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Sample records for compound-based diluted magnetic

  1. Magnetic properties of diluted magnetic semiconductors

    NARCIS (Netherlands)

    Jonge, de W.J.M.; Swagten, H.J.M.

    1991-01-01

    A review will be given of the magnetic characteristics of diluted magnetic semiconductors and the relation with the driving exchange mechanisms. II–VI as well as IV–VI compounds will be considered. The relevance of the long-range interaction and the role of the carrier concentration will be

  2. Ab-initio calculations of Co-based diluted magnetic semiconductors Cd 1-xCoxX (X=S, Se, Te)

    KAUST Repository

    Saeed, Yasir; Nazir, Safdar; Shaukat, Ali; Reshak, A. H.

    2010-01-01

    Ab-initio calculations are performed to investigate the structural, electronic and magnetic properties of spin-polarized diluted magnetic semiconductors composed of IIVI compounds Cd1-xCoxX (X=S, Se, Te) at x=0.25. From the calculated results

  3. Diluted magnetic semiconductor nanowires exhibiting magnetoresistance

    Science.gov (United States)

    Yang, Peidong [El Cerrito, CA; Choi, Heonjin [Seoul, KR; Lee, Sangkwon [Daejeon, KR; He, Rongrui [Albany, CA; Zhang, Yanfeng [El Cerrito, CA; Kuykendal, Tevye [Berkeley, CA; Pauzauskie, Peter [Berkeley, CA

    2011-08-23

    A method for is disclosed for fabricating diluted magnetic semiconductor (DMS) nanowires by providing a catalyst-coated substrate and subjecting at least a portion of the substrate to a semiconductor, and dopant via chloride-based vapor transport to synthesize the nanowires. Using this novel chloride-based chemical vapor transport process, single crystalline diluted magnetic semiconductor nanowires Ga.sub.1-xMn.sub.xN (x=0.07) were synthesized. The nanowires, which have diameters of .about.10 nm to 100 nm and lengths of up to tens of micrometers, show ferromagnetism with Curie temperature above room temperature, and magnetoresistance up to 250 Kelvin.

  4. Initial magnetic susceptibility of the diluted magnetopolymer elastic composites

    International Nuclear Information System (INIS)

    Borin, D.Yu.; Odenbach, S.

    2017-01-01

    In this work diluted magnetopolymer elastic composites based on magnetic microparticles are experimentally studied. Considered samples have varied concentration of the magnetic powder and different structural anisotropy. Experimental data on magnetic properties are accomplished by microstructural observations performed using X-Ray tomography. Influence of the particles amount and structuring effects on the initial magnetic susceptibility of the composites as well as the applicability of the Maxwell-Garnett approximation, which is widely used in considerations of magnetopolymer elastic composites, are evaluated. It is demonstrated that the approximation works well for diluted samples containing randomly distributed magnetic particles and for the diluted samples with chain-like structures oriented perpendicular to an externally applied field, while it fails to predict the susceptibility of the samples with structures oriented parallel to the field. Moreover, it is shown, that variation of the chains morphology does not significantly change the composite initial magnetic susceptibility. - Highlights: • The Maxwell-Garnet prediction works well for the diluted isotropic composites. • The Maxwell-Garnet prediction can be used for composites with structures oriented perpendicular to an applied field. • Chains oriented parallel to an applied field significantly increase the composite initial magnetic susceptibility. • The number and thickness of chains is not of the highest importance for the diluted composites. • The crucial reason of the observed effect is expected to be the demagnetisation factor of the chains.

  5. Ultrafast magnetization dynamics in diluted magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Morandi, O [INRIA Nancy Grand-Est and Institut de Recherche en Mathematiques Avancees, 7 rue Rene Descartes, F-67084 Strasbourg (France); Hervieux, P-A; Manfredi, G [Institut de Physique et Chimie des Materiaux de Strasbourg, 23 rue du Loess, F-67037 Strasbourg (France)], E-mail: morandi@dipmat.univpm.it

    2009-07-15

    We present a dynamical model that successfully explains the observed time evolution of the magnetization in diluted magnetic semiconductor quantum wells after weak laser excitation. Based on the pseudo-fermion formalism and a second-order many-particle expansion of the exact p-d exchange interaction, our approach goes beyond the usual mean-field approximation. It includes both the sub-picosecond demagnetization dynamics and the slower relaxation processes that restore the initial ferromagnetic order in a nanosecond timescale. In agreement with experimental results, our numerical simulations show that, depending on the value of the initial lattice temperature, a subsequent enhancement of the total magnetization may be observed within the timescale of a few hundred picoseconds.

  6. Novel aspects of diluted and digital magnetic heterostructures

    International Nuclear Information System (INIS)

    Bonanni, A.

    1999-04-01

    In the present work novel aspects of diluted and digital II-VI-based heterostructures containing Mn ions are investigated. All the structures under study were fabricated by means of molecular beam epitaxy. Digital magnetic heterostructures have been prepared by incorporating discrete (sub)monolayers of the purely magnetic semiconductor MnTe into otherwise non magnetic CdTe quantum wells embedded in CdMgTe barriers. Formation and binding energy of magnetic polarons have been investigated in these structures and compared with the diluted case. Reflectance difference spectroscopy (RDS) performed ex-situ allowed to distinguish between signals due to the crystal anisotropy solely and those induced by the presence a magnetic elements. The problem of p-type doping of bulk diluted magnetic semiconductors II-VI-based is tackled. During and upon growth of ZnMnTe highly doped with N, in-situ RDS was carried out in order to investigate intra-ion transitions within the half filled 3d shell of Mn. Transport measurements and magnetometry at low temperature were performed to study, on the tracks of recent theoretical works, the influence of free carriers on the interaction between magnetic ions. As expected, indications of ferromagnetic ordering were found for the DMS with the highest concentration of carriers. Special attention was given to the formation of Mn islands on a II-VI substrate and to their change in morphology upon overgrowth with a mismatched material. A rich zoology of regularly shaped nanostructures could be produced. (author)

  7. Specific heat in diluted magnetic semiconductor quantum ring

    Science.gov (United States)

    Babanlı, A. M.; Ibragimov, B. G.

    2017-11-01

    In the present paper, we have calculated the specific heat and magnetization of a quantum ring of a diluted magnetic semiconductor (DMS) material in the presence of magnetic field. We take into account the effect of Rashba spin-orbital interaction, the exchange interaction and the Zeeman term on the specific heat. We have calculated the energy spectrum of the electrons in diluted magnetic semiconductor quantum ring. Moreover we have calculated the specific heat dependency on the magnetic field and Mn concentration at finite temperature of a diluted magnetic semiconductor quantum ring.

  8. Experimentally evaluating the origin of dilute magnetism in nanomaterials

    International Nuclear Information System (INIS)

    Pereira, L M C

    2017-01-01

    Reports of room-temperature ferromagnetism continue to emerge for an ever-growing range of nanomaterials with a small or even vanishing concentration of magnetic atoms. Dilute magnetic semiconductors (DMS) are the most representative class of such materials, but similar magnetic properties have been reported in many others. Challenging our understanding of magnetic order in solids, as well as our ability to experimentally assess it, these remarkable magnetic phenomena have become one of the most controversial topics in magnetism. Various non-intrinsic sources of ferromagnetism (e.g. instrumental artifacts and magnetic contamination) are becoming well documented, and rarely are all of them taken into account when room-temperature ferromagnetism is reported. This topical review is intended to serve as a guide when evaluating to what extent a given data set supports the claim of intrinsic ferromagnetism in dilute nanomaterials. It compiles the most relevant sources of non-intrinsic ferromagnetism which have been reported, as well as guidelines for how to minimize them. It also provides an overview of complementary structural and magnetic characterization techniques which can be combined to provide different levels of scrutiny of the intrinsic nature of experimentally observed ferromagnetism. In particular, it gives some notable examples of how comprehensive studies based on those techniques have led to a remarkably detailed understanding of model DMS materials, with strong evidence of absence of room-temperature ferromagnetism. Although mostly based on DMS research, this review provides a set of guidelines and cautionary notes of broader relevance, including some emerging new fields of dilute nanomagnetism such as magnetically doped 3D topological insulators, 3D Dirac semimetals, and 2D materials. (topical review)

  9. Experimentally evaluating the origin of dilute magnetism in nanomaterials

    Science.gov (United States)

    Pereira, L. M. C.

    2017-10-01

    Reports of room-temperature ferromagnetism continue to emerge for an ever-growing range of nanomaterials with a small or even vanishing concentration of magnetic atoms. Dilute magnetic semiconductors (DMS) are the most representative class of such materials, but similar magnetic properties have been reported in many others. Challenging our understanding of magnetic order in solids, as well as our ability to experimentally assess it, these remarkable magnetic phenomena have become one of the most controversial topics in magnetism. Various non-intrinsic sources of ferromagnetism (e.g. instrumental artifacts and magnetic contamination) are becoming well documented, and rarely are all of them taken into account when room-temperature ferromagnetism is reported. This topical review is intended to serve as a guide when evaluating to what extent a given data set supports the claim of intrinsic ferromagnetism in dilute nanomaterials. It compiles the most relevant sources of non-intrinsic ferromagnetism which have been reported, as well as guidelines for how to minimize them. It also provides an overview of complementary structural and magnetic characterization techniques which can be combined to provide different levels of scrutiny of the intrinsic nature of experimentally observed ferromagnetism. In particular, it gives some notable examples of how comprehensive studies based on those techniques have led to a remarkably detailed understanding of model DMS materials, with strong evidence of absence of room-temperature ferromagnetism. Although mostly based on DMS research, this review provides a set of guidelines and cautionary notes of broader relevance, including some emerging new fields of dilute nanomagnetism such as magnetically doped 3D topological insulators, 3D Dirac semimetals, and 2D materials.

  10. Introduction to the Physics of Diluted Magnetic Semiconductors

    CERN Document Server

    Gaj, Jan A

    2010-01-01

    The book deals with diluted magnetic semiconductors, a class of materials important to the emerging field of spintronics. In these materials semiconducting properties, both transport and optical, are influenced by the presence of magnetic ions. It concentrates on basic physical mechanisms (e.g. carrier-ion and ion-ion interactions) and resulting phenomena (e.g. magnetic polaron formation and spin relaxation). Introduction to the Physics of Diluted Magnetic Semiconductors is addressed to graduate-level and doctoral students and young researchers entering the field. The authors have been actively involved in the creation of this branch of semiconductor physics.

  11. Ab-initio calculations of Co-based diluted magnetic semiconductors Cd 1-xCoxX (X=S, Se, Te)

    KAUST Repository

    Saeed, Yasir

    2010-10-01

    Ab-initio calculations are performed to investigate the structural, electronic and magnetic properties of spin-polarized diluted magnetic semiconductors composed of IIVI compounds Cd1-xCoxX (X=S, Se, Te) at x=0.25. From the calculated results of band structure and density of states, the half-metallic character and stability of ferromagnetic state for Cd1-xCoxS, Cd1-xCoxSe and Cd 1-xCoxTe alloys are determined. It is found that the tetrahedral crystal field gives rise to triple degeneracy t2g and double degeneracy eg. Furthermore, we predict the values of spin-exchange splitting energies Δx(d) and Δ x(p-d) and exchange constants N0α and N 0β produced by the Co 3d states. Calculated total magnetic moments and the robustness of half-metallicity of Cd1-xCo xX (X=S, Se, Te) with respect to the variation in lattice parameters are also discussed. We also extend our calculations to x=0.50, 0.75 for S compounds in order to observe the change due to increase in Co. © 2010 Elsevier B.V.

  12. Hall effect driven by non-collinear magnetic polarons in diluted magnetic semiconductors

    Science.gov (United States)

    Denisov, K. S.; Averkiev, N. S.

    2018-04-01

    In this letter, we develop the theory of Hall effect driven by non-collinear magnetic textures (topological Hall effect—THE) in diluted magnetic semiconductors (DMSs). We show that a carrier spin-orbit interaction induces a chiral magnetic ordering inside a bound magnetic polaron (BMP). The inner structure of non-collinear BMP is controlled by the type of spin-orbit coupling, allowing us to create skyrmion- (Rashba) or antiskyrmion-like (Dresselhaus) configurations. The asymmetric scattering of itinerant carriers on polarons leads to the Hall response which exists in weak external magnetic fields and at low temperatures. We point out that DMS-based systems allow one to investigate experimentally the dependence of THE both on a carrier spin polarization and on a non-collinear magnetic texture shape.

  13. Enhancement of surface magnetism due to bulk bond dilution

    International Nuclear Information System (INIS)

    Tsallis, C.; Sarmento, E.F.; Albuquerque, E.L. de

    1985-01-01

    Within a renormalization group scheme, the phase diagram of a semi-infinite simple cubic Ising ferromagnet is discussed, with arbitrary surface and bulk coupling constants, and including possible dilution of the bulk bonds. It is obtained that dilution makes easier the appearance of surface magnetism in the absence of bulk magnetism. (Author) [pt

  14. EDITORIAL: Focus on Dilute Magnetic Semiconductors FOCUS ON DILUTE MAGNETIC SEMICONDUCTORS

    Science.gov (United States)

    Chambers, Scott A.; Gallagher, Bryan

    2008-05-01

    Chisholm, J D Budai and D P Norton Role of charge carriers for ferromagnetism in cobalt-doped rutile TiO2 T Fukumura, H Toyosaki, K Ueno, M Nakano and M Kawasaki Ab-initio study of exchange constants and electronic structure in diluted magnetic group-IV semiconductors Silvia Picozzi and Marjana Ležaić Phase coherent transport in (Ga,Mn)As D Neumaier, K Wagner, U Wurstbauer, M Reinwald, W Wegscheider and D Weiss Hydrogen interstitials-mediated ferromagnetism in MnxGe1-x magnetic semiconductors Xin-Xin Yao, Shi-Shen Yan, Shu-Jun Hu, Xue-Ling Lin, Chong Han, Yan-Xue Chen, Guo-Lei Liu and Liang-Mo Mei Electronic structures of magnetic semiconductors FeCr2Se4 and Fe0.5Cu0.5Cr2Se4 B I Min, Seung Su Baik, H C Choi, S K Kwon and J-S Kang Investigation of pure and Co2+-doped ZnO quantum dot electronic structures using the density functional theory: choosing the right functional Ekaterina Badaeva, Yong Feng, Daniel R Gamelin and Xiaosong Li Magnetic properties of sol-gel-derived doped ZnO as a potential ferromagnetic semiconductor: a synchrotron-based study N R S Farley, K W Edmonds, A A Freeman, G van der Laan, C R Staddon, D H Gregory and B L Gallagher Local electronic structure of Cr in the II-VI diluted ferromagnetic semiconductor Zn1-xCrxTe M Kobayashi, Y Ishida, J I Hwang, G S Song, A Fujimori, C S Yang, L Lee, H-J Lin, D J Huang, C T Chen, Y Takeda, K Terai, S-I Fujimori, T Okane, Y Saitoh, H Yamagami, K Kobayashi, A Tanaka, H Saito and K Ando Lack of ferromagnetism in n-type cobalt-doped ZnO epitaxial thin films T C Kaspar, T Droubay, S M Heald, P Nachimuthu, C M Wang, V Shutthanandan, C A Johnson, D R Gamelin and S A Chambers XMCD studies on Co and Li doped ZnO magnetic semiconductors Thomas Tietze, Milan Gacic, Gisela Schütz, Gerhard Jakob, Sebastian Brück and Eberhard Goering Ferromagnetic semiconductors and the role of disorder B W Wessels An extensive comparison of anisotropies in MBE grown (Ga,Mn)As material C Gould, S Mark, K Pappert, R G Dengel, J Wenisch, R P

  15. Time-resolved optically-detected magnetic resonance of II-VI diluted-magnetic-semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, V.Yu.; Karczewski, G. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Godlewski, M. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Dept. Mathem. and Natural Sci. College of Sci., Card. S. Wyszynski Univ., Warsaw (Poland); Yakovlev, D.R. [Experimental Physics 2, University of Dortmund, 44221 Dortmund (Germany); A. F. Ioffe Physico-Technical Institute, 194017 St. Petersburg (Russian Federation); Ryabchenko, S.M. [Institute of Physics NAS Ukraine, 03028 Kiev (Ukraine); Waag, A. [Institute of Semiconductor Technology, Braunschweig Technical University, 38106 Braunschweig (Germany)

    2007-01-15

    Time-resolved optically-detected magnetic resonance (ODMR) technique was used to study spin dynamics of Mn{sup 2+} ions in (Zn,Mn)Se- and (Cd,Mn)Te-based diluted magnetic semiconductor quantum wells. Times of spin-lattice relaxation have been measured directly from a dynamical shift of exciton luminescence lines after a pulsed impact of 60 GHz microwave radiation. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Entanglement and Zeeman interaction in diluted magnetic semiconductor quantum dot

    International Nuclear Information System (INIS)

    Hichri, A.; Jaziri, S.

    2004-01-01

    We present theoretically the Zeeman coupling and exchange-induced swap action in spin-based quantum dot quantum computer models in the presence of magnetic field. We study the valence and conduction band states in a double quantum dots made in diluted magnetic semiconductor. The latter have been proven to be very useful in building an all-semiconductor platform for spintronics. Due to a strong p-d exchange interaction in diluted magnetic semiconductor (Cd 0.57 Mn 0.43 Te), the relative contribution of this component is strongly affected by an external magnetic field, a feature that is absent in nonmagnetic double quantum dots. We determine the energy spectrum as a function of magnetic field within the Hund-Mulliken molecular-orbit approach and by including the Coulomb interaction. Since we show that the ground state of the two carriers confined in a vertically coupled quantum dots provide a possible realization for a gate of a quantum computer, the crossing between the lowest states, caused by the giant spin splitting, can be observed as a pronounced jump in the magnetization of small magnetic field amplitude. Finally, we determine the swap time as a function of magnetic field and the inter dot distance. We estimate quantitatively swap errors caused by the field, establishing that error correction would, in principle, be possible in the presence of nonuniform magnetic field in realistic structures

  17. Coexistence of magnetism and superconductivity in the hole doped FeAs-based superconducting compound

    International Nuclear Information System (INIS)

    Lu, T.P.; Wu, C.C.; Chou, W.H.; Lan, M.D.

    2010-01-01

    The magnetic and superconducting properties of the Sm-doped FeAs-based superconducting compound were investigated under wide ranges of temperature and magnetic field. After the systematical magnetic ion substitution, the superconducting transition temperature decreases with increasing magnetic moment. The hysteresis loop of the La 0.87-x Sm x Sr 0.13 FeAsO sample shows a superconducting hysteresis and a paramagnetic background signal. The paramagnetic signal is mainly attributed to the Sm moments. The experiment demonstrates that the coexistence of magnetism and superconductivity in the hole doped FeAs-based superconducting compounds is possible. Unlike the electron doped FeAs-based superconducting compounds SmFeAsOF, the hole doped superconductivity is degraded by the substitution of La by Sm. The hole-doped and electron-doped sides are not symmetric.

  18. Li(Zn,Co,MnAs: A bulk form diluted magnetic semiconductor with Co and Mn co-doping at Zn sites

    Directory of Open Access Journals (Sweden)

    Bijuan Chen

    2016-11-01

    Full Text Available We report the synthesis and characterization of a series of bulk forms of diluted magnetic semiconductors Li(Zn1-x-yCoxMnyAs with a crystal structure close to that of III-V diluted magnetic semiconductor (Ga,MnAs. No ferromagnetic order occurs with single (Zn,Co or (Zn, Mn substitution in the parent compound LiZnAs. Only with co-doped Co and Mn ferromagnetic ordering can occur at the Curie temperature ∼40 K. The maximum saturation moment of the this system reached to 2.17μB/Mn, which is comparable to that of Li (Zn,MnAs. It is the first time that a diluted magnetic semiconductor with co-doping Co and Mn into Zn sites is achieved in “111” LiZnAs system, which could be utilized to investigate the basic science of ferromagnetism in diluted magnetic semiconductors. In addition, ferromagnetic Li(Zn,Co,MnAs, antiferromagnetic LiMnAs, and superconducting LiFeAs share square lattice at As layers, which may enable the development of novel heterojunction devices in the future.

  19. Structural, morphological and magnetic analysis of Cd–Co–S dilute magnetic semiconductor nanofilms

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Suresh [Department of Physics and Materials Science, Jaypee University of Information Technology, Waknaghat, Solan, Himachal Pradesh 173234 (India); Negi, N.S. [Department of Physics, Himachal Pradesh University, Summer Hill, Shimla, Himachal Pradesh 171005 (India); Katyal, S.C. [Department of Physics, Jaypee Institute of Information Technology, Sec-128, Noida, Uttar Pradesh 201301 (India); Sharma, Pankaj, E-mail: pankaj.sharma@juit.ac.in [Department of Physics and Materials Science, Jaypee University of Information Technology, Waknaghat, Solan, Himachal Pradesh 173234 (India); Sharma, Vineet [Department of Physics and Materials Science, Jaypee University of Information Technology, Waknaghat, Solan, Himachal Pradesh 173234 (India)

    2014-10-01

    Cd{sub 1−x}Co{sub x}S dilute magnetic semiconductor nanofilms (0≤x≤0.08 at%) deposited by chemical bath deposition have been investigated using grazing angle x-ray diffraction, atomic force microscopy and vibrating sample magnetometer. The introduction of Co{sup 2+} ions in CdS structure induces structural disorders and hence, results in degradation of crystallinity. The crystallite size, interplanar spacing and lattice parameter ratio decrease with increasing Co{sup 2+} concentration in CdS. The diamagnetic state of CdS disappears with increase in Co concentration and films with x>0.02 exhibit ferromagnetism. This may be explained in terms of the spin–orbit interactions and Co{sup 2+} ion induced the lattice defects and phase separation. - Highlights: • Cd{sub 1−x}Co{sub x}S dilute magnetic semiconductor nanofilms (0≤x≤0.08 at%) deposited by CBD. • The diamagnetic state of CdS vanishes for x=0.02. • For x>0.02, dilute magnetic semiconductor nanofilms shows a ferromagnetic state.

  20. Optical investigation of effective permeability of dilute magnetic dielectrics with magnetic field

    Science.gov (United States)

    Banerjee, Ananya; Sarkar, A.

    2016-05-01

    The prime objective of this paper is to investigate the magnetic nature of dilute magnetic dielectrics (DMD) under variation of external magnetic field. The said variation is studied over developed nano-sized Gadolinium Oxide as a DMD system. The observed experimental field variation of the effective magnetic permeability is analyzed results of optical experiment. The experiment records the variation of Brewster angle of incident polarized LASER beam from the surface of developed DMD specimen with applied out of plane external magnetic field. The effective refractive index and hence relative magnetic permeability were estimated following electro-magnetic theory. The overall results obtained and agreement between theory and experiment are good.

  1. Optical investigation of effective permeability of dilute magnetic dielectrics with magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Ananya, E-mail: banerjee.ananya2008@gmail.com; Sarkar, A. [Dept. of Physics, Bijoy Krishna Girls’ College, 5/3 M.G. Road, Howrah 711101, W.B. (India)

    2016-05-06

    The prime objective of this paper is to investigate the magnetic nature of dilute magnetic dielectrics (DMD) under variation of external magnetic field. The said variation is studied over developed nano-sized Gadolinium Oxide as a DMD system. The observed experimental field variation of the effective magnetic permeability is analyzed results of optical experiment. The experiment records the variation of Brewster angle of incident polarized LASER beam from the surface of developed DMD specimen with applied out of plane external magnetic field. The effective refractive index and hence relative magnetic permeability were estimated following electro-magnetic theory. The overall results obtained and agreement between theory and experiment are good.

  2. Quest for high-Curie temperature MnxGe1-x diluted magnetic semiconductors for room-temperature spintronics applications

    Science.gov (United States)

    Nie, Tianxiao; Tang, Jianshi; Wang, Kang L.

    2015-09-01

    In this paper, we report the non-equilibrium growth of various Mn-doped Ge dilute magnetic semiconductor nanostructures using molecular-beam epitaxy, including quantum dots, nanodisks and nanowires. Their detailed structural and magnetic properties are characterized. By comparing the results with those in MnxGe1-x thin films, it is affirmed that the use of nanostructures helps eliminate crystalline defects and meanwhile enhance the carrier-mediate ferromagnetism from substantial quantum confinements. Our systematic studies provide a promising platform to build nonvolatile spinFET and other novel spintronic devices based upon dilute magnetic semiconductor nanostructures.

  3. Mössbauer Studies of dilute Magnetic Semiconductors

    CERN Multimedia

    Gislason, H P; Debernardi, A; Dlamini, W B

    2002-01-01

    The recent discovery of (dilute) magnetic semiconductors with wide band gaps, e.g. GaN, ZnO and other oxides, having Curie temperatures, T$_{\\textrm{c}}$, well above room temperature, has prompted extraordinary experimental and theoretical efforts to understand, control and exploit this unexpected finding not least in view of the obvious potential of such materials for the fabrication of "spin-(elec)tronic" or magneto-optic devices. Ferromagnetism (FM) was achieved mostly by doping with dilute 3d transition metal impurities, notably Mn, Fe, and Co (in \\% concentrations), during growth or by subsequent ion implantation. However, it is fair to state that experimentally the conditions for the occurrence of ferro-, antiferro- or paramagnetism with these impurities are not yet controlled as generally at least two conflicting forms of magnetism or none have been reported for each system - albeit often produced by different techniques. Theory is challenged as "conventional" models seem to fail and no generally accep...

  4. Low temperature anomaly of light stimulated magnetization and heat capacity of the 1D diluted magnetic semiconductors

    Science.gov (United States)

    Geffe, Chernet Amente

    2018-03-01

    This article reports magnetization and specific heat capacity anomalies in one dimensional diluted magnetic semiconductors observed at very low temperatures. Based on quantum field theory double time temperature dependent Green function technique is employed to evaluate magnon dispersion and the time correlation function. It is understood that magnon-photon coupling and magnetic impurity concentration controls both, such that near absolute temperature magnetization is nearly zero and abruptly increase to saturation level with decreasing magnon-photon coupling strength. We also found out dropping of magnetic specific heat capacity as a result of increase in magnetic impurity concentration x, perhaps because of inter-band disorder that would suppress the enhancement of density of spin waves.

  5. Low temperature anomaly of light stimulated magnetization and heat capacity of the 1D diluted magnetic semiconductors

    Directory of Open Access Journals (Sweden)

    Chernet Amente Geffe

    2018-03-01

    Full Text Available This article reports magnetization and specific heat capacity anomalies in one dimensional diluted magnetic semiconductors observed at very low temperatures. Based on quantum field theory double time temperature dependent Green function technique is employed to evaluate magnon dispersion and the time correlation function. It is understood that magnon-photon coupling and magnetic impurity concentration controls both, such that near absolute temperature magnetization is nearly zero and abruptly increase to saturation level with decreasing magnon-photon coupling strength. We also found out dropping of magnetic specific heat capacity as a result of increase in magnetic impurity concentration x, perhaps because of inter-band disorder that would suppress the enhancement of density of spin waves.

