Fe(001) epitaxial thin films
Energy Technology Data Exchange (ETDEWEB)
Brambilla, A [Dipartimento di Fisica-Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milan (Italy); Biagioni, P [Dipartimento di Fisica-Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milan (Italy); Rougemaille, N [National Center for Electron Microscopy, Lawrence Berkeley National Lab, Berkeley, CA 94720 (United States); Schmid, A K [National Center for Electron Microscopy, Lawrence Berkeley National Lab, Berkeley, CA 94720 (United States); Lanzara, A [Department of Physics, University of California at Berkeley, Berkeley, CA 94720 (United States); Duo, L [Dipartimento di Fisica-Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milan (Italy); Ciccacci, F [Dipartimento di Fisica-Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milan (Italy); Finazzi, M [Dipartimento di Fisica-Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milan (Italy)
2006-10-25
We report on a magnetic imaging study of the Fe/NiO/Fe(001) trilayer structure, by means of X-ray photoemission electron microscopy (XPEEM) and spin-polarised low-energy electron microscopy (SPLEEM). Two different magnetic couplings between the Fe layers are observed depending on the NiO thickness being greater or smaller than a critical value. Very small magnetic domains and domain walls are observed in the top Fe layer. They are dramatically smaller than those observed in the Fe substrate, and have a convoluted topology. Furthermore they seem to be unstable with respect to an applied magnetic field for any NiO thickness except that corresponding to the transition between the different coupling regimes. The phenomenology of such magnetic nano-structures and the dependence of the magnetic behaviour of the layered structure on the NiO spacer thickness are discussed on the basis of the experimental results and of state-of-the-art theoretical models.
Nano-sized magnetic instabilities in Fe/NiO/Fe(001) epitaxial thin films
International Nuclear Information System (INIS)
Brambilla, A.; Biagioni, P.; Rougemaille, N.; Schmid, A.K.; Lanzara, A.; Duo, L.; Ciccacci, F.; Finazzi, M.
2006-01-01
We report on a magnetic imaging study of the Fe/NiO/Fe(001) trilayer structure, by means of X-ray photoemission electron microscopy (XPEEM) and spin-polarised low-energy electron microscopy (SPLEEM). Two different magnetic couplings between the Fe layers are observed depending on the NiO thickness being greater or smaller than a critical value. Very small magnetic domains and domain walls are observed in the top Fe layer. They are dramatically smaller than those observed in the Fe substrate, and have a convoluted topology. Furthermore they seem to be unstable with respect to an applied magnetic field for any NiO thickness except that corresponding to the transition between the different coupling regimes. The phenomenology of such magnetic nano-structures and the dependence of the magnetic behaviour of the layered structure on the NiO spacer thickness are discussed on the basis of the experimental results and of state-of-the-art theoretical models
Irradiation-induced patterning in dilute Cu–Fe alloys
International Nuclear Information System (INIS)
Stumphy, B.; Chee, S.W.; Vo, N.Q.; Averback, R.S.; Bellon, P.; Ghafari, M.
2014-01-01
Compositional patterning in dilute Cu 1−x Fe x (x ≈ 12%) induced by 1.8 MeV Kr + irradiation was studied as a function of temperature using atom probe tomography. Irradiation near room temperature led to homogenization of the sample, whereas irradiation at 300 °C and above led to precipitation and macroscopic coarsening. Between these two temperatures the irradiated alloys formed steady state patterns of composition where precipitates grew to a fixed size. The size in this regime increased somewhat with temperature. It was also observed that the steady state concentrations of Fe in Cu matrix and Cu in the Fe precipitates both greatly exceeded their equilibrium solubilities, with the degree of supersaturation in each phase decreasing with increasing temperature. In the macroscopic coarsening regime, the Fe-rich precipitates showed indications of a “cherry-pit” structure, with Cu precipitates forming within the Fe precipitates. In the patterning regime, interfaces between Fe-rich precipitates and the Cu-rich matrix were irregular and diffuse
Surface coating and magnetic properties of Sm2Fe17Nx materials
International Nuclear Information System (INIS)
Noguchi, K.; Machida, K.; Nishimura, M.; Adachi, G.
1998-01-01
Surface coating for finely ground Sm 2 Fe 17 N x (x=-3) powders (diameter 2 Fe 17 N x and (Zn,In)/Cu/Sm 2 Fe 17 N x , showed good oxidation-resistivity and thermal stability compared with the samples prepared without the Cu metal pre-coating, Zn/Sm 2 Fe 17 N x . The epoxy resin- or In metal-bonded magnets produced from the above coated powders, Zn/Cu/Sm 2 Fe 17 N x and (Zn,In)/Cu/Sm 2 Fe 17 N x , under warm molding conditions provided a flux loss of around -15% after standing in air at 120 C for 1000 h, but 30-40% for the conventional injection-type resin-bonded magnets prepared from Nd-Fe-B powders. (orig.)
Latif, C.; Negara, V. S. I.; Wongtepa, W.; Thamatkeng, P.; Zainuri, M.; Pratapa, S.
2018-03-01
XANES analysis has been performed with the aim of knowing the Fe oxidation state in a synthesized LiFePO4 and its base materials. XANES measurements were performed at SLRI on energy around Fe K-edge. An XRD analysis has also been performed with the aim of knowing the phase composition, lattice parameters and crystallite size of the LiFePO4 as well as the base materials. From the XRD analysis, it was found that the dominating phase in the iron sand sample was Fe3O4 and the only phase found after calcination was LiFePO4. The latter phase exhibited crystallite size of 100 nm and lattice parameters a = 10.169916 Å, b = 5.919674 Å, c = 4.627893 Å. Qualitative analysis of XANES data revealed that the oxidation number of Fe in the sample before calcination was greater than that after calcination and Fe in the natural iron sand, indicated by the E0 values of 7129.2 eV, 7120.6 eV and 7124.4 eV respectively.
Studies on the valence electronic structure of Fe and Ni in FexNi1−x ...
Indian Academy of Sciences (India)
structure of Fe and Ni in various Fex Ni1−x alloys. Since Kβ-to-Kα X-ray intensity ratio has been reported [2–7] to be a sensitive physical parameter to investigate the changes in the valence electronic structure of 3d-transition metals [2], we have undertaken the study of the valence electronic structure of Fe and Ni in the Fex ...
Magnetic and electrical properties of (FeIn2S4)1−x(CuIn5S8)x solid solutions
International Nuclear Information System (INIS)
Trukhanov, S.V.; Bodnar, I.V.; Zhafar, M.A.
2015-01-01
In this study, single crystals of FeIn 2 S 4 and CuIn 5 S 8 compounds, and (FeIn 2 S 4 ) 1−x (CuIn 5 S 8 ) x solid solutions were grown using the Bridgman method. The magnetic and electrical properties of the samples obtained were investigated at temperatures of 5–300 K and in a magnetic field range of 0–14 T. It was established that all of the solid solutions were paramagnets down to low temperatures of ~10 K. It was shown that the ground state of the magnetic phase of the samples was a spin glass state, where the freezing temperature increased monotonically with the increase in the concentration of Fe 2+ cations. All of the samples exhibited semiconductor characteristics in terms of electrical resistivity. The concentration-dependent critical magnetic temperatures, magnetic moment, and activation energy were plotted, which are probably explained by the magnetic state formation of the (FeIn 2 S 4 ) 1−x (CuIn 5 S 8 ) x solid solution single crystals based on the empirical Goodenough–Kanamori rules
Energy Technology Data Exchange (ETDEWEB)
Ackermann, Sonia; Kunz, Martin; Armbruster, Thomas; Schefer,Jurg; Hanni, Henry
2005-05-02
We determined the cation distribution and ordering of Si, Al and Fe on the tetrahedral sites of a monoclinic low-sanidine from Itrongay, Madagascar, by combined neutron- and X-ray single-crystal diffraction. The cation distribution was determined by means of a simultaneous refinement using neutron- and X-ray data, as well as by combining scattering densities obtained from separate refinements with chemical data from a microprobe experiment. The two methods give the same results and show that Fe is fully ordered on T1, whereas Al shows a high degree of disorder. Based on this and previously published temperature-dependent X-ray data, we conclude that it is preferential ordering of Fe on T1 even at high temperature, rather than a high diffusion kinetics of Fe, which causes this asymmetry in ordering behavior between Al and Fe. The preferential ordering of Fe3+ relative to Al3+ in T1 is consistent with its 25 percent larger ionic radius.
Fe-doping effect on the Bi{sub 3}Ni superconductor microstructure
Energy Technology Data Exchange (ETDEWEB)
Gonsalves, Silvio Henrique; Monteiro, Joao Frederico Haas Leandro; Leal, Adriane Consuelo da Silva; Andrade, Andre Vitor Chaves de; Souza, Gelson Biscaia de; Siqueira, Ezequiel Costa; Serbena, Francisco Carlos; Jurelo, Alcione Roberto, E-mail: arjurelo@uepg.br [Universidade Estadual de Ponta Grossa (UEPG), PR (Brazil). Departamento de Fisica
2017-05-15
The substitution effects of Fe ion on the structure of the intermetallic Bi{sub 3}Ni{sub 1-x}Fe{sub x} (0 ≤ x ≤ 0.10) superconductor were studied. The morphology of samples consists of an inhomogeneous laminar slab-like microstructure. The main phase corresponds to Bi{sub 3}Ni{sub 1-x}Fe{sub x} with an orthorhombic structure (Pnma), but with very small quantities of impurities of BiNi and Bi as revealed by X-ray diffraction. SEM and AFM reveal that the Bi3{sub N}i1{sub -x}Fe{sub x} phase consists of two regions. One region is Bi richer and Ni and Fe poorer than the other region.Raman spectroscopy revealed two phonon modes at room temperature. No significant changes were observed in the spectra with Fe doping and in different regions of the Bi{sub 3}Ni{sub 1-x}Fe{sub x} phase. Superconductivity is observed below a transition temperature T{sub C} = 4 K and regardless of iron doping. (author)
Exchange bias in sputtered FeNi/FeMn systems: Effect of short low-temperature heat treatments
Energy Technology Data Exchange (ETDEWEB)
Savin, Peter, E-mail: peter.savin@urfu.ru [Department of Magnetism and Magnetic Nanomaterials, Laboratory of Magnetic Sensors, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Guzmán, Jorge [Instituto de Ciencia de Materiales de Madrid-CSIC, 28049 Madrid (Spain); Lepalovskij, Vladimir [Department of Magnetism and Magnetic Nanomaterials, Laboratory of Magnetic Sensors, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Svalov, Andrey; Kurlyandskaya, Galina [Department of Magnetism and Magnetic Nanomaterials, Laboratory of Magnetic Sensors, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Departamento de Electricidad y Electrónica, Universidad del País Vasco (UPV/EHU), 48940 Leioa, Vizcaya (Spain); Asenjo, Agustina [Instituto de Ciencia de Materiales de Madrid-CSIC, 28049 Madrid (Spain); Vas’kovskiy, Vladimir [Department of Magnetism and Magnetic Nanomaterials, Laboratory of Magnetic Sensors, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Vazquez, Manuel [Department of Magnetism and Magnetic Nanomaterials, Laboratory of Magnetic Sensors, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Instituto de Ciencia de Materiales de Madrid-CSIC, 28049 Madrid (Spain)
2016-03-15
Short (5 min) post-deposition thermal treatments under magnetic field at low temperature (up to 200 °C) performed in exchange-coupled FeNi(40 nm)/FeMn(20 nm) bilayer thin films prepared by magnetron sputtering are shown to be effective to significantly modify their exchange field (from around 40 Oe down to 27 Oe) between FeNi and FeMn layers. A similar exchange field decrease was observed for the first deposited FeNi layer of the FeNi(40 nm)/FeMn(20 nm)/FeNi(40 nm) trilayer films after the same thermal treatments. The exchange field value for the second FeNi layer was not substantially changed. The X-ray diffraction patterns indicates that such a heat treatment has no effect on the grain size and crystalline texture of the films, while atomic force microscope studies reveal an increase of the surface roughness after the treatment which is more noticeable in the case of the trilayer film. Analysis of the experimental results leads us to conclude that the variations of the exchange field after heat treatment are likely caused by a modification of interfacial roughness and/or interfacial magnetic structure, but unlikely by the changes in the microstructure and/or changes of composition of the antiferromagnetic FeMn layer. - Highlights: • FeNi/FeMn bilayers and FeNi/FeMn/FeNi trilayers were prepared by magnetron sputtering. • Post-deposition heat treatments at the temperatures below 200 °C during 5 min were made. • Annealing reduces the exchange field for the first FeNi layer in trilayers. • The exchange field value for the second FeNi layer was not substantially changed. • Exchange field changes are most likely caused by a modification of interface roughness.
Oxidation of methanol to formaldehyde over a series of Fe1-xAlx-V-oxide catalysts
DEFF Research Database (Denmark)
Häggblad, Robert; Wagner, Jakob Birkedal; Hansen, Staffan
2008-01-01
A series of triclinic Fe1−xAlxVO4 phases with 0x1 were prepared and used in the oxidation of methanol to formaldehyde. The activity measurements revealed that both the activity and especially the selectivity to formaldehyde increased with time of operation for at least 16 h, indicating...... restructuring of the catalysts. Characterisation of the catalysts with XRD, XANES, and electron microscopy after use in methanol oxidation showed that the stability of the bulk phases improved when Al was substituted for Fe in the structure. XRD and XANES of the used FeVO4 showed that it partly transformed...... in methanol oxidation revealed no significant change in the metal composition, in good agreement with the corresponding bulk values, except for a lower Fe value. Steady-state activity data showed a modest increase in specific activity with the Al content, whereas the selectivity to formaldehyde was about 90...