  6. Transverse gradient diffusion in a polydisperse dilute suspension of magnetic spheres during sedimentation

    International Nuclear Information System (INIS)

    Cunha, F R; Couto, H L G

    2008-01-01

    In this work we investigate the pair interaction of magnetic particles in a dilute polydisperse sedimenting suspension. The suspension is composed of magnetic spherical forms of different radii and densities immersed in a Newtonian fluid, settling due to the gravity. When in close contact, the particles may exert on each other a magnetic force due to a permanent magnetization. We restrict our attention to dispersions of micromagnetic composite with negligible Brownian motion. The calculations of the relative particle trajectories are based on direct computations of the hydrodynamic interactions among rigid spheres in the regime of low particle Reynolds number. Depending on the relative importance of the interparticle forces and gravity, the collisions may result in aggregation or simply in a breaking of the particle relative trajectory time reversibility. After summing over all possible encounters, the transverse self-diffusion and down-gradient diffusion coefficients that describe the cross-flow migration of the particles are calculated. Our calculation shows first evidence and the significance of the diffusion process arising from magnetic interactions in dilute non-Brownian suspensions

  7. Transverse gradient diffusion in a polydisperse dilute suspension of magnetic spheres during sedimentation

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, F R; Couto, H L G [Departamento de Engenharia Mecanica, Universidade de Brasilia, Faculdade de Tecnologia, Grupo de Mecanica dos Fluidos de Escoamentos Complexos-VORTEX, Campus Universitario Darcy Ribeiro, 70910-900, Brasilia, DF (Brazil)], E-mail: frcunha@unb.br

    2008-05-21

    In this work we investigate the pair interaction of magnetic particles in a dilute polydisperse sedimenting suspension. The suspension is composed of magnetic spherical forms of different radii and densities immersed in a Newtonian fluid, settling due to the gravity. When in close contact, the particles may exert on each other a magnetic force due to a permanent magnetization. We restrict our attention to dispersions of micromagnetic composite with negligible Brownian motion. The calculations of the relative particle trajectories are based on direct computations of the hydrodynamic interactions among rigid spheres in the regime of low particle Reynolds number. Depending on the relative importance of the interparticle forces and gravity, the collisions may result in aggregation or simply in a breaking of the particle relative trajectory time reversibility. After summing over all possible encounters, the transverse self-diffusion and down-gradient diffusion coefficients that describe the cross-flow migration of the particles are calculated. Our calculation shows first evidence and the significance of the diffusion process arising from magnetic interactions in dilute non-Brownian suspensions.

  8. A theory for the anisotropic interaction between two substitutional magnetic impurities and the magnetic anisotropic effect in dilute magnetic alloys

    International Nuclear Information System (INIS)

    Satter, M.A.

    1990-08-01

    In this paper, a formalism for studying the anisotropic interaction between two substitutional magnetic impurities and the magnetic anisotropic effect in a dilute noble metal- transition metal magnetic alloy has been developed from relativistic scattering theory. The theoretical development and the computational techniques of this formalism are based on relativistic spin-polarized scattering theory and relativistic band structure frameworks. For studying the magnetic anisotropic effect a convenient ''working'' frame of reference with its axes oriented along the fcc crystal axes is set up. This formalism is applied to study the situation for two Fe impurities in paramagnetic Au hosts. For AuFe dilute alloy, the two impurity site interaction as a function of separation is not oscillatory and the anisotropic effect is found to be less than the two site interaction itself only by an order of magnitude. Apart from the anisotropic coupling of the two impurity spins to the separation vector, for the first time, another weak anisotropic coupling to the crystal axes is also contained in the two site interaction. These anisotropic effects are the results of the relativistic spin-orbit interaction which are incorporated into the formalism. (author). 22 refs, 5 figs

  9. Magnetic hyperfine field at a Cd impurity diluted in RCo{sub 2} at finite temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, A.L. de, E-mail: alexandre.oliveira@ifrj.edu.br [Instituto Federal de Educação, Ciência e Tecnologia do Rio de Janeiro, Campus Nilópolis – RJ (Brazil); Chaves, C.M., E-mail: cmch@cbpf.br [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro (Brazil); Oliveira, N.A. de [Instituto de Física Armando Dias Tavares, Universidade do Estado do Rio de Janeiro, Rio de Janeiro (Brazil); Troper, A. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro (Brazil)

    2015-06-15

    The local magnetic moments and the magnetic hyperfine fields at an s–p Cd impurity diluted in inter-metallic Laves phase compounds RCo{sub 2} (R=Gd, Tb) at finite temperatures are calculated. For other rare earth elements (light or heavy) the pure compounds display a magnetic first order transition and are not describable by our formalism. The host has two coupled lattices (R and Co) both having itinerant d electrons but only the rare earth lattice has localized f electrons. They all contribute to the magnetization of the host and also to the local moment and to the magnetic hyperfine field at the impurity. The investigation of magnetic hyperfine field in these materials then provides valuable information on the d-itinerant electrons and also on the localized (4f) magnetic moments. For the d–d electronic interaction we use the Hubbard–Stratonovich identity thus allowing the employment of functional integral in the static saddle point approximation. Our model reproduces quite well the experimental data. - Highlights: • A functional integral method in the static limit, producing site disorder, is used. • The site disorder is treated with the coherent potential approximation (CPA) • A Friedel sum rule gives a self-consistency condition for the impurity energy. • The experimental curve of hyperfine fields×temperature is very well reproduced.

  10. Nonequilibrium spin transport through a diluted magnetic semiconductor quantum dot system with noncollinear magnetization

    International Nuclear Information System (INIS)

    Ma, Minjie; Jalil, Mansoor Bin Abdul; Tan, Seng Gee

    2013-01-01

    The spin-dependent transport through a diluted magnetic semiconductor quantum dot (QD) which is coupled via magnetic tunnel junctions to two ferromagnetic leads is studied theoretically. A noncollinear system is considered, where the QD is magnetized at an arbitrary angle with respect to the leads’ magnetization. The tunneling current is calculated in the coherent regime via the Keldysh nonequilibrium Green’s function (NEGF) formalism, incorporating the electron–electron interaction in the QD. We provide the first analytical solution for the Green’s function of the noncollinear DMS quantum dot system, solved via the equation of motion method under Hartree–Fock approximation. The transport characteristics (charge and spin currents, and tunnel magnetoresistance (TMR)) are evaluated for different voltage regimes. The interplay between spin-dependent tunneling and single-charge effects results in three distinct voltage regimes in the spin and charge current characteristics. The voltage range in which the QD is singly occupied corresponds to the maximum spin current and greatest sensitivity of the spin current to the QD magnetization orientation. The QD device also shows transport features suitable for sensor applications, i.e., a large charge current coupled with a high TMR ratio. - Highlights: ► The spin polarized transport through a diluted magnetic quantum dot is studied. ► The model is based on the Green’s function and the equation of motion method.► The charge and spin currents and tunnel magnetoresistance (TMR) are investigated. ► The system is suitable for current-induced spin-transfer torque application. ► A large tunneling current and a high TMR are possible for sensor application.

  11. A plastic dilution refrigerator in a 35 T magnet

    International Nuclear Information System (INIS)

    Oliveira, N.F.Jr; Bindilatti, V.; Haar, E. ter; Martin, R.V.; McNiff, E.J.Jr.

    1996-01-01

    We have built a plastic dilution refrigerator, small enough to fit in the bore of the 35 T hybrid magnet at MIT. The base temperature at H = 0 was 20 mK, measured with a CMN thermometer. In the field, we used capacitive glass thermometers and Matsushita resistors. All data obtained were consistent with a field independent glass thermometer and a negligible magnetoresistance of the Matsushitas at high fields. The minimum temperature measured at 34 T was 25 mK. The effect of magnet vibrations as well as field sweeps (≅ 1 T/min) corresponded to less than 1 μW heating. We observed that, above 29 T, the temperature gradients existent inside the mixing chamber suddenly disappeared, with the temperature becoming homogeneous from top to bottom. We attribute this fact to the effect of the magnetic forces on the liquid. (author)

  12. Effect of Al doping on the magnetic and electrical properties of Zn(Cu)O based diluted magnetic semiconductors

    Science.gov (United States)

    Chakraborti, D.; Trichy, G.; Narayan, J.; Prater, J. T.; Kumar, D.

    2007-12-01

    The effect of Al doping on the magnetic properties of Zn(Cu)O based dilute magnetic semiconducting thin films has been systematically investigated. Epitaxial thin films have been deposited onto sapphire c-plane single crystals using pulsed laser deposition technique. X-ray diffraction and high resolution transmission electron microscopy studies show that the Zn(Cu,Al)O films are epitaxially grown onto (0001) sapphire substrates with a 30°/90° rotation in the basal plane. The large lattice misfit of the order of 16% is accommodated by matching integral multiples of lattice and substrate planes. In these large mismatch systems, the resulting films are fully relaxed following deposition of the first complete monolayer of ZnO (consistent with a critical thickness that is less than one monolayer). Magnetic hysteresis measurements indicate that the pure Zn(Cu)O thin films are ferromagnetic at room temperature. Doping with up to 5% Al (n type) does not significantly affect the ferromagnetism even though it results in an increase in carrier densities of more than 3 orders of magnitude, rising from 1×1017 to 1.5×1020 cm-3. However, for Al additions above 5%, a drop in net magnetization is observed. Annealing the films in an oxygen atmosphere at 600 °C also resulted in a dramatic drop in magnetic moment of the samples. These results strongly suggest that carrier induced exchange is not directly responsible for the magnetic properties of these materials. Rather, a defect mediated exchange mechanism needs to be invoked for this system.

  13. Properties of magnetically diluted nanocrystals prepared by mechanochemical route

    International Nuclear Information System (INIS)

    Balaz, P.; Skorvanek, I.; Fabian, M.; Kovac, J.; Steinbach, F.; Feldhoff, A.; Sepelak, V.; Jiang, J.; Satka, A.; Kovac, J.

    2010-01-01

    The bulk and surface properties of magnetically diluted Cd 0.6 Mn 0.4 S nanocrystals synthesized by solid state route in a planetary mill were studied. XRD, SEM, TEM (HRTEM), low-temperature N 2 sorption, nanoparticle size distribution as well as SQUID magnetometry methods have been applied. The measurements identified the aggregates of small nanocrystals, 5-10 nm in size. The homogeneity of produced particles with well developed specific surface area (15-66 m 2 g -1 ) was documented. The transition from the paramagnetic to the spin-glass-like phase has been observed below ∼40 K. The changes in the magnetic behaviour at low temperatures seem to be correlated with the formation of the new surface area as a consequence of milling. The magnetically diluted Cd 0.6 Mn 0.4 S nanocrystals are obtained in the simple synthesis step, making the process attractive for industrial applications.

  14. First-principles calculation on dilute magnetic alloys in zinc blend crystal structure

    International Nuclear Information System (INIS)

    Ullah, Hamid; Inayat, Kalsoom; Khan, S.A; Mohammad, S.; Ali, A.; Alahmed, Z.A.; Reshak, A.H.

    2015-01-01

    Ab-initio calculations are performed to investigate the structural, electronic and magnetic properties of spin-polarized diluted magnetic alloys in zinc blende structure. The first-principles study is carried out on Mn doped III–V semiconductors. The calculated band structures, electronic properties and magnetic properties of Ga 1−x Mn x X (X=P, As) compounds reveal that Ga 0.75 Mn 0.25 P is half metallic turned to be metallic with increasing x to 0.5 and 0.75, whereas substitute P by As cause to maintain the half-metallicity nature in both of Ga 0.75 Mn 0.25 As and Ga 0.5 Mn 0.5 As and tune Ga 0.25 Mn 0.75 As to be metallic. Calculated total magnetic moments and the robustness of half-metallicity of Ga 0.75 Mn 0.25 P, Ga 0.75 Mn 0.25 As and Ga 0.5 Mn 0.5 As with respect to the variation in lattice parameters are also discussed. The predicted theoretical evidence shows that some Mn-doped III–V semiconductors can be effectively used in spintronic devices

  15. High pressure phase transition and anharmonic properties of Zn1-xMxSe (M=Cd, Fe and Mn) diluted magnetic semiconductor

    International Nuclear Information System (INIS)

    Talati, Mina; Shinde, Satyam; Jha, Prafulla K.

    2004-01-01

    The present work employs interionic potential approach based on charge transfer effect to calculate and describe the high pressure phase transition and elastic behaviour of the diluted magnetic semiconductors Zn 1-x M x Se (M=Cd, Fe and Mn). We have obtained a reasonably good agreement between present calculated values and experimentally observed data on the phase transition pressures. The volume collapses and high pressure behaviours are also in reasonably good agreement with the available data for all compounds under consideration. The variations of elastic constants and their combinations with pressure follow a systematic trend, identical to that observed in other compounds of zinc blende structure family. The present approach has also succeeded in predicting the Born and relative stability criteria

  16. Hydrogen isotope exchange of organic compounds in dilute acid at elevated temperatures

    International Nuclear Information System (INIS)

    Werstiuk, N.H.

    1987-01-01

    Introduction of one or more deuterium (or tritium) atoms into organic molecules can be accomplished in many ways depending on the nature of the substrate and the extent and sterochemistry of deuteriation or tritiation required. Some of the common methods include acid- and base-catalyzed exchange of carbonyl compounds, metal hydride reductions, dissolving metal reductions, catalytic reduction of double bonds, chromatographic exchange, homogeneous and heterogeneous metal-catalyzed exchange, base-catalyzed exchange of carbon acids other than carbonyl compounds and acid-catalyzed exchange via electrophilic substitution. Only the latter three methods have been used for perdeuteriation of organic compounds. A very useful compendium of labeling methods with examples has been available to chemists for some time. Although metal-catalyzed exchange has been used extensively, the method suffers from some deficiencies: irreproducibility of catalyst surfaces, catalyst poisoning, side reactions such as coupling and hydrogenolysis of labile groups and low deuterium incorporation. Usually a number of cycles are required with fresh catalyst and fresh deuterium source to achieve substantial isotope incorporation. Acid-catalyzed exchange of aromatics and alkenes, strongly acidic media such as liquid DBr, concentrated DBr, acetic acid/stannic chloride, concentrated D 3 PO 4 , concentrated DC1, D 3 PO 4 /BF 3 SO 2 , 50-80% D 2 SO 4 and DFSO 4 /SbF 5 at moderate temperatures (<100 degrees) have been used to effect exchange. The methods are not particularly suitable for large scale deuteriations because of the cost and the fact that the recovery and upgrading of the diluted deuterium pool is difficult. This paper describes the hydrogen isotope exchange of a variety of organic compounds in dilute aqueous acid (0.1-0.5 M) at elevated temperatures (150-300 degrees)

  17. Spin and energy transfer between magnetic ions and free carriers in diluted-magnetic semiconductor heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Yakovlev, D.R. [Experimental Physics 2, University of Dortmund, 44227 Dortmund (Germany); Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Kneip, M.; Bayer, M. [Experimental Physics 2, University of Dortmund, 44227 Dortmund (Germany); Maksimov, A.A.; Tartakovskii, I.I. [Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka (Russian Federation); Keller, D.; Ossau, W.; Molenkamp, L.W. [Physikalisches Institut der Universitaet Wuerzburg, 97074 Wuerzburg (Germany); Scherbakov, A.V.; Akimov, A.V. [Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021 St. Petersburg (Russian Federation); Waag, A. [Abteilung Halbleiterphysik, Universitaet Ulm, 89081 Ulm (Germany)

    2004-03-01

    In this paper we give a brief overview of our studies on dynamical processes in diluted-magnetic-semiconductor heterostructures based on (Zn,Mn)Se and (Cd,Mn)Te. Presence of free carriers is an important factor which determines the energy- and spin transfer in a coupled systems of magnetic ions, lattice (the phonon system) and carriers. We report also new data on dynamical response of magnetic ions interacting with photogenerated electron-hole plasma. (Zn,Mn)Se/(Zn,Be)Se structures with relatively high Mn content of 11% provide spin-lattice relaxation time of about 20 ns, which is considerably shorter then the characteristic times of nonequilibrium phonons ranging to 1 {mu}s. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Cobalt-doped ZnO as dilute magnetic semiconductor; Cobalt dotiertes ZnO als verduennter magnetischer Halbleiter

    Energy Technology Data Exchange (ETDEWEB)

    Gacic, Milan

    2009-04-24

    Dilute magnetic semiconductors (DMS) are technologically promising materials that show ferromagnetic as well as semiconducting properties. These are one of the crucial compounds concerning the development of spintronic devices. The main problem so far ist that for applications the Curie temperature of most of the DMS compounds is much too low. However, DMS compounds based on ZnO as Zn{sub 1-x}Co{sub x}O seem to show ferromagnetism above room temperature, but the ferromagnetic exchange is not fully understood. Intensive experimental investigations need to be done. In the course of this theses Zn{sub 0.95}Co{sub 0.05}O thin films were fabricated by pulsed laser deposition and investigated concerning their magnetic, magnetoelectric and structural properties in order to understand the ferromagnetism in this material. Different experimental methods have been used, as magnetometry, X-ray diffraction (XRD), X-ray magnetic circular dichroism (XMCD), electron spin resonance (ESR) and magnetoelectric transport measurements. At special preparation conditions, where a high defect density is induced, the samples are clearly ferromagnetic above room temperature with a saturation magnetization of 2 {mu}{sub b}/Co and a remanence of 90%. Electrical transport measurements show a clear magnetoresistance as well as a anomalous Hall effect. The anomalous Hall effect rises with the magnetization indicating intrinsic ferromagnetism and a certain degree of spin polarization. As the ferromagnetism disappears with rising charge carrier density the ferromagnetic interaction cannot be mediated by the conduction electrons. A more precise evaluation of the magnetoelectric results shows that there is an additional conducting impurity band which could even be spinpolarized. So there are indications that the ferromagnetism is due to magnetic polarons. Some of the structural and magnetometric results as well as the electron spin resonance measurements suggest an additional extrinsic contribution

  19. Magnetite and magnetite/silver core/shell nanoparticles with diluted magnet-like behavior

    International Nuclear Information System (INIS)

    Garza-Navarro, Marco; Torres-Castro, Alejandro; Gonzalez, Virgilio; Ortiz, Ubaldo; De la Rosa, Elder

    2010-01-01

    In the present work is reported the use of the biopolymer chitosan as template for the preparation of magnetite and magnetite/silver core/shell nanoparticles systems, following a two step procedure of magnetite nanoparticles in situ precipitation and subsequent silver ions reduction. The crystalline and morphological characteristics of both magnetite and magnetite/silver core/shell nanoparticles systems were analyzed by high resolution transmission electron microscopy (HRTEM) and nanobeam diffraction patterns (NBD). The results of these studies corroborate the core/shell morphology and the crystalline structure of the magnetite core and the silver shell. Moreover, magnetization temperature dependent, M(T), measurements show an unusual diluted magnetic behavior attributed to the dilution of the magnetic ordering in the magnetite and magnetite/silver core/shell nanoparticles systems. - Graphical abstract: Biopolymer chitosan was used as stabilization media to synthesize both magnetite and magnetite/silver core/shell nanoparticles. Results of HRTEM and NBD patterns confirm core/shell morphology of the obtained nanoparticles. It was found that the composites show diluted magnet-like behavior.

  20. Size and diluted magnetic properties of diamond shaped graphene quantum dots: Monte Carlo study

    Science.gov (United States)

    Masrour, R.; Jabar, A.

    2018-05-01

    The magnetic properties of diamond shaped graphene quantum dots have been investigated by varying their sizes with the Monte Carlo simulation. The magnetizations and magnetic susceptibilities have been studied with dilutions x (magnetic atom), several sizes L (carbon atom) and exchange interaction J between the magnetic atoms. The all magnetic susceptibilities have been situated at the transitions temperatures of each parameters. The obtained values increase when increases the values of x, L and J. The effect of exchanges interactions and crystal field on the magnetization has been discussed. The magnetic hysteresis cycles for several dilutions x, sizes L, exchange interactions J and temperatures T. The magnetic coercive increases with increasing the exchange interactions and decreases when the temperatures values increasing.

  1. First-principles calculation on dilute magnetic alloys in zinc blend crystal structure

    Energy Technology Data Exchange (ETDEWEB)

    Ullah, Hamid, E-mail: hamidullah@yahoo.com [Department of Physics, Government Post Graduate Jahanzeb College, Saidu Sharif Swat (Pakistan); Inayat, Kalsoom [Department of Physics, Government Post Graduate Jahanzeb College, Saidu Sharif Swat (Pakistan); Khan, S.A; Mohammad, S. [Department of Physics, Materials Modeling Laboratory, Hazara University, Mansehra 21300 (Pakistan); Ali, A. [Department of Advanced Materials Science & Engineering, Hanseo University, Seosan-si, Chungnam-do 356-706 (Korea, Republic of); Alahmed, Z.A. [Department of Physics and Astronomy, King Saud University, Riyadh 11451 (Saudi Arabia); Reshak, A.H. [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia)

    2015-07-01

    Ab-initio calculations are performed to investigate the structural, electronic and magnetic properties of spin-polarized diluted magnetic alloys in zinc blende structure. The first-principles study is carried out on Mn doped III–V semiconductors. The calculated band structures, electronic properties and magnetic properties of Ga{sub 1−x}Mn{sub x}X (X=P, As) compounds reveal that Ga{sub 0.75}Mn{sub 0.25}P is half metallic turned to be metallic with increasing x to 0.5 and 0.75, whereas substitute P by As cause to maintain the half-metallicity nature in both of Ga{sub 0.75}Mn{sub 0.25}As and Ga{sub 0.5}Mn{sub 0.5}As and tune Ga{sub 0.25}Mn{sub 0.75}As to be metallic. Calculated total magnetic moments and the robustness of half-metallicity of Ga{sub 0.75}Mn{sub 0.25}P, Ga{sub 0.75}Mn{sub 0.25}As and Ga{sub 0.5}Mn{sub 0.5}As with respect to the variation in lattice parameters are also discussed. The predicted theoretical evidence shows that some Mn-doped III–V semiconductors can be effectively used in spintronic devices.

  2. Ab-initio calculations for dilute magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Belhadji, Brahim

    2008-03-03

    This thesis focusses on ab-initio calculations for the electronic structure and the magnetic properties of dilute magnetic semiconductors (DMS). In particular we aim at the understanding of the complex exchange interactions in these systems. Our calculations are based on density functional theory, being ideally suited for a description of the material specific properties of the considered DMS. Moreover we use the KKR Green function method in connection with the coherent potential approximation (CPA), which allows to include the random substitutional disorder in a mean field-like approximation for the electronic structure. Finally we calculate the exchange coupling constants J{sub ij} between two impurities in a CPA medium by using the Lichtenstein formula and from this calculate the Curie temperature by a numerically exact Monte Carlo method. Based on this analysis we found and investigated four different exchange mechanisms being of importance in DMS systems: Double exchange, p-d exchange, antiferromagnetic superexchanges, and ferromagnetic superexchange. A second topic we have investigated in this thesis is the pressure dependence of the exchange interactions and the Curie temperatures in (Ga,Mn)As and (In,Mn)As, using the LDA and the LDA+U approximations. Exact calculations of T{sub C} by Monte Carlo simulations show a somehow different behavior. (orig.)

  3. Prediction of two-dimensional diluted magnetic semiconductors: Doped monolayer MoS2 systems

    KAUST Repository

    Cheng, Yingchun

    2013-03-05

    Using first-principles calculations, we propose a two-dimensional diluted magnetic semiconductor: monolayer MoS2 doped by transition metals. Doping of transition metal atoms from the IIIB to VIB groups results in nonmagnetic states, since the number of valence electrons is smaller or equal to that of Mo. Doping of atoms from the VIIB to IIB groups becomes energetically less and less favorable. Magnetism is observed for Mn, Fe, Co, Zn, Cd, and Hg doping, while for the other dopants from these groups it is suppressed by Jahn-Teller distortions. Analysis of the binding energies and magnetic properties indicates that (Mo,X)S2 (X=Mn, Fe, Co, and Zn) are promising systems to explore two-dimensional diluted magnetic semiconductors.

  4. Correlation between electronic and magnetic properties in the IV–VI group diluted magnetic semiconductor SnMnTe

    NARCIS (Netherlands)

    Eltink, S.J.E.A.; Swagten, H.J.M.; Stoffels, N.M.J.; Jonge, de W.J.M.

    1990-01-01

    The diluted magnetic semiconductor Sn1-xMnxTe exhibits a critical carrier density above which ferromagnetic interactions are dominant. On the basis of preliminary experiments on the low temperature magnetic phases no clear evidence for re-entrant behavior can be submitted.

  5. A Comparison of the Valence Band Structure of Bulk and Epitaxial GeTe-based Diluted Magnetic Semiconductors

    International Nuclear Information System (INIS)

    Pietrzyk, M.A.; Kowalski, B.J.; Orlowski, B.A.; Knoff, W.; Story, T.; Dobrowolski, W.; Slynko, V.E.; Slynko, E.I.; Johnson, R.L.

    2010-01-01

    In this work we present a comparison of the experimental results, which have been obtained by the resonant photoelectron spectroscopy for a set of selected diluted magnetic semiconductors based on GeTe, doped with manganese. The photoemission spectra are acquired for the photon energy range of 40-60 eV, corresponding to the Mn 3p → 3d resonances. The spectral features related to Mn 3d states are revealed in the emission from the valence band. The Mn 3d states contribution manifests itself in the whole valence band with a maximum at the binding energy of 3.8 eV. (authors)

  6. Scanning Hall probe microscopy of a diluted magnetic semiconductor

    International Nuclear Information System (INIS)

    Kweon, Seongsoo; Samarth, Nitin; Lozanne, Alex de

    2009-01-01

    We have measured the micromagnetic properties of a diluted magnetic semiconductor as a function of temperature and applied field with a scanning Hall probe microscope built in our laboratory. The design philosophy for this microscope and some details are described. The samples analyzed in this work are Ga 0.94 Mn 0.06 As films grown by molecular beam epitaxy. We find that the magnetic domains are 2-4 μm wide and fairly stable with temperature. Magnetic clusters are observed above T C , which we ascribe to MnAs defects too small and sparse to be detected by a superconducting quantum interference device magnetometer.

  7. Scanning Hall probe microscopy of a diluted magnetic semiconductor

    Science.gov (United States)

    Kweon, Seongsoo; Samarth, Nitin; de Lozanne, Alex

    2009-05-01

    We have measured the micromagnetic properties of a diluted magnetic semiconductor as a function of temperature and applied field with a scanning Hall probe microscope built in our laboratory. The design philosophy for this microscope and some details are described. The samples analyzed in this work are Ga0.94Mn0.06As films grown by molecular beam epitaxy. We find that the magnetic domains are 2-4 μm wide and fairly stable with temperature. Magnetic clusters are observed above TC, which we ascribe to MnAs defects too small and sparse to be detected by a superconducting quantum interference device magnetometer.

  8. Spin diffusion in the Mn2+ ion system of II-VI diluted magnetic semiconductor heterostructures

    Science.gov (United States)

    Maksimov, A. A.; Yakovlev, D. R.; Debus, J.; Tartakovskii, I. I.; Waag, A.; Karczewski, G.; Wojtowicz, T.; Kossut, J.; Bayer, M.

    2010-07-01

    The magnetization dynamics in diluted magnetic semiconductor heterostructures based on (Zn,Mn)Se and (Cd,Mn)Te were studied optically and simulated numerically. In samples with inhomogeneous magnetic ion distribution, these dynamics are contributed by spin-lattice relaxation and spin diffusion in the Mn spin system. A spin-diffusion coefficient of 7×10-8cm2/s was evaluated for Zn0.99Mn0.01Se from comparison of experiment and theory. Calculations of the exciton giant Zeeman splitting and the magnetization dynamics in ordered alloys and digitally grown parabolic quantum wells show perfect agreement with the experimental data. In both structure types, spin diffusion contributes essentially to the magnetization dynamics.

  9. Structure and magnetism of transition-metal implanted dilute magnetic semiconductors

    CERN Document Server

    Pereira, Lino; Temst, K; Araújo, JP; Wahl, U

    The discovery of a dilute magnetic semiconductor (DMS) in which ferromagnetism is carrier-mediated and persists above room temperature is a critical step towards the development of semiconductor-based spintronics. Among the many types of DMS materials which have been investigated, the current research interest can be narrowed down to two main classes of materials: (1) narrow-gap III-V semiconductors, mostly GaAs and InAs, doped with Mn; (2) wide-gap oxides and nitrides doped with 3d transition metals, mostly Mn- and Co-doped ZnO and Mn-doped GaN. With a number of interesting functionalities deriving from the carrier-mediated ferromagnetism and demonstrated in various proof-of-concept devices, Mn-doped GaAs has become, among DMS materials, one of the best candidates for technological application. However, despite major developments over the last 15 years, the maximum Curie temperature (185 K) remains well below room temperature. On the other hand, wide-gap DMS materials appear to exhibit ferromagnetic behavior...

  10. Ab initio description of the diluted magnetic semiconductor Ga1-xMnxAs: Ferromagnetism, electronic structure, and optical response

    Science.gov (United States)

    Craco, L.; Laad, M. S.; Müller-Hartmann, E.

    2003-12-01

    Motivated by a study of various experiments describing the electronic and magnetic properties of the diluted magnetic semiconductor Ga1-xMnxAs, we investigate its physical response in detail using a combination of first-principles band structure with methods based on dynamical mean field theory to incorporate strong, dynamical correlations, and intrinsic as well as extrinsic disorder in one single theoretical picture. We show how ferromagnetism is driven by double exchange (DE), in agreement with very recent observations, along with a good quantitative description of the details of the electronic structure, as probed by scanning tunneling microscopy and optical conductivity. Our results show how ferromagnetism can be driven by DE even in diluted magnetic semiconductors with small carrier concentration.

  11. Pressure dependence of magnetic ordering temperatures of rare earth-Sn/sub 3/ compounds

    Energy Technology Data Exchange (ETDEWEB)

    Foner, S [Massachusetts Inst. of Tech., Cambridge (USA). Francis Bitter National Magnet Lab.

    1979-12-01

    Measurements of the hydrostatic pressure dependence of the Neel temperatures, Tsub(N), are reported for PrSn/sub 3/, NdSn/sub 3/, GdSn/sub 3/ and CeIn/sub 3/. Tsub(N) is found to increase with applied pressure for PrSn/sub 3/ and NdSn/sub 3/, whereas Tsub(N) is pressure independent within experimental error for GdSn/sub 3/ and CeIn/sub 3/. Slightly Sn-deficient RESn/sub 3/ (RE = rare earth) compounds are found consistently to be weakly ferromagnetic. The physical properties of the RESn/sub 3/ compounds exhibit analogies with the corresponding properties of dilute superconducting (LaRE)Sn/sub 3/ alloys. The high pressure data for PrSn/sub 3/ and CeIn/sub 3/ are qualitatively consistent with a 'Kondo necklace' model for magnetically ordered RE compounds with unstable 4f shells.

  12. Pressure dependence of magnetic ordering temperatures of rare earth - Sn/sub 3/ compounds

    Energy Technology Data Exchange (ETDEWEB)

    DeLong, L E [Virginia Univ., Charlottesville (USA). Dept. of Physics; Guertin, R P; Foner, S

    1979-12-01

    Measurements of the hydrostatic pressure dependence of the Neel temperatures, Tsub(N), are reported for PrSn/sub 3/, NdSn/sub 3/, GdSn/sub 3/ and CeIn/sub 3/. Tsub(N) is found to increase with applied pressure for PrSn/sub 3/ and NdSn/sub 3/, whereas Tsub(N) is pressure independent within experimental error for GdSn/sub 3/ and CeIn/sub 3/. Slightly Sn-deficient RESn/sub 3/ (RE=rare earth) compounds are found consistently to be weakly ferromagnetic. The physical properties of the RESn/sub 3/ compounds exhibit analogies with the corresponding properties of dilute superconducting (LaRE)Sn/sub 3/ alloys. The high pressure data for PrSn/sub 3/ and CeIn/sub 3/ are qualitatively consistent with a 'Kondo necklace' model for magnetically ordered RE compounds with unstable 4f shells.

  13. Temperature dependence of the magnetic hyperfine field at an s–p impurity diluted in RNi_2

    International Nuclear Information System (INIS)

    Oliveira, A.L. de; Chaves, C.M.; Oliveira, N.A. de; Troper, A.

    2016-01-01

    We study the formation of local magnetic moments and magnetic hyperfine fields at an s–p impurity diluted in intermetallic Laves phase compounds RNi_2 (R=Nd, Sm, Gd, Tb, Dy) at finite temperatures. We start with a clean host and later the impurity is introduced. The host has two-coupled (R and Ni) sublattice Hubbard Hamiltonians but the Ni sublattice can be disregarded because its d band, being full, is magnetically ineffective. Also, the effect of the 4f electrons of R is represented by the polarization they produce on the d band. This leaves us with a lattice of effective rare earth R-ions with polarized electrons. For the dd electronic interaction we use the Hubbard–Stratonovich identity in a functional integral approach in the static saddle point approximation. - Highlights: • Functional integral method in the static limit, producing site disorder, is used. • The site disorder is treated with the Coherent Potential Approximation (CPA). • Non magnetic Ni generates an effective lattice with only a polarized R d band. • The effective R lattice differ from the pure R metal: Results and Discussions. • The experimental curve of hyperfine fields × temperature are very well reproduced.

  14. Structural and magnetic investigation of dilute magnetic semiconductors based on GaN and ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Kammermeier, Tom

    2010-01-19

    The two wide band gap dilute magnetic semiconductors (DMS) Gd:GaN and Co:ZnO are among the most favored materials for spintronic applications. Despite intense research efforts during the last years, the origin of the magnetic order is still under debate. This work reports structural and magnetic investigations on these DMS materials employing several complementary techniques. The X-ray linear dichroism (XLD) has been used to gain element-specific insight into the local structure of dopants and cations. X-ray diffraction (XRD) was used to probe the global structural properties. Magnetic characterization by superconducting quantum interference device (SQUID) has been complemented by electron spin resonance (ESR) and X-ray magnetic circular dichroism (XMCD). Gd:GaN samples were fabricated by focused-ion-beam (FIB) implantation and molecular beam epitaxy (MBE). Room temperature ferromagnetic-like behavior as found for some of our samples by SQUID could not be reliably reproduced. Instead XMCD measurements at the Gd L{sub 3}-edge reveal paramagnetic behavior of the dopant. Additionally a possible magnetic polarization of Ga atoms of the host crystal is shown to be too small to explain the total magnetization of these samples. In some samples the formation of Gd and GdN clusters was evidenced by ESR measurements but it can only account for low temperature ferromagnetic-like behavior. Intrinsic room temperature ferromagnetism of this material as seen by SQUID cannot be confirmed by any other technique - neither ESR nor XMCD. Co:ZnO samples used for this work were predominantly grown by reactive magnetron sputtering (RMS). As shown by XLD analysis, 95% of the Co atoms are incorporated on substitutional Zn-sites in samples of best structural quality. These samples consistently show paramagnetic behavior as found by SQUID, XMCD and ESR. RMS growth of Co:ZnO with reduced oxygen partial pressure yields a magnetic behavior known from ferromagnetic nanoclusters. The X

  15. Tunable spin waves in diluted magnetic semiconductor nanoribbon

    Science.gov (United States)

    Lyu, Pin; Zhang, Jun-Yi

    2018-01-01

    The spin wave excitation spectrum in diluted magnetic semiconductor (DMS) nanoribbons was calculated by taking account of the quantum confinement effect of carriers and spin waves. By introducing the boundary condition for the spin waves, we derived the spin wave dispersion using the path-integral formulation and Green's function method. It was shown that the spin wave excitation spectrum is discrete due to the confinement effect and strongly dependent on the carrier density, the magnetic ion density, and the width of the nanoribbon. When the width of the nanoribbon is beyond the typical nanoscales, the size effect on the excitation energies of the spin waves disappears in our calculation, which is in qualitative agreement with no obvious size effect observed in the as-made nanodevices of (Ga,Mn)As in this size regime. Our results provide a potential way to control the spin waves in the DMS nanoribbon not only by the carrier density and the magnetic ion density but also by the nanostructure geometry.

  16. Ferromagnetic quantum criticality in the uranium-based ternary compounds URhSi, URhAl, and UCoAl

    International Nuclear Information System (INIS)

    Combier, Tristan

    2014-01-01

    In this thesis we explore the ferromagnetic quantum criticality in three uranium-based ternary compounds, by means of thermodynamical and transport measurements on single crystal samples, at low temperature and high pressure. URhSi and URhAl are itinerant ferromagnets, while UCoAl is a paramagnet being close to a ferromagnetic instability. All of them have Ising-type magnetic ordering. In the orthorhombic compound URhSi, we show that the Curie temperature decreases upon applying a magnetic field perpendicular to the easy magnetization axis, and a quantum phase transition is expected around 40 T. In the hexagonal system URhAl, we establish the pressure-temperature phase diagram for the first time, indicating a quantum phase transition around 5 GPa. In the isostructural compound UCoAl, we investigate the metamagnetic transition with measurements of magnetization, Hall effect, resistivity and X-ray magnetic circular dichroism. Some intriguing magnetic relaxation phenomena are observed, with step-like features. Hall effect and resistivity have been measured at dilution temperatures, under hydrostatic pressure up to 2.2 GPa and magnetic field up to 16 T. The metamagnetic transition terminates under pressure and magnetic field at a quantum critical endpoint. In this region, a strong effective mass enhancement occurs, and an intriguing difference between up and down field sweeps appears in transverse resistivity. This may be the signature of a new phase, supposedly linked to the relaxation phenomena observed in magnetic measurements, arising from frustration on the quasi-Kagome lattice of uranium atoms in this crystal structure. (author) [fr

  17. Mixed (phthalocyaninato)(Schiff-base) di-dysprosium sandwich complexes. Effect of magnetic coupling on the SMM behavior.

    Science.gov (United States)

    Wang, Hailong; Liu, Chenxi; Liu, Tao; Zeng, Suyuan; Cao, Wei; Ma, Qi; Duan, Chunying; Dou, Jianmin; Jiang, Jianzhuang

    2013-11-21

    Reaction between Schiff-base ligand and half-sandwich complex M(Pc)(acac) led to the isolation of new sandwich-type mixed (phthalocyaninato)(Schiff-base) di-lanthanide compounds M2(Pc)2(L)H2O (M = Dy, Gd) (1, 2) [H2Pc = metal free phthalocyanine, Hacac = acetylacetone, H2L = N,N'-bis(3-methyloxysalicylidene)benzene-1,2-diamine] with the triple-decker molecular structure clearly revealed by single crystal X-ray diffraction analysis. For the comparative studies, sandwich triple-decker analogues with pure Schiff-base ligand M2(L)3H2O (M = Dy, Gd) (3, 4) were also prepared. Dynamic magnetic measurement result reveals the single-molecule magnet (SMM) nature of the di-dysprosium derivative 1, while the static magnetic investigation over both pure and the diamagnetic diluted samples of this compound discloses the interionic ferromagnetic coupling between the two dysprosium ions, which in turn effectively suppresses the QTM and enhances the energy barrier of this SMM. Nevertheless, comparative studies over the static magnetic properties of the di-dysprosium triple-decker complexes 1 and 3 indicate the stronger magnetic coupling between the two lanthanide ions in mixed (phthalocyaninato)(Schiff-base) species than in the pure Schiff-base triple-decker analogue, suggesting the special coordination sphere around the dysprosium ions in the former compound over the latter one on the more intense inter-ionic ferromagnetic coupling. As a very small step towards understanding the structure-property relationship, the present result will be surely helpful for the design and synthesis of the multinuclear lanthanide-based SMMs with good properties.

  18. Magnetic and structural properties of yellow europium oxide compound and Eu(OH)3

    International Nuclear Information System (INIS)

    Lee, Dongwook; Seo, Jiwon; Valladares, Luis de los Santos; Avalos Quispe, O.; Barnes, Crispin H.W.

    2015-01-01

    A new material based on a yellow europium oxide compound was prepared from europium oxide in a high vacuum environment. The structural and magnetic properties of the material were investigated. Owing to the absence of a crystal structure, the material exhibited a disordered magnetic behavior. In a reaction with deionized (DI) water without applied heat, the compound assumed a white color as soon as the DI water reached the powder, and the structure became polycrystalline Eu(OH) 3 . The magnetic properties, such as the thermal hysteresis, disappeared after the reaction with DI water, and the magnetic susceptibility of the yellow oxide compound weakened. The magnetic properties of Eu(OH) 3 were also examined. Although Eu 3+ is present in Eu(OH) 3 , a high magnetic moment due to the crystal field effect was observed. - Graphical abstract: (top left) Optical image of the yellow europium oxide compound. (top right) Optical image of the product of DI water and yellow europium oxide. (bottom) Magnetization curves as a function of temperature measured in various magnetic field. - Highlights: • We prepared a new material based on a yellow europium oxide compound from europium oxide. • We characterized the magnetic properties of the material which exhibits a disordered magnetic behavior such as thermal hysteresis. • The compound turned white (Eu(OH) 3 ) as soon as the DI water reached the powder. • The thermal hysteresis disappeared after the reaction with DI water and the magnetic susceptibility of the yellow oxide compound weakened

  19. Hole-hole correlation effects on magnetic properties of Mn.sub.x./sub.III.sub.1-x./sub.V diluted magnetic semiconductors

    Czech Academy of Sciences Publication Activity Database

    Jungwirth, Tomáš; Byounghak, L.; MacDonald, A. H.

    2001-01-01

    Roč. 10, - (2001), s. 153-156 ISSN 1386-9477 Institutional research plan: CEZ:AV0Z1010914 Keywords : diluted magnetic semiconductors * ferromagnetism * electronic correlation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.009, year: 2001

  20. Mn-AlInN: a new diluted magnetic semiconductor

    International Nuclear Information System (INIS)

    Majid, Abdul; Ali, Akbar; Sharif, Rehana; Zhu, J.J.

    2009-01-01

    Mn ions have been incorporated into MOCVD grown Al 1-x In x N/GaN thin films by ion implantation to achieve the room temperature ferromagnetism in the samples. Magnetic characterizations revealed the presence of two ferromagnetic transitions: one has Curie points at ∝260 K and the other above room temperature. In-diffusion of indium caused by the Mn implantation leads to the partition of AlInN epilayer into two diluted magnetic semiconductor sub-layers depending on the Mn concentration. The Curie temperature of 260 K is assigned to the layer having lower concentration, whereas T c above room temperature is assumed to be associated to the layer having higher Mn concentration. (orig.)

  1. Tailoring spin-orbit torque in diluted magnetic semiconductors

    KAUST Repository

    Li, Hang; Wang, Xuhui; Doǧan, Fatih; Manchon, Aurelien

    2013-01-01

    We study the spin orbit torque arising from an intrinsic linear Dresselhaus spin-orbit coupling in a single layer III-V diluted magnetic semiconductor. We investigate the transport properties and spin torque using the linear response theory, and we report here: (1) a strong correlation exists between the angular dependence of the torque and the anisotropy of the Fermi surface; (2) the spin orbit torque depends nonlinearly on the exchange coupling. Our findings suggest the possibility to tailor the spin orbit torque magnitude and angular dependence by structural design.

  2. Tailoring spin-orbit torque in diluted magnetic semiconductors

    KAUST Repository

    Li, Hang

    2013-05-16

    We study the spin orbit torque arising from an intrinsic linear Dresselhaus spin-orbit coupling in a single layer III-V diluted magnetic semiconductor. We investigate the transport properties and spin torque using the linear response theory, and we report here: (1) a strong correlation exists between the angular dependence of the torque and the anisotropy of the Fermi surface; (2) the spin orbit torque depends nonlinearly on the exchange coupling. Our findings suggest the possibility to tailor the spin orbit torque magnitude and angular dependence by structural design.

  3. Concentration dependence of the wings of a dipole-broadened magnetic resonance line in magnetically diluted lattices

    Energy Technology Data Exchange (ETDEWEB)

    Zobov, V. E., E-mail: rsa@iph.krasn.ru [Russian Academy of Sciences, Kirenskii Institute of Physics, Siberian Branch (Russian Federation); Kucherov, M. M. [Siberian Federal University, Institute of Space and Information Technologies (Russian Federation)

    2017-01-15

    The singularities of the time autocorrelation functions (ACFs) of magnetically diluted spin systems with dipole–dipole interaction (DDI), which determine the high-frequency asymptotics of autocorrelation functions and the wings of a magnetic resonance line, are studied. Using the self-consistent fluctuating local field approximation, nonlinear equations are derived for autocorrelation functions averaged over the independent random arrangement of spins (magnetic atoms) in a diamagnetic lattice with different spin concentrations. The equations take into account the specificity of the dipole–dipole interaction. First, due to its axial symmetry in a strong static magnetic field, the autocorrelation functions of longitudinal and transverse spin components are described by different equations. Second, the long-range type of the dipole–dipole interaction is taken into account by separating contributions into the local field from distant and near spins. The recurrent equations are obtained for the expansion coefficients of autocorrelation functions in power series in time. From them, the numerical value of the coordinate of the nearest singularity of the autocorrelation function is found on the imaginary time axis, which is equal to the radius of convergence of these expansions. It is shown that in the strong dilution case, the logarithmic concentration dependence of the coordinate of the singularity is observed, which is caused by the presence of a cluster of near spins whose fraction is small but contribution to the modulation frequency is large. As an example a silicon crystal with different {sup 29}Si concentrations in magnetic fields directed along three crystallographic axes is considered.

  4. Crystal Fields in Dilute Rare-Earth Metals Obtained from Magnetization Measurements on Dilute Rare-Earth Alloys

    DEFF Research Database (Denmark)

    Touborg, P.; Høg, J.

    1974-01-01

    Crystal field parameters of Tb, Dy, and Er in Sc, Y, and Lu are summarized. These parameters are obtained from magnetization measurements on dilute single crystals, and successfully checked by a number of different methods. The crystal field parameters vary unpredictably with the rare-earth solute....... B40, B60, and B66 are similar in Y and Lu. Crystal field parameters for the pure metals Tb, Dy, and Er are estimated from the crystal fields in Y and Lu....

  5. Mn-AlInN: a new diluted magnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Majid, Abdul; Ali, Akbar [Quaid-i-Azam University, Advance Materials Physics Laboratory, Physics Department, Islamabad (Pakistan); Sharif, Rehana [University of Engineering and Technology, Department of Physics, Lahore (Pakistan); Zhu, J.J. [Chinese Academy of Sciences, State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Beijing (China)

    2009-09-15

    Mn ions have been incorporated into MOCVD grown Al{sub 1-x}In{sub x}N/GaN thin films by ion implantation to achieve the room temperature ferromagnetism in the samples. Magnetic characterizations revealed the presence of two ferromagnetic transitions: one has Curie points at {proportional_to}260 K and the other above room temperature. In-diffusion of indium caused by the Mn implantation leads to the partition of AlInN epilayer into two diluted magnetic semiconductor sub-layers depending on the Mn concentration. The Curie temperature of 260 K is assigned to the layer having lower concentration, whereas T{sub c} above room temperature is assumed to be associated to the layer having higher Mn concentration. (orig.)

  6. Large reversible magnetostrictive effect of MnCoSi-based compounds prepared by high-magnetic-field solidification

    Science.gov (United States)

    Hu, Q. B.; Hu, Y.; Zhang, S.; Tang, W.; He, X. J.; Li, Z.; Cao, Q. Q.; Wang, D. H.; Du, Y. W.

    2018-01-01

    The MnCoSi compound is a potential magnetostriction material since the magnetic field can drive a metamagnetic transition from an antiferromagnetic phase to a high magnetization phase in it, which accompanies a large lattice distortion. However, a large driving magnetic field, magnetic hysteresis, and poor mechanical properties seriously hinder its application for magnetostriction. By substituting Fe for Mn and introducing vacancies of the Mn element, textured and dense Mn0.97Fe0.03CoSi and Mn0.88CoSi compounds are prepared through a high-magnetic-field solidification approach. As a result, large room-temperature and reversible magnetostriction effects are observed in these compounds at a low magnetic field. The origin of this large magnetostriction effect and potential applications are discussed.

  7. Magnetic and structural properties of yellow europium oxide compound and Eu(OH){sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dongwook, E-mail: dongwookleedl324@gmail.com [Cavendish Laboratory, University of Cambridge, J. J Thomson Av., Cambridge CB3 0HE (United Kingdom); Seo, Jiwon, E-mail: jiwonseo@yonsei.ac.kr [Department of Physics and IPAP, Yonsei University, Seoul 120-749 (Korea, Republic of); Valladares, Luis de los Santos [Cavendish Laboratory, University of Cambridge, J. J Thomson Av., Cambridge CB3 0HE (United Kingdom); Avalos Quispe, O. [Laboratorio de Cerámicos y Nanomateriales, Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Ap. Postal 14-0149, Lima, Perú (Peru); Barnes, Crispin H.W. [Cavendish Laboratory, University of Cambridge, J. J Thomson Av., Cambridge CB3 0HE (United Kingdom)

    2015-08-15

    A new material based on a yellow europium oxide compound was prepared from europium oxide in a high vacuum environment. The structural and magnetic properties of the material were investigated. Owing to the absence of a crystal structure, the material exhibited a disordered magnetic behavior. In a reaction with deionized (DI) water without applied heat, the compound assumed a white color as soon as the DI water reached the powder, and the structure became polycrystalline Eu(OH){sub 3}. The magnetic properties, such as the thermal hysteresis, disappeared after the reaction with DI water, and the magnetic susceptibility of the yellow oxide compound weakened. The magnetic properties of Eu(OH){sub 3} were also examined. Although Eu{sup 3+} is present in Eu(OH){sub 3}, a high magnetic moment due to the crystal field effect was observed. - Graphical abstract: (top left) Optical image of the yellow europium oxide compound. (top right) Optical image of the product of DI water and yellow europium oxide. (bottom) Magnetization curves as a function of temperature measured in various magnetic field. - Highlights: • We prepared a new material based on a yellow europium oxide compound from europium oxide. • We characterized the magnetic properties of the material which exhibits a disordered magnetic behavior such as thermal hysteresis. • The compound turned white (Eu(OH){sub 3}) as soon as the DI water reached the powder. • The thermal hysteresis disappeared after the reaction with DI water and the magnetic susceptibility of the yellow oxide compound weakened.

  8. Prediction of two-dimensional diluted magnetic semiconductors: Doped monolayer MoS2 systems

    KAUST Repository

    Cheng, Yingchun; Guo, Z. B.; Mi, W. B.; Schwingenschlö gl, Udo; Zhu, Zhiyong

    2013-01-01

    Using first-principles calculations, we propose a two-dimensional diluted magnetic semiconductor: monolayer MoS2 doped by transition metals. Doping of transition metal atoms from the IIIB to VIB groups results in nonmagnetic states, since the number

  9. Spin-canting magnetization in an unusual Co4 cluster-based layer compound from a 2,3-dihydroxyquinoxaline ligand.

    Science.gov (United States)

    Yang, Chen-I; Chuang, Po-Hsiang; Lee, Gene-Hsiang; Peng, Shie-Ming; Lu, Kuang-Lieh

    2012-01-16

    The self-assembly of Co(O(2)CPh)(2) with a 2,3-dihydroxyquinoxaline (H(2)dhq) linker has revealed a new two-dimensional cluster-based compound, [Co(4)(OMe)(2)(O(2)CPh)(2)(dhq)(2)(MeOH)(2)](n), which shows spin-canted magnetization and a definite magnetic hysteresis loop.

  10. Temperature dependence of the magnetic hyperfine field at an s–p impurity diluted in RNi{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, A.L. de, E-mail: alexandre.oliveira@ifrj.edu.br [Instituto Federal de Educação, Ciência e Tecnologia do Rio de Janeiro, Campus Nilópolis, RJ (Brazil); Chaves, C.M., E-mail: cmch@cbpf.br [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro, RJ (Brazil); Oliveira, N.A. de [Instituto de Física Armando Dias Tavares, Universidade do Estado do Rio de Janeiro, Rio de Janeiro (Brazil); Troper, A. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro, RJ (Brazil)

    2016-03-01

    We study the formation of local magnetic moments and magnetic hyperfine fields at an s–p impurity diluted in intermetallic Laves phase compounds RNi{sub 2} (R=Nd, Sm, Gd, Tb, Dy) at finite temperatures. We start with a clean host and later the impurity is introduced. The host has two-coupled (R and Ni) sublattice Hubbard Hamiltonians but the Ni sublattice can be disregarded because its d band, being full, is magnetically ineffective. Also, the effect of the 4f electrons of R is represented by the polarization they produce on the d band. This leaves us with a lattice of effective rare earth R-ions with polarized electrons. For the dd electronic interaction we use the Hubbard–Stratonovich identity in a functional integral approach in the static saddle point approximation. - Highlights: • Functional integral method in the static limit, producing site disorder, is used. • The site disorder is treated with the Coherent Potential Approximation (CPA). • Non magnetic Ni generates an effective lattice with only a polarized R d band. • The effective R lattice differ from the pure R metal: Results and Discussions. • The experimental curve of hyperfine fields × temperature are very well reproduced.