Scaling of the anomalous Hall current in Fe100−x(SiO2)x films
Xu, W. J.; Zhang, Bei; Wang, Q. X.; Mi, W. B.; Wang, Z.; Li, W.; Yu, R. H.; Zhang, Xixiang
2011-01-01
To study the origin of the anomalous Hall effect, Fe100−x(SiO2)x granular films with a volume fraction of SiO2 (0 ⩽ x ⩽ 40.51) were fabricated using cosputtering. Hall and longitudinal resistivities were measured in the temperature range of 5–350 K
Magnetism and superconductivity in LaFeP{sub 1-x}As{sub x}O
Energy Technology Data Exchange (ETDEWEB)
Kamusella, Sirko; Sarkar, Rajib; Klauss, Hans-Henning [Institut fuer Festkoerperphysik, Technische Universitaet Dresden (Germany); Luetkens, Hubertus [Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, Villigen (Switzerland); Tajima, Setsuko [Department of Physics, Osaka University, Osaka (Japan)
2016-07-01
The LaFeP{sub 1-x}As{sub x}O series bridges the gap between two parent compounds, whose Fermi surfaces differ in dimensionality and position of hole pockets. The resulting phase diagram consists of a superconducting two-dome structure separated by a novel AFM2 magnetic phase. Electron doping by (O,F) substitution allows to investigate superconductivity in the full x-range. {sup 57}Fe Moessbauer spectroscopy successfully depicts the temperature dependence of the tiny 0.1 μ{sub B} magnetic moment in the AFM2 phase and its rigidity in applied field; with the help of a line width reference absorber. This uncommon approach makes Moessbauer measurements competitive to other local probe methods such as NMR or μSR. μSR measurements can prove the long range character of this novel AFM2 phase and show the continuous change from a nodal to a nodeless symmetry of the superconducting order parameter upon substitution of P by As. AFM spin fluctuations suggested by NMR before did not become evident in μSR decoupling experiments.
Energy Technology Data Exchange (ETDEWEB)
Pearce, Carolyn I.; Liu, Juan; Baer, Donald R.; Qafoku, Odeta; Heald, Steve M.; Arenholz, Elke; Grosz, Andrew E.; McKinley, James P.; Resch, Charles T.; Bowden, Mark E.; Engelhard, Mark H.; Rosso, Kevin M.
2014-03-01
Sediments with basaltic provenance, such as those at the Hanford nuclear reservation, Washington, USA, are rich in Fe-bearing minerals of mixed valence. These minerals are redox reactive with aqueous O2 or Fe(II), and have the potential to react with important environmental contaminants including Tc. Here we isolate, identify and characterize natural Fe(II)/Fe(III)-bearing microparticles from Hanford sediments, develop synthetic analogues and investigate their batch redox reactivity with aqueous Tc(VII). Natural Fe-rich mineral samples were isolated by magnetic separation from sediments collected at several locations on Hanford’s central plateau. This magnetic mineral fraction was found to represent up to 1 wt% of the total sediment, and be composed of 90% magnetite with minor ilmenite and hematite, as determined by X-ray diffraction. The magnetite contained variable amounts of transition metalsconsistent with alio- and isovalent metal substitutions for Fe. X-ray microprobe analysis showed that Ti was the most significant substituent, and that these grains could be described with the titanomagnetite formula Fe3_xTixO4, which falls between endmember magnetite (x = 0) and ulvo¨ spinel (x = 1). The dominant composition was determined to be x = 0.15 by chemical analysis and electron probe microanalysis in the bulk, and by L-edge X-ray absorption spectroscopy and X-ray photoelectron spectroscopy at the surface. Site-level characterization of the titanomagnetites by X-ray magnetic circular dichroism showed that despite native oxidation, octahedral Fe(II) was detectable within 5 nm of the mineral surface. By testing the effect of contact with oxic Hanford and Ringold groundwaters to reduced Ringold groundwater, it was found that the concentration of this near-surface structural Fe(II) was strongly dependent on aqueous redox condition. This highlights the potential for restoring reducing equivalents and thus reduction capacity to oxidized Fe-mineral surfaces through
Magnetic behavior of NixFe(100-x) (65=<x=<100) nanowire arrays
International Nuclear Information System (INIS)
Navas, D.; Asenjo, A.; Jaafar, M.; Pirota, K.R.; Hernandez-Velez, M.; Sanz, R.; Lee, W.; Nielsch, K.; Batallan, F.; Vazquez, M.
2005-01-01
Arrays of magnetic nanowires with composition Ni x Fe (100-x) (65= 2 and 105nm lattice parameter of hexagonal symmetry, is achieved by self-ordering process, and characterized by SEM and AFM. Magnetic behavior of the arrays has been determined by VSM. Maximum coercivity of around 1.23kOe and reduced remanence (about 0.8 saturation magnetization) is observed for x=77, while minimum values are observed for x=100. Detailed AFM and MFM studies allow us to gain additional information of the filling degree of pores which can result in a distributed nanowires length that finally correlates with a deterioration of macroscopic magnetic behavior of the array
Sherman, David M.
1990-01-01
Metal-metal charge-transfer and magnetic exchange interactions have important effects on the optical spectra, crystal chemistry, and physics of minerals. Previous molecular orbital calculations have provided insight on the nature of Fe2+-Fe3+ and Fe2+-Ti4+ charge-transfer transitions in oxides and silicates. In this work, spin-unrestricted molecular orbital calculations on (FeMnO10) clusters are used to study the nature of magnetic exchange and electron delocalization (charge transfer) associated with Fe3+-Mn2+, Fe3+-Mn3+, and Fe2+-Mn3+ interactions in oxides and silicates.
Synthesis, structure and chemical bonding of CaFe2−xRhxSi2 (x=0, 1.32, and 2) and SrCo2Si2
International Nuclear Information System (INIS)
Hlukhyy, Viktor; Hoffmann, Andrea V.; Fässler, Thomas F.
2013-01-01
The finding of superconductivity in Ba 0.6 K 0.4 Fe 2 As 2 put the attention on the investigation of compounds that crystallize with ThCr 2 Si 2 structure type such as AT 2 X 2 (A=alkali/alkaline earth/rare earth element; T=transition metal and X=element of the 13–15th group). In this context the silicides CaFe 2 Si 2 , CaFe 0.68(6) Rh 1.32(6) Si 2 , CaRh 2 Si 2 and SrCo 2 Si 2 have been synthesized by reaction of the elements under an argon atmosphere. Single crystals were obtained by special heat treatment in welded niobium/tantalum ampoules. The compounds were investigated by means of powder and single crystal X-ray diffraction. All compounds crystallize in the ThCr 2 Si 2 -type structure with space group I4/mmm (No. 139): a=3.939(1) Å, c=10.185(1) Å, R 1 =0.045, 85 F 2 values, 8 variable parameters for CaFe 2 Si 2 ; a=4.0590(2) Å, c=9.9390(8) Å, R 1 =0.030, 90 F 2 values, 10 variable parameters for CaFe 0.68(6) Rh 1.32(6) Si 2 ; a=4.0695(1) Å, c=9.9841(3) Å, R 1 =0.031, 114 F 2 values, 9 variable parameters for CaRh 2 Si 2 ; and a=3.974(1) Å, c=10.395(1) Å, R 1 =0.036, 95 F 2 values, 8 variable parameters for SrCo 2 Si 2 . The structure of SrCo 2 Si 2 contains isolated [Co 2 Si 2 ] 2− 2D-layers in the ab-plane whereas in CaFe 2−x Rh x Si 2 the [T 2 Si 2 ] layers (T=Fe and Rh) are interconnected along the c-axis via Si3Si bonds resulting in a three-dimentional (3D) [T 2 Si 2 ] 2− polyanions and therefore belong to the so-called collapsed form of the ThCr 2 Si 2 -type structure. The SrCo 2 Si 2 and CaRh 2 Si 2 are isoelectronic to the parent 122 iron–pnictide superconductors AeFe 2 As 2 (Ae=alkaline earth elements), whereas CaFe 2 Si 2 is a full substituted variant (As/Si) of CaFe 2 As 2 . The crystal chemistry and chemical bonding in the title compounds are discussed in terms of LMTO band structure calculations and a topological analysis using the Electron Localization Function (ELF). - Graphical abstract: The SrCo 2 Si 2 and CaFe 2−x Rh x Si
Energy Technology Data Exchange (ETDEWEB)
Komędera, K.; Jasek, A.K.; Błachowski, A. [Mössbauer Spectroscopy Laboratory, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Ruebenbauer, K., E-mail: sfrueben@cyf-kr.edu.pl [Mössbauer Spectroscopy Laboratory, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Żukrowski, J. [AGH University of Science and Technology, Academic Center for Materials and Nanotechnology, Av. A. Mickiewicza 30, PL-30-059 Kraków (Poland); Krztoń-Maziopa, A. [Warsaw University of Technology, Faculty of Chemistry, ul. Noakowskiego 3, PL-00-664 Warsaw (Poland); Conder, K. [Laboratory for Developments and Methods, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)
2016-05-15
Two iron-chalcogenide superconductors Li{sub x}(C{sub 5}H{sub 5}N){sub y}Fe{sub 2−z}Se{sub 2} and Cs{sub x}Fe{sub 2–z}Se{sub 2} in the as-prepared and annealed state have been investigated by means of the Mössbauer spectroscopy versus temperature. Multi-component spectra are obtained. One can see a non-magnetic component due to iron located in the unperturbed Fe–Se sheets responsible for superconductivity. Remaining components are magnetically ordered even at room temperature. There is some magnetically ordered iron in Fe–Se sheets perturbed by presence of the iron vacancies. Additionally, one can see iron dispersed between sheets in the form of magnetically ordered high spin trivalent ions, some clusters of above ions, and in the case of pyridine intercalated compound in the form of α-Fe precipitates. Pyridine intercalated sample shows traces of superconductivity in the as-prepared state, while cesium intercalated sample in the as-prepared state does not show any superconductivity. Superconductors with transition temperatures being 40 K and 25 K, respectively, are obtained upon annealing. Annealing leads to removal/ordering of the iron vacancies within Fe–Se sheets, while clusters of α-Fe grow in the pyridine intercalated sample. - Highlights: • Secondary phases dispersed in single crystal of Cs{sub x}Fe{sub 2−z}Se{sub 2}. • α-Fe precipitates between Fe–Se layers in Li{sub x}(C{sub 5}H{sub 5}N){sub y}Fe{sub 2−z}Se{sub 2}. • Superconductivity is obtained by removing of the iron vacancies within Fe–Se sheets.
Synthesis, structure and properties of layered iron-oxychalcogenides Nd2Fe2Se2−xSxO3
International Nuclear Information System (INIS)
Liu, Y.; Zhang, S.B.; Tan, S.G.; Yuan, B.; Kan, X.C.; Zu, L.; Sun, Y.P.