  11. Domain walls in (Ga,Mn)As diluted magnetic semiconductor

    Czech Academy of Sciences Publication Activity Database

    Sugawara, A.; Kasai, H.; Tonomura, A.; Brown, P.D.; Campion, R. P.; Edmonds, K. W.; Gallagher, B. L.; Zemen, Jan; Jungwirth, Tomáš

    2008-01-01

    Roč. 100, č. 4 (2008), 047202/1-047202/4 ISSN 0031-9007 R&D Projects: GA MŠk LC510; GA ČR GEFON/06/E002; GA ČR GA202/05/0575; GA ČR GA202/04/1519 EU Projects: European Commission(XE) 015728 - NANOSPIN Institutional research plan: CEZ:AV0Z10100521 Keywords : dilute ferromagnetic semiconductor * Néel domain walls * electron holography * Landau-Lifshitz-Gilbert simulation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.180, year: 2008

  12. 119Sn Moessbauer spectroscopy in the magnetically diluted Heusler-type systems

    International Nuclear Information System (INIS)

    Ruebenbauer, K.

    1981-01-01

    119 Sn Moessbauer investigations of the ferromagnetically diluted Nisub(2)Mnsub(x)Bsub(1-x)Sn(B=Ti, V) and Pdsub(2)Mnsub(x)Vsub(1-x)Sn Heusler-type systems have been performed and the results are reviewed and discussed. It has been found that distributions of the transferred hyperfine magnetic field as seen by a tin nucleus are very sensitive for a type of the local magnetic interaction in these simple ferromagnets, especially when studied versus the sample temperature. This sensitivity allows to reach some conclusions about the coupling mechanism between localised manganese magnetic moments. Namely, it is concluded that the interaction beyond the second neighbour shell is practically irrelevant for the magnetic ordering process. This very fact means that the free electron approach to the calculation of exchange integrals can not be applied for these particular systems. (Author)

  13. On exceeding the solubility limit of Cr+3 dopants in SnO2 nanoparticles based dilute magnetic semiconductors

    Science.gov (United States)

    URS, Kusuma; Bhat, S. V.; Kamble, Vinayak

    2018-04-01

    The paper investigates the magnetic behavior of chromium doped SnO2 Dilute Magnetic Semiconductor (DMS) nanoparticles, through structural, spectroscopic, and magnetic studies. A non-equilibrium solution combustion method is adopted to synthesize 0-5 at. % Cr doped SnO2 nanoparticles. The detailed spectroscopic studies on the system using micro-Raman spectroscopy, x-ray photoelectron spectroscopy, and electron paramagnetic resonance spectroscopy along with the structural analysis confirm the presence of Cr in 3+ oxidation state, which substitutes at Sn4+ site in SnO6 octahedra of the rutile structure. This doping is found to enhance the defects in the system, i.e., oxygen vacancies. All the synthesized SnO2 nanoparticles (with or without dopants) are found to exhibit Room Temperature Ferromagnetism (RTFM). This occurrence of RTFM is attributed to the magnetic exchange interaction through F-centers of oxygen vacancies as well as dopant magnetic impurities and explained through the Bound Magnetic Polaron (BMP) model of DMS systems. Nonetheless, as the doping of Cr is further increased beyond 2%, the solubility limit is achieved. This antiferromagnetic exchange interaction from interstitial Cr dopants dominates over the BMP mechanism and, hence, leads to the decrease in the net magnetic moment drastically.

  14. Effect of crystalline electric fields and long-range magnetic order on superconductivity in rare earth alloys and compounds

    International Nuclear Information System (INIS)

    McCallum, R.W.

    1977-01-01

    The behavior of rare earth ions in a superconducting matrix has been studied in two distinct regimes. First, the effects of crystal field splitting of the 4f levels of a magnetic rare earth ion in the alloy system (LaPr)Sn 3 were investigated in the limit of low Pr 3+ concentration. In this system the rare earth impurity ions occupy random La sites in the crystal lattice. Second, the interaction of long-range magnetic order and superconductivity was explored in the ternary rare earth molybdenum chalcogenide systems. In these compounds the rare earth ions occupy periodic lattice sites in contrast to the random distribution of magnetic ions in dilute impurity alloy systems such as (LaPr)Sn 3

  15. Magnetic behaviour of new Ce compounds

    Energy Technology Data Exchange (ETDEWEB)

    Sampathkumaran, E V [Tata Inst. of Fundamental Research, Bombay (India); Mallik, R [Tata Inst. of Fundamental Research, Bombay (India)

    1996-07-01

    We report initial results of our investigation on the magnetic behaviour of some new Ce compounds. The compounds, CeIr{sub 2}B{sub 2}C and CeIr{sub 2}Ge{sub 2}, do not appear to exhibit bulk magnetic ordering down to 2 K. The alloys, Ce{sub 2}Pd{sub 2}In and Ce{sub 2}Cu{sub 2}In, order magnetically below 4 and 6 K, respectively, and a marginal change in the Pd(Cu)/In composition does not significantly influence the ordering temperatures. (orig.).

  16. A dynamic dilution system-based evaluation of the procedure adopted for determining ozone precursor volatile compounds.

    Science.gov (United States)

    Palluau, Fabienne; Mirabel, Philippe; Millet, Maurice

    2005-02-01

    A dynamic dilution system was created to evaluate the performance and the reliability of ozone precursor volatile organic compound (VOC) sampling ("TO-Can" canisters) and analysis (thermal desorption/gas chromatography/flame ionisation detection) techniques used by the "Laboratoire Interregional de Chimie du Grand Est (LIC)". Different atmospheres of VOCs were generated at concentrations between 0.8 and 25 ppb, with temperatures of 0, 10, 20 and 30 degrees C, and with relative humidities of 0, 30, 50, 70 and 90%. These conditions are generally representative of those commonly observed in ambient air in the eastern France. This dynamic dilution allows the simulation of a wide range of scenarios (concentrations, temperatures and relative humidities). After assessing the capacity and performance of the system, it was applied in order to evaluate the recoveries and stabilities of VOCs from canisters used for the collection and analysis of two mixtures of VOCs. The first mixture contained six alkanes (ethane, propane, butane, pentane, hexane and heptane), and the second contained five alkenes (ethene, propene, butene, 1-pentene and 1-hexene), five aromatics (benzene, toluene, ethylbenzene, m-xylene and o-xylene), acetylene, and 1,3-butadiene. No significant losses of alkanes from the canisters were observed after 21 days of storage, and good recoveries of alkanes from the canisters (>80%) were obtained regardless of the concentration, the temperature and the relative humidity. However, losses of certain aromatics were noted at low relative humidity.

  17. Magnetic structure of RPdSn (R=Tb, Ho) single crystal compounds under strong magnetic field

    International Nuclear Information System (INIS)

    Andoh, Y.; Kurisu, M.; Nakamoto, G.; Tsutaoka, T.; Kawano, S.

    2003-01-01

    Rare earth compounds RTX, where R stands for rare earth elements, T for Ni, Pd or Rh, and X for Sn or Ge, crystallize to a rhombic ε-TiNiSi structure. Only rare earth elements R contribute to magnetic properties since T and X atoms are nonmagnetic. The competition between RKKY indirect interaction and large magnetic anisotropy generates many complicated magnetic phases. At a low temperature phase, complicated magnetisms such as meta-magnetism were observed in magnetization curves with many steps. In previous experiments dealing with RPdSn where R means Tb or Ho, some characteristics of magnetic properties of these compounds were deduced from magnetization measurements and neutron diffraction without external magnetic field. In this report, the change of magnetic scattering of neutron diffraction was studied under external magnetic fields in order to reveal the mechanism of the phase transformations of the compounds. The difference between TbPdSn and HoPdSn compounds was observed in magnetic field dependence of the wave vectors of the magnetic scattering. Two independent wave vectors in magnetic scattering existed in HoPdSn compound. (Y. Kazumata)

  18. Growth and XRD analysis of the diluted magnetic semiconductor Zn{sub 1-x}Ni{sub x}O

    Energy Technology Data Exchange (ETDEWEB)

    Syed Ali, K.S. [Department of Science, Estill High School, Post Office Box 754, Estill, South Carolina - 29918 (United States); Saravanan, R. [Department of Physics, The Madura College, Madurai - 625 011 (India); Acikgoez, M. [Bahcesehir University, Faculty of Arts and Sciences, Besiktas - 34349 (Turkey)

    2011-01-15

    Diluted magnetic semiconductor compound Zn{sub 1-x}Ni{sub x} O(x =0.01, 0.02, 0.03, 0.04 and 0.05) was prepared by sol-gel method and characterized using powder XRD for the distribution of electrons and bonding in the unit cell. The electronic structural studies of this material were carried out by maximum entropy method (MEM) for the quantitative and qualitative measurement on the inclusion and the effect induced on bonding by Ni doping. The spatial arrangement of charge and the bonding behavior of this material were analyzed from 3D, 2D and 1D density distributions. The evidence for the addition of Ni in the host lattice of Zn is realized. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Self-bound droplets of a dilute magnetic quantum liquid

    Science.gov (United States)

    Schmitt, Matthias; Wenzel, Matthias; Böttcher, Fabian; Ferrier-Barbut, Igor; Pfau, Tilman

    2016-11-01

    Self-bound many-body systems are formed through a balance of attractive and repulsive forces and occur in many physical scenarios. Liquid droplets are an example of a self-bound system, formed by a balance of the mutual attractive and repulsive forces that derive from different components of the inter-particle potential. It has been suggested that self-bound ensembles of ultracold atoms should exist for atom number densities that are 108 times lower than in a helium droplet, which is formed from a dense quantum liquid. However, such ensembles have been elusive up to now because they require forces other than the usual zero-range contact interaction, which is either attractive or repulsive but never both. On the basis of the recent finding that an unstable bosonic dipolar gas can be stabilized by a repulsive many-body term, it was predicted that three-dimensional self-bound quantum droplets of magnetic atoms should exist. Here we report the observation of such droplets in a trap-free levitation field. We find that this dilute magnetic quantum liquid requires a minimum, critical number of atoms, below which the liquid evaporates into an expanding gas as a result of the quantum pressure of the individual constituents. Consequently, around this critical atom number we observe an interaction-driven phase transition between a gas and a self-bound liquid in the quantum degenerate regime with ultracold atoms. These droplets are the dilute counterpart of strongly correlated self-bound systems such as atomic nuclei and helium droplets.

  20. Enhanced nuclear magnetic resonance in a non-magnetic cubic doublet

    International Nuclear Information System (INIS)

    Veenendaal, E.J.

    1982-01-01

    In this thesis two lanthanide compounds are studied which show enhanced nuclear magnetism at low temperatures: Rb 2 NaHoF 6 and CsNaHoF 6 . Chapter II gives a description of the 4 He-circulating refrigerator, which was built to provide the low temperatures required for the polarization of the enhanced nuclear moments. This type of dilution refrigerator was chosen because of its simple design and large cooling power. Chapter III is devoted to a comparison of the different types of dilution refrigerators. A theoretical discussion is given of their performance, starting from the differential equations, which govern the temperature distribution in the refrigerator. In chapter IV the actual performance of the refrigerator, described in chapter II is discussed. In chapter V a description of the NMR-apparatus, developed for very-low-temperature NMR experiments is given. In chapter VI experimental results on the compound Rb 2 NaHoF 6 are presented. The CEF-ground state of this compound is probably the non-magnetic doublet GAMMA 3 , but at a temperature of 170 K a structural phase transition lowers the crystal symmetry from cubic to tetragonal and the doublet is split into two singlets. In chapter VII specific heat, (enhanced) nuclear magnetic resonance and magnetization measurements on the compound Cs 2 NaHoF 6 are presented which also has a GAMMA 3 -doublet ground state. In zero magnetic field the degeneracy of the doublet is removed at a temperature of 393 mK, where a phase transition is induced by quadrupolar interactions. (Auth.)

  1. Phase diagrams and switching of voltage and magnetic field in dilute magnetic semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Escobedo, R. [Departamento de Matematica Aplicada y Ciencias de la Computacion, Universidad de Cantabria, 39005 Santander (Spain); Carretero, M.; Bonilla, L.L. [G. Millan Institute, Fluid Dynamics, Nanoscience and Industrial Maths., Universidad Carlos III de Madrid, 28911 Leganes (Spain); Unidad Asociada al Instituto de Ciencia de Materiales, CSIC, 28049 Cantoblanco, Madrid (Spain); Platero, G. [Instituto de Ciencia de Materiales, CSIC, 28049 Cantoblanco, Madrid (Spain)

    2010-04-15

    The response of an n-doped dc voltage biased II-VI multi-quantum well dilute magnetic semiconductor nanostructure having its first well doped with magnetic (Mn) impurities is analyzed by sweeping wide ranges of both the voltage and the Zeeman level splitting induced by an external magnetic field. The level splitting versus voltage phase diagram shows regions of stable self-sustained current oscillations immersed in a region of stable stationary states. Transitions between stationary states and self-sustained current oscillations are systematically analyzed by both voltage and level splitting abrupt switching. Sudden voltage or/and magnetic field changes may switch on current oscillations from an initial stationary state, and reciprocally, current oscillations may disappear after sudden changes of voltage or/and magnetic field changes into the stable stationary states region. The results show how to design such a device to operate as a spin injector and a spin oscillator by tuning the Zeeman splitting (through the applied external magnetic field), the applied voltage and the sample configuration parameters (doping density, barrier and well widths, etc.) to select the desired stationary or oscillatory behavior. Phase diagram of Zeeman level splitting {delta} vs. dimensionless applied voltage {phi} for N = 10 QWs. White region: stable stationary states; black: stable self-sustained current oscillations. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Role of 3d electrons in formation of ionic-covalent bonds in II-VI based ternary compounds

    International Nuclear Information System (INIS)

    Lawniczak-Jablonska, K.; Iwanowski, R.J.; Perera, R.C.C.

    1997-01-01

    In the II-VI compounds doped with transition metals (diluted magnetic semiconductors) a substitution of cation by the introduced magnetic ion leads to hybridization of its 3d states with the sp states of the host semiconductor. The degree of hybridization of the 3d states and its interaction with the host material band states has been a subject of numerous discussions. Inner shell absorption spectroscopy provides very useful means of electronic structure analysis in a wide variety of systems. Due to its selectivity for atomic species and the selection rules for electron transitions, the soft X-ray absorption technique offers quite unique opportunity to measure directly the site-selective local density of the unoccupied d states in the compounds studied. Results are reported for ZnS compounds with Mn, Fe, Co or Ni substitutions for Zn

  3. Ferromagnetic clusters induced by a nonmagnetic random disorder in diluted magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bui, Dinh-Hoi [Institute of Research and Development, Duy Tan University, K7/25 Quang Trung, Danang (Viet Nam); Physics Department, Hue University’s College of Education, 34 Le Loi, Hue (Viet Nam); Phan, Van-Nham, E-mail: phanvannham@dtu.edu.vn [Institute of Research and Development, Duy Tan University, K7/25 Quang Trung, Danang (Viet Nam)

    2016-12-15

    In this work, we analyze the nonmagnetic random disorder leading to a formation of ferromagnetic clusters in diluted magnetic semiconductors. The nonmagnetic random disorder arises from randomness in the host lattice. Including the disorder to the Kondo lattice model with random distribution of magnetic dopants, the ferromagnetic–paramagnetic transition in the system is investigated in the framework of dynamical mean-field theory. At a certain low temperature one finds a fraction of ferromagnetic sites transiting to the paramagnetic state. Enlarging the nonmagnetic random disorder strength, the paramagnetic regimes expand resulting in the formation of the ferromagnetic clusters.

  4. What are the mesoscopic magnetic inhomogeneities in the dilute PdFeMn alloy? Polarized neutron study

    Energy Technology Data Exchange (ETDEWEB)

    Gordeev, G.; Axelrod, L.; Zabenkin, V.; Lazebnik, I.; Grigoriev, S.; Wagner, V.; Eckerlebe, H

    2003-07-01

    The 3D analysis of neutron depolarization was carried out for different thermomagnetic treatment of the dilute PdFeMn alloy versus temperature and magnetic field applied in magnetizing/demagnetizing cycles. Both the macroscopic magnetization and the mean fluctuation of local magnetization behavior were subtracted from experimental data. A complicated behavior of the latter was observed. The hysteresis of local magnetization fluctuations is found out but that of macroscopic magnetization is practically absent. The effort to apply the simple model for the description of magnetic inhomogeneities was made in order to understand the mesostructure of this alloy.

  5. Electronic structure and magnetic properties of dilute U impurities in metals

    Science.gov (United States)

    Mohanta, S. K.; Cottenier, S.; Mishra, S. N.

    2016-05-01

    The electronic structure and magnetic moment of dilute U impurity in metallic hosts have been calculated from first principles. The calculations have been performed within local density approximation of the density functional theory using Augmented plane wave+local orbital (APW+lo) technique, taking account of spin-orbit coupling and Coulomb correlation through LDA+U approach. We present here our results for the local density of states, magnetic moment and hyperfine field calculated for an isolated U impurity embedded in hosts with sp-, d- and f-type conduction electrons. The results of our systematic study provide a comprehensive insight on the pressure dependence of 5f local magnetism in metallic systems. The unpolarized local density of states (LDOS), analyzed within the frame work of Stoner model suggest the occurrence of local moment for U in sp-elements, noble metals and f-block hosts like La, Ce, Lu and Th. In contrast, U is predicted to be nonmagnetic in most transition metal hosts except in Sc, Ti, Y, Zr, and Hf consistent with the results obtained from spin polarized calculation. The spin and orbital magnetic moments of U computed within the frame of LDA+U formalism show a scaling behavior with lattice compression. We have also computed the spin and orbital hyperfine fields and a detail analysis has been carried out. The host dependent trends for the magnetic moment, hyperfine field and 5f occupation reflect pressure induced change of electronic structure with U valency changing from 3+ to 4+ under lattice compression. In addition, we have made a detailed analysis of the impurity induced host spin polarization suggesting qualitatively different roles of f-band electrons on moment stability. The results presented in this work would be helpful towards understanding magnetism and spin fluctuation in U based alloys.

  6. Magnetic properties and magnetocaloric effect of HoCo3B2 compound

    Science.gov (United States)

    Zheng, X. Q.; Xu, J. W.; Zhang, H.; Zhang, J. Y.; Wang, S. G.; Zhang, Y.; Xu, Z. Y.; Wang, L. C.; Shen, B. G.

    2018-05-01

    A sample of HoCo3B2 compound was synthesized, and the magnetic and MCE properties were investigated. Compound shows a change corresponding to R-R (R = rare earth) sublattice magnetic order transition and the transition temperature is determined to be 11.8 K (TC). The characteristic of Arrott plots with positive slope around TC was observed, indicating a second-order phase transition. Based on isothermal magnetization data, together with Maxwell's relationship, the magnetic entropy change (-ΔSM) was calculated. The maximum -ΔSM reaches 7.8, 12.7 and 14.4 J/kg K for field range of 0-2 T, 0-5 T and 0-7 T, respectively. Accordingly, the value of RC (refrigerant capacity) is 99, 289 and 432 J/kg for above field ranges. The large MCE of HoCo3B2 compound indicates its potential application for magnetic refrigeration in low temperature range.

  7. Defects in dilute nitrides

    International Nuclear Information System (INIS)

    Chen, W.M.; Buyanova, I.A.; Tu, C.W.; Yonezu, H.

    2005-01-01

    We provide a brief review our recent results from optically detected magnetic resonance studies of grown-in non-radiative defects in dilute nitrides, i.e. Ga(In)NAs and Ga(Al,In)NP. Defect complexes involving intrinsic defects such as As Ga antisites and Ga i self interstitials were positively identified.Effects of growth conditions, chemical compositions and post-growth treatments on formation of the defects are closely examined. These grown-in defects are shown to play an important role in non-radiative carrier recombination and thus in degrading optical quality of the alloys, harmful to performance of potential optoelectronic and photonic devices based on these dilute nitrides. (author)

  8. Design and performance of an ultra-high vacuum scanning tunneling microscope operating at dilution refrigerator temperatures and high magnetic fields.

    Science.gov (United States)

    Misra, S; Zhou, B B; Drozdov, I K; Seo, J; Urban, L; Gyenis, A; Kingsley, S C J; Jones, H; Yazdani, A

    2013-10-01

    We describe the construction and performance of a scanning tunneling microscope capable of taking maps of the tunneling density of states with sub-atomic spatial resolution at dilution refrigerator temperatures and high (14 T) magnetic fields. The fully ultra-high vacuum system features visual access to a two-sample microscope stage at the end of a bottom-loading dilution refrigerator, which facilitates the transfer of in situ prepared tips and samples. The two-sample stage enables location of the best area of the sample under study and extends the experiment lifetime. The successful thermal anchoring of the microscope, described in detail, is confirmed through a base temperature reading of 20 mK, along with a measured electron temperature of 250 mK. Atomically resolved images, along with complementary vibration measurements, are presented to confirm the effectiveness of the vibration isolation scheme in this instrument. Finally, we demonstrate that the microscope is capable of the same level of performance as typical machines with more modest refrigeration by measuring spectroscopic maps at base temperature both at zero field and in an applied magnetic field.

  9. Magnetic properties and magnetocaloric effect of HoCo3B2 compound

    Directory of Open Access Journals (Sweden)

    X. Q. Zheng

    2018-05-01

    Full Text Available A sample of HoCo3B2 compound was synthesized, and the magnetic and MCE properties were investigated. Compound shows a change corresponding to R-R (R = rare earth sublattice magnetic order transition and the transition temperature is determined to be 11.8 K (TC. The characteristic of Arrott plots with positive slope around TC was observed, indicating a second-order phase transition. Based on isothermal magnetization data, together with Maxwell’s relationship, the magnetic entropy change (-ΔSM was calculated. The maximum -ΔSM reaches 7.8, 12.7 and 14.4 J/kg K for field range of 0-2 T, 0-5 T and 0-7 T, respectively. Accordingly, the value of RC (refrigerant capacity is 99, 289 and 432 J/kg for above field ranges. The large MCE of HoCo3B2 compound indicates its potential application for magnetic refrigeration in low temperature range.

  10. Pressure effect on magnetic and magnetotransport properties of intermetallic and colossal magnetoresistance oxide compounds

    International Nuclear Information System (INIS)

    Arnold, Z; Ibarra, M R; Algarabel, P A; Marquina, C; Teresa, Jose MarIa de; Morellon, L; Blasco, J; Magen, C; Prokhnenko, O; Kamarad, J; Ritter, C

    2005-01-01

    The joint power of neutron diffraction and pressure techniques allows us to characterize under unique conditions the nature and different role of basic interactions in solids. We have covered a broad phenomenology in archetypical compounds: intermetallics and magnetic oxides. We have selected compounds in which the effect of moderate pressure is able to modify the electronic structure and bond angles that in turn are in the bases of magnetic and structural transitions. Complex magnetic and structural phase diagrams are reported for compounds with magnetic (Tb 1-X Y X Mn 2 ) and structural (RE 5 Si 4-X Ge X ) instabilities. Pressure-induced change of the magnetic structure in (R 2 Fe 17 ) intermetallics and the effect on the colossal magnetoresistance manganites are described

  11. Spin polarization in rare earth intermetallic compounds

    International Nuclear Information System (INIS)

    Steenwijk, F.J. van

    1976-01-01

    In this thesis the results of Moessbauer experiments performed on a series of intermetallic compounds of europium and gadolinium are reported. For each of these compounds the magnetic hyperfine field, the electric field gradient at the nuclear site and the isomer shift were determined. For most of the compounds the magnetic ordering temperature was also measured. For some of the europium compounds (e.g. EuAu 5 , EuAg 5 , and EuCu 5 ) it could be derived from the measurements that the easy direction of magnetization falls along the crystallographic c-axis. In a number of compounds (e.g. EuCu 5 , EuZn 5 , EuAu 2 and GdCu 5 ), the various contributions to the magnetic hyperfine field were disentangled by the investigation of suitable pseudobinary compounds that are dilute in Eu. The neighbour contribution Hsub(N) and the paramagnetic Curie temperature thetasub(p) were compared with each other in terms of the RKKY model for EuCu 5 and GdCu 5 . Since the correspondence was found to be poor it was concluded that the magnetic behaviour in these compounds cannot be described by a simple free electron picture as is the basis for the RKKY model

  12. 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.

  13. Unstable magnetic moments in Ce compounds

    International Nuclear Information System (INIS)

    Aarts, J.

    1984-01-01

    The problems which are connected with the appearance or disappearance of local moments in metals are well reflected in the magnetic behaviour of Ce intermetallic compounds. This work describes experiments on two Ce compounds which are typical examples of unstable moment systems. The first of these is CeAl 2 which at low temperatures, shows coexistence of antiferromagnetic order and the Kondo effect. Measurements are presented of the magnetization and the susceptibility in different magnetic field and temperature regions. An analysis of these measurements, using a model for the crystal field effects, shows the agreement between the measurements and the calculations to be reasonably good for CeAl 2 , but this agreement becomes worse upon decreasing Ce concentration. A phenomenological description of the observations is given. The second compound reported on is CeCu 2 Si 2 , the first 'heavy-fermion' superconductor to be investigated. The superconducting state is possibly formed by the quasi-particles of a non-magnetic many body singlet state, and not simply by the (sd) conduction electrons. This being a novel phenomenon, a number of experiments were performed to test this picture and to obtain a detailed description of the behaviour of CeCu 2 Si 2 . Measurements of the Meissner volume, confirmed the superconductivity to be intrinsic. (Auth.)

  14. Holistic electronic response underlying the development of magnetism in co-doped diluted magnetic semiconductors

    Science.gov (United States)

    Andriotis, Antonis N.; Menon, Madhu

    2018-05-01

    A systematic analysis of the properties of codoped diluted magnetic semiconductors (DMSs) reveals the role and the effect of the codopants in dictating the magnetic features of the DMSs. Our results indicate that the magnetic features of a codoped DMS is the outcome of synergistic electronic processes of the whole system rather than a local hybridization process isolated from the rest of the system. Specifically, the d-orbital hybridization of the (co)dopants and the introduction of their impurity bands lead to the readjustment of the position of the p-band center of the host’s anions and that of the valence band maximum (VBM). The overall effect of these is to pull the hybridized d-bands of the (co)dopants relative to the Fermi energy, E F , which in turn dictate the value of the magnetic moment of both the dopant as well as the codopant. More precisely, the magnetic moment of a dopant shows an almost linearly increasing (decreasing) variation as the dopant’s d-band center (the latter dictated by the codopant) moves away from (gets closer to) E F . Our results thus suggest a completely new approach in the investigation and understanding of the origin of the defect induced magnetism and support previous reports suggesting the Fermi-energy engineering as a mean for developing high T C DMSs. These trends are demonstrated with results obtained for GaN, GaP, and CdS doped with one of the V, Mn, Co and Cu dopants and codoped with the transition metals of the 3d-series.