2015-01-01
A new series of sulfur-substituted iron-oxychalcogenides Nd 2 Fe 2 Se 2−x S x O 3 (0≤x≤0.4) was synthesized by solid state reaction method, and investigated by structure, transport, magnetic and specific heat measurements. The compounds crystallize in the layered tetragonal structure with I4/mmm space group, and show semiconducting behavior. The large discrepancy between the activation energies for conductivity, E ρ (152–202 meV), and thermopower, E S (15.6–39.8 meV), indicates the polaronic transport mechanism of the carrier. The parent compound Nd 2 Fe 2 Se 2 O 3 exhibits a frustrated antiferromagnetic (AFM) ground state, and the S-substitution induces an enhanced ferromagnetic (FM) component and possible increased degree of frustration. - Graphical abstract: The crystal structure of Nd 2 Nd 2 Fe 2 Se 2−x S x O 3 is built up by stacking fluorite-like Nd 2 O 2 layers and anti-CuO 2 -type Fe 2 O(Se/S) 2 layers with Fe 2+ cations coordinated by two in-plane O 2- and four Se 2- above and below the square Fe 2 O plane. - Highlights: • We have synthesized a new series of layered iron-oxychalcogenides Nd 2 Fe 2 Se 2−x S x O 3 . • They crystallize in layered tetragonal structure and show semiconducting behavior. • The transport analysis indicates the polaronic transport mechanism of the carrier. • The parent compound shows a frustrated antiferromagnetic (AFM) ground state. • The S-substitution induces an enhanced ferromagnetic (FM) component
A TEST OF THE NATURE OF THE FE K LINE IN THE NEUTRON STAR LOW-MASS X-RAY BINARY SERPENS X-1
Energy Technology Data Exchange (ETDEWEB)
Chiang, Chia-Ying; Cackett, Edward M. [Department of Physics and Astronomy, Wayne State University, 666 W. Hancock, Detroit, MI 48202 (United States); Miller, Jon M. [Department of Astronomy, The University of Michigan, 500 Church Street, Ann Arbor, MI48109-1046 (United States); Barret, Didier [Universite de Toulouse, UPS-OMP, Toulouse (France); Fabian, Andy C.; Parker, Michael L. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); D’Aì, Antonino [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica di Palermo, via U. La Malfa 153, I-90146 Palermo (Italy); Bhattacharyya, Sudip [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, Mumbai 400005 (India); Burderi, Luciano [Dipartimento di Fisica, Università degli Studi di Cagliari, SP Monserrato-Sestu, KM 0.7, I-09042 Monserrato (Italy); Salvo, Tiziana Di; Iaria, Rosario [Dipartimento di Fisica e Chimica, Universitá di Palermo, via Archirafi 36, I-90123 Palermo (Italy); Egron, Elise [INAF-Osservatorio Astronomico di Cagliari, via della Scienza 5, I-09047 Selargius (Italy); Homan, Jeroen [MIT Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Avenue 37-582D, Cambridge, MA 02139 (United States); Lin, Dacheng [Space Science Center, University of New Hampshire, Durham, NH 03824 (United States); Miller, M. Coleman, E-mail: ft8320@wayne.edu [Department of Astronomy and Joint Space-Science Institute, University of Maryland, College Park, MD 20742-2421 (United States)
2016-04-20
Broad Fe K emission lines have been widely observed in the X-ray spectra of black hole systems as well as in neutron star systems. The intrinsically narrow Fe K fluorescent line is generally believed to be part of the reflection spectrum originating in an illuminated accretion disk which is broadened by strong relativistic effects. However, the nature of the lines in neutron star low-mass X-ray binaries (LMXBs) has been a matter of debate. We therefore obtained the longest, high-resolution X-ray spectrum of a neutron star LMXB to date with a 300 ks Chandra High Energy Transmission Grating Spectrometer (HETGS) observation of Serpens X-1. The observation was taken under the “continuous clocking” mode, and thus was free of photon pile-up effects. We carry out a systematic analysis and find that the blurred reflection model fits the Fe line of Serpens X-1 significantly better than a broad Gaussian component does, implying that the relativistic reflection scenario is much preferred. Chandra HETGS also provides a highest spectral resolution view of the Fe K region and we find no strong evidence for additional narrow lines.
International Nuclear Information System (INIS)
Jo, Youn Jung; Eom, Man Jin; Kim, Jun Sung; Kang, W.
2014-01-01
The upper critical field (H c 2 ) was determined by applying a magnetic field along the ab plane and c axis for two single crystals of BaFe 2-x Ru x As 2 (x=0.48 and 0.75). The anisotropy of the H c 2 (0), γ(0)=H c 2 ab (0)/H c 2 c (0), was ∼1.6 for x=0.48 and ∼2.3 for x=0.75. The angle-dependent resistance measured below T c allowed perfect scaling features based on anisotropic Ginzburg-Landau theory, leading to consistent anisotropy values. Because only one fitting parameter γ is used in the scaling for each temperature, the validity of the γ value was compared with that determined from γ=H c 2 ab /H c 2 c . The γ obtained at a temperature close to Tc was 3.0 and decreased to 2.0 at low temperatures. Comparing to the anisotropy determined for electron- or hole-doped BaFe 2 As 2 using the same method, the present results point to consistent anisotropy in Ru-doped BaFe 2 As 2 with other electron- or hole-doped BaFe 2 As 2 .
Walker, James D S; Grosvenor, Andrew P
2013-08-05
Magnetoelectric materials couple both magnetic and electronic properties, making them attractive for use in multifunctional devices. The magnetoelectric AFeO3 compounds (Pna2(1); A = Al, Ga) have received attention as the properties of the system depend on composition as well as the synthetic method used. Al(1-x)Ga(x)FeO3. (0 ≤ x ≤ 1) was synthesized by the sol-gel and coprecipitation methods and studied by X-ray absorption near-edge spectroscopy (XANES). Al L(2,3-), Ga K-, and Fe K-edge XANES spectra were collected to examine how the average metal coordination number (CN) changes with the synthetic method. Al and Fe were found to prefer octahedral sites, while Ga prefers the tetrahedral site. It was found that composition played a larger role in determining site occupancies than synthetic method. Samples made by the sol-gel or ceramic methods (reported previously; Walker, J. D. S.; Grosvenor, A. P. J. Solid State Chem. 2013, 197, 147-153) showed smaller spectral changes than samples made via the coprecipitation method. This is attributed to greater ion mobility in samples synthesized via coprecipitation as the reactants do not have a long-range polymeric or oxide network during synthesis like samples synthesized via the sol-gel or ceramic method. Increasing annealing temperature increases the average coordination number of Al, and to a lesser extent Ga, while the average coordination number of Fe decreases. This study indicates that greater disorder is observed when the Al(1-x)Ga(x)FeO3. compounds have high Al content, and when annealed at higher temperatures.
Influence of Fe-doping on the structural, optical and magnetic properties of ZnO nanoparticles
International Nuclear Information System (INIS)
Liu Changzhen; Meng Dawei; Pang Haixia; Wu Xiuling; Xie Jing; Yu Xiaohong; Chen Long; Liu Xiaoyang
2012-01-01
Zn 1–x Fe x O (x=0–0.05) nanoparticles were synthesized without a catalyst by a two-step method. Fe was doped into ZnO by a source of metallic Fe sheets in a solid–liquid system at 80 °C, and the Zn 1−x Fe x O nanoparticles were obtained by annealing at 300 °C. X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy were used to characterize the structural properties of the as-grown Zn 1−x Fe x O. The optical properties were determined by Infrared and Ultraviolet–visible spectroscopy. The results confirm that the crystallinity of the ZnO is deteriorated due to Fe-doping. XPS results show that there is a mixture of Fe 0+ and the Fe 3+ in the representative Zn 0.95 Fe 0.05 O sample. The optical band gap of Zn 1−x Fe x O is enhanced with increasing of Fe-doping. Room temperature ferromagnetism was observed in all the Fe-doped ZnO samples. - Highlights: ► Zn 1−x Fe x O nanoparticles were synthesized with a simple two-step method. ► The Zn 1−x Fe x O predecessors were synthesized at a low temperature. ► Fe element was readily doped from the source of metallic Fe sheet. ► All the Fe doping ZnO samples have room temperature ferromagnetism. ► The structural and properties of the Zn 1−x Fe x O are regular with different x.
Magnetic properties of Fe-doped NiO nanoparticles
Kurokawa, A.; Sakai, N.; Zhu, L.; Takeuchi, H.; Yano, S.; Yanoh, T.; Onuma, K.; Kondo, T.; Miike, K.; Miyasaka, T.; Ichiyanagi, Y.
2013-08-01
Ni1- x Fe x O ( x = 0, 0.05, 0.1) nanoparticles with several nanometers encapsulated with amorphous SiO2 were prepared by our novel preparation method. A NiO single phase structure was confirmed using the X-ray diffraction measurements. It is considered that Ni ions are replaced by Fe ions because it is observed that the lattice constant decreases. The temperature dependence behavior of the magnetization revealed that the blocking temperature, T B , shifted from 17 to 57 K as the amount of Fe ions increased, and that below T B , ferromagnetic behaviors were exhibited. The coercive force, H C , increased from 0.8 to 1.5 kOe as the amount of Fe ions increased.
International Nuclear Information System (INIS)
Lavrentyev, A.A.; Gabrelian, B.V.; Shkumat, P.N.; Nikiforov, I.Ya.; Zavaliy, I.Yu.; Sinelnichenko, A.K.; Izvekov, A.V.; Khyzhun, O.Yu.
2010-01-01
Electronic properties of Ti 4 Fe 2 O oxide, a very promising hydrogen-storage material, were studied both from theoretical and experimental points of view employing the first-principles band-structure augmented plane wave + local orbitals (APW + LO) method with the WIEN2k code as well as X-ray photoelectron spectroscopy (XPS) and soft X-ray emission spectroscopy (SXES). Total and partial densities of states of the constituent atoms of Ti 4 Fe 2 O have been derived from the APW + LO calculations. The XPS valence-band spectra as well as the SXES Ti Lα, Fe Lα and O Kα bands have been measured for a series of Ti 4 Fe 2 O x oxides (x = 1.0, 0.5, and 0.25). The present APW + LO calculations reveal that, the O 2p-like states are the dominant contributors into the bottom of the valence band, whilst the top of the valence band and the bottom of the conduction band of Ti 4 Fe 2 O are dominated by contributions of the Fe 3d- and Ti 3d-like states. The APW + LO results are confirmed experimentally by a comparison on a common energy scale of the XPS valence-band spectra and the SXES Ti Lα, Fe Lα and O Kα bands of the Ti 4 Fe 2 O x oxides. The XPS Ti 2p, Fe 2p and O 1s core-level binding energies have been measured for the compounds under consideration.
(Ga,Fe)Sb: A p-type ferromagnetic semiconductor
Energy Technology Data Exchange (ETDEWEB)
Tu, Nguyen Thanh; Anh, Le Duc; Tanaka, Masaaki [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Hai, Pham Nam [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656 (Japan); Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-0033 (Japan)
2014-09-29
A p-type ferromagnetic semiconductor (Ga{sub 1−x},Fe{sub x})Sb (x = 3.9%–13.7%) has been grown by low-temperature molecular beam epitaxy (MBE) on GaAs(001) substrates. Reflection high energy electron diffraction patterns during the MBE growth and X-ray diffraction spectra indicate that (Ga,Fe)Sb layers have the zinc-blende crystal structure without any other crystallographic phase of precipitates. Magnetic circular dichroism (MCD) spectroscopy characterizations indicate that (Ga,Fe)Sb has the zinc-blende band structure with spin-splitting induced by s,p-d exchange interactions. The magnetic field dependence of the MCD intensity and anomalous Hall resistance of (Ga,Fe)Sb show clear hysteresis, demonstrating the presence of ferromagnetic order. The Curie temperature (T{sub C}) increases with increasing x and reaches 140 K at x = 13.7%. The crystal structure analyses, magneto-transport, and magneto-optical properties indicate that (Ga,Fe)Sb is an intrinsic ferromagnetic semiconductor.
Structural transformation in mechanosynthesized bcc Fe-Al-Si(Ge) solid solutions during heating
International Nuclear Information System (INIS)
Kubalova, L.M.; Sviridov, I.A.; Vasilyeva, O.Ya.; Fadeeva, V.I.
2007-01-01
X-ray diffractometry and Moessbauer spectroscopy study of Fe 50 Al 25 Si 25 and Fe 50 Al 25 Ge 25 alloys obtained by mechanical alloying (MA) of elementary powders was carried out. Phase transformation during heating of synthesized products was studied using differential scanning calorimetry (DSC). After 2.5 h of MA monophase alloys containing bcc Fe(Al, Ge) solid solutions Fe(Al, Si) are formed. Fe(Al, Si) is partially ordered B2 type and Fe(Al, Ge) is completely disordered. DSC curves of synthesized alloys displayed the presence of exothermal peaks caused by phase transformation. The metastable Fe(Al, Si) solid solution transformed into FeAl 1-x Si x (B2) and FeSi 1-x Al x (B20) equilibrium phases. The Fe(Al, Ge) solid solution transformed into equilibrium phases through intermediate stage of Fe 6 Ge 3 Al 2 metastable phase formation. The Fe 6 Ge 3 Al 2 phase dissociated into three equilibrium phases: FeAl 1-x Ge x (B2), χ-Fe 6 Ge 5 and η-Fe 13 (Ge, Al) 8 (B8 2 ). The structure of Fe 6 Ge 3 Al 2 was calculated by Rietveld method, the distribution of Al and Ge in the elementary cell and its parameters were calculated. Moessbauer study showed that Fe(Al, Si) and Fe(Al, Ge) solid solutions are paramagnetic. In the equilibrium state the alloy containing Si is also paramagnetic while the alloy with Ge showed ferromagnetic properties
Spin-polarized electron tunneling in bcc FeCo/MgO/FeCo(001) magnetic tunnel junctions.
Bonell, F; Hauet, T; Andrieu, S; Bertran, F; Le Fèvre, P; Calmels, L; Tejeda, A; Montaigne, F; Warot-Fonrose, B; Belhadji, B; Nicolaou, A; Taleb-Ibrahimi, A
2012-04-27
In combining spin- and symmetry-resolved photoemission, magnetotransport measurements and ab initio calculations we detangled the electronic states involved in the electronic transport in Fe(1-x)Co(x)(001)/MgO/Fe(1-x)Co(x)(001) magnetic tunnel junctions. Contrary to previous theoretical predictions, we observe a large reduction in TMR (from 530 to 200% at 20 K) for Co content above 25 atomic% as well as anomalies in the conductance curves. We demonstrate that these unexpected behaviors originate from a minority spin state with Δ(1) symmetry that exists below the Fermi level for high Co concentration. Using angle-resolved photoemission, this state is shown to be a two-dimensional state that occurs at both Fe(1-x)Co(x)(001) free surface, and more importantly at the interface with MgO. The combination of this interface state with the peculiar density of empty states due to chemical disorder allows us to describe in details the complex conduction behavior in this system.