  15. Magnetic and superconducting order in some random pseudobinary compounds

    International Nuclear Information System (INIS)

    Dongen, J.C.M. van.

    1982-01-01

    This thesis presents the results of a study on the magnetic and superconducting ordering phenomena in some random pseudobinary compounds. In the investigations ternary systems are utilised in which two of the elements form a binary intermetallic compound, e.g. PdH, GdCu and YCo 2 . A third element is then randomly substituted into one of the sublattices without changing the basic intermetallic compound structure. In chapter II a study is presented on the Kondo effect and spin-glass freezing of the magnetic impurities Cr, Mn, and Fe in superconducting palladium hydride. Chapter III contains a study on crystal structure transformations and magnetic ordering phenomena in GdCusub(1-x)Gasub(x) and related pseudobinary compounds. In Chapter IV experiments on the magnetic properties and the electrical resistivity of the transition metal Laves phase compounds Y(Cosub(1-x)Fesub(x)) 2 , Y(Irsub(1-x)Fesub(x)) 2 and Hf(Cosub(1-x)Fesub(x)) 2 are described. (Auth.)

  16. Influence of hydrogen absorption on magnetic ordering in some zirconium-based Laves phase compounds

    International Nuclear Information System (INIS)

    Fujii, H.; Pourarian, F.; Wallace, W.E.

    1982-01-01

    Magnetization measurements were carried out on several zirconium-based hexagonal Laves phase compounds, i.e. the ZrMnsub(2+delta), (Zr,Ti)Mn 2 , Zr(Mn,Fe) 2 and Zr(Fe,Al) 2 systems and their hydrides. The absorbed hydrogen leads to a large increase (20%-30%) in volume without a change in the crystal structure. ZrMnsub(2+delta) is a weak Pauli paramagnet but becomes a spin glass near-ferromagnet by hydriding, indicating that the manganese moments are subjected to competing ferromagnetic and antiferromagnetic coupling tendencies. In the (Zrsub(1-x)Tisub(x))Mn 2 hydrides, ferromagnetic, spin-glass-like, ferromagnetic and antiferromagnetic behaviors appear at 4.2 K in the sequence of increasing x and/or decrease in hydrogen concentration. In the Zr(Mn,Fe) 2 system, the hydrogen absorption increases both the magnetic moments and the magnetic transition temperatures, while absorbed hydrogen leads to suppression of ferromagnetism in the Zr(Fe,Al) 2 system. These varied and complex magnetic behaviors are attributed to the effects of (1) variations in the interatomic distances, (2) changes in the 3d electron concentration and (3) varying local hydrogen concentrations occurring as a result of statistical fluctuations. (Auth.)

  17. Spin polarization and magnetization of conduction-band dilute-magnetic-semiconductor quantum wells with non-step-like density of states

    International Nuclear Information System (INIS)

    Simserides, Constantinos

    2005-01-01

    We study the magnetization, M, and the spin polarization, ζ, of n-doped non-magnetic-semiconductor (NMS)/narrow to wide dilute-magnetic-semiconductor (DMS)/n-doped NMS quantum wells, as a function of the temperature, T, and the in-plane magnetic field, B. Under such conditions the density of states (DOS) deviates from the occasionally stereotypic step-like form, both quantitatively and qualitatively. The DOS modification causes an impressive fluctuation of M in cases of vigorous competition between spatial and magnetic confinement. At low T, the enhanced electron spin-splitting, U oσ , acquires its bigger value. At higher T, U oσ decreases, augmenting the influence of the spin-up electrons. Increasing B, U oσ increases and accordingly electrons populate spin-down subbands while they abandon spin-up subbands. Furthermore, due to the DOS modification, all energetically higher subbands become gradually depopulated

  18. Investigation of magnetic interactions in sulfides by means of magnetic resonance

    International Nuclear Information System (INIS)

    Veen, G. van.

    1978-01-01

    Investigations have been designed to gather more information about magnetic pair interactions in sulfides by isomorphic substitution of the magnetic ions in suitable chosen diamagnetic host lattices and measurement of electron spin resonance of coupled pairs and of electron spin resonance or electron nuclear double resonance of the hyperfine interaction due to the nuclei of diamagnetic cations. The greater part of this thesis is devoted to preliminaries of magnetic resonance interpretation and sample selection and preparation. The measurements on the magnetically diluted compounds, which are described, only have an exploratory nature. (Auth.)

  19. Synthesis and characterization of montmorillonite clay intercalated with molecular magnetic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Marcel G.; Martins, Daniel O.T.A.; Carvalho, Beatriz L.C. de [Instituto de Química, Universidade Federal Fluminense, Niterói, RJ 24.020–150 (Brazil); Mercante, Luiza A. [Laboratório Nacional de Nanotecnologia para o Agronegócio (LNNA), Embrapa Instrumentação, São Carlos, SP 13560 970 (Brazil); Soriano, Stéphane [Instituto de Física, Universidade Federal Fluminense, Niterói, RJ 24.210 346 (Brazil); Andruh, Marius [Inorganic Chemistry Laboratory, Faculty of Chemistry, University of Bucharest, Str. Dumbrava Rosie nr. 23, Bucharest (Romania); Vieira, Méri D., E-mail: gqimeri@vm.uff.br [Instituto de Química, Universidade Federal Fluminense, Niterói, RJ 24.020–150 (Brazil); Vaz, Maria G.F., E-mail: mariavaz@vm.uff.br [Instituto de Química, Universidade Federal Fluminense, Niterói, RJ 24.020–150 (Brazil)

    2015-08-15

    In this work montmorillonite (MMT) clay, whose matrix was modified with an ammonium salt (hexadecyltrimethylammonium bromide – CTAB), was employed as an inorganic host for the intercalation of three different molecular magnetic compounds through ion exchange: a nitronyl nitroxide derivative 2-[4-(N-ethyl)-pyridinium]-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (p-EtRad{sup +}) and two binuclear coordination compounds, [Ni(valpn)Ln]{sup 3+}, where H{sub 2}valpn stands for 1,3-propanediyl-bis(2-iminomethylene-6-methoxy-phenol), and Ln=Gd{sup III}; Dy{sup III}. The pristine MMT and the intercalated materials were characterized by X-ray powder diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and magnetic measurements. The X-ray diffraction data analysis showed an increase of the interlamellar space of the intercalated MMT, indicating the intercalation of the magnetic compounds. Furthermore, the magnetic properties of the hybrid compounds were investigated, showing similar behavior as the pure magnetic guest species. - Graphical abstract: Montmorillonite clay was employed as inorganic host for the intercalation of three different molecular magnetic compounds through ion exchange - Highlights: • Montmorillonite was employed as a host material. • Three molecular magnetic compounds were intercalated through ion exchange. • The compounds were successful intercalated maintaining the layered structure. • The hybrid materials exhibited similar magnetic behavior as the pure magnetic guest.

  20. Synthesis and magnetic properties of heteronuclear 3d-4f compound

    International Nuclear Information System (INIS)

    Cristovao, B.; Ferenc, W.

    2007-01-01

    A novel heteronuclear 3d-4f compound having formula NdCu 3 L 3 ·13H 2 O (where H 3 L = Schiff base derived from 5-bromosalicylaldehyde and glycylglycine and L 3 = C 11 H 8 N 2 O 4 Br) was obtained. It was characterized by elemental and thermal analyses and magnetic measurements. The Cu(II)-Nd(III) compound is stable up to 323 K. During dehydration process the water molecules are lost in two stages. The magnetic susceptibility data for this complex change with temperature according to the Curie-Weiss law with Θ = -35 K. The magnetic moment values decrease from 5.00μ B at 303 K to 4.38μB at 76 K. (author)

  1. Kondo effect and heavy fermions in Yb compounds

    International Nuclear Information System (INIS)

    Bonville, P.

    1987-01-01

    The Kondo properties of Yb dilute alloys and intermetallics have been investigated using Moessbauer spectroscopy on 170 Yb. In the dilute alloys AuYb and LaBe 13 Yb, the Kondo logarithmic anomaly of the impurity relaxation rate has been detected, and in the concentrated Yb compounds YbBe 13 , YbP and YbAs, and YbCuAl, the manifestations of the interplay between the Kondo effect and the magnetic ordering due to the RKKY interaction have been characterized

  2. Effects of dilution on the magnetic ordering of a two-dimensional lattice of dipolar magnets

    International Nuclear Information System (INIS)

    Patchedjiev, S M; Whitehead, J P; De'Bell, K

    2005-01-01

    Monte Carlo simulations are used to study the effects of dilution by random vacancies on the phenomenon of order arising from disorder in an ultrathin magnetic film. At very low concentrations of vacancies, both the collinear ordered phase observed in the undiluted system and the microvortex state are observed, and the boundary on which the reorientation transition between these states occurs is found to be consistent with the predictions of earlier work. However, even at vacancy densities as low as 0.5% there is evidence that the vacancies result in a energy landscape with a number of very nearly degenerate minima

  3. Magnetic behavior of binary intermetallic compound YPd{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Abhishek [S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Mazumdar, Chandan [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)], E-mail: chandan.mazumdar@saha.ac.in; Ranganathan, R. [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India)

    2009-05-12

    We report the results of detailed magnetic studies on binary rare-earth-transition metal compound YPd{sub 3}. The results of temperature and magnetic field dependent DC-magnetic measurements along with the results of powder X-ray diffraction measurement and electrical transport have been discussed. The X-ray data suggest a well-defined ordered crystal lattice, free from any detectable impurity phase. Magnetization data exhibits predominant diamagnetic character at higher fields. However, the compound exhibits anomalous behavior at low fields.

  4. Structural evolution of dilute magnetic (Sn,Mn)Se films grown by molecular beam epitaxy

    Science.gov (United States)

    Kanzyuba, Vasily; Dong, Sining; Liu, Xinyu; Li, Xiang; Rouvimov, Sergei; Okuno, Hanako; Mariette, Henri; Zhang, Xueqiang; Ptasinska, Sylwia; Tracy, Brian D.; Smith, David J.; Dobrowolska, Margaret; Furdyna, Jacek K.

    2017-02-01

    We describe the structural evolution of dilute magnetic (Sn,Mn)Se films grown by molecular beam epitaxy on GaAs (111) substrates, as revealed by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. When the Mn concentration is increased, the lattice of the ternary (Sn,Mn)Se films evolves quasi-coherently from a SnSe2 two-dimensional (2D) crystal structure into a more complex quasi-2D lattice rearrangement, ultimately transforming into the magnetically concentrated antiferromagnetic MnSe 3D rock-salt structure as Mn approaches 50 at. % of this material. These structural transformations are expected to underlie the evolution of magnetic properties of this ternary system reported earlier in the literature.

  5. Design of a new two-dimensional diluted magnetic semiconductor: Mn-doped GaN monolayer

    International Nuclear Information System (INIS)

    Zhao, Qian; Xiong, Zhihua; Luo, Lan; Sun, Zhenhui; Qin, Zhenzhen; Chen, Lanli; Wu, Ning

    2017-01-01

    Highlights: • It is found nonmagnetic GaN ML exhibits half-metallic FM behavior by Mn doping due to double exchange mechanism. • Interestingly, the FM coupling is enhanced with the increasing tensile strain due to stronger interaction between Mn-3d and N-2p state. • While, the FM interaction is weakened with the increasing compressive strain until it transforms into AFM under strain of −9.5%. • These results provide a feasible approach for the fabrication of 2D DMS based GaN ML. - Abstract: To meet the need of low-dimensional spintronic devices, we investigate the electronic structure and magnetic properties of Mn-doped GaN monolayer using first-principles method. We find the nonmagnetic GaN monolayer exhibits half-metallic ferromagnetism by Mn doping due to double-exchange mechanism. Interestingly, the ferromagnetic coupling in Mn-doped GaN monolayer is enhanced with tensile strain and weakened with compressive strain. What is more, the ferromagnetic–antiferromagnetic transformation occurs under compressive strain of −9.5%. These results provide a feasible approach for fabrication of a new GaN monolayer based diluted magnetic semiconductor.

  6. Design of a new two-dimensional diluted magnetic semiconductor: Mn-doped GaN monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Qian [Key Laboratory for Optoelectronics and Communication of Jiangxi Province, Jiangxi Science & Technology Normal University, Nanchang 330038 (China); Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Xiong, Zhihua, E-mail: xiong_zhihua@126.com [Key Laboratory for Optoelectronics and Communication of Jiangxi Province, Jiangxi Science & Technology Normal University, Nanchang 330038 (China); Luo, Lan [School of Materials Science and Engineering, Nanchang University, Nanchang 330031 (China); Sun, Zhenhui [Key Laboratory for Optoelectronics and Communication of Jiangxi Province, Jiangxi Science & Technology Normal University, Nanchang 330038 (China); Qin, Zhenzhen [College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071 (China); Chen, Lanli [Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Wu, Ning [Key Laboratory for Optoelectronics and Communication of Jiangxi Province, Jiangxi Science & Technology Normal University, Nanchang 330038 (China)

    2017-02-28

    Highlights: • It is found nonmagnetic GaN ML exhibits half-metallic FM behavior by Mn doping due to double exchange mechanism. • Interestingly, the FM coupling is enhanced with the increasing tensile strain due to stronger interaction between Mn-3d and N-2p state. • While, the FM interaction is weakened with the increasing compressive strain until it transforms into AFM under strain of −9.5%. • These results provide a feasible approach for the fabrication of 2D DMS based GaN ML. - Abstract: To meet the need of low-dimensional spintronic devices, we investigate the electronic structure and magnetic properties of Mn-doped GaN monolayer using first-principles method. We find the nonmagnetic GaN monolayer exhibits half-metallic ferromagnetism by Mn doping due to double-exchange mechanism. Interestingly, the ferromagnetic coupling in Mn-doped GaN monolayer is enhanced with tensile strain and weakened with compressive strain. What is more, the ferromagnetic–antiferromagnetic transformation occurs under compressive strain of −9.5%. These results provide a feasible approach for fabrication of a new GaN monolayer based diluted magnetic semiconductor.

  7. Ferromagnetism in diluted magnetic semiconductors: A comparision between AB INITIO mean-field, RPA, and Monte Carlo treatments

    Czech Academy of Sciences Publication Activity Database

    Bouzerar, G.; Kudrnovský, Josef; Bergqist, L.; Bruno, P.

    2003-01-01

    Roč. 68, č. 8 (2003), s. 081203-1 - 081203-4 ISSN 0163-1829 R&D Projects: GA AV ČR IAA1010203 Grant - others:RTN(XX) HPRN-CT-2000-00143 Institutional research plan: CEZ:AV0Z1010914 Keywords : Curie temperature * diluted magnetic semiconductors * mean-field * RPA * Monte-Carlo Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.962, year: 2003

  8. Magnetic re-entrance in intermediate valence compounds

    International Nuclear Information System (INIS)

    Allub, R.; Machiavelli, O.; Balseiro, C.; Alascio, B.

    1980-01-01

    The possibility is explored of magnetic re-entrance in intermediate valence compounds. Using a simplified Anderson-Lattice model the pressure-temperature magnetic phase diagram is obtained. This diagram shows that for some value of the microscopic parameters the temperature induced two transitions (non-magnetic to magnetically ordered to paramagnetic). The magnetization and the average occupation number of the localized state are calculated. Estimations of the observability of the effect in systems like CeAl 2 are made. (author)

  9. Self-consistent electronic structure of spin-polarized dilute magnetic semiconductor quantum wells

    International Nuclear Information System (INIS)

    Hong, S. P.; Yi, K. S.; Quinn, J. J.

    2000-01-01

    The electronic properties of spin-symmetry-broken dilute magnetic semiconductor quantum wells are investigated self-consistently at zero temperature. The spin-split subband structure and carrier concentration of modulation-doped quantum wells are examined in the presence of a strong magnetic field. The effects of exchange and correlations of electrons are included in a local-spin-density-functional approximation. We demonstrate that exchange correlation of electrons decreases the spin-split subband energy but enhances the carrier density in a spin-polarized quantum well. We also observe that as the magnetic field increases, the concentration of spin-down (majority) electrons increases but that of spin-up (minority) electrons decreases. The effect of orbital quantization on the in-plane motion of electrons is also examined and shows a sawtoothlike variation in subband electron concentrations as the magnetic-field intensity increases. The latter variation is attributed to the presence of ionized donors acting as the electron reservoir, which is partially responsible for the formation of the integer quantum Hall plateaus. (c) 2000 The American Physical Society

  10. Charge and Spin Transport in Dilute Magnetic Semiconductors. Final report

    International Nuclear Information System (INIS)

    Ullrich, Carsten A.

    2009-01-01

    This proposal to the DOE outlines a three-year plan of research in theoretical and computational condensed-matter physics, with the aim of developing a microscopic theory for charge and spin dynamics in disordered materials with magnetic impurities. Important representatives of this class of materials are the dilute magnetic semiconductors (DMS), which have attracted great attention as a promising basis for spintronics devices. There is an intense experimental effort underway to study the transport properties of ferromagnetic DMS such as (Ga,Mn)As, and a number of interesting features have emerged: negative magnetoresistance, anomalous Hall effect, non-Drude dynamical conductivity, and resistivity maxima at the Curie temperature. Available theories have been able to account for some of these features, but at present we are still far away from a systematic microscopic understanding of transport in DMS. We propose to address this challenge by developing a theory of charge and spin dynamics based on a combination of the memory-function formalism and time-dependent density functional theory. This approach will be capable of dealing with two important issues: (a) the strong degree of correlated disorder in DMS, close to the localization transition (which invalidates the usual relaxation-time approximation to the Boltzmann equation), (b) the essentially unknown role of dynamical many-body effects such as spin Coulomb drag. We will calculate static and dynamical conductivities in DMS as functions of magnetic order and carrier density, which will advance our understanding of recent transport and infrared absorption measurements. Furthermore, we will study collective plasmon excitations in DMS (3D, 2D and quantum wells), whose linewidths could constitute a new experimental probe of the correlation of disorder, many-body effects and charge and spin dynamics in these materials.

  11. Electronic and magnetic structures of ferrimagnetic Mn{sub 2}Sb compound

    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, 63 46000 Safi (Morocco); LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Mounkachi, O.; El moussaoui, H. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco)

    2015-01-15

    The Self-consistent ab initio calculations, based on DFT (Density Functional Theory) approach and using FLAPW (Full potential Linear Augmented Plane Wave) method, are performed to investigate both electronic and magnetic properties of the Mn{sub 2}Sb compound. Polarized spin and spin–orbit coupling are included in calculations within the framework of the antiferromagnetic state between two adjacent Mn{sub 1} and Mn{sub 2} atoms. Magnetic moment considered to lie along (0 0 1) axes are computed. The antiferromagnetic energy of Mn{sub 2}Sb systems is obtained. Obtained data from ab initio calculations are used as input for the high temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The exchange interactions between the magnetic atoms Mn{sub 1}−Mn{sub 2} in Mn{sub 2}Sb are given by using the mean field theory. The HTSEs of the magnetic susceptibility of with the magnetic moments in Mn{sub 2}Sb (m{sub Mn{sub 1}}and m{sub Mn{sub 2}}) through Ising model is given up to tenth order series in (x=J(Mn{sub 1}−Mn{sub 2})/k{sub B}T). The Néel temperature T{sub N}(K) is obtained by HTSEs applied to the magnetic susceptibility series combined with the Padé approximant method. The critical exponent γ associated with the magnetic susceptibility is deduced as well. - Highlights: • Ab initio calculations is using to investigate both electronic and magnetic properties of the Mn{sub 2}Sb compound. • Obtained data from ab initio calculations are used as input for the HTSEs. • The Néel temperature is obtained for Mn{sub 2}Sb compound.

  12. Structural stability at high pressure, electronic, and magnetic properties of BaFZnAs: A new candidate of host material of diluted magnetic semiconductors

    International Nuclear Information System (INIS)

    Chen Bi-Juan; Deng Zheng; Wang Xian-Cheng; Feng Shao-Min; Yuan Zhen; Zhang Si-Jia; Liu Qing-Qing; Jin Chang-Qing

    2016-01-01

    The layered semiconductor BaFZnAs with the tetragonal ZrCuSiAs-type structure has been successfully synthesized. Both the in-situ high-pressure synchrotron x-ray diffraction and the high-pressure Raman scattering measurements demonstrate that the structure of BaFZnAs is stable under pressure up to 17.5 GPa at room temperature. The resistivity and the magnetic susceptibility data show that BaFZnAs is a non-magnetic semiconductor. BaFZnAs is recommended as a candidate of the host material of diluted magnetic semiconductor. (special topic)

  13. Electronic structure, local magnetism, and spin-orbit effects of Ir(IV)-, Ir(V)-, and Ir(VI)-based compounds

    Energy Technology Data Exchange (ETDEWEB)

    Laguna-Marco, M. A.; Kayser, P.; Alonso, J. A.; Martínez-Lope, M. J.; van Veenendaal, M.; Choi, Y.; Haskel, D.

    2015-06-01

    Element- and orbital-selective x-ray absorption and magnetic circular dichroism measurements are carried out to probe the electronic structure and magnetism of Ir 5d electronic states in double perovskite Sr2MIrO6 (M = Mg, Ca, Sc, Ti, Ni, Fe, Zn, In) and La2NiIrO6 compounds. All the studied systems present a significant influence of spin-orbit interactions in the electronic ground state. In addition, we find that the Ir 5d local magnetic moment shows different character depending on the oxidation state despite the net magnetization being similar for all the compounds. Ir carries an orbital contribution comparable to the spin contribution for Ir4+ (5d(5)) and Ir5+ (5d(4)) oxides, whereas the orbital contribution is quenched for Ir6+ (5d(3)) samples. Incorporation of a magnetic 3d atom allows getting insight into the magnetic coupling between 5d and 3d transition metals. Together with previous susceptibility and neutron diffractionmeasurements, the results indicate that Ir carries a significant local magnetic moment even in samples without a 3d metal. The size of the (small) net magnetization of these compounds is a result of predominant antiferromagnetic interactions between local moments coupled with structural details of each perovskite structure

  14. Electronic and magnetic properties of intermetallic compound YCo5

    International Nuclear Information System (INIS)

    Zhang, G.W.; Feng, Y.P.; Ong, C.K.

    1998-01-01

    The electronic and magnetic properties of the intermetallic compound YCo 5 have been studied using density functional theory with the local spin density approximation. The calculated magnetic moments of Y, Co(2c) and Co(3g) are -0.61, 1.68 and 2.04 μ B , respectively, and the total magnetic moment is about 8.87 μ B per formula unit, which agrees well with the previous experimental results. The dependence of the magnetic moments of Y, Co(2c) and Co(3g) on the lattice spacing has been investigated. The local electronic structure of Y, Co(2c) and Co(3g) are discussed in detail. The local magnetic susceptibilities of Y, Co(2c) and Co(3g) are calculated. Based on our results, YCo 5 was found to have characteristic of a strong ferromagnet. (orig.)

  15. Polarization-preserving confocal microscope for optical experiments in a dilution refrigerator with high magnetic field.

    Science.gov (United States)

    Sladkov, Maksym; Bakker, M P; Chaubal, A U; Reuter, D; Wieck, A D; van der Wal, C H

    2011-04-01

    We present the design and operation of a fiber-based cryogenic confocal microscope. It is designed as a compact cold-finger that fits inside the bore of a superconducting magnet, and which is a modular unit that can be easily swapped between use in a dilution refrigerator and other cryostats. We aimed at application in quantum optical experiments with electron spins in semiconductors and the design has been optimized for driving with and detection of optical fields with well-defined polarizations. This was implemented with optical access via a polarization maintaining fiber together with Voigt geometry at the cold finger, which circumvents Faraday rotations in the optical components in high magnetic fields. Our unit is versatile for use in experiments that measure photoluminescence, reflection, or transmission, as we demonstrate with a quantum optical experiment with an ensemble of donor-bound electrons in a thin GaAs film. © 2011 American Institute of Physics

  16. Construction and performance of a dilution-refrigerator based spectroscopic-imaging scanning tunneling microscope.

    Science.gov (United States)

    Singh, U R; Enayat, M; White, S C; Wahl, P

    2013-01-01

    We report on the set-up and performance of a dilution-refrigerator based spectroscopic imaging scanning tunneling microscope. It operates at temperatures below 10 mK and in magnetic fields up to 14T. The system allows for sample transfer and in situ cleavage. We present first-results demonstrating atomic resolution and the multi-gap structure of the superconducting gap of NbSe(2) at base temperature. To determine the energy resolution of our system we have measured a normal metal/vacuum/superconductor tunneling junction consisting of an aluminum tip on a gold sample. Our system allows for continuous measurements at base temperature on time scales of up to ≈170 h.

  17. Carbon based magnetism an overview of the magnetism of metal free carbon-based compounds and materials

    CERN Document Server

    Makarova, Tatiana

    2006-01-01

    Magnetism is one of the most intriguing phenomena observed in nature. Magnetism is relevant to physics and geology, biology and chemistry. Traditional magnets, an ubiquitous part of many everyday gadgets, are made of heavy iron- or nickel based materials. Recently there have been reports on the observation of magnetism in carbon, a very light and biocompatible element. Metal-free carbon structures exhibiting magnetic ordering represent a new class of materials and open a novel field of research that could lead to many new technologies. · The most complete, detailed, and accurate Guide in the magnetism of carbon · Dynamically written by the leading experts · Deals with recent scientific highlights · Gathers together chemists and physicists, theoreticians and experimentalists · Unified treatment rather than a series of individually authored papers · Description of genuine organic molecular ferromagnets · Unique description of new carbon materials with Curie temperatures well above ambient.

  18. Magnetic properties of Fe-rich rare-earth intermetallic compounds with a ThMn12 structure

    International Nuclear Information System (INIS)

    Ohashi, K.; Tawara, Y.; Osugi, R.; Shimao, M.