Parker, David S
2017-06-13
We present a comparative theoretical study of the hexagonal forms of the Fe-chalcogenides FeS, FeSe and FeTe with their better known tetragonal forms. While the tetragonal forms exhibit only an incipient antiferromagnetism and experimentally show superconductivity when doped, the hexagonal forms of FeS and FeSe display a robust magnetism. We show that this strong magnetism arises from a van Hove singularity associated with the direct Fe-Fe c-axis chains in the generally more three-dimensional NiAs structure. We also find that hexagonal FeTe is much less magnetic than the other two hexagonal materials, so that unconventional magnetically-mediated superconductivity is possible, although a large T c value is unlikely.
Energy Technology Data Exchange (ETDEWEB)
Lozano, D. Oyola, E-mail: doyola@ut.edu.co [University of Tolima, Department of Physics (Colombia); Zamora, L. E.; Perez Alcazar, G. A. [University of Valle, Department of Physics (Colombia); Rojas, Y. A.; Bustos, H. [University of Tolima, Department of Physics (Colombia); Greneche, J. M. [UMR CNRS 6087, Laboratoire de Physique de l' Etat Condense (France)
2005-02-15
In this work we report the magnetic and structural properties obtained by Moessbauer spectrometry, Vibrating Sample Magnetometer and X-ray diffraction of milled powders with initial composition Nd{sub 2}(Fe{sub 100-x}Nb{sub x}){sub 14}B with x = 0 and x = 4. The mixtures were ball milled for different times up to 240 h. Structural and microstructural parameters were derived from high statistics X-ray patterns and discussed as a function of milling time. The Moessbauer spectra of the samples were fitted by means of a sextet and an hyperfine field distribution, associated to a pure iron phase ({alpha}-Fe) and a disordered iron-based phase, respectively. The {alpha}-Fe grain size decreases from 50 nm for 6 h up to 5 nm for 240 h milling time. The Vibrating Sample Magnetometer results allow to conclude that these samples behave as soft ferromagnets.
Electrical transport properties in Fe-Cr nanocluster-assembled granular films
Wang, Xiong-Zhi; Wang, Lai-Sen; Zhang, Qin-Fu; Liu, Xiang; Xie, Jia; Su, A.-Mei; Zheng, Hong-Fei; Peng, Dong-Liang
2017-09-01
The Fe100-xCrx nanocluster-assembled granular films with Cr atomic fraction (x) ranging from 0 to 100 were fabricated by using a plasma-gas-condensation cluster deposition system. The TEM characterization revealed that the uniform Fe clusters were coated with a Cr layer to form a Fe-Cr core-shell structure. Then, the as-prepared Fe100-xCrx nanoclusters were randomly assembled into a granular film in vacuum environments with increasing the deposition time. Because of the competition between interfacial resistance and shunting effect of Cr layer, the room temperature resistivity of the Fe100-xCrx nanocluster-assembled granular films first increased and then decreased with increasing the Cr atomic fraction (x), and revealed a maximum of 2 × 104 μΩ cm at x = 26 at.%. The temperature-dependent longitudinal resistivity (ρxx), magnetoresistance (MR) effect and anomalous Hall effect (AHE) of these Fe100-xCrx nanocluster-assembled granular films were also studied systematically. As the x increased from 0 to 100, the ρxx of all samples firstly decreased and then increased with increasing the measuring temperature. The dependence of ρxx on temperature could be well addressed by a mechanism incorporated for the fluctuation-induced-tunneling (FIT) conduction process and temperature-dependent scattering effect. It was found that the anomalous Hall effect (AHE) had no legible scaling relation in Fe100-xCrx nanocluster-assembled granular films. However, after deducting the contribution of tunneling effect, the scaling relation was unambiguous. Additionally, the Fe100-xCrx nanocluster-assembled granular films revealed a small negative magnetoresistance (MR), which decreased with the increase of x. The detailed physical mechanism of the electrical transport properties in these Fe100-xCrx nanocluster-assembled granular films was also studied.
Ferromagnetic resonance linewidth and two-magnon scattering in Fe1-xGdx thin films
Directory of Open Access Journals (Sweden)
Sheng Jiang
2017-05-01
Full Text Available Magnetization dynamics of Fe1-xGdx thin films (0 ≤ x ≤ 22% has been investigated by ferromagnetic resonance (FMR. Out-of-plane magnetic field orientation dependence of resonance field and linewidth has been measured. Resonance field and FMR linewidth have been fitted by the free energy of our system and Landau-Lifshitz-Gilbert (LLG equation. It is found that FMR linewidth contains huge extrinsic components including two-magnon scattering contribution and inhomogeneous broadening for FeGd alloy thin films. In addition, the intrinsic linewidth and real damping constants have been obtained by extracting the extrinsic linewidth. The damping constant enhanced from 0.011 to 0.038 as Gd dopants increase from 0 to 22% which originates from the enhancement of L-S coupling in FeGd thin films. Besides, gyromagnetic ratio, Landé factor g and magnetic anisotropy of our films have also been determined.
Structural and magnetic properties of Mn{sub 50}Fe{sub 50−x}Sn{sub x} (x=10, 15 and 20) alloys
Energy Technology Data Exchange (ETDEWEB)
Ghosh, Tanmoy [LCMP, S.N. Bose National Centre for Basic Sciences, Kolkata 700106 (India); Agarwal, Sandeep [Haldia Institute of Technology, Haldia 721657 (India); Mukhopadhyay, P.K., E-mail: pkm@bose.res.in [LCMP, S.N. Bose National Centre for Basic Sciences, Kolkata 700106 (India)
2016-11-15
In this work we report measurements and comparisons of the structural, magnetic and transport properties of a series of Mn{sub 50}Fe{sub 50−x}Sn{sub x} alloys (x=10, 15 and 20). We found that while the lower Sn composition sample stabilized in β-Mn-type crystallographic phase, the higher Sn composition alloys contained both β-Mn-type as well as Mn{sub 3}Sn-type hexagonal DO{sub 19} phases. Through d.c. and a.c. magnetic property measurements we have established the existence of a ferromagnetic transition near room temperature followed by a spin reorientation at lower temperature in the Mn{sub 3}Sn-type crystallographic phase of the alloys. Our resistivity study also revealed an interesting behavior with negative temperature coefficient (TCR) in these alloys. - Highlights: • Mn{sub 50}Fe{sub 50-x}Sn{sub x} alloys were studied over a limited concentration range. • Lower Sn alloys behaved similar to ß-Mn alloys both structurally and magnetically. • Higher Sn alloys showed magnetic transitions similar to Mn{sub 3}Sn and Fe{sub 3}Sn. • Resistivity showed bad metallic behavior with negetive temperature coefficient.
Determination of Fe charge-state distributions in PLT by Bragg crystal x-ray spectroscopy
International Nuclear Information System (INIS)
Hill, K.W.; von Goeler, S.; Bitter, M.
1978-08-01
A curved-crystal Bragg x-ray spectrometer has been used to measure Kα or 1s-2p radiation from highly stripped Fe XVIII to Fe XXV impurity ions in the PLT tokamak. The spectrometer has sufficient energy resolution (approximately < 4 eV at 6400 eV) to distinguish between the different ionization states of iron by measuring the energy shift of the Kα x rays. The measured wavelengths agree well with theory and with spectra from solar flares and from laser-produced plasmas. The distribution of Fe charge states in the center of the discharge has been inferred from a comparison of the measured x-ray spectrum with theory. The shape of the spectrum depends strongly on electron temperature (T/sub e/) in the range T/sub e/ = 800 to 1500 eV. Within the factor of two uncertainty in L-shell ionization cross sections, measured intensities agree with theory, which is based on coronal equilibrium, indicating that the ion life-time in the center of the plasma is approximately equal to or greater than the equilibration time
Energy Technology Data Exchange (ETDEWEB)
Ranchal, R., E-mail: rociran@fis.ucm.es [Dpto. Física de Materiales, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, Madrid 28040 (Spain); Fin, S. [Dipartimento di Fisica, Università di Ferrara, Via Saragat 1, 44122 Ferrara (Italy); Bisero, D. [CNISM and Dipartimento di Fisica, Università di Ferrara, Via Saragat 1, 44122 Ferrara (Italy)
2016-05-15
Tb{sub x}Fe{sub 73}Ga{sub 27-x} (7 at.% ≤ x ≤ 11 at.%) ternary alloys have been obtained by cosputtering from Tb{sub 33}Fe{sub 67} and Fe{sub 72}Ga{sub 28} targets. In contrast with other Tb–Fe–Ga compounds that consist of just one structural phase, the diffraction pattern of the Tb{sub 7}Fe{sub 73}Ga{sub 20} shows the presence of two different phases related to binary Tb–Fe and Fe–Ga alloys. This microstructure evolves as the Tb content is increased, and for a Tb of 11 at.% X-ray diffractometry only evidences the presence of a phase close to the TbFe{sub 2}. Although none of the studied samples show perpendicular magnetic anisotropy, there is a significant component of the magnetization perpendicular to the sample plane. The increase of the Tb content on the compounds from 7 at.% to 11 at.% enhances this component most probably due to the shift of the microstructure towards one similar to the TbFe{sub 2}. - Highlights: • Tb{sub x}Fe{sub 73}Ga{sub 27-x} (7 at.% ≤ x ≤ 11 at.%) thin films grown by cosputtering. • Evolution of the microstructure upon the increase of Tb. • Out of plane component of the magnetization stable up to 800 Oe.
International Nuclear Information System (INIS)
Berrocal, Teresa; Mesa, Jose L.; Pizarro, Jose L.; Bazan, Begona; Lezama, Luis; Arriortua, Maria I.; Rojo, Teofilo
2009-01-01
The (NH 4 )[Fe(AsO 4 ) 1-x (PO 4 ) x F] (x=0.3, 0.6, 0.8) series of compounds has been synthesized under mild hydrothermal conditions. The compounds crystallize in the orthorhombic Pna2 1 space group, with the unit-cell parameters a=13.1718(1), b=6.5966(6), c=10.797(1) A for x=0.3; a=13.081(1), b=6.5341(6), c=10.713(1) A for x=0.6 and a=13.0329(9), b=6.4994(4), c=10.6702(6) A for x=0.8, with the volumes 938.6(1), 915.7(1) and 903.8(1) A 3 , respectively, with Z=8. Single crystals of (NH 4 )[Fe(AsO 4 ) 0.7 (PO 4 ) 0.3 F] heated under air atmosphere at 465 deg. C remain as single crystals, changing the composition to Fe(AsO 4 ) 0.7 (PO 4 ) 0.3 . This later phase belongs to the orthorhombic Imam space group, with the unit cell parameters a=13.328(2), b=6.5114(5), c=10.703(1) A, V=928.9(2) A 3 and Z=12. The crystal structure of the ammonium phases consists of a KTP three-dimensional framework constructed by chains formed by alternating Fe(2)O 4 F 2 or Fe(1)O 4 F 2 octahedra and As/P(2)O 4 or As/P(1)O 4 tetrahedra, respectively. These octahedra and tetrahedra are linked by a common oxygen vertex. The chains run along the 'a' and 'b' crystallographic axes. The crystal structure of Fe(AsO 4 ) 0.7 (PO 4 ) 0.3 is a three-dimensional skeleton derived from that of the precursor, formed from (100) sheets stacked along the [001] direction, and interconnected by chains of alternating Fe(2)O 6 octahedra and As/P(2)O 4 tetrahedra sharing a vertex in the 'a' direction. Transmission electronic microscopy of this compound indicates the existence of unconnected external cavities with a BET surface area of 3.91(3) m 2 g -1 . The diffuse reflectance spectra in the visible region show the forbidden electronic transitions characteristic of the Fe(III) d 5 -high spin cation in slightly distorted octahedral geometry, for all the compounds. The ESR spectra for all the compounds, carried out from room temperature to 4.2 K, remain isotropic with variation in temperature; the g-value is 1
In Situ X-ray Diffraction Study of the Formation of Fe(Se,Te) from Various Precursors
DEFF Research Database (Denmark)
Grivel, Jean-Claude; Yue, Zhao; Wulff, Anders Christian
2012-01-01
The formation of the FeSe0.5Te0.5 phase was studied by means of high energy synchrotron x-ray diffraction. The precursors consisted of Fe, Se and Te or Se0.5Te0.5 powder mixtures and were encased in a metal (Cu/Nb) composite sheath to prevent evaporation of Se and Te during high temperature...... equilibria of the Se – Te system. The grain size of the starting Fe powder has no influence on the reaction path for the grain sizes used in the present study. However, the reaction rate for Fe(Se,Te) formation is clearly sensitive to this parameter....
Moment mapping of body-centered-cubic Fe{sub x}Mn{sub 1−x} alloy films on MgO(001)
Energy Technology Data Exchange (ETDEWEB)
Idzerda, Y. U., E-mail: idzerda@physics.montana.edu; Bhatkar, H. [Department of Physics, Montana State University, Bozeman, Montana 59717 (United States); Arenholz, E. [Advanced Light Source, Lawrence Berkeley National Laboratories, Berkeley, California 59717 (United States)
2015-05-07
The alloy composition and elemental magnetic moments of bcc single crystal films of compositionally graded Fe{sub x}Mn{sub 1−x} films (20 nm thick films with 0.8 ≤ x ≤ 0.9) grown on MgO(001) are spatially mapped using X-ray absorption spectroscopy and magnetic circular dichroism. Electron diffraction measurements on single composition samples confirmed that the structure of Fe{sub x}Mn{sub 1−x} films remained epitaxial and in the bcc phase from 0.65 ≤ x ≤ 1, but rotated 45° with respect to the MgO(001) surface net. This is beyond the bulk bcc stability limit of x = 0.88. The Fe moment is found to gradually reduce with increasing Mn content with a very abrupt decline at x = 0.85, a slightly higher composition than observed in the bulk. Surprisingly, the Mn exhibits a very small net moment (<0.1 μ{sub B}) at all compositions, suggesting a complex Mn spin structure.