    1988-01-01

    Sm(Fe/sub 1-//sub x/M/sub x/) 12 ternary compounds based on the tetragonal ThMn 12 structure where M is Ti, Si, V, Cr, and Mo were investigated. M atoms have a preference for site occupation. Ti atoms occupy the 8i or 8j site and Cr atoms occupy the 8i site. Curie temperatures on Sm(M,Fe) 12 compounds are around 590 K except for the SmMo 2 Fe 10 compound (T/sub c/ = 483 K). The SmTiFe 11 and SmSi 2 Fe 10 compounds have a high saturation magnetization and magnetic anisotropy

  19. Study of the magnetic properties of Tb(Cosub(1-x)Nisub(x))sub(5) compounds

    International Nuclear Information System (INIS)

    Pirogov, A.N.; Kelarev, V.V.; Ermolenko, A.S.; Chuev, V.V.; Sidorov, S.K.; Artamonova, A.M.

    1982-01-01

    The crystal and magnetic structures of Tb(Cosub(1-x)Nisub(x))sub(5) compounds are investigated by neutron-diffraction and magnetic techniques. It is shown that the Ni ions occupy predominantly the 2c positions and the Co ions 3g positions in the crystal unit of the CaCu 5 type of structure. The magnetic phase diagram is set up. From an analysis of the concentration dependence of the magnetizations of the 2c- and 3g-sublattices it is concluded that the magnetic moments at the Co ions are constant. The magnetic moment of the Ni ions in the compounds studied are found to depend on the concentration x. Estimations based on the assumption of constancy of the R-R and R-Co exchange interaction energies indicate that Co-Co interactions contribute significantly to the Curie temperature of compounds with a low Co content (x=0.8). It is found that the temperature dependence of the magnetization of the 2c-sublattice is related to the direction of the easy magnetization axis of the crystal, a consequence being a jump of the magnetization in the easy plane - easy axis transition. On this basis it is concluded that Co atoms in the 2c positions give the major contribution to the magnetic anisotropy of Co sublattice for compounds of the RCo 5 type

  20. Identification of compounds with binding affinity to proteins via magnetization transfer from bulk water

    International Nuclear Information System (INIS)

    Dalvit, Claudio; Pevarello, Paolo; Tato, Marco; Veronesi, Marina; Vulpetti, Anna; Sundstroem, Michael

    2000-01-01

    A powerful screening by NMR methodology (WaterLOGSY), based on transfer of magnetization from bulk water, for the identification of compounds that interact with target biomolecules (proteins, RNA and DNA fragments) is described. The method exploits efficiently the large reservoir of H 2 O magnetization. The high sensitivity of the technique reduces the amount of biomolecule and ligands needed for the screening, which constitutes an important requirement for high throughput screening by NMR of large libraries of compounds. Application of the method to a compound mixture against the cyclin-dependent kinase 2 (cdk2) protein is presented

  1. Key volatile aroma compounds of lactic acid fermented malt based beverages - impact of lactic acid bacteria strains.

    Science.gov (United States)

    Nsogning Dongmo, Sorelle; Sacher, Bertram; Kollmannsberger, Hubert; Becker, Thomas

    2017-08-15

    This study aims to define the aroma composition and key aroma compounds of barley malt wort beverages produced from fermentation using six lactic acid bacteria (LAB) strains. Gas chromatography mass spectrometry-olfactometry and flame ionization detection was employed; key aroma compounds were determined by means of aroma extract dilution analysis. Fifty-six detected volatile compounds were similar among beverages. However, significant differences were observed in the concentration of individual compounds. Key aroma compounds (flavor dilution (FD) factors ≥16) were β-damascenone, furaneol, phenylacetic acid, 2-phenylethanol, 4-vinylguaiacol, sotolon, methional, vanillin, acetic acid, nor-furaneol, guaiacol and ethyl 2-methylbutanoate. Furthermore, acetaldehyde had the greatest odor activity value of up to 4266. Sensory analyses revealed large differences in the flavor profile. Beverage from L. plantarum Lp. 758 showed the highest FD factors in key aroma compounds and was correlated to fruity flavors. Therefore, we suggest that suitable LAB strain selection may improve the flavor of malt based beverages. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. Magnetic moment densities in selected UTX compounds

    Czech Academy of Sciences Publication Activity Database

    Javorský, P.; Schweizer, J.; Givord, F.; Boucherle, J.-X.; Andreev, Alexander V.; Diviš, M.; Lelievre-Berna, E.; Sechovský, V.

    2004-01-01

    Roč. 350, - (2004), e131-e134 ISSN 0921-4526 R&D Projects: GA ČR GA202/03/0550 Institutional research plan: CEZ:AV0Z1010914 Keywords : uranium compound * polarized neutron scattering * magnetic moment Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.679, year: 2004

  3. Comparative Study of Magnetic Instabilities in Cerium Compounds

    International Nuclear Information System (INIS)

    Pedrazzini, Pablo

    2003-01-01

    The variety of new phases and physical phenomena discovered in intermetallic compounds containing Rare Earths or Actinides has motivated, during the last four decades, the sustained study of their magnetic phase diagrams.The current interest is focused on the investigation of the region of the phase diagram where the magnetic order of Cerium, Ytterbium and Uranium based systems is destabilized.In this region different behaviours have been detected, such as non conventional superconductivity and the anomalous dependencies of the thermal, magnetic and transport properties at very low temperatures, associated to non-Fermi liquid behaviour.A simple model, the Doniach diagram, has guided the interpretation of the destabilization of the magnetic order in the previously mentioned systems.However, most of the systems that have been studied so far cannot be described within this model.This fact has motivated the development of a phenomenological classification of phase diagrams that has been mostly applied to cerium based compounds.This classification defines three types of phase diagrams, that can be distinguished by the way in which the magnetic transition is suppressed when a control parameter (such as doping or pressure) is driven towards its critical value.Within this scenario, we study the suppression of the antiferromagnetic order of the intermetallic compounds CeIn 3 , CeRh 2 Si 2 and CePd 2 Al 3 as a function of Ce-ligand alloying.The resulting systems, CeIn 3-x Sn x , Ce(Cu x Rh 1-x ) 2 Si 2 and CePd 2-x Ni x Al 3 , present different crystalline structures and the effects produced by the alloying process are different in each case.We analyse the resulting magnetic phase diagrams, and compare them with the above mentioned phenomenological classification.With such a purpose, we study in detail the region in which the magnetic instability takes place, in the proximity of the respective critical concentrations.Taking into account both our results and those reported in

  4. Nuclear magnetic resonance of randomly diluted magnetic materials

    International Nuclear Information System (INIS)

    Magon, C.J.

    1985-01-01

    The temperature dependence of the nuclear relaxation rates and line shapes of the F O resonance in the diluted antiferromagnet Fe x Zn 1-x F 2 and Mn x Zn 1-x F 2 are studied over a large temperature range T N 1 ) of the F O nuclei, which are not transfer hyperfine coupled to the Fe (or Mn) spins, have been measured and calculated as a function of the concentration x. Good agreement with experiment is found for the theoretical results, which have been obtained in the range 0.1 ≤ x ≤ 0.8. The temperature dependence of 1/T 1 for T N 1 data near T N was used to study Random Field Effects on the critical behavior of Mn .65 Zn . 3 5 F 2 , for fields applied parallel and perpendicular to the easy (C) axis. It was found that the transition temperature T N depressed substantially with field only for H o || C. The experimental results are in general accord with the theory for Random Field Effects in disordered, anisotropic antiferromagnets. The critical divergence of the inhomogeneously broadened F O NMR was studied in Fe .6 Zn .4 F 2 above T N . The experimental results agree with Heller's calculation of the NMR line broadening by Random Field Effects. With H o || C the line shape changes from Gaussian towards Lozentzian for t -2 and below T N its line width increase qualitatively following the increase in the sublattice magnetization. (author)

  5. Magnetic susceptibility of Dirac fermions, Bi-Sb alloys, interacting Bloch fermions, dilute nonmagnetic alloys, and Kondo alloys

    Energy Technology Data Exchange (ETDEWEB)

    Buot, Felix A., E-mail: fbuot@gmu.edu [Computational Materials Science Center, George Mason University, Fairfax, VA 22030 (United States); TCSE Center, Spintronics Group, Physics Department, University of San Carlos, Talamban, Cebu 6000 (Philippines); C& LB Research Institute, Carmen, Cebu 6005 (Philippines); Otadoy, Roland E.S.; Rivero, Karla B. [TCSE Center, Spintronics Group, Physics Department, University of San Carlos, Talamban, Cebu 6000 (Philippines)

    2017-03-01

    Wide ranging interest in Dirac Hamiltonian is due to the emergence of novel materials, namely, graphene, topological insulators and superconductors, the newly-discovered Weyl semimetals, and still actively-sought after Majorana fermions in real materials. We give a brief review of the relativistic Dirac quantum mechanics and its impact in the developments of modern physics. The quantum band dynamics of Dirac Hamiltonian is crucial in resolving the giant diamagnetism of bismuth and Bi-Sb alloys. Quantitative agreement of the theory with the experiments on Bi-Sb alloys has been achieved, and physically meaningful contributions to the diamagnetism has been identified. We also treat relativistic Dirac fermion as an interband dynamics in uniform magnetic fields. For the interacting Bloch electrons, the role of translation symmetry for calculating the magnetic susceptibility avoids any approximation to second order in the field. The expressions for magnetic susceptibility of dilute nonmagnetic alloys give a firm theoretical foundation of the empirical formulas used in fitting experimental results. The unified treatment of all the above calculations is based on the lattice Weyl-Wigner formulation of discrete phase-space quantum mechanics. For completeness, the magnetic susceptibility of Kondo alloys is also given since Dirac fermions in conduction band and magnetic impurities exhibit Kondo effect.

  6. Pump-probe spectroscopy of spin-injection dynamics in double quantum wells of diluted magnetic semiconductor

    International Nuclear Information System (INIS)

    Nishibayashi, K.; Aoshima, I.; Souma, I.; Murayama, A.; Oka, Y.

    2006-01-01

    Dynamics of spin injection has been investigated in a double quantum well (DQW) composed of a diluted magnetic semiconductor by the pump-probe transient absorption spectroscopy in magnetic field. The DQW consists of a non-magnetic well (NMW) of CdTe and a magnetic well (MW) of Cd 0.92 Mn 0.08 Te. The MW shows a transient absorption saturation in the exciton band for more than 200 ps after the optical pumping, while the exciton photoluminescence does not arise from the MW. In the NMW, the circular polarization degree of the transient absorption saturation shows an increase with increasing time. The results are interpreted by the individual tunneling of spin-polarized electrons and holes from the MW to the NMW with different tunneling times. Depolarization processes of the carrier spins in the MW and the NMW are also discussed

  7. Approaches of aroma extraction dilution analysis (AEDA) for headspace solid phase microextraction and gas chromatography-olfactometry (HS-SPME-GC-O): Altering sample amount, diluting the sample or adjusting split ratio?

    Science.gov (United States)

    Feng, Yunzi; Cai, Yu; Sun-Waterhouse, Dongxiao; Cui, Chun; Su, Guowan; Lin, Lianzhu; Zhao, Mouming

    2015-11-15

    Aroma extract dilution analysis (AEDA) is widely used for the screening of aroma-active compounds in gas chromatography-olfactometry (GC-O). In this study, three aroma dilution methods, (I) using different test sample volumes, (II) diluting samples, and (III) adjusting the GC injector split ratio, were compared for the analysis of volatiles by using HS-SPME-AEDA. Results showed that adjusting the GC injector split ratio (III) was the most desirable approach, based on the linearity relationships between Ln (normalised peak area) and Ln (normalised flavour dilution factors). Thereafter this dilution method was applied in the analysis of aroma-active compounds in Japanese soy sauce and 36 key odorants were found in this study. The most intense aroma-active components in Japanese soy sauce were: ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, ethyl 4-methylpentanoate, 3-(methylthio)propanal, 1-octen-3-ol, 2-methoxyphenol, 4-ethyl-2-methoxyphenol, 2-methoxy-4-vinylphenol, 2-phenylethanol, and 4-hydroxy-5-ethyl-2-methyl-3(2H)-furanone. Copyright © 2015. Published by Elsevier Ltd.

  8. Large magnetocaloric effect of NdGa compound due to successive magnetic transitions

    Science.gov (United States)

    Zheng, X. Q.; Xu, J. W.; Shao, S. H.; Zhang, H.; Zhang, J. Y.; Wang, S. G.; Xu, Z. Y.; Wang, L. C.; Chen, J.; Shen, B. G.

    2018-05-01

    The magnetic behavior and MCE property of NdGa compound were studied in detail. According to the temperature dependence of magnetization (M-T) curve at 0.01 T, two sharp changes were observed at 20 K (TSR) and 42 K (TC), respectively, corresponding to spin reorientation and FM-PM transition. Isothermal magnetization curves up to 5 T at different temperatures were measured and magnetic entropy change (ΔSM) was calculated based on M-H data. Temperature dependences of -ΔSM for a field change of 0-2 T and 0-5 T show that there are two peaks on the curves corresponding to TSR and TC, respectively. The value of the two peaks is 6.4 J/kg K and 15.5 J/kg K for the field change of 0-5 T. Since the two peaks are close, the value of -ΔSM in the temperature range between TSR and TC keeps a large value. The excellent MCE performance of NdGa compound benefits from the existence of two successive magnetic transitions.

  9. Magneto-transport and optical control of magnetization in organic systems: From polymers to molecule-based magnets

    Science.gov (United States)

    Bozdag, Kadriye Deniz

    Organic systems can be synthesized to have various impressive properties such as room temperature magnetism, electrical conductivity as high as conventional metals and magnetic field dependent transport. In this dissertation, we report comprehensive experimental studies in two different classes of organic systems, V-Cr Prussian blue molecule-based magnets and polyaniline nanofiber networks. The first system, V-Cr Prussian blue magnets, belongs to a family of cyano-bridged bi-metallic compounds which display a broad range of interesting photoinduced magnetic properties. A notable example for optically controllable molecule-based magnets is Co-Fe Prussian blue magnet (Tc ˜ 12 K), which exhibits light-induced changes in between magnetic states together with glassy behavior. In this dissertation, the first reports of reversible photoinduced magnetic phenomena in V-Cr Prussian blue analogs and the analysis of its AC and DC magnetization behavior are presented. Optical excitation of V-Cr Prussian blue, one of the few room temperature molecule-based magnets, with UV light (lambda = 350 nm) suppresses magnetization, whereas subsequent excitation with green light (lambda = 514 nm) increases magnetization. The partial recovery effect of green light is observed only when the sample is previously UV-irradiated. Moreover the photoinduced state has a long lifetime at low temperatures (tau > 106 s at T = 10 K) indicating that V-Cr Prussian blue reaches a hidden metastable state upon illumination with UV light. The effects of optical excitation are maintained up to 200 K and completely erased when the sample is warmed above 250 K. Results of detailed magnetic studies and the likely microscopic mechanisms for the photo illumination effects on magnetic properties are discussed. The second organic system, polyaniline nanofiber networks, was synthesized via dilute polymerization and studied at low and high electric and magnetic fields for temperatures 2 K--250 K for their magneto

  10. On the influence of the hydrodynamic interactions on the aggregation rate of magnetic spheres in a dilute suspension

    International Nuclear Information System (INIS)

    Cunha, F.R.; Couto, H.L.G.

    2011-01-01

    Magnetostatic attraction may lead to formation of aggregates in stable colloidal magnetic suspensions and magneto-rheological suspensions. The aggregation problem of magnetic composites under differential sedimentation is a key problem in the control of the instability of non-Brownian suspensions. Against these attractive forces are the electrostatic repulsion and the hydrodynamic interactions acting as stabilizing effects to the suspension. This work concerns an investigation of the pairwise interaction of magnetic particles in a dilute sedimenting suspension. We focus attention on suspensions where the Peclet number is large (negligible Brownian motion) and where the Reynolds number (negligible inertia) is small. The suspension is composed of magnetic micro-spheres of different radius and density immersed in a Newtonian fluid moving under the action of gravity. The theoretical calculations are based on direct computations of the hydrodynamic and the magnetic interactions among the rigid spheres in the regime of low particle Reynolds number. From the limiting trajectory in which aggregation occurs, we calculate the collision efficiency, representing the dimensionless rate at which aggregates are formed. The numerical results show clear evidence that the hydrodynamic interactions are of fundamental relevance in the process of magnetic particle aggregation. We compare the stabilizing effects between electrostatic repulsion and hydrodynamic interactions.

  11. On the influence of the hydrodynamic interactions on the aggregation rate of magnetic spheres in a dilute suspension

    Energy Technology Data Exchange (ETDEWEB)

    Cunha, F.R., E-mail: frcunha@unb.b [Universidade de Brasilia, Faculdade de Tecnologia, Depto. de Engenharia Mecanica, Grupo de Mecanica dos Fluidos de Escoamentos Complexos - VORTEX, Campus Universitario Darcy Ribeiro, 70910-900, Brasilia, DF (Brazil); Couto, H.L.G. [Universidade de Brasilia, Faculdade de Tecnologia, Depto. de Engenharia Mecanica, Grupo de Mecanica dos Fluidos de Escoamentos Complexos - VORTEX, Campus Universitario Darcy Ribeiro, 70910-900, Brasilia, DF (Brazil)

    2011-01-15

    Magnetostatic attraction may lead to formation of aggregates in stable colloidal magnetic suspensions and magneto-rheological suspensions. The aggregation problem of magnetic composites under differential sedimentation is a key problem in the control of the instability of non-Brownian suspensions. Against these attractive forces are the electrostatic repulsion and the hydrodynamic interactions acting as stabilizing effects to the suspension. This work concerns an investigation of the pairwise interaction of magnetic particles in a dilute sedimenting suspension. We focus attention on suspensions where the Peclet number is large (negligible Brownian motion) and where the Reynolds number (negligible inertia) is small. The suspension is composed of magnetic micro-spheres of different radius and density immersed in a Newtonian fluid moving under the action of gravity. The theoretical calculations are based on direct computations of the hydrodynamic and the magnetic interactions among the rigid spheres in the regime of low particle Reynolds number. From the limiting trajectory in which aggregation occurs, we calculate the collision efficiency, representing the dimensionless rate at which aggregates are formed. The numerical results show clear evidence that the hydrodynamic interactions are of fundamental relevance in the process of magnetic particle aggregation. We compare the stabilizing effects between electrostatic repulsion and hydrodynamic interactions.

  12. Magnetic resonance studies of intercalation compounds

    International Nuclear Information System (INIS)

    Miller, G.R.

    1990-01-01

    During the last three or four years, nearly tow hundred papers have been published that used NMR or ESR spectroscopy to study compounds formed by the intercalation of molecules or ions into the van der Waals gap of a layered hast compound. The host lattices have ranged from the simple, such as graphite, to the complex, such as clay. In many cases, magnetic resonance techniques now enable one to obtain quite detailed information on even fairly complex intercalated species, on the nature of the changes in the host lattice accompanying intercalation, and on the nature of the interactions between the intercalant species and the host lattice. Magnetic resonance is used in conunction with many other techniques to obtain a fuller picture of these interesting systems, but this review will limit its focus to the use of NMR and ESR techniques. (author). 51 refs

  13. Self-assembly of novel manganese (II) compounds based on bifunctional-group ligands: Synthesis, structures, and magnetic properties

    Science.gov (United States)

    Yan, Juan-zhi; Lu, Li-ping; Zhu, Miao-li; Feng, Si-si

    2018-06-01

    Four manganese (II) compounds are obtained by the reaction of manganese salts, triazole-derivatives and auxiliary reagents in aqueous solution or mix-solvents by routine or hydrothermal reactions. X-ray crystal structure analyses reveal that a neutral 0D compound [Mn(Hmctrz)2(H2O)2] (1) (H2mctrz = 1H-1,2,4-triazole-3-carboxylic acid) displays a centro-symmetric mononuclear octahedral entity with two Hmctrz- anions and two water molecules; two neutral 2D clusters [Mn(Hdctrz)(H2O)2]n (2) (H3dctrz = 1H-1,2,4-triazole-3,5-dicarboxylic acid) and [Mn2(pbtrz)(btca)]n·4nH2O (3) (pbtrz = 1,3-bis(1,2,4-triazol-1-yl)-propane&H4btca = benzene-1,2,4,5-tetracarboxylic acid) possess layer structures with Hdctrz2- linkers (2) and Mn(II)-pbtrz-Mn(II) building blocks periodically extended by μ-btca4- connectors (3); [Mn(pbtrz)]n·nOAc·nOH (4) shows a 3D diamond-shaped cationic framework with the anion void volume of 49.2%. Nitrogenous bases are used as the auxiliary ligand in compound 3 and the temple ligand in compounds 1, 2, and 4. Compounds 1-4 show antiferromagnetic coupling that has been fitted by different models with the molecular field approximate with D = - 0.129(1) cm-1 for 1, J = - 0.354(4) cm-1 for 2 and J = - 0.696(6) cm-1 for 3, respectively. The magnetic differences can be related to different superexchange interactions transmitted by the crystal lattice and/or the zero field splitting (ZFS) of the 6A1g single-ion states of 1 and the syn-anti-COO- of 2 as well as the mixed magnetic bridges of μ1-O and μ-pbtrz-μ-COO- of 3.

  14. Universal water-dilutable inhibited protective lubricants

    International Nuclear Information System (INIS)

    Mamtseva, M.V.; Kardash, N.V.; Latynina, M.B.

    1993-01-01

    In the interest of environmental protection, improvement of working conditions, and reduced fire hazard in production operations, water-based protective lubricants are now available in a wide assortment, and the production volume has increased greatly. The term water-dilutable inhibited protective lubricants (WDIPL) means water-soluble, water-emulsifiable, or water-dispersible products with the dual function of reducing friction and wear and protecting metal surfaces against corrosion for specified periods of time. According to the standard Unified System of Protection Against Corrosion and Aging (COST 9.103-78), WDIPLs are classed as products for the temporary corrosion protection of metals and end-items. In the general class of WDIPLs one can identify water-dilutable combination corrosion inhibitors, film-forming inhibited petroleum compositions (FIPC-d), detergent-preservative fluids, operational-preservative lubricating-cooling process compounds (ICPC), and, finally, universal multifunctional products. Combined corrosion inhibitors may consist of water-soluble organic and inorganic compounds; water/oil and oil-soluble surfactants - corrosion inhibitors of the chemisorption type or donor and/or acceptor types; shielding inhibitors of the adsorption type; and fast-acting water-displacing components. 23 refs

  15. Magnetic ordering in dilute YTb and YEr alloys

    International Nuclear Information System (INIS)

    Rainford, B.D.; Kilcoyne, S.H.; Mohammed, K.A.; Lanchester, P.C.; Stanley, H.B.; Caudron, R.

    1988-01-01

    Dilute YEr alloys (Er concentration between 3% and 10%) show the existence of sinusoidally modulated antiferromagnetism down to the lowest impurity concentrations studied. Extrapolation of the Neel temperatures for both YEr and YTb suggests a critical concentration is ≅ 0.8% Tb, Er. Ordering in such dilute alloys may result from exchange enhancement in the yttrium host

  16. Magnetic ordering in dilute YTb and YEr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Rainford, B.D.; Kilcoyne, S.H.; Mohammed, K.A.; Lanchester, P.C.; Stanley, H.B.; Caudron, R.

    1988-12-01

    Dilute YEr alloys (Er concentration between 3% and 10%) show the existence of sinusoidally modulated antiferromagnetism down to the lowest impurity concentrations studied. Extrapolation of the Neel temperatures for both YEr and YTb suggests a critical concentration is /approx equal/ 0.8% Tb, Er. Ordering in such dilute alloys may result from exchange enhancement in the yttrium host.

  17. Analysis of Magnetic Anisotropy and the Role of Magnetic Dilution in Triggering Single-Molecule Magnet (SMM) Behavior in a Family of CoII YIII Dinuclear Complexes with Easy-Plane Anisotropy.

    Science.gov (United States)

    Palacios, María A; Nehrkorn, Joscha; Suturina, Elizaveta A; Ruiz, Eliseo; Gómez-Coca, Silvia; Holldack, Karsten; Schnegg, Alexander; Krzystek, Jurek; Moreno, José M; Colacio, Enrique

    2017-08-25

    Three new closely related Co II Y III complexes of general formula [Co(μ-L)(μ-X)Y(NO 3 ) 2 ] (X - =NO 3 - 1, benzoate 2, or 9-anthracenecarboxylato 3) have been prepared with the compartmental ligand N,N',N''-trimethyl-N,N''-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H 2 L). In these complexes, Co II and Y III are triply bridged by two phenoxide groups belonging to the di-deprotonated ligand (L 2- ) and one ancillary anion X - . The change of the ancillary bridging group connecting Co II and Y III ions induces small differences in the trigonally distorted CoN 3 O 3 coordination sphere with a concomitant tuning of the magnetic anisotropy and intermolecular interactions. Direct current magnetic, high-frequency and -field EPR (HFEPR), frequency domain Fourier transform THz electron paramagnetic resonance (FD-FT THz-EPR) measurements, and ab initio theoretical calculations demonstrate that Co II ions in compounds 1-3 have large and positive D values (≈50 cm -1 ), which decrease with increasing the distortion of the pseudo-octahedral Co II coordination sphere. Dynamic ac magnetic susceptibility measurements indicate that compound 1 exhibits field-induced single-molecule magnet (SMM) behavior, whereas compounds 2 and 3 only display this behavior when they are magnetically diluted with diamagnetic Zn II (Zn/Co=10:1). In view of this, it is always advisable to use magnetically diluted complexes, in which intermolecular interactions and quantum tunneling of magnetism (QTM) would be at least partly suppressed, so that "hidden single-ion magnet (SIM)" behavior could emerge. Field- and temperature-dependence of the relaxation times indicate the prevalence of the Raman process in all these complexes above approximately 3 K. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. InSb semiconductors and (In,Mn)Sb diluted magnetic semiconductors. Growth and properties

    Energy Technology Data Exchange (ETDEWEB)

    Tran, Lien

    2011-04-13

    This dissertation describes investigations of the growth by molecular beam epitaxy and the characterization of the semiconductor InSb as well as the diluted magnetic semiconductor (DMS) In{sub 1-x}Mn{sub x}Sb. The InSb films were grown on GaAs (001) substrate and Si (001) offcut by 4 toward (110) substrate up to a thickness of about 2 {mu}m, in spite of a large lattice mismatch between the epi-layer and substrate (14.6% between InSb and GaAs, and 19.3% between InSb and Si). After optimizing the growth conditions, the best InSb films grown directly on GaAs without any special technique results in a high crystal quality, low noise, and an electron mobility of 41100 cm{sup 2}/V s Vs with associated electron concentration of 2.9.10{sup 6} cm{sup -3} at 300 K. Such structures could be used, for example, for infrared detector structures. The growth of InSb on Si, however, is a challenge. In order to successfully grow InSb on Si, tilted substrates and the insertion of buffer layers were used, which helps to reduce the lattice mismatch as well as the formation of defects, and hence to improve the crystal quality. An electron mobility of 24000 cm{sup 2}/V s measured at 300 K, with an associated carrier concentration of 2.6.10{sup 1}6 cm{sup -3} is found for the best sample that was grown at 340 C with a 0.06 {mu}m-thick GaSb/AlSb superlattice buffer layer. The smaller value of electron mobility (compared to the best GaAsbased sample) is related to a higher density of microtwins and stacking faults as well as threading dislocations in the near-interface region as shown by transmission electron microscopy. Deep level noise spectra indicate the existence of deep levels in both GaAs and Si-based samples. The samples grown on Si exhibit the lowest Hooge factor at 300 K, lower than the samples grown on GaAs. Taking the optimized growth conditions of InSb/GaAs, the diluted magnetic semiconductor In{sub 1-x}Mn{sub x}Sb/GaAs (001) is prepared by adding a few percent of Mn into the

  19. Characterization of the Major Odor-Active Compounds in the Leaves of the Curry Tree Bergera koenigii L. by Aroma Extract Dilution Analysis.