International Nuclear Information System (INIS)
Chikamatsu, Akira; Matsuyama, Toshiya; Hirose, Yasushi; Kumigashira, Hiroshi; Oshima, Masaharu; Hasegawa, Tetsuya
2012-01-01
Highlights: ► Electronic states of infinite-layer SrFeO 2 films have been experimentally observed. ► Fe 3d states have higher densities of states in the valence-band region. ► Three peaks derived from Fe 3d states were observed in the conduction-band region. ► Indirect bandgap value was determined to be 1.3 eV. - Abstract: We investigated the electronic states of a single-crystal SrFeO 2 epitaxial thin film in the valence-band and conduction-band regions using synchrotron-radiation X-ray photoemission and absorption spectroscopies. Fe 2p–3d resonant photoemission measurements revealed that the Fe 3d states have higher densities of states at binding energies of 3–5 eV and 5–8.5 eV in the valence-band region. The O K-edge X-ray absorption spectrum exhibited three peaks in the Fe 3d-derived conduction band hybridized with O 2p states; these can be assigned to Fe 3d xy , 3d xz + 3d yz , and 3d x 2 –y 2 . In addition, the indirect bandgap value of the SrFeO 2 film was determined to be 1.3 eV by transmission and absorption spectroscopies.
Magnetic properties of CE(Fe sub(1-x) Al sub(x))2 for x<=0.20
International Nuclear Information System (INIS)
Franceschini, D.F.; Cunha, S.F. da.
1985-01-01
Magnetization measurements of the system Ce(Fe sub(1-x) Al sub(x)) 2 for x 2 has not a simple dilution effect. Together with a accentuated decrease in the iron mean magnetic moment and in Curie temperatures was observed, above a certain concentration, a transition from ferromagnetism to a canted spin phase upon decreasing temperature. For the higher concentration range the system exhibits magnetic freezing effects. A preliminary magnetic phase diagram was proposed. (Author) [pt
International Nuclear Information System (INIS)
Teh, G.B.; Saravanan, N.; Jefferson, D.A.
2007-01-01
Cobalt(II)-titanium(IV)-substituted barium ferrite forming the chemical formula of BaCo x Ti x Fe 12-2x O 19 (x = 1-6) have been investigated using X-ray diffraction spectroscopy (XRD), Superconducting Quantum Interference Device (SQUID) and high-resolution transmission electron microscopy (HRTEM). The specimen of magnetoplumbite (M-type) Co-Ti-substituted BaFe 12 O 19 were synthesised via sol-gel method using ethylene glycol as precursor. Significant increase in line broadening of the XRD patterns were observed indicating the decrease of particle sizes due to the Co(II)-Ti(IV) substitution. BaCo 3 Ti 3 Fe 6 O 19 showed the highest coercivity but moderate saturation and remnant magnetisations. HRTEM imaging showed that Co(II)-Ti(IV) substitution in the system of BaCo x Ti x Fe 12-2x O 19 (x = 1-6) produced no drastic change in the structure of the M-type ferrites. Most of the M-types crystals examined by HRTEM displayed a long axis perpendicular to the c-axis of the M-type structure. Disordered crystals showing the intergrowth between Co-Ti-substituted barium ferrite and the spinel-structured iron oxide were detected
Amorphization of Fe-Nb by mechanical alloying
International Nuclear Information System (INIS)
Yang, J.Y.; Zhang, T.J.; Cui, K.; Li, X.G.; Zhang, J.
1996-01-01
Elemental powder mixtures of Fe x Nb 1-x were mechanically alloyed in a planetary ball mill. Powders milled for different times were characterized by X-ray diffraction, transmission and scanning electron microscopy, differential thermal analysis and microhardness measurement. The results show that powders with 0.30≤x≤0.70 could be amorphized after 30 h milling; the maximum hardness (Hv) of milled Fe 50 Nb 50 powders attained was 1490. Based on a thermodynamical analysis, the glass forming range of the Fe-Nb system was calculated, and found to agree with the experimental result very well. (orig.)
Profound Interfacial Effects in CoFe2O4/Fe3O4 and Fe3O4/CoFe2O4 Core/Shell Nanoparticles
Polishchuk, Dmytro; Nedelko, Natalia; Solopan, Sergii; Ślawska-Waniewska, Anna; Zamorskyi, Vladyslav; Tovstolytkin, Alexandr; Belous, Anatolii
2018-03-01
Two sets of core/shell magnetic nanoparticles, CoFe2O4/Fe3O4 and Fe3O4/CoFe2O4, with a fixed diameter of the core ( 4.1 and 6.3 nm for the former and latter sets, respectively) and thickness of shells up to 2.5 nm were synthesized from metal chlorides in a diethylene glycol solution. The nanoparticles were characterized by X-ray diffraction, transmission electron microscopy, and magnetic measurements. The analysis of the results of magnetic measurements shows that coating of magnetic nanoparticles with the shells results in two simultaneous effects: first, it modifies the parameters of the core-shell interface, and second, it makes the particles acquire combined features of the core and the shell. The first effect becomes especially prominent when the parameters of core and shell strongly differ from each other. The results obtained are useful for optimizing and tailoring the parameters of core/shell spinel ferrite magnetic nanoparticles for their use in various technological and biomedical applications.
Energy Technology Data Exchange (ETDEWEB)
Parker, David S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2017-06-13
We present a comparative theoretical study of the hexagonal forms of the Fe-chalcogenides FeS, FeSe and FeTe with their better known tetragonal forms. While the tetragonal forms exhibit only an incipient antiferromagnetism and experimentally show superconductivity when doped, the hexagonal forms of FeS and FeSe display a robust magnetism. We show that this strong magnetism arises from a van Hove singularity associated with the direct Fe-Fe c-axis chains in the generally more three-dimensional NiAs structure. We also find that hexagonal FeTe is much less magnetic than the other two hexagonal materials, so that unconventional magnetically-mediated superconductivity is possible, although a large Tc value is unlikely.
Redox reactions of [FeFe]-hydrogenase models containing an internal amine and a pendant phosphine.
Zheng, Dehua; Wang, Mei; Chen, Lin; Wang, Ning; Sun, Licheng
2014-02-03
A diiron dithiolate complex with a pendant phosphine coordinated to one of the iron centers, [(μ-SCH2)2N(CH2C6H4-o-PPh2){Fe2(CO)5}] (1), was prepared and structurally characterized. The pendant phosphine is dissociated together with a CO ligand in the presence of excess PMe3, to afford [(μ-SCH2)2N(CH2C6H4-o-PPh2){Fe(CO)2(PMe3)}2] (2). Redox reactions of 2 and related complexes were studied in detail by in situ IR spectroscopy. A series of new Fe(II)Fe(I) ([3](+) and [6](+)), Fe(II)Fe(II) ([4](2+)), and Fe(I)Fe(I) (5) complexes relevant to Hox, Hox(CO), and Hred states of the [FeFe]-hydrogenase active site were detected. Among these complexes, the molecular structures of the diferrous complex [4](2+) with the internal amine and the pendant phosphine co-coordinated to the same iron center and the triphosphine diiron complex 5 were determined by X-ray crystallography. To make a comparison, the redox reactions of an analogous complex, [(μ-SCH2)2N(CH2C6H5){Fe(CO)2(PMe3)}2] (7), were also investigated by in situ IR spectroscopy in the absence or presence of extrinsic PPh3, which has no influence on the oxidation reaction of 7. The pendant phosphine in the second coordination sphere makes the redox reaction of 2 different from that of its analogue 7.
Structure and magnetic properties of (Nd1-xErx)3Fe25Cr4.0 (0 ≤ x ≤ 0.8) compounds
International Nuclear Information System (INIS)
Luo Hongzhi; Jia Lin; Li Yangxian; Meng Fanbin; Shen Jiang; Chen Nanxian; Wu Guangheng; Yang Fuming
2004-01-01
The structure and magnetic properties of (Nd 1-x Er x ) 3 Fe 25 Cr 4.0 compounds with x = 0-0.8 have been investigated using x-ray powder diffraction (XRD) and magnetic measurements. It has been found that all the compounds crystallize in a Nd 3 (Fe,Ti) 29 -type structure. Substitution of Er for Nd leads to a contraction of the unit-cell volume. The Curie temperature, T c , and the saturation magnetization, M s , of (Nd 1-x Er x ) 3 Fe 25 Cr 4.0 decrease monotonically with increasing Er content. The easy magnetization direction (EMD) of Nd 3 Fe 25 Cr 4.0 at room temperature is close to the [040] direction but may be a little out of the basal plane. With increasing Er content, the EMD changes closer to the [40-2] direction and the tilt angle increases. Both the XRD patterns and ac susceptibility indicate the appearance of a spin reorientation for x = 0-0.4 as the temperature decreases from room temperature to 77 K. The spin reorientation temperature, T sr , increases monotonically with increasing Er content from 158 K for x = 0 to 198 K for x = 0.4. A first order magnetization process (FOMP) occurs for all the compounds, and the critical field of the FOMP decreases with increasing Er content from 6.6 T for x = 0 to 2.0 T for x = 0.7
Tang, Jin; Liu, Xiansong; Mehmood Ur Rehman, Khalid; Li, Dan; Li, Mingling; Yang, Yujie
2018-04-01
We report a successful preparation of Ba1-xLaxFe22+Fe163+O27 (x = 0.00-0.10) W-type hexagonal ferrites by standard ceramic method in a reduced oxygen atmosphere. In this work, the effect of the substitution La3+ rare-earth ions for Ba2+ ions on the structural and magnetic properties of the prepared samples have been studied. The phase identification of magnetic powders was performed by X-ray diffraction. The results of XRD show that the single phase was observed in the W-type ferrites with different La content. The SEM micrographs showed that the ferrites have formed the hexagonal structure. The magnetic properties of the samples were metric by a vibrating sample magnetometer. The coercivity (Hc) of the particles decreases with the increase of La content(x), while the saturation magnetization (Ms) of the particles first increases with x from 0 to 0.05, and then begins to decrease when x continues to increase. The monotonic dependence of the magnetic anisotropy field Ha and coercivity Hc on the La3+ doping amount is found to be mainly dominated by the competition between Ms and Keff.
Structural Investigation of Rapidly Quenched FeCoPtB Alloys
International Nuclear Information System (INIS)
Grabias, A.; Kopcewicz, M.; Latuch, J.; Oleszak, D.
2011-01-01
Two sets of Fe 52-x Co x Pt 28 B 20 (x = 0-26 at.%) and Fe 60-x Co x Pt 25 B 15 (x = 0-40 at.%) alloys were prepared in the form of ribbons by the rapid quenching technique. Structure of the samples was characterized by Moessbauer spectroscopy and X-ray diffraction. In the as-quenched alloys the amorphous phase coexisted with the fcc-(Fe,Co)Pt disordered solid solution. Differential scanning calorimetry measurements performed in the range 50-720 ± C revealed one or two exothermal peaks. The magnetically hard ordered L1 0 (Fe,Co)Pt and magnetically soft (Fe,Co) 2 B nanocrystalline phases were formed due to thermal treatment of the alloys. The influence of Co content on the structure of the as-quenched and heated alloys was studied. (authors)
Rodak, D.; Kroll, E.; Tsoi, G. M.; Vaishnava, P. P.; Naik, R.; Wenger, L. E.; Suryanarayanan, R.; Naik, V. M.; Boolchand, P.
2003-03-01
Magnetic nanoparticles have potential applications ranging from drug delivery and imaging in the medical field to sensing and memory storage in technology. The preparation, structure, and physical properties of iron oxide-based nanoparticles synthesized by ion exchange in a polystyrene resin matrix have been investigated. Employing a synthesis method developed originally by Ziolo, et. al^1, nanoparticles were prepared in a sulfonated divinyl benzene polystyrene resin matrix using various aqueous solutions of (1) FeCl_2, (2) FeCl_3, (3) FeCl2 : 2FeCl3 , (4) 9FeCl2 : CoCl_2, and (5) 4FeCl2 : CoCl_2. Powder x-ray diffraction measurements were used to identify the phases present while transmission electron microscopy was used for particle size distribution determinations. SQUID magnetization measurements (field-cooled and zero-field-cooled) and Fe^57 Mössbauer effect measurements indicate the presence of ferromagnetic iron oxide phases and a superparamagnetic behavior with blocking temperatures (T_B) varying from 50 K to room temperature. Nanoparticles synthesized using a stoichiometric mixture of FeCl2 and FeCl3 exhibit the lowest TB and smallest particle size distribution. The Mössbauer effect measurements have also been used to identify the iron oxides phases present and their relative amounts in the nanoparticles ^1R.F. Ziolo, et al., Science 207, 219 (1992). *Permanent address: Kettering University, Flint, MI 48504
Fe3Nb3N precipitates of the Fe3W3C type in Nb stabilized ferritic stainless steel
International Nuclear Information System (INIS)
Malfliet, A.; Van den Broek, W.; Chassagne, F.; Mithieux, J.-D.; Blanpain, B.; Wollants, P.
2011-01-01
Highlights: → The precipitation in Nb stabilized ferritic stainless steel at 950 deg. C is investigated. → We characterized the Fe 3 Nb 3 X precipitates with SAED, EELS, WDS and AES. → We found that Fe 3 Nb 3 X precipitates are stabilized by N and not by C or O. → This insight is new and important for future development of this type of steel grade. - Abstract: A Nb stabilized ferritic stainless steel with 0.45 wt.%Nb, 82 ppm C and 170 ppm N is investigated to reveal the nature of the precipitates present at 950 deg. C. In particular, Fe 3 Nb 3 X precipitates of the Fe 3 W 3 C type are analyzed with WDS and EELS to determine the light elements X stabilizing this phase in the steel. According to WDS on large precipitates after 500 h at 950 deg. C, the Fe 3 Nb 3 X phase contains 10.4 at.% N, 1.2 at.% O and 1.0 at.% C. Auger Electron Spectroscopy on the same precipitates confirms the presence of N. In addition, it is revealed that the C and O peaks observed with WDS result from surface contamination as they disappear after Ar sputtering. The presence of a N peak in the EELS spectra of small Fe 3 Nb 3 X precipitates which have formed after 6 min at 950 deg. C indicate that N stabilizes this phase already from the initial precipitation stage. With this analysis it is demonstrated that N is an effective stabilizer of Fe 3 Nb 3 X precipitates in ferritic stainless steels. The formation of this phase should therefore be considered when predicting the precipitation behavior of Nb in industrial Nb stabilized ferritic stainless steels containing residual N.
Energy Technology Data Exchange (ETDEWEB)
Teh, G.B. [Department of Bioscience and Chemistry, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, 53300 Kuala Lumpur (Malaysia)], E-mail: tehgb@mail.utar.edu.my; Saravanan, N. [Department of Bioscience and Chemistry, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, 53300 Kuala Lumpur (Malaysia); Jefferson, D.A. [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom)
2007-10-15
Cobalt(II)-titanium(IV)-substituted barium ferrite forming the chemical formula of BaCo{sub x}Ti{sub x}Fe{sub 12-2x}O{sub 19} (x = 1-6) have been investigated using X-ray diffraction spectroscopy (XRD), Superconducting Quantum Interference Device (SQUID) and high-resolution transmission electron microscopy (HRTEM). The specimen of magnetoplumbite (M-type) Co-Ti-substituted BaFe{sub 12}O{sub 19} were synthesised via sol-gel method using ethylene glycol as precursor. Significant increase in line broadening of the XRD patterns were observed indicating the decrease of particle sizes due to the Co(II)-Ti(IV) substitution. BaCo{sub 3}Ti{sub 3}Fe{sub 6}O{sub 19} showed the highest coercivity but moderate saturation and remnant magnetisations. HRTEM imaging showed that Co(II)-Ti(IV) substitution in the system of BaCo{sub x}Ti{sub x}Fe{sub 12-2x}O{sub 19} (x = 1-6) produced no drastic change in the structure of the M-type ferrites. Most of the M-types crystals examined by HRTEM displayed a long axis perpendicular to the c-axis of the M-type structure. Disordered crystals showing the intergrowth between Co-Ti-substituted barium ferrite and the spinel-structured iron oxide were detected.
Objectives of the study were to determine effects of Fe source on plant growth, plant nutrition, substrate chemistry and runoff chemistry. Iron source (FS) treatments consisted of Fe-aminopolycarboxylic acid (APCA) complexones iron ethylenediaminetetraacetic acid (FeEDTA), iron [S, S']-ethylenediam...
The energy band structure of A{sub x}Fe{sub 2}Se{sub 2} (A = K, Rb) superconductors
Energy Technology Data Exchange (ETDEWEB)
Zabidi, Noriza A. [Physics Department, Centre for Defence Foundation Studies, Universiti Pertahanan Nasional Malaysia, Kuala Lumpur 59200 (Malaysia); Azhan, Muhd. Z. [Defence Science Department, Faculty of Defence Science and Technology, Universiti Pertahanan Nasional Malaysia, Kuala Lumpur 59200 (Malaysia); Rosli, A. N. [Faculty of Science and Technology, Universiti Sains Islam Malaysia, Nilai 71800, Negeri Sembilan (Malaysia); Shrivastava, Keshav N. [School of Physics, University of Hyderabad, Hyderabad 500046 (India)
2014-03-05
We study the band structure of antiferromagnetic A{sub x}Fe{sub 2}Se{sub 2} (A = K, Rb) superconductors by using first-principles electronic structure calculations which is density functional theory. In the vicinity of iron-vacancy, we identify the valence electrons of A{sub x}Fe{sub 2}Se{sub 2} will be filled up to the Fermi level and no semiconducting gap is observed. Hence, the A{sub x}Fe{sub 2}Se{sub 2} is a metallic instead of semiconducting which leads to superconductivity in the orbital-selective Mott phase. Similarly, there is non-vanishing density of states at the Fermi level.
High field properties of superconducting BaFe{sub 2-x}Ni{sub x}As{sub 2} thin films
Energy Technology Data Exchange (ETDEWEB)
Richter, Stefan [Institute for Metallic Materials, IFW Dresden (Germany); Technical University Dresden (Germany); Kurth, Fritz; Grinenko, Vadim; Nielsch, Kornelius; Huehne, Ruben [Institute for Metallic Materials, IFW Dresden (Germany); Iida, Kazumasa [Nagoya University (Japan); Pervakov, Kirill [Russian Academy of Sciences (Russian Federation); Tarantini, Chiara; Jaroszynski, Jan [National High Magnetic Field Laboratory (United States); Pukenas, Aurimas; Skrotzki, Werner [Technical University Dresden (Germany)
2016-07-01
Fe based superconductors combine the advantages of cuprates (high upper critical field) with the small Hc{sub 2} anisotropy of classic low temperature superconductors, which makes them suitable candidates for high field applications. The study of Fe-based superconducting thin films is one crucial step to explore this potential in more detail. We present results for epitaxial BaFe{sub 2-x}Ni{sub x}As{sub 2} thin films, which have been successfully grown for the first time using pulsed laser deposition. Superconducting transition temperatures of up to 19 K have been realized in slightly overdoped films, which is in good agreement with results obtained for single crystals. The behavior of the upper critical field and critical current density has been measured in high magnetic fields up to 35 T. The results will be correlated to the observed microstructure and compared to high field data for single crystals with similar composition.
Preparation and chemical properties of the skutterudites (Ce-Yb) yFe4-x(Co/Ni) xSb12
International Nuclear Information System (INIS)
Berardan, D.; Alleno, E.; Godart, C.; Rouleau, O.; Rodriguez-Carvajal, J.
2005-01-01
The double-filled skutterudites Ce y/2 Yb y/2 Fe 4-x Co x Sb 12 and Ce y/2 Yb y/2 Fe 4-x Ni x Sb 12 have been synthesized as single phase materials. The evolution of the lattice parameters and of the filling fractions with substitutions on the transition metal site have been studied by X-ray diffraction and electron probe microanalysis, respectively. Both results were compared to that of single filled series (Ce/Yb) y Fe 4-x (Co/Ni) x Sb 12 . It shows that double-filled skutterudites can be understood as a solid solution between single filled ones. The valence states of Ce and Yb in all series have been studied using X-ray absorption spectroscopy at the L 3 edges, and we discuss their relationships with structural parameters. Ce is always trivalent, whereas Yb valence state decreases as Yb fraction increases. No distortion of the environment or sub-position of Yb in the cage have been seen by neutron diffraction. The Seebeck coefficient has been measured using a home made apparatus from 120 K to 300 K. It shows a crossover from p- to n-type conductivity for Co or Ni rich skutterudites in the six series. We discuss the influence on the room temperature thermopower of valence states, filling fractions and substitution rate on the transition metal site. Thermopower seems to be only driven by charge carriers concentration
Energy Technology Data Exchange (ETDEWEB)
Lim, Edmund H.H.; Liew, Josephine Y.C.; Awang Kechik, M.M.; Halim, S.A.; Chen, S.K. [Universiti Putra Malaysia (UPM), Department of Physics, Faculty of Science, Serdang, Selangor (Malaysia); Tan, K.B. [Universiti Putra Malaysia (UPM), Department of Chemistry, Faculty of Science, Serdang, Selangor (Malaysia); Qi, X. [National Cheng Kung University, Department of Materials Science and Engineering, Tainan City (China)
2017-06-15
Polycrystalline samples with nominal composition FeTe{sub 1-x}S{sub x} (x = 0.00-0.30) were synthesized via solid state reaction method with intermittent grinding in argon gas flow. X-ray diffraction (XRD) patterns revealed the tetragonal structure (space group P4/nmm) of the samples with the presence of impurities Fe{sub 3}O{sub 4} and FeTe{sub 2}. By substitution with S, the a and c lattice parameters shrink probably due to the smaller ionic radius of S{sup 2-} compared to Te{sup 2-}. Scanning electron microscopy images showed that the samples developed plate-like grains with increasing S substitution. Substitution of Te with S suppresses the structural transition of the parent compound FeTe as shown by both the temperature dependence of resistance and magnetic moment measurements. All of the S-substituted samples showed a rapid drop of resistance at around 9-10 K but zero resistance down to 4 K was not observed. In addition, negative magnetic moment corresponds to diamagnetism was detected in the samples for x = 0.25 and 0.30 suggesting the coexistence of magnetic and superconducting phase in these samples. The magnetization hysteresis loops measured at room temperature showed ferromagnetic behavior for the pure and S substituted samples. However, the magnetization, rentivity and coercivity decreased with S content. (orig.)
In situ observation of the formation of FeSe
DEFF Research Database (Denmark)
Grivel, Jean-Claude; Wulff, Anders Christian; Yue, Zhao
2011-01-01
The formation of the FeSe compound from a mixture of Fe and Se powders encased in a composite Cu/Nb sheath was studied in situ by means of high-energy synchrotron x-ray diffraction. Tetragonal beta-FeSe does not seem to form directly from the starting elements. Instead, a sequence of FeSe2, Fe3Se...
Structural and electrochemical properties of La{sub 0.8}Sr{sub 0.2}Ga{sub 1-x}Fe{sub x}O{sub 3}
Energy Technology Data Exchange (ETDEWEB)
Mori, Kazuhiro [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan)], E-mail: kmori@rri.kyoto-u.ac.jp; Onodera, Yohei [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan); Kiyanagi, Ryoji; Richardson, James W. [Intense Pulsed Neutron Source Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Itoh, Keiji; Sugiyama, Masaaki [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan); Kamiyama, Takashi [Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801 (Japan); Fukunaga, Toshiharu [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka 590-0494 (Japan)
2009-02-21
Mixed ionic-electronic conductor of Fe doped lanthanum gallate, La{sub 0.8}Sr{sub 0.2}Ga{sub 1-x}Fe{sub x}O{sub 3}, has been studied by the dc four-probe method and the neutron powder diffraction. In the electrical conductivity measurement at RT, insulator-metal transition-like phenomenon was observed at around x{approx}0.35; this suggests an existence of the percolation limit for the electronic conductivity. Simultaneously, a bond length between O atoms, l{sub O-O}, in a MO{sub 6} octahedron (M=Ga{sub 1-x}Fe{sub x}) drastically expands over x{approx}0.4, according to the result of crystal structure refinement based on the hexagonal phase. Such a drastic expansion in the l{sub O-O} would induce the decrease in the oxygen ionic conductivity.
International Nuclear Information System (INIS)
Deb, A.; Bergmann, U.; Cairns, E.L.; California Univ., Berkeley, CA; Cramer, S.P.; California Univ., Davis, CA
2004-01-01
The extraction and insertion of lithium in LiFePO 4 has been investigated in practical Li-ion intercalation electrodes for Li-ion batteries using Fe K-edge X-ray absorption spectroscopy (XAS). A versatile electrochemical in situ reaction cell was utilized, specifically designed for long-term X-ray experiments on battery electrodes during the lithium-extraction/insertion process in electrode materials for Li-ion batteries. The electrode contained about 7.7 mg of LiFePO 4 on a 20 μm-thick Al foil. In order to determine the charge compensation mechanism and structural perturbations occurring in the system during cycling, in situ X-ray absorption fine-structure spectroscopy (XAFS) measurements were conducted on the cell at a moderate rate using typical Li-ion battery operating voltages (3.0-4.1 V versus Li/Li + ).XAS studies of the LiFePO 4 electrode measured at the initial state (LiFePO 4 ) showed iron to be in the Fe(II) state corresponding to the initial state (0.0 mAh) of the battery, whereas in the delithiated state (FePO 4 ) iron was found to be in the FE(III) state corresponding to the final charged state (3 m Ah) of the battery. The X-ray absorption near-edge structure (XANES) region of the XAS spectra revealed a high-spin configuration for the two states [Fe(II), d 6 and Fe(III), d 5 ]. The XAFS data analysis confirmed that the olivine structure of the LeFePO 4 and FePO 4 is retained by the electrodes, which is in agreement with the X-ray diffraction observations on these compounds. The XAFS data that were collected continuously during cycling revealed details about the response of the cathode to Li insertion and extraction. These measurements on the LiFePO 4 cathode show that the material retains good structural short-range order leading to superior cycling
A study on magnetoelastic properties of Tb3 (Fe28-xCox) V1.0 (x=0, 3, 6) compounds
International Nuclear Information System (INIS)
Gholizadeh, A.; Tajabor, N.; Pourarian, F.