    Science.gov (United States)

    Steinhaus, Martin

    2015-04-29

    Curry leaves are a popular seasoning herb with a pronounced sulfury and burnt odor, the molecular background of which was yet unclear. Application of an aroma extract dilution analysis to the volatile fraction of curry leaves isolated by solvent extraction and solvent-assisted flavor evaporation afforded 23 odor-active compounds with flavor dilution (FD) factors ranging from 1 to 8192. On the basis of the comparison of their retention indices, mass spectra, and odor properties with data of reference compounds, the structures of 22 odorants could be assigned, 15 of which had not been reported in curry leaves before. Odorants with high FD factors included 1-phenylethanethiol (FD factor 8192), linalool (4096), α-pinene (2048), 1,8-cineole (1024), (3Z)-hex-3-enal (256), 3-(methylsulfanyl)propanal (128), myrcene (64), (3Z)-hex-3-en-1-ol (32), and (2E,6Z)-nona-2,6-dienal (32). The unique sulfury and burnt odor exhibited by 1-phenylethanethiol in combination with its high FD factor suggested that it constitutes the character impact compound of fresh curry leaf aroma.

  20. Influence of dilution and nature of the interaction on surface and interface magnetism

    International Nuclear Information System (INIS)

    Tsallis, C.

    1986-01-01

    The recent theoretical effort of the Rio de Janeiro/CBPF group on surface magnetism is tutorially reviewed. Within a real space renormalization group framework, we analyse the influence of factors such as the number of states per spin (q-state Potts model), the signs of the coupling constants (mixed ferro and antiferromagnetic interactions), the presence of a second semi-infinite bulk (interface case), the symmetry of the interaction (anisotropic Heisenberg model), and surface and/or bulk dilution (bond quenched model). A variety of interesting physical effects emerges. (Autor) [pt

  1. Experimental design-based isotope-dilution SPME-GC/MS method development for the analysis of smoke flavouring products.

    Science.gov (United States)

    Giri, Anupam; Zelinkova, Zuzana; Wenzl, Thomas

    2017-12-01

    For the implementation of Regulation (EC) No 2065/2003 related to smoke flavourings used or intended for use in or on foods a method based on solid-phase micro extraction (SPME) GC/MS was developed for the characterisation of liquid smoke products. A statistically based experimental design (DoE) was used for method optimisation. The best general conditions to quantitatively analyse the liquid smoke compounds were obtained with a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre, 60°C extraction temperature, 30 min extraction time, 250°C desorption temperature, 180 s desorption time, 15 s agitation time, and 250 rpm agitation speed. Under the optimised conditions, 119 wood pyrolysis products including furan/pyran derivatives, phenols, guaiacol, syringol, benzenediol, and their derivatives, cyclic ketones, and several other heterocyclic compounds were identified. The proposed method was repeatable (RSD% <5) and the calibration functions were linear for all compounds under study. Nine isotopically labelled internal standards were used for improving quantification of analytes by compensating matrix effects that might affect headspace equilibrium and extractability of compounds. The optimised isotope dilution SPME-GC/MS based analytical method proved to be fit for purpose, allowing the rapid identification and quantification of volatile compounds in liquid smoke flavourings.

  2. Room temperature ferromagnetism in magic-sized Cr-doped CdS diluted magnetic semiconducting quantum dots

    International Nuclear Information System (INIS)

    Srivastava, Punita; Kumar, Pushpendra; Singh, Kedar

    2011-01-01

    Manipulation of carrier spins in semiconductors for spintronics applications has received great attention driven by improved functionalities and higher speed operation. Doping of semiconductor nanocrystals by transition-metal ions pronounced as diluted magnetic semiconductors (DMS) has attracted tremendous attention. Such doping is, however, difficult to achieve in low-dimensional strongly quantum-confined nanostructures by conventional growth procedures. In the present case, magic-sized, pure, and Cr-doped CdS DM-QDs have been synthesized by solution phase chemistry (lyothermal method). Structural, optical, and magnetic investigation suggest an intrinsic nature of ferromagnetism with highly quantum-confined system. Optical and magnetic results of pure and doped QDs reveal major physical consequences of dopant localization within the capacity to engineer dopant-carrier exchange interactions introducing magnetic functionalities within the host semiconductor lattice. Unpaired Cr ions in Cd substitutional sites could create spin ordering and ferromagnetic coupling. The results presented herein illustrate some of the remarkable and unexpected complexities that can arise in doped QDs.

  3. Magnetic surfactants as molecular based-magnets with spin glass-like properties

    International Nuclear Information System (INIS)

    Brown, Paul; Hatton, T Alan; Smith, Gregory N; Hernández, Eduardo Padrón; James, Craig; Eastoe, Julian; Nunes, Wallace C; Settens, Charles M; Baker, Peter J

    2016-01-01

    This paper reports the use of muon spin relaxation spectroscopy to study how the aggregation behavior of magnetic surfactants containing lanthanide counterions may be exploited to create spin glass-like materials. Surfactants provide a unique approach to building in randomness, frustration and competing interactions into magnetic materials without requiring a lattice of ordered magnetic species or intervening ligands and elements. We demonstrate that this magnetic behavior may also be manipulated via formation of micelles rather than simple dilution, as well as via design of surfactant molecular architecture. This somewhat unexpected result indicates the potential of using novel magnetic surfactants for the generation and tuning of molecular magnets. (paper)

  4. Transition-metal-doped group-IV monochalcogenides: a combination of two-dimensional triferroics and diluted magnetic semiconductors

    Science.gov (United States)

    Yang, Liu; Wu, Menghao; Yao, Kailun

    2018-05-01

    We report the first-principles evidence of a series of two-dimensional triferroics (ferromagnetic + ferroelectric + ferroelastic), which can be obtained by doping transition-metal ions in group-IV monochalcogenide (SnS, SnSe, GeS, GeSe) monolayers, noting that a ferromagnetic Fe-doped SnS2 monolayer has recently been realized (Li B et al 2017 Nat. Commun. 8 1958). The ferroelectricity, ferroelasticity and ferromagnetism can be coupled and the magnetization direction may be switched upon ferroelectric/ferroelastic switching, rendering electrical writing + magnetic reading possible. They can be also two-dimensional half-metals or diluted magnetic semiconductors, where p/n channels or even multiferroic tunneling junctions can be designed by variation in doping and incorporated into a monolayer wafer.

  5. Insights into the Key Aroma Compounds in Mango (Mangifera indica L. 'Haden') Fruits by Stable Isotope Dilution Quantitation and Aroma Simulation Experiments.

    Science.gov (United States)

    Munafo, John P; Didzbalis, John; Schnell, Raymond J; Steinhaus, Martin

    2016-06-01

    Thirty-four aroma-active compounds, previously identified with high flavor dilution factors by application of an aroma extract dilution analysis, were quantified in tree-ripened fruits of mango (Mangifera indica L. 'Haden'). From the results, the odor activity value (OAV) was calculated for each compound as the ratio of its concentration in the mangoes to its odor threshold in water. OAVs > 1 were obtained for 24 compounds, among which ethyl 2-methylbutanoate (fruity; OAV 2100), (3E,5Z)-undeca-1,3,5-triene (pineapple-like; OAV 1900), ethyl 3-methylbutanoate (fruity; OAV 1600), and ethyl butanoate (fruity; OAV 980) were the most potent, followed by (2E,6Z)-nona-2,6-dienal (cucumber-like), ethyl 2-methylpropanoate (fruity), (E)-β-damascenone (cooked apple-like), ethyl hexanoate (fruity), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (caramel-like), 3-methylbut-2-ene-1-thiol (sulfurous), γ-decalactone (peach-like), β-myrcene (terpeny), (3Z)-hex-3-enal (green), 4-methyl-4-sulfanylpentan-2-one (tropical fruit-like), and ethyl octanoate (fruity). Aroma simulation and omission experiments revealed that these 15 compounds, when combined in a model mixture in their natural concentrations, were able to mimic the aroma of the fruits.

  6. Theoretical modeling of diluted antiferromagnetic systems

    International Nuclear Information System (INIS)

    Pozo, J; Elgueta, R; Acevedo, R

    2000-01-01

    Some magnetic properties of a Diluted Antiferromagnetic System (DAFS) are studied. The model of the two sub-networks for antiferromagnetism is used and a Heisenberg Hamiltonian type is proposed, where the square operators are expressed in terms of boson operators with the approach of spin waves. The behavior of the diluted system's fundamental state depends basically on the competition effect between the anisotropy field and the Weiss molecular field. The approach used allows the diluted system to be worked for strong anisotropies as well as when these are very weak

  7. Crystal fields of dilute Tb, Dy, Ho, or Er in Lu obtained by magnetization measurements

    International Nuclear Information System (INIS)

    Touborg, P.; Hog, J.

    1975-01-01

    Magnetization measurements are reported on single crystals of dilute Tb, Dy, Ho, or Er in Lu. These measurements were performed in the temperature range 1.5--100 K and field range 0--6 T and include measurements of initial susceptibility, isothermal and isofield magnetization, and basal-plane anisotropy. The results show features similar to the corresponding Y-R alloys, where R is a rare earth. Crystal-field and molecular-field parameters could be unabiguously deduced from the experimental data. The effects of crystal-field level broadening were investigated and demonstrated for Ho. Comparison of the Y-R and Lu-R results makes possible an estimate of the crystal-field parameters in the pure-rare-earth metals

  8. Crystal and magnetic structure of TbFe{sub 0.25}Ge{sub 2} compound

    Energy Technology Data Exchange (ETDEWEB)

    Gil, A., E-mail: a.gil@ajd.czest.pl [Faculty of Mathematics and Natural Sciences, Jan Długosz University in Częstochowa, Armii Krajowej 13/15, 42-200 Częstochowa (Poland); Hoser, A. [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14-109 Berlin (Germany); Penc, B.; Szytuła, A. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków (Poland)

    2013-10-15

    The crystal and magnetic structure of polycrystalline TbFe{sub 0.25}Ge{sub 2} sample have been determined. X-ray and neutron diffraction studies indicate that this compound has the orthorhombic CeNiSi{sub 2}-type crystal structure (space group Cmcm). The magnetic ordering, based on the neutron diffraction data in low temperature, is described by two components: a collinear antiferromagnetic G-type and a cosine-wave modulated one. In the collinear G-type structure the Tb magnetic moment is equal to 3.81(5) µ{sub B} and it is parallel to the c-axis. The modulated structure is described by the propagation vector k=(0.460(8), 0, 0.305(1)), the Tb magnetic moment equals 7.75(8) µ{sub B,} lies in b–c and forms an angle 23(2)° with the c-axis. The collinear component decreases to zero at 22.6 K while the modulated one at 190.8 K. - Highlights: • We determine crystal and magnetic structure of TbFe{sub 0.25}Ge{sub 2} compound. • We compare the results with other TbT{sub x}Ge{sub 2} compounds. • We observe the complex magnetic structure in TbFe{sub 0.25}Ge{sub 2} with two components: collinear and cosine-wave modulated. • T (3d) element have got significant influence on the interactions in Tb sublattice.

  9. The influence of the magnetic state on the thermal expansion in 1:2 rare earth intermetallic compounds

    International Nuclear Information System (INIS)

    Gratz, E.; Lindbaum, A.

    1994-01-01

    The attempt is made to demonstrate on some selected rare earth intermetallics the influence of the magnetic state on the thermal expansion. Using the X-ray powder diffraction method we investigated the thermal expansion of some selected nonmagnetic compounds (YAl 2 , YNi 2 and YCo 2 ) and some magnetic RE (rare earth) - cobalt compounds (RCo 2 ) in the temperature range from 4 up to 450 K. All these compounds crystallize in the C15-type structure (cubic Laves phase structure). By comparing the nonmagnetic Y-based compounds we could show that there is an enhanced contribution of the 3d electrons to the thermal expansion in YCo 2 . In the magnetic RCo 2 compounds the induced 3d magnetism gives rise to large volume anomalies at the magnetic ordering temperature T c . Below T c there is in addition a distortion of the cubic unit cell due to the interaction of the magnetically ordered RE ions with the anisotropic crystal field.The thermal expansion of the orthorhombic TmCu 2 , GdCu 2 and YCu 2 compounds has also been investigated for comparison. The influence of the crystal field on the thermal expansion in TmCu 2 in the paramagnetic range (TmCu 2 orders magnetically at T N =6.3 K) has been determined by comparing the thermal expansion of the nonmagnetic YCu 2 with that of TmCu 2 . The data thus obtained are compared with a theoretical model. GdCu 2 , for which the influence of the crystal field can be neglected, has been investigated in order to study the influence of the exchange interaction in the magnetically ordered state (below 42 K). ((orig.))

  10. Structural, magnetic and optical properties of a dilute magnetic semiconductor based on Ce{sub 1−x}Co{sub x}O{sub 2} thin film grown on LaAlO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Mahmoud, Waleed E., E-mail: w_e_mahmoud@yahoo.com [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Suez Canal University, Faculty of Science, Department of Physics, Ismailia (Egypt); Al-Ghamdi, A.A. [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Al-Agel, F.A. [Hail University, College of Science, Department of Physics, Hail (Saudi Arabia); Al-Arfaj, E. [Umm Alqura University, Department of Physics, Makkah (Saudi Arabia); Qassim University, College of Science, Physics Department, Buraidah 5145 (Saudi Arabia); Shokr, F.S. [King Abdulaziz University, Faculty of Science & Arts, Department of Physics, Rabigh (Saudi Arabia); Al-Gahtany, S.A. [King Abdulaziz University, Faculty of Science for Girls, Department of Physics, Jeddah (Saudi Arabia); Alshahrie, Ahmed [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Jalled, Ouissem [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Laboratory of Applied Mineral Chemistry, Department of Chemistry, University Tunis ElManar, Faculty of Sciences, Campus 2092, Tunis (Tunisia); Bronstein, L.M. [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Texas State University-San Marcos, Department of Chemistry and Biochemistry, 601 University Dr., San Marcos, TX 78666 (United States); Beall, Gary W. [King Abdulaziz University, Faculty of Science, Department of Physics, Jeddah (Saudi Arabia); Indiana University, Department of Chemistry, Bloomington, IN 47405 (United States)

    2015-12-15

    Highlights: • Co doped CeO{sub 2} was grown on LaAlO{sub 3} (0 0 1) via a modified sol–gel spin-coating technique. • The concentration of the Co ions was varied from 1 to 15 at.%. • The incorporation of 5 at.% of Mn ions was found to provide formation of exceptionally magnetic moment. • This amount demonstrated a giant magnetic moment of 1.09 μ{sub B}/Co. • This amount reduced the optical band gap and enhanced the optical performance. - Abstract: The enhancement of the room temperature ferromagnetism and optical properties of the dilute magnetic metal oxides is a crucial clue to construct spin-based optoelectronic devices. In this work, Ce{sub 1−x}Co{sub x}O{sub 2} (0.01 ≤ x ≤0.15) thin films were prepared via ethylene glycol modified sol–gel spin coating technique on the LaAlO{sub 3} (0 0 1) substrate to enhance their room temperature ferromagnetism and optical properties. The structures, magnetic and optical properties of the prepared films were characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, SQUID magnetometer, X-ray photoelectron spectroscopy and UV–vis spectrophotometer. The results demonstrated that a single phase cubic structure was formed, implying the substitution of Co ions into the Ce ions sites. The prepared films showed room temperature ferromagnetism with saturation magnetic moment of 1.09 μ{sub B}/Co was achieved for 5 at.% Co-doped CeO{sub 2}. This film exhibited high optical transparency of 85% and low optical band energy gap of 3.39 eV. The improved magnetic and optical properties are argued to the increase of the density of the oxygen vacancies into the cerium oxide crystal structure due to the incorporation of Co ions.

  11. Magnetic and electronic properties of some actinide intermetallic compounds

    International Nuclear Information System (INIS)

    Yaar, Ilan

    1992-06-01

    The electronic structure and magnetic properties of the light actinide intermetallic compounds are often related to interplay between localized and itinerant (band like) behavior of the 5f- electrons. In the present work, the properties of some actinide, mainly Np, intermetallic compounds were studied by Mossbauer effect, ac and dc susceptibility, X-ray and Neutron diffraction techniques. 1. NpX 2 (X=Ga,Si) - Both compounds order ferromagnetically at TC=55(2) and 48(2) K respectively. A comparison of our data with the results for other NpX 2 (X=Al,As,Sb,Tl) compounds indicates that NpGa 2 is a highly localized 5f electron system, whereas in NpSi 2 the 5f electrons are partially delocalized. The magnetic properties of NpX 2 compounds can neither be consistently explained within the conventional crystal electric field picture (CEF) nor by takink into account hybridization dressing of local spin density models. 2. NpX 3 (X=Ga,Si,In,Al) in the cubic AuCu 3 (Pm3m) crystallographic structure - From the Mossbauer isomer shift (IS) data we argue that the Np ion in the NpX 3 family is close to the formal 3+ (5I 4 ) charge state. The magnetic moment of the Np in NpSi 3 is totally suppressed whereas in NpGa 3 and NpAl 3 a localized (narrow band) moment is established. However, in NpIn 3 at 4.2 K, a modulated magnetic moment (0-1.5μB) is observed. Comparing the magnetic behavior of the NpX 3 family (X=Si,Ge,Ga, Al,In and Sn), we find an impressive variation of the magnetic properties, from temperature independent paramagnetism (TIP), localized and modulated ordered moments, to the formation of a concentrated Kondo lattice. Hybridization of 5f electrons with ligand electrons appears to play a crucial role in establishing these magnetic properties. However, at present a consistent theoretical picture can not be drawn. 3. XFe 4 Al 8 (X=Ho,Np,U) spin galss (SG) systems in the ThMn 12 (I 4 /mmm) crystallographic structure - Localized and itinerant behaviour of the f electrons

  12. A Study on Magnetic Decoupling of Compound-Structure Permanent-Magnet Motor for HEVs Application

    Directory of Open Access Journals (Sweden)

    Qiwei Xu

    2016-10-01

    Full Text Available The compound-structure permanent-magnet (CSPM motor is used for an electrical continuously-variable transmission (E-CVT in a hybrid electric vehicle (HEV. It can make the internal combustion engine (ICE independent of the road loads and run in the high efficiency area to improve the fuel economy and reduce the emissions. This paper studies the magnetic coupling of a new type of CSPM motor used in HEVs. Firstly, through the analysis of the parameter matching with CSPM in the HEV, we receive the same dynamic properties’ design parameters between the CSPM motor and the THS (Toyota Hybrid System of the Toyota Prius. Next, we establish the equivalent magnetic circuit model of the overall and the secondary model considering the tangential and radial flux distribution in the outer rotor of the CSPM motor. Based on these two models, we explore the internal magnetic coupling rule of the CSPM motor. Finally, finite element method analysis in 2D-ansoft is used to analyze the magnetic field distribution of the CSPM motor in different operation modes. By the result of the finite element method analysis, the internal magnetic decoupling scheme is put forward, laying the theoretical foundation for the further application of the CSPM motor in HEVs.

  13. Synthesis, growth, and studies (crystal chemistry, magnetic chemistry) of actinide-based intermetallic compounds and alloys with a 1.1.1 stoichiometry

    International Nuclear Information System (INIS)

    Kergadallan, Yann

    1993-01-01

    The first part of this research thesis reports the study of the synthesis and reactivity of intermetallic compounds with a 1.1.1 stoichiometry. It presents the thermal properties of 1.1.1 compounds: general presentation of physical transitions, and of solid solutions and formation heat, application to actinides (reactivity analysis from phase diagrams, techniques of crystal synthesis and crystal growth. It describes experimental techniques: synthesis, determination of fusion temperature by dilatometry, methods used for crystal growth, characterisation techniques (metallography, X ray diffraction on powders, dilatometry). It discusses the obtained results in terms of characterisation of synthesised samples, of crystal growth, and of measurements of fusion temperature. The second part addresses crystal chemistry studies: structure of compounds with a 1.1.1 stoichiometry (Laves structures, Zr, Ti and Pu compounds), techniques of analysis by X-ray diffraction (on powders and on single crystals), result interpretation (UNiX compounds, AnTAl compounds with T being a metal from group VIII, AnTGa compounds, AnNiGe compounds, distance comparison, structure modifications under pressure). The third part concerns physical issues. The author addresses the following topics: physical properties of intermetallic 1.1.1 compounds (magnetism of yttrium phases, behaviour of uranium-based Laves phases, analysis of pseudo-binary diagrams, physical characteristics of uranium-based 1.1.1 compounds, predictions of physical measurements), analysis techniques (Moessbauer spectroscopy, SQUID for Superconducting Quantum Interference Device), and result interpretation

  14. Magnetic Decoupling Design and Experimental Validation of a Radial-Radial Flux Compound-Structure Permanent-Magnet Synchronous Machine for HEVs

    Directory of Open Access Journals (Sweden)

    Zhiyi Song

    2012-10-01

    Full Text Available The radial-radial flux compound-structure permanent-magnet synchronous machine (CS-PMSM, integrated by two concentrically arranged permanent-magnet electric machines, is an electromagnetic power-splitting device for hybrid electric vehicles (HEVs. As the two electric machines share a rotor as structural and magnetic common part, their magnetic paths are coupled, leading to possible mutual magnetic-field interference and complex control. In this paper, a design method to ensure magnetic decoupling with minimum yoke thickness of the common rotor is investigated. A prototype machine is designed based on the proposed method, and the feasibility of magnetic decoupling and independent control is validated by experimental tests of mutual influence. The CS-PMSM is tested by a designed driving cycle, and functions to act as starter motor, generator and to help the internal combustion engine (ICE operate at optimum efficiency are validated.

  15. Magnetic phenomena in UNi1-xRhxAl compounds

    International Nuclear Information System (INIS)

    Andreev, A.V.; Dremov, R.V.; Uwatoko, Y.; Mushnikov, N.V.; Goto, T.; Shiokawa, Y.; Homma, Y.; Hagmusa, I.H.; Klaasse, J.C.P.

    1999-01-01

    We report on structure investigation and magnetization study of UNi 1-x Rh x Al solid solutions between an antiferromagnet UNiAl and a ferromagnet URhAl. The ZrNiAl-type hexagonal crystal structure of the parent compounds is preserved in the whole concentration range. Magnetization was measured as a function of magnetic field, temperature and external hydrostatic pressure. The observed complex evolution of magnetic phenomena with Rh substitution for Ni is discussed in terms of effects of the varying 5f-ligand hybridization. A tentative magnetic phase diagram is proposed. (orig.)

  16. High-Tc Superconductors Based on FeAs Compounds

    CERN Document Server

    Izyumov, Yuri

    2010-01-01

    Physical properties and models of electronic structure are analyzed for a new class of high-TC superconductors which belong to iron-based layered compounds. Despite their variable chemical composition and differences in the crystal structure, these compounds possess similar physical characteristics, due to electron carriers in the FeAs layers and the interaction of these carriers with fluctuations of the magnetic order. A tremendous interest towards these materials is explained by the prospects of their practical use. In this monograph, a full picture of the formation of physical properties of these materials, in the context of existing theory models and electron structure studies, is given. The book is aimed at a broad circle of readers: physicists who study electronic properties of the FeAs compounds, chemists who synthesize them and specialists in the field of electronic structure calculations in solids. It is helpful not only to researchers active in the fields of superconductivity and magnetism, but also...

  17. Cd{sub 0.9375}Mn{sub 0.0625}S diluted magnetic semiconductor: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Rani, Anita [Guru Nanak College for Girls, Sri Muktsar Sahib, Punjab (India); Kaur, Kulwinder; Kumar, Ranjan, E-mail: ranianita64@gmail.com [Department of Physics, Punjab University, Chandigarh-160014 (India)

    2015-08-28

    We studied the spin polarized electronic band structures and magnetic properties of the diluted magnetic semiconductor Cd{sub 1-x}Mn{sub x}S in Zinc Blende phase (B3) with 0.0625 Mn by using ab initio method. The calculations were performed by using Density Functional Theory as implemented in the Spanish Initiative for Electronic Simulations with Thousands of Atoms code using local density approximation (LDA). Calculated electronic band structures and magnetic properties of Cd{sub 1-x}Mn{sub x}S are discussed in terms of contribution of Mn 3d{sup 5} 4s{sup 2}, Cd 4d{sup 10} 5s{sup 2}, S 3s{sup 2} 3p{sup 4} orbitals. The total magnetic moment is found to be 5.00 µb for Cd{sub 1−x}Mn{sub x}S at x=0.0625. This value indicate that Mn atom adds no hole carrier to the perfect CdS crystal. We found that Mn doped systems are ferromagnetic. Calculated results are in good agreement with previous studies.

  18. Structural and magnetic properties of MnCo1-xVxGe compounds

    International Nuclear Information System (INIS)

    Meng, G.H.; Tegus, O.; Zhang, W.G.; Song, L.; Huang, J.H.

    2010-01-01

    The structural and magnetic properties of MnCo 1-x V x Ge (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10, 0.20 and 0.30) compounds were investigated by means of X-ray diffraction, scanning electron microscopy and magnetization measurements. The MnCo 1-x V x Ge compounds crystallize in the orthorhombic TiNiSi-type crystal structure for x ≤ 0.02 and in the hexagonal Ni 2 In-type structure for x > 0.02. The magnetization measurements show that the MnCo 1-x V x Ge compounds exhibit a complex magnetic behavior. The Curie temperature can be tuned from 360 K to 148 K by increasing x. The maximal magnetic-entropy change is 3.9 J/kg K for x = 0.06 at a field change from 0 to 1.5 T at about 265 K.