2012-01-01
In this work, The magnetoelastic properties of polycrystalline samples of Tb 3 (Fe 28-x Co x ) V 1.0 (x=0, 3, 6) intermetallic compounds are investigated by means of linear thermal expansion and magnetostriction measurements in the temperature range of 77-515 K under applied magnetic fields up to 1.5 T. The linear thermal expansion increases with the Co content. The well-defined anomalies observed in the linear thermal expansion coefficients for Tb 3 (Fe 28-x Co x ) V 1.0 (x=0, 3, 6) compounds are associated with the magnetic ordering temperature for x=0 and spin reorientation temperatures for x=3, 6. Below transition temperatures, the value of the longitudinal magnetostriction (λ Pa ) at 1.6 T increases with Co content.
Effect of Fe substitution on multiferroic hexagonal YMnO{sub 3}
Energy Technology Data Exchange (ETDEWEB)
Zaghrioui, M., E-mail: zaghrioui@univ-tours.f [Laboratoire d' electrodynamique des materiaux avances, UMR CNRS 6157 - CEA Universite F. Rabelais-IUT de Blois, 3 place Jean Jaures, C. S. 2903, 41029 Blois Cedex - France (France); Greneche, J.M. [Laboratoire de Physique de l' Etat Condense, UMR CNRS 6087, Universite du Maine, Avenue Olivier Messiaen, 72085 Le Mans (France); Autret-Lambert, C.; Gervais, M. [Laboratoire d' electrodynamique des materiaux avances, UMR CNRS 6157 - CEA Universite F. Rabelais-IUT de Blois, 3 place Jean Jaures, C. S. 2903, 41029 Blois Cedex (France)
2011-03-15
Polycrystalline YMn{sub 1-x}Fe{sub x}O{sub 3} (x=0.02-0.20) powders were synthesized by means of modified citrate method. Powder X-ray diffraction gives evidence that all the samples are single phase and exhibit hexagonal structure with P6{sub 3}cm space group as observed for YMnO{sub 3}. The solubility limit of Fe was determined as about 6 wt.%. Cell parameter values were found to increase with Fe content, since Fe{sup 3+} and Mn{sup 3+} have the same ionic radii. This can be attributed to the increase of the tilting of MnO{sub 5} bipyramid and the buckling of Y atoms. In addition, {sup 57}Fe Moessbauer spectrometry provides evidence of two Fe{sup 3+} sites attributed to two different nearest atomic neighbours. Magnetic properties reveal a paramagnetic-to-antiferromagnetic transition, a possible increase of the magnetic anisotropy, and a competition between ferromagnetic and antiferromagnetic interactions. - Research highlights: The increase of the tilting of MnO{sub 5} bipyramid and the buckling of Y atoms leads to the increase of cell parameter in YMn{sub 1-x}Fe{sub x}O{sub 3}. {sup 57}Fe Moessbauer spectrometry provides evidence of two Fe{sup 3+} sites.
Deuterium absorption and material phase characteristics of Zr2Fe
International Nuclear Information System (INIS)
Nobile, A.; Mosley, W.C.; Holder, J.S.; Brooks, K.N.
1992-01-01
Scanning electron microscope (SEM) images of polished surfaces, electron probe microanalysis, and X-ray powder diffractometry indicated the presence of a continuous Zr 2 Fe phase with secondary phases of ZrFe 2 , Zr 5 FeSn, α-Zr, and Zr 6 Fe 3 O. A statistically-designed experiment to determine the effects of temperature, time, and vacuum quality On activation of St 198 revealed that when activated at low temperature (350 degrees C) deuterium absorption rate was slower when the vacuum quality was pwr (2.5 Pa vs. 3x10 -4 Pa). However, at higher activation temperature (500 degrees C), deuterium absorption rate was fast and was independent of vacuum quality. Deuterium pressure-composition-temperature (P-C-T) data are reported for St 198 in the temperature range 200--500 degrees C. The P-C-T data over the full range of deuterium loading and at temperatures of 350 degrees C and below is described by: K 0e -(ΔH α /RT)=PD 2 q 2 /(q*-q) 2 where ΔHα and K 0 have values of 101.8 kJ·mole -1 and 3.24x10 -8 Pa -1 , and q* is 15.998 kPa·L -1 ·g -1 . At higher temperatures, one or more secondary reactions in the solid phase occur that slowly consume D 2 from the gas phase. XRD suggests these reactions to be: 2 Zr 2 FeD x → x ZrD 2 + x/3 ZrFe 2 + (2 - 2/3x) Zr 2 Fe and Zr 2 FeD x + (2 -1/2x) D 2 → ZrD 2 + Fe, where 0 < x < 3. Reaction between gas phase deuterium and Zr2FC formed in the first reaction accounts for the observed consumption of deuterium from the gas phase by this reaction
57Fe Mössbauer and X-ray characterisation of sandstones
International Nuclear Information System (INIS)
Mulaba-Bafubiandi, A. F.; Waanders, F. B.
2013-01-01
Sandstones from the Free State province in South Africa have been mined and processed mainly by small scale and artisanal miners in the rural areas. In the present investigation basic fire proof and water absorption tests, X-ray and γ-ray based characterisation techniques were used to study the sandstones. The collected samples were grouped according to their apparent colour in day light conditions and the elemental analysis showed the presence of a high amount of oxygen (>52%) and silicon (>38%) with Mn, Al, Fe and Ca as major elements in proportions related to the colour distribution of the various sandstones. The uniaxial compressive stress was found to be the highest (56 MPa) for the greyish sandstone and the lowest (8 MPa) for the white sandstone sample, also associated with the lowest (Al+Fe)/Si value of 0.082. The humidity test showed that the 6 % water absorption was lower than the recommended ASTM value of 8 %. The sandstone samples were also subjected to various high temperatures to simulate possible fire conditions and it was found that the non alteration of the mineral species might be one of the reasons why the sandstones are regarded as the most refractory amongst the building materials typically used. Mössbauer spectroscopy revealed that iron is present in all the sandstones, mainly as Fe 3 + with the black sandstone showing an additional presence of 3 % Fe 2 + indicating that a higher iron content coupled to higher silicon content, contributes to an increase in the uniaxial compressive strength.
Urata, T.; Tanabe, Y.; Huynh, K. K.; Heguri, S.; Oguro, H.; Watanabe, K.; Tanigaki, K.
2015-05-01
In Fe pnictide (Pn) superconducting materials, neither Mn nor Cr doping to the Fe site induces superconductivity, even though hole carriers are generated. This is in strong contrast with the superconductivity appearing when holes are introduced by alkali-metal substitution on the insulating blocking layers. We investigate in detail the effects of Mn doping on magnetotransport properties in Ba (Fe1 -xMnxAs )2 for elucidating the intrinsic reason. The negative Hall coefficient for x =0 estimated in the low magnetic field (B ) regime gradually increases as x increases, and its sign changes to a positive one at x =0.020 . Hall resistivities as well as simultaneous interpretation using the magnetoconductivity tensor including both longitudinal and transverse transport components clarify that minority holes with high mobility are generated by the Mn doping via spin-density wave transition at low temperatures, while original majority electrons and holes residing in the paraboliclike Fermi surfaces of the semimetallic Ba (FeAs )2 are negligibly affected. Present results indicate that the mechanism of hole doping in Ba (Fe1 -xMnxAs )2 is greatly different from that of the other superconducting FePn family.
Formation of tavorite-type LiFeSO4F followed by in situ X-ray diffraction
Eriksson, Rickard; Sobkowiak, Adam; Ångström, Jonas; Sahlberg, Martin; Gustafsson, Torbjörn; Edström, Kristina; Björefors, Fredrik
2015-12-01
The tavorite-type polymorph of LiFeSO4F has recently attracted substantial attention as a positive electrode material for lithium ion batteries. The synthesis of this material is generally considered to rely on a topotactic exchange of water (H2O) for lithium (Li) and fluorine (F) within the structurally similar hydrated iron sulfate precursor (FeSO4·H2O) when reacted with lithium fluoride (LiF). However, there have also been discussions in the literature regarding the possibility of a non-topotactic reaction mechanism between lithium sulfate (Li2SO4) and iron fluoride (FeF2) in tetraethylene glycol (TEG) as reaction medium. In this work, we use in situ X-ray diffraction to continuously follow the formation of LiFeSO4F from the two suggested precursor mixtures in a setup aimed to mimic the conditions of a solvothermal autoclave synthesis. It is demonstrated that LiFeSO4F is formed directly from FeSO4·H2O and LiF, in agreement with the proposed topotactic mechanism. The Li2SO4 and FeF2 precursors, on the other hand, are shown to rapidly transform into FeSO4·H2O and LiF with the water originating from the highly hygroscopic TEG before a subsequent formation of LiFeSO4F is initiated. The results highlight the importance of the FeSO4·H2O precursor in obtaining the tavorite-type LiFeSO4F, as it is observed in both reaction routes.
International Nuclear Information System (INIS)
Dou, Lintao; Liu, Haishun; Hou, Long; Xue, Lin; Yang, Weiming; Zhao, Yucheng; Chang, Chuntao
2014-01-01
The effects of Cu substitution for Fe on the glass-forming ability (GFA) and soft magnetic properties for Fe 72−x Cu x B 20 Si 4 Nb 4 (x=0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) bulk metallic glasses (BMGs) are investigated. It is found that the investigated BMGs exhibit large GFA as well as excellent soft magnetic properties, and proper substitution of Fe by Cu improves the saturation magnetization, coercive force, and effective permeability without obvious deterioration of the GFA. - Highlights: • Fully glassy rods of Fe 72−x Cu x B 20 Si 4 Nb 4 BMGs were produced above 1 mm in diameter. • Investigated BMGs exhibit large glass-forming ability and excellent soft magnetic properties. • Proper Cu substitution improves magnetic properties without obvious deterioration of glass-forming ability
Energy Technology Data Exchange (ETDEWEB)
Abouhaswa, A.S., E-mail: aliabohaswa@hotmail.com [Institute of Natural Sciences, Ural Federal University, 620083, Ekaterinburg (Russian Federation); Merentsov, A.I. [Institute of Natural Sciences, Ural Federal University, 620083, Ekaterinburg (Russian Federation); Baranov, N.V. [Institute of Natural Sciences, Ural Federal University, 620083, Ekaterinburg (Russian Federation); M.N. Miheev Institute of Metal Physics, Ural Branch of RAS, 620990, Ekaterinburg (Russian Federation)
2016-08-15
Highlights: • The Fe{sub 1.02}Se{sub 0.5}Te{sub 0.5−x}S{sub x} and Fe{sub 1.02}Se{sub 0.4}Te{sub 0.6−x}S{sub x} samples have been synthesized. • The S for Te substitution results in a small expansion of the crystal lattice of the PbO-type phase. • This expansion is attributed to changes in the phase relation and chemical composition of phases. • There is a correlation between the changes of T{sub c} and lattice parameters of the PbO-type phase. - Abstract: Two series of the Fe{sub 1.02}Se{sub 0.5}Te{sub 0.5–x}S{sub x} (I) and Fe{sub 1.02}Se{sub 0.4}Te{sub 0.6–x}S{sub x} (II) samples with the sulfur for tellurium substitution and with the invariable Se concentrations have been synthesized and studied by means of X-ray diffraction, scanning electron microscopy, electrical resistivity and magnetic susceptibility measurements. The superconducting PbO-type phase is found to persists in the first series up to x = 0.4 and in the second one up to x = 0.5. Despite the lower ionic radius of sulfur in comparison with tellurium the replacement of tellurium by sulfur does not lead to contraction of the unit cell volume of the superconducting phase in both I and II series with ternary mixture of chalcogens. Variations of the lattice parameters caused by the S for Te substitution in the Fe{sub 1.02}Se{sub 0.5}Te{sub 0.5–x}S{sub x} and Fe{sub 1.02}Se{sub 0.4}Te{sub 0.6–x}S{sub x} samples are found to be less pronounced than that reported for the Fe{sub 1.02}Te{sub 0.5}Se{sub 0.5-x}S{sub x} system and are accompanied by lowering of the critical temperature. The behavior of the lattice parameters and critical temperature of Fe(S,Se,Te) materials with the ternary mixture of chalcogens at substitutions is ascribed to the changes in the volume fraction and chemical compositions of the coexisting tetragonal and hexagonal phases.
Epitaxial Fe3Si/Ge/Fe3Si thin film multilayers grown on GaAs(001)
International Nuclear Information System (INIS)
Jenichen, B.; Herfort, J.; Jahn, U.; Trampert, A.; Riechert, H.
2014-01-01
We demonstrate Fe 3 Si/Ge/Fe 3 Si/GaAs(001) structures grown by molecular-beam epitaxy and characterized by transmission electron microscopy, electron backscattered diffraction, and X-ray diffraction. The bottom Fe 3 Si epitaxial film on GaAs is always single crystalline. The structural properties of the Ge film and the top Fe 3 Si layer depend on the substrate temperature during Ge deposition. Different orientation distributions of the grains in the Ge and the upper Fe 3 Si film were found. The low substrate temperature T s of 150 °C during Ge deposition ensures sharp interfaces, however, results in predominantly amorphous films. We find that the intermediate T s (225 °C) leads to a largely [111] oriented upper Fe 3 Si layer and polycrystal films. The high T s of 325 °C stabilizes the [001] oriented epitaxial layer structure, i.e., delivers smooth interfaces and single crystal films over as much as 80% of the surface area. - Highlights: • Fe 3 Si/Ge/Fe 3 Si/GaAs(001) structures are grown by MBE. • The bottom Fe 3 Si film is always single crystalline. • The properties of the Ge film depend on the substrate temperature during deposition. • Optimum growth conditions lead to almost perfect epitaxy of Ge on Fe 3 Si
International Nuclear Information System (INIS)
Chettah, A.; Wang, Z.G.; Kac, M.; Kucal, H.; Meftah, A.; Toulemonde, M.
2006-01-01
Knowing that Fe is sensitive to swift heavy ion irradiations whereas Au and Al are not, the behavior of nanometric metallic multilayer systems, like [Fe(3 nm)/Au(x)] y and [Fe(3 nm)/Al(x)] y with x ranging between 1 and 10 nm, were studied within the inelastic thermal spike model. In addition to the usual cylindrical geometry of energy dissipation perpendicular to the ion projectile direction, the heat transport along the ion path was implemented in the electronic and atomic sub-systems. The simulations were performed using three different values of linear energy transfer corresponding to 3 MeV/u of 208 Pb, 132 Xe and 84 Kr ions. For the Fe/Au system, evidence of appearance of a molten phase was found in the entire Au layer, provided the Au thickness is less than 7 nm and 3 nm for Pb and Xe ions, respectively. For the Fe/Al(x) system irradiated with Pb ions, the Al layers with a thickness less than 4 nm melt along the entire ion track. Surprisingly, the Fe layer does not melt if the Al thickness is larger than 2 nm, although the deposited energy surpasses the electronic stopping power threshold of track formation in Fe. For Kr ions melting does not occur in any of the multilayer systems
Modeling thermodynamics of Fe-N phases; characterisation of e-Fe2N1-z
DEFF Research Database (Denmark)
Pekelharing, M.I.; Böttger, A.; Somers, Marcel A.J.
1999-01-01
In order to arrive at modeling the thermodynamics of Fe-N phases, including long-range (LRO) and short-range ordering (SRO) of the N atoms, it is important to understand the role of N interstitially dissolved in an Fe-host lattice. The crystal structure of -Fe2N1-z consists of an h.c.p. iron...... sublattice and a hexagonal nitrogen sublattice formed by octahedral interstices of the Fe sublattice [1]. Two ground-state structures have been proposed for the ordered arrangement of the N atoms on their own sublattice [1], which were shown to be thermodynamically favourable [2]: configuration A for Fe2N1...... investigated with X-ray diffraction (XRD) and Mössbauer spectroscopy. A thermodynamic model accounting for the two configurations of LRO of the N atoms [2,3] was fitted to the N-absorption isotherm at 723 K and resulted in the occupancies of the sites of the nitrogen sublattice. A miscibility gap between...
Energy Technology Data Exchange (ETDEWEB)
Reshak, Ali H., E-mail: maalidph@yahoo.co.uk [School of Complex Systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic); School of Material Engineering, Malaysia University of Perlis, P.O. Box 77, d/a Pejabat Pos Besar, 01007 Kangar, Perlis (Malaysia); Charifi, Z., E-mail: charifizoulikha@gmail.com [Physics Department, Faculty of Science, University of M' sila, 28000 M' sila (Algeria); Baaziz, H. [Physics Department, Faculty of Science, University of M' sila, 28000 M' sila (Algeria)
2013-01-15
The optical dielectric functions of Fe{sub 2}MnSi{sub 1-x}Ge{sub x} alloys for selected concentrations (x=0.0, 0.25, 0.5, 0.75 and 1.0) were investigated. The ferromagnetic Fe{sub 2}MnSi{sub x}Ge{sub 1-x} is semiconducting with optical band gaps 0.507, 0.531, 0.539, 0.514 and 0.547 eV for the minority spin and is metallic for the majority spin. From the calculated results the half-metallic character and stability of ferromagnetic state for Fe{sub 2}MnSi{sub x}Ge{sub 1-x} is determined. The total magnetic moment is found to be 3.0{mu}{sub B} for all alloys with the most contribution from Mn local magnetic moments. Iron atoms however exhibit much smaller spin moments, about 10% of the bulk value, and the sp atoms have induced magnetic moments due to the proximity of Fe first nearest neighbors, which couple antiferromagnetically with Fe and Mn spin moments. We have employed full-potential linearized augmented plane wave method based on spin-polarized density functional theory. The generalized gradient approximation exchange-correlation potential was used. The edge of optical absorption for {epsilon}{sub 2}({omega}) of spin-down varies between 0.507 (Fe{sub 2}MnGe) and 0.547 eV (Fe{sub 2}MnSi). Since the spin-up shows metallic nature, the Drude term was included in the spin-up optical dielectric functions. This confirms our finding that these materials are half-metallic. Furthermore, the reflectivity, refractivity and the absorption coefficient were calculated. These results show that the materials possess half-metallic character. - Highlights: Black-Right-Pointing-Pointer The optical dielectric functions of Fe{sub 2}MnSi{sub 1-x}Ge{sub x} were investigated. Black-Right-Pointing-Pointer Fe{sub 2}MnSi{sub x}Ge{sub 1-x} is semiconducting for majority spin and is metallic for minority spin. Black-Right-Pointing-Pointer The total magnetic moment is found to be 3.0{mu}{sub B} for all alloys. Black-Right-Pointing-Pointer The edge of optical absorption for {epsilon}{sub 2
Phase equilibrium of the Gd-Fe-Co system at 873 K
International Nuclear Information System (INIS)
Huang Jinli; Zhong Haichang; Xia Xiuwen; He Wei; Zhu Jinming; Deng Jianqiu; Zhuang Yinghong
2009-01-01
Phase equilibrium of the ternary Gd-Fe-Co system at 873 K was investigated by using X-ray diffraction technique, electron probe microanalysis, metallographic analysis and differential thermal analysis. The 873 K isothermal section of the phase diagram of the Gd-Fe-Co ternary system consists of 11 single-phase regions, 16 two-phase regions and 6 three-phase regions. Three pairs of corresponding compounds of Gd-Co and Gd-Fe, i.e., Gd 2 Co 17 and Gd 2 Fe 17 , GdCo 3 and GdFe 3 , GdCo 2 and GdFe 2 , form a continuous series of solid solution. The compound Gd 2 Co 7-x Fe x was found to have a broad solubility range from 0 to 31 at.% Fe. The maximum solubility of Co in Gd 6 Fe 23 is about 7 at.% Co. At 873 K, the maximum solubilities of Fe in Gd 3 Co and Gd 4 Co 3 are about 3 and 1 at.% Fe, respectively. No ternary compound was found in all ternary alloy samples
Anomalous superconducting spin-valve effect in NbN/FeN/Cu/FeN/FeMn multilayers
Energy Technology Data Exchange (ETDEWEB)
Hwang, Tae Jong; Kim, Dong Ho [Yeungnam University, Gyeongsan (Korea, Republic of)
2017-09-15
We have studied magnetic and transport properties of NbN/FeN/Cu/FeN/FeMn spin-valve structure. In-plane magnetic moment exhibited typical hysteresis loops of spin valves in the normal state of NbN film at 20 K. On the other hand, the magnetic hysteresis loop in the superconducting state exhibited more complex behavior in which exchange bias provided by antiferrmagnetic FeMn layer to adjacent FeN layer was disturbed by superconductivity. Because of this, the ideal superconducting spin-valve effect was not detected. Instead the stray field originated from unsaturated magnetic states dominated the transport properties of NbN/FeN/Cu/FeN/FeMn multilayer.
Enthalpy of mixing of liquid Cu-Fe-Hf alloys at 1873 K
Energy Technology Data Exchange (ETDEWEB)
Agraval, Pavel; Turchanin, Mikhail [Donbass State Engineering Academy, Kramatorsk (Ukraine). Metallurgical Dept.; Dreval, Liya [Donbass State Engineering Academy, Kramatorsk (Ukraine). Metallurgical Dept.; Materials Science International Services GmbH (MSI), Stuttgart (Germany)
2016-12-15
In the ternary Cu-Fe-Hf system, the mixing enthalpies of liquid alloys were investigated at 1873 K using a high-temperature isoperibolic calorimeter. The experiments were performed along the sections x{sub Cu}/x{sub Fe} = 3/1, 1/1 at x{sub Hf} = 0-0.47 and along the section x{sub Cu}/x{sub Fe} = 1/3 at x{sub Hf} = 0-0.13. The limiting partial enthalpies of mixing of undercooled liquid hafnium in liquid Cu-Fe alloys, Δ{sub mix} anti H{sub Hf}{sup ∞}, are (-122 ± 9) kJ mol{sup -1} (section x{sub Cu}/x{sub Fe} = 3/1), (-106 ± 9) kJ mol{sup -1} (section x{sub Cu}/x{sub Fe} = 1/1), and (-105 ± 2) kJ mol{sup -1} (section x{sub Cu}/x{sub Fe} = 1/3). In the investigated composition range, the integral mixing enthalpies are sign-changing. For the integral mixing enthalpy, an analytical expression was obtained by the least squares fit of the experimental results using the Redlich-Kister-Muggianu polynomial.
Energy Technology Data Exchange (ETDEWEB)
Rahimi, Hamed; Ghasemi, Ali, E-mail: ali13912001@yahoo.com; Mozaffarinia, Reza; Tavoosi, Majid
2017-02-15
In current work, Nd2Fe14B nanoparticles was synthesized by sol-gel method. Dysprosium powders were added into Nd2Fe14B nanoparticles by mechanical alloying process in order to enhancement of coercivity. The phase analysis, structure, and magnetic properties of annealed (Nd{sub 1−x}Dy{sub x}){sub 2}Fe{sub 14}B nanoparticles with different Dy-content (x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6) were investigated by employing X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive spectroscopy, field emission scanning electron microscope, transmission electron microscope and vibrating sample magnetometer techniques. The results showed that with an increase in Dy amounts, the coercivity of particles increased from 2.9 kOe to 13.4 kOe and then decreased to 5.6 kOe. By adding an optimum amount of Dy (x=0.4), the coercivity was significantly increased from 2.9 kOe to 13.4 kOe. The average particle size of annealed (Nd{sub 1−x}Dy{sub x}){sub 2}Fe{sub 14}B nanoparticles was below 10 nm. Magnetization reversal studies indicate that the coercivity of milled and annealed (Nd{sub 1−x}Dy{sub x}){sub 2}Fe{sub 14}B nanoparticles is controlled by the nucleation of reversed magnetic domains. The experimental results in the angular dependence of coercivity for (Nd{sub 1−x}Dy{sub x}){sub 2}Fe{sub 14}B permanent magnets showed that the normalized coercivity of the permanent magnets H{sub c}(θ)/H{sub c}(0) increases from 1 to about 1.2–1.5 with increasing θ from 0 to about π/3, for x=0.4–0.6. - Highlights: • Dy was added to Nd{sub 2}Fe{sub 14}B nanoparticles to improve the coercivity. • A maximum squareness ratio of 0.99 was obtained. • The average particle size decreased with an increase in Dy-content.
Room temperature multiferroic properties of (Fe{sub x}, Sr{sub 1−x})TiO{sub 3} thin films
Energy Technology Data Exchange (ETDEWEB)
Kim, Kyoung-Tae; Kim, Cheolbok; Fang, Sheng-Po; Yoon, Yong-Kyu, E-mail: ykyoon@ece.ufl.edu [Department of Electrical and Computer Engineering, University of Florida, Gainesville, Florida 32611 (United States)
2014-09-08
This letter reports the structural, dielectric, ferroelectric, and magnetic properties of Fe substituted SrTiO{sub 3} thin films in room temperature. The structural data obtained from x-ray diffraction indicates that (Fe{sub x},Sr{sub 1−x})TiO{sub 3}, the so called FST, transforms from pseudocubic to tetragonal structures with increase of the Fe content in SrTiO{sub 3} thin films, featuring the ferroelectricity, while vibrating sample magnetometer measurements show magnetic hysteresis loops for the samples with low iron contents indicating their ferromagnetism. The characterized ferroelectricity and ferromagnetism confirms strong multiferroitism of the single phase FST thin films in room temperature. Also, an FST thin film metal-insulator-metal multiferroic capacitor has been fabricated and characterized in microwave frequencies between 10 MHz and 5 GHz. A capacitor based on Fe{sub 0.1}Sr{sub 0.9}TiO{sub 3} with a thickness of 260 nm shows a high electric tunability of 18.6% at 10 V and a maximum magnetodielectric value of 1.37% at 0.4 mT with a loss tangent of 0.021 at 1 GHz. This high tuning and low loss makes this material as a good candidate for frequency agile microwave devices such as tunable filters, phase shifters, and antennas.