  19. Spin injection in self-assembled quantum dots coupled with a diluted magnetic quantum well

    International Nuclear Information System (INIS)

    Murayama, A.; Asahina, T.; Souma, I.; Koyama, T.; Hyomi, K.; Nishibayashi, K.; Oka, Y.

    2007-01-01

    Spin injection is studied in self-assembled quantum dots (QDs) of CdSe coupled with a diluted magnetic semiconductor quantum well (DMS-QW) of Zn 1- x - y Cd x Mn y Se, by means of time-resolved circularly polarized photoluminescence (PL). Excitonic PL from the CdSe QDs shows σ - -circular polarization in magnetic fields, mainly due to negative g-values of individual dots, when the energy difference of excitons between the QDs and DMS-QW is large as 300 meV. However, when such energy difference is comparable with LO-phonon energy in the QD, we observe an additional PL peak with the long lifetime as 3.5 ns and σ + -polarization in magnetic fields. It can be attributed to a type-II transition between the down-spin electron injected from the DMS-QW into the QDs, via LO-phonon-assisted resonant tunneling, and the down-spin heavy hole in the DMS-QW. In addition, the electron spin-injection is also evidenced by σ + -polarized PL with the fast rise-time of 20 ps in the QDs

  20. 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

  1. Crystal structure and magnetism of layered perovskites compound EuBaCuFeO5

    Science.gov (United States)

    Lal, Surender; Mukherjee, K.; Yadav, C. S.

    2018-04-01

    Layered perovskite compounds have interesting multiferroic properties.YBaCuFeO5 is one of the layered perovskite compounds which have magnetic and dielectric transition above 200 K. The multiferroic properties can be tuned with the replacement of Y with some other rare earth ions. In this manuscript, structural and magnetic properties of layered perovskite compound EuBaCuFeO5 have been investigated. This compound crystallizes in the tetragonal structure with P4mm space group and is iso-structural with YBaCuFeO5. The magnetic transition has been found to shift to 120 K as compared to YBaCuFeO5 which has the transition at 200 K. This shift in the magnetic transition has been ascribed to the decrease in the chemical pressure that relaxes the magnetic moments.

  2. Synthesis of dilute magnetic semiconductors by ion implantation

    International Nuclear Information System (INIS)

    Braunstein, G.H.; Dresselhaus, G.; Withrow, S.P.

    1986-01-01

    We have synthesized layers of CdMnTe by implantation of Mn into CdTe. Samples of CdTe have been implanted with Mn ions of 60 keV energy to fluences in the range 1 x 10 13 cm -2 to 2 x 10 16 cm -2 resulting in local concentrations of up to 10% at the maximum of the Mn distribution. Rutherford backscattering-channeling analysis has been used to study the radiation damage after implantation and after subsequent rapid thermal annealing (RTA). These experiments reveal that RTA for 15 sec at a temperature T greater than or equal to 700 0 C results in the complete recovery of the lattice order, without affecting the stoichiometry of CdTe. Photoluminescence (PL) measurements of a sample showing complete annealing reveal an increase in the band gap corresponding to the synthesis of very dilute (x approx. = 0.004) Cd/sub 1-x/Mn/sub x/Te. A shift of the excitonic PL peak to lower energies is observed when a magnetic field H less than or equal to 1T is applied. These measurements provide clear evidence for the synthesis of a DMS by ion implantation of Mn into CdTe

  3. Magnetism in ordered metallic perovskite compound GdPd3BxC1-x

    International Nuclear Information System (INIS)

    Pandey, Abhishek; Mazumdar, Chandan; Ranganathan, R.; Dattagupta, S.

    2009-01-01

    We report results of dc-magnetization, ac-susceptibility and magnetoresistance measurements on crystalline metallic-perovskite compounds GdPd 3 B x C 1-x (x=0.25, 0.50, 0.75 and 1.00) and the parent cubic compound GdPd 3 . The interest in these materials stems from the observation of negative temperature coefficient of resistance and negative thermal expansion in some of the members of this series. In the present study, we show that by substitution of non-magnetic elements, boron and carbon, the nature of the magnetic interaction can be varied from dominating ferromagnetic to antiferromagnetic and finally to a canted magnetic structure without altering the crystal symmetry of the compounds. The variation of magnetic interaction by modifying the lattice parameter resembles Ruderman-Kittel-Kasuya-Yosida (RKKY) oscillations.

  4. Modulation of structural, electrical, and magnetic features with dilute Zr substitution in Bi0.8La0.2Fe1-xZrxO3 system

    Science.gov (United States)

    Usama, Hasan M.; Akter, Ayesha; Zubair, M. A.

    2017-12-01

    A significant structural modification and enhancement of the electrical and magnetic properties with dilute substitution of Zr (≤1 mol. %) in the Bi0.8La0.2Fe1-xZrxO3 system has been reported. A mixture of rhombohedral and orthorhombic phases was detected in these conventionally sintered ceramics. Transition from a leaky state to an insulating state was observed upon Zr substitution. This is the first time that a drop in the electrical conductivity as large as 6 orders of magnitude for doping as small as 0.25 mol. % in bismuth ferrite systems has been reported. An investigation on the nature of this abrupt transition revealed the dominant role of defects. A proper consideration of possible defect reactions taking place during and after sintering satisfactorily accounts for the observed modulation in the electrical properties. Both AC and DC measurements indicate that, before Zr substitution, p-type hopping conduction prevails with an activation energy as low as ˜0.57 eV, whereas the Zr substitution makes oxide ion migration the central mechanism for conduction with the activation energy of ˜0.96-1.08 eV. In contrast to that, the magnetic properties of the compounds experience a more subtle effect; a gradual modification of saturation magnetization and coercivity with Zr substitution is observed. Curve fitting of the magnetic hysteresis loops not only allowed extraction of three separate contributions from the magnetic response but also helped to explain the effects of Zr on the magnetic properties. Modifications of structural characteristics and magnetic anisotropy of the samples are believed to be the primary driving force behind the improvement in the magnetic properties.

  5. High field Moessbauer study of dilute Ir-(Fe) alloys

    International Nuclear Information System (INIS)

    Takabatake, Toshiro; Mazaki, Hiromasa; Shinjo, Teruya.

    1981-01-01

    The magnetic behavior of very dilute Fe impurities in Ir has been studied by means of Moessbauer measurement in external fields up to 80 kOe at 4.2 K. The saturation hyperfine field increases in proportion to the external field up to the maximum magnetic field available. This means that for a localized spin fluctuation system IrFe, the effective magnetic moment associated with Fe impurities is induced in proportion to the external field. No anomalous spectrum was observed with a very dilute sample (--10 ppm 57 Co), indicating that the interaction between impurities is responsible for the anomalous spectrum previously observed with a less homogeneous sample. (author)

  6. 3D Printing of Polymer-Bonded Rare-Earth Magnets With a Variable Magnetic Compound Fraction for a Predefined Stray Field.

    Science.gov (United States)

    Huber, Christian; Abert, Claas; Bruckner, Florian; Groenefeld, Martin; Schuschnigg, Stephan; Teliban, Iulian; Vogler, Christoph; Wautischer, Gregor; Windl, Roman; Suess, Dieter

    2017-08-25

    Additive manufacturing of polymer-bonded magnets is a recently developed technique, for single-unit production, and for structures that have been impossible to manufacture previously. Also, new possibilities to create a specific stray field around the magnet are triggered. The current work presents a method to 3D print polymer-bonded magnets with a variable magnetic compound fraction distribution. This means the saturation magnetization can be adjusted during the printing process to obtain a required external field of the manufactured magnets. A low-cost, end-user 3D printer with a mixing extruder is used to mix permanent magnetic filaments with pure polyamide (PA12) filaments. The magnetic filaments are compounded, extruded, and characterized for the printing process. To deduce the quality of the manufactured magnets with a variable magnetic compound fraction, an inverse stray field framework is developed. The effectiveness of the printing process and the simulation method is shown. It can also be used to manufacture magnets that produce a predefined stray field in a given region. This opens new possibilities for magnetic sensor applications. This setup and simulation framework allows the design and manufacturing of polymer-bonded permanent magnets, which are impossible to create with conventional methods.

  7. Rapid Immunoenzyme Assay of Aflatoxin B1 Using Magnetic Nanoparticles

    Directory of Open Access Journals (Sweden)

    Alexandr E. Urusov

    2014-11-01

    Full Text Available The main limitations of microplate-based enzyme immunoassays are the prolonged incubations necessary to facilitate heterogeneous interactions, the complex matrix and poorly soluble antigens, and the significant sample dilutions often required because of the presence of organic extractants. This study presents the use of antibody immobilization on the surface of magnetic particles to overcome these limitations in the detection of the mycotoxin, aflatoxin B1. Features of the proposed system are a high degree of nanoparticle dispersion and methodologically simple immobilization of the antibodies by adsorption. Reactions between the immobilized antibodies with native and labeled antigens are conducted in solution, thereby reducing the interaction period to 5 min without impairing the analytical outcome. Adsorption of immunoglobulins on the surface of magnetic nanoparticles increases their stability in aqueous-organic media, thus minimizing the degree of sample dilution required. Testing barley and maize extracts demonstrated a limit of aflatoxin B1 detection equal to 20 pg/mL and total assay duration of 20 min. Using this method, only the 3-fold dilution of the initial methanol/water (60/40 extraction mixture in the microplate wells is necessary. The proposed pseudo-homogeneous approach could be applied toward immunodetection of a wide range of compounds.

  8. Similarities in magnetic behavior of cerium and plutonium compounds

    International Nuclear Information System (INIS)

    Cooper, B.R.; Thayamballi, P.; Spirlet, J.C.; Mueller, W.; Vogt, O.

    1983-01-01

    The first sizable single crystals have been prepared of plutonium compounds. The field and temperature dependence of magnetization of single-crystal PuSb is highly evocative of that of CeSb or CeBi, and PuSb gives anisotropy and magnetic structural behavior as expected from hybridization-mediated interionic interactions for moderately delocalized f-electron systems

  9. Fe-Cluster Compounds of Chalcogenides: Candidates for Rare-Earth-Free Permanent Magnet and Magnetic Nodal-Line Topological Material.

    Science.gov (United States)

    Zhao, Xin; Wang, Cai-Zhuang; Kim, Minsung; Ho, Kai-Ming

    2017-12-04

    Fe-cluster-based crystal structures are predicted for chalcogenides Fe 3 X 4 (X = S, Se, Te) using an adaptive genetic algorithm. Topologically different from the well-studied layered structures of iron chalcogenides, the newly predicted structures consist of Fe clusters that are either separated by the chalcogen atoms or connected via sharing of the vertex Fe atoms. Using first-principles calculations, we demonstrate that these structures have competitive or even lower formation energies than the experimentally synthesized Fe 3 X 4 compounds and exhibit interesting magnetic and electronic properties. In particular, we show that Fe 3 Te 4 can be a good candidate as a rare-earth-free permanent magnet and Fe 3 S 4 can be a magnetic nodal-line topological material.

  10. Effects of Conventional Heating on the Stability of Major Olive Oil Phenolic Compounds by Tandem Mass Spectrometry and Isotope Dilution Assay

    Directory of Open Access Journals (Sweden)

    Giovanni Sindona

    2010-12-01

    Full Text Available The quality of olive oils is sensorially tested by accurate and well established methods. It enables the classification of the pressed oils into the classes of extra virgin oil, virgin oil and lampant oil. Nonetheless, it would be convenient to have analytical methods for screening oils or supporting sensorial analysis using a reliable independent approach based on exploitation of mass spectrometric methodologies. A number of methods have been proposed to evaluate deficiencies of extra virgin olive oils resulting from inappropriate technological treatments, such as high or low temperature deodoration, and home cooking processes. The quality and nutraceutical value of extra virgin olive oil (EVOO can be related to the antioxidant property of its phenolic compounds. Olive oil is a source of at least 30 phenolic compounds, such as oleuropein, oleocanthal, hydroxytyrosol, and tyrosol, all acting as strong antioxidants, radical scavengers and NSAI-like drugs. We now report the efficacy of MRM tandem mass spectrometry, assisted by the isotope dilution assay, in the evaluation of the thermal stability of selected active principles of extra virgin olive oil.

  11. Effects of conventional heating on the stability of major olive oil phenolic compounds by tandem mass spectrometry and isotope dilution assay.

    Science.gov (United States)

    Attya, Mohamed; Benabdelkamel, Hicham; Perri, Enzo; Russo, Anna; Sindona, Giovanni

    2010-12-01

    The quality of olive oils is sensorially tested by accurate and well established methods. It enables the classification of the pressed oils into the classes of extra virgin oil, virgin oil and lampant oil. Nonetheless, it would be convenient to have analytical methods for screening oils or supporting sensorial analysis using a reliable independent approach based on exploitation of mass spectrometric methodologies. A number of methods have been proposed to evaluate deficiencies of extra virgin olive oils resulting from inappropriate technological treatments, such as high or low temperature deodoration, and home cooking processes. The quality and nutraceutical value of extra virgin olive oil (EVOO) can be related to the antioxidant property of its phenolic compounds. Olive oil is a source of at least 30 phenolic compounds, such as oleuropein, oleocanthal, hydroxytyrosol, and tyrosol, all acting as strong antioxidants, radical scavengers and NSAI-like drugs. We now report the efficacy of MRM tandem mass spectrometry, assisted by the isotope dilution assay, in the evaluation of the thermal stability of selected active principles of extra virgin olive oil.

  12. Contribution to the study of magnetic properties of rare-earth iron intermetallic compounds

    International Nuclear Information System (INIS)

    Morariu, M.

    1976-01-01

    The intermetallic binary compounds Ysub(x)Fesub(y)(YFe 2 ,YFe 3 ,Y 6 Fe 23 ,Y 2 Fe 17 ), RFe 2 (R=Gd,Tb,Dy,Ho,Er and Tm) and the intermetallic pseudobinary compounds (Gdsub(x)Ysub(1-x))Fe 2 and Dy(Fesub(x)Nisub(1-x)) 3 were studied, using magnetic measurements and Moessbauer spectroscopy, in order to obtain information on their magnetic behaviour. The different models which describe magnetic interactions in rare-earths with 3d transition element compounds are reviewed. The magnetic hyperfine field Hsub(n) at the Fe 57 nucleus, measured by Moessbauer spectroscopy, depends on the atom position in the lattice, being sensitive to magnetic interactions with neighbouring atoms. The mean value of the magnetic hyperfine field, average Hsub(n) is proportional to the mean magnetic moment of the iron atom: average Hsub(n)/average μsub(Fe) approximately 150 kOe. The comparative study of the temperature dependence of average Hsub(n) and average μsub(Fe) values shows that this relation is valid for the whole range of magnetic ordering (T>Tsub(c)). The mean magnetic hyperfine fields at the Fe 57 nucleus in RFe 2 compounds depend on the rare-earth partner and vary approximative linearly with the Gennes factor. The spin reorientation diagram for the (Gdsub(x)Ysub(1-x))Fe 2 system is obtained. All results on Moessbauer spectroscopy are in good agreement with the magnetic measurements. The magnetic behaviour of iron atoms is justified using a model in which the most electrons are in a narrow band, so they could be considered localized, and the magnetic interactions between these atoms take place through a fraction (<5%) of 3d itinerant electrons. (author)

  13. Effective equations for the precession dynamics of electron spins and electron–impurity correlations in diluted magnetic semiconductors

    International Nuclear Information System (INIS)

    Cygorek, M; Axt, V M

    2015-01-01

    Starting from a quantum kinetic theory for the spin dynamics in diluted magnetic semiconductors, we derive simplified equations that effectively describe the spin transfer between carriers and magnetic impurities for an arbitrary initial impurity magnetization. Taking the Markov limit of these effective equations, we obtain good quantitative agreement with the full quantum kinetic theory for the spin dynamics in bulk systems at high magnetic doping. In contrast, the standard rate description where the carrier–dopant interaction is treated according to Fermi’s golden rule, which involves the assumption of a short memory as well as a perturbative argument, has been shown previously to fail if the impurity magnetization is non-zero. The Markov limit of the effective equations is derived, assuming only a short memory, while higher order terms are still accounted for. These higher order terms represent the precession of the carrier–dopant correlations in the effective magnetic field due to the impurity spins. Numerical calculations show that the Markov limit of our effective equations reproduces the results of the full quantum kinetic theory very well. Furthermore, this limit allows for analytical solutions and for a physically transparent interpretation. (paper)

  14. Calculations of the magnetic properties of R2M14B intermetallic compounds (R=rare earth, M=Fe, Co)

    International Nuclear Information System (INIS)

    Ito, Masaaki; Yano, Masao; Dempsey, Nora M.; Givord, Dominique

    2016-01-01

    The hard magnetic properties of “R–M–B” (R=rare earth, M=mainly Fe) magnets derive from the specific intrinsic magnetic properties encountered in Fe-rich R 2 M 14 B compounds. Exchange interactions are dominated by the 3d elements, Fe and Co, and may be modeled at the macroscopic scale with good accuracy. Based on classical formulae that relate the anisotropy coefficients to the crystalline electric field parameters and exchange interactions, a simple numerical approach is used to derive the temperature dependence of anisotropy in various R 2 Fe 14 B compounds (R=Pr, Nd, Dy). Remarkably, a unique set of crystal field parameters give fair agreement with the experimentally measured properties of all compounds. This implies reciprocally that the properties of compounds that incorporate a mixture of different rare-earth elements may be predicted accurately. This is of special interest for material optimization that often involves the partial replacement of Nd with another R element and also the substitution of Co for Fe. - Highlights: • Anisotropy constants derived from CEF parameters of R 2 M 14 B compounds (M=Fe, Co). • Anisotropy constants of all R 2 Fe 14 B compounds using unique set of CEF parameters. • Moment non-collinearity in magnetization processes under B app along hard axis.

  15. Characterization of magnetic phase transitions in PrMn2Ge2 compound investigated by magnetization and hyperfine field measurements

    Directory of Open Access Journals (Sweden)

    B. Bosch-Santos

    2017-05-01

    Full Text Available The magnetic properties of PrMn2Ge2 compound have been investigated by perturbed γ−γ angular correlation (PAC spectroscopy using 111In(111Cd as probe nuclei as well as by magnetization measurements. This ternary intermetallic compound exhibits different magnetic structures depending on the temperature. The magnetic ordering is mainly associated with the magnetic moment of 3d-Mn sublattice but at low temperatures a magnetic contribution due to ordering of the magnetic moment from 4f-Pr sublattice appears. PAC results with 111Cd probe nuclei at Mn sites show that the temperature dependence of hyperfine field Bhf(T follows the expected behavior for the host magnetization, which could be fitted by two Brillouin functions, one for antiferromagnetic phase and the other for ferromagnetic phase, associated with the magnetic ordering of Mn ions. Magnetization measurements showed the magnetic behavior due to Mn ions highlighting the antiferromagnetic to ferromagnetic transition around 326 K and an increase in the magnetization around 36 K, which is ascribed to Pr ions ordering.

  16. Double-flat-spiral magnetic structures: Theory and application to the RMn6X6 compounds

    International Nuclear Information System (INIS)

    Rosenfeld, E.V.; Mushnikov, N.V.

    2008-01-01

    We studied magnetic structure of a layered magnetic material, the lattice of which consists of magnetic layers separated by alternating non-magnetic layers (slabs) of two different types. For such structure, the exchange integrals between the nearest magnetic layers separated by different slabs may have different values, while the next-nearest neighbor exchange integral is the same for all magnetic layers. We developed a model based on three different interlayer exchange integrals. In the framework of this model we analyzed conditions of the appearance of a magnetic structure of the double-flat-spiral type and its distortion in external magnetic field. The results are most obtained in the analytical form. The model was applied to analyze the magnetic structure and magnetization process of the RMn 6 X 6 (R=Y, Sc, Lu; X=Sn, Ge) compounds with the layered crystal structure

  17. Simultaneous speciation of mercury and butyltin compounds in natural waters and snow by propylation and species-specific isotope dilution mass spectrometry analysis

    Energy Technology Data Exchange (ETDEWEB)

    Monperrus, M.; Tessier, E.; Veschambre, S.; Amouroux, D.; Donard, O. [Universite de Pau et des Pays de L' Adour, Laboratoire de Chimie Analytique Bio-inorganique et Environnement, CNRS UMR 5034, Helioparc, Pau (France)

    2005-02-01

    A robust method has been developed for simultaneous determination of mercury and butyltin compounds in aqueous samples. This method is capable of providing accurate results for analyte concentrations in the picogram per liter to nanogram per liter range. The simultaneous determination of the mercury and tin compounds is achieved by species-specific isotope dilution, derivatization, and gas chromatography-inductively coupled plasma mass spectrometer (GC-ICP-MS). In derivatization by ethylation and propylation, reaction conditions such as pH and the effect of chloride were carefully studied. Ethylation was found to be more sensitive to matrix effects, especially for mercury compounds. Propylation was thus the preferred derivatization method for simultaneous determination of organomercury and organotin compounds in environmental samples. The analytical method is highly accurate and precise, with RSD values of 1 and 3% for analyte concentrations in the picogram per liter to nanogram per liter range. By use of cleaning procedures and SIDMS blank measurements, detection limits in the range 10-60 pg L{sup -1} were achieved; these are suitable for determination of background levels of these contaminants in environmental samples. This was demonstrated by using the method for analysis of real snow and seawater samples. This work illustrates the great advantage of species-specific isotope dilution for the validation of an analytical speciation method - the possibility of overcoming species transformations and non-quantitative recovery. Analysis time is saved by use of the simultaneous method, because of the use of a single sample-preparation procedure and one analysis. (orig.)

  18. Synthesis and characterization of Mn-doped ZnO diluted magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Abdel-Galil, A. [Solid State Physics and Accelerators Department, NCRRT, Atomic Energy Authority, Cairo (Egypt); Balboul, M.R., E-mail: m_balboul@yahoo.com [Solid State Physics and Accelerators Department, NCRRT, Atomic Energy Authority, Cairo (Egypt); Sharaf, A. [Radiation Engineering Department, NCRRT, Atomic Energy Authority, Cairo (Egypt)

    2015-11-15

    In the present work undoped and Mn doped ZnO nanoparticles (ZnO:Mn), diluted magnetic semiconductors, were successfully synthesized by the sol–gel method at room temperature. The morphology of ZnO nanoparticles constituted by flower-like structures with hexagonal morphologies that changed significantly after the incorporation of Mn. Rietveld refinements results showed that Mn ions are successfully doped into ZnO matrix without altering its wurtzite phase. Meanwhile, Raman spectroscopy analyses confirm the wurtzite structure of undoped ZnO and ZnO:Mn nanoparticles. The lattice parameters increase with increasing Mn content due to the large ionic radius of Mn{sup 2+} compared to that of Zn{sup 2+}. Electron spin resonance measurements were performed to gain information about oxidation state and site occupancy of the magnetic Mn ions in the ZnO lattice. Moreover, UV–vis absorption spectra have been utilized to calculate the optical band gap of the undoped ZnO and ZnO:Mn nanoparticles before and after different γ-irradiation doses. The band gap of ZnO:Mn (2%) is 2.62 eV which is noticeably smaller than the 3.26 eV of undoped ZnO. The thermal decomposition properties of the prepared nanoparticle samples were also studied using simultaneous Thermogravimetric analysis in temperature range from 30 to 500 °C.

  19. Synthesis and characterization of three-dimensional transition metal ions doped zinc oxide based dilute magnetic semiconductor thin films

    Science.gov (United States)

    Samanta, Kousik

    Dilute magnetic semiconductors (DMS), especially 3d-transition metal (TM) doped ZnO based DMS materials are the most promising candidates for optoelectronics and spintronics applications; e.g. in spin light emitting diode (SLED), spin transistors, and spin field effect transistors (SFET), etc. In the present dissertation, thin films of Zn1-xTMxO (TM = Co2+, Cu2+, and Mn2+) were grown on (0001) oriented Al2O3 substrates by pulsed laser deposition (PLD) technique. The films were highly c-axis oriented, nearly single crystalline, and defects free for a limited concentration of the dilution of transition metal ions. In particular, we have obtained single crystalline phases of Zn1-xTMxO thin films for up to 10, 3, and 5 stoichiometric percentages of Co2+, Cu2+, and Mn2+ respectively. Raman micro-probe system was used to understand the structural and lattice dynamical properties at different physical conditions. The confinement of optical phonons in the disorder lattice was explained by alloy potential fluctuation (APF) using a spatial correlation (SC) model. The detailed analysis of the optical phonon behavior in disorder lattice confirmed the substitution of the transition metal ions in Zn 2+ site of the ZnO host lattice. The secondary phases of ZnCo 2O4, CuO, and ZnMn2O4 were detected in higher Co, Cu, and Mn doped ZnO thin films respectively; where as, XRD did not detect these secondary phases in the same samples. Room temperature ferromagnetism was observed in Co2+ and Cu2+ ions doped ZnO thin films with maximum saturation magnetization (Ms) of 1.0 and 0.76 muB respectively. The origin of the observed ferromagnetism in Zn1-xCoxO thin films was tested by the controlled introduction of shallow donors (Al) in Zn0.9-x Co0.1O:Alx (x = 0.005 and 0.01) thin films. The saturation magnetization for the 10% Co-doped ZnO (1.0 muB /Co) at 300K reduced (˜0.25 muB/Co) due to Al doping. The observed ferromagnetism and the reduction due to Al doping can be explained by the Bound

  20. Nuclear Magnetic Resonance Study of Fluorine-Graphite Intercalation Compounds

    International Nuclear Information System (INIS)

    Panich, A.M.; Goren, S.D.; Nakajima, T.; Vieth, H.-M.; Privalov, A.

    1998-01-01

    To study the origin of semimetal-metal and metal-insulator transformations, localization effects and C-E bonding in fluorine-intercalated graphite C x F, 13 C and 19 F NMR investigations have been carried out for a wide range of fluorine content, 3.8 8, are attributed to mobile fluorine acceptor species which are responsible for the increase of electric conductivity in the dilute compound. When increasing the fluorine content to x ∼ 8 corresponding to the maximum electric conductivity, covalent C-P bonds start to oc- cur. The number of these bonds grows with fluorine content resulting in the decrease in conductivity which is caused by a percolation mechanism rather than by a change in bond length. A difference in 19 F chemical shift for fluorine-intercalated graphite C x F and covalent graphite fluoride (CF) n has been observed and is attributed to different C-P bonding in these compounds

  1. High blocking temperature in SnO{sub 2} based super-paramagnetic diluted magnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Mounkachi, O., E-mail: o.mounkachi@mascir.com [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble cedex 9 (France); Salmani, E. [LMPHE, associé au CNRST (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Rabat (Morocco); El Moussaoui, H. [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); Masrour, R. [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Safi (Morocco); Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble cedex 9 (France); Hamedoun, M. [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); Ez-Zahraouy, H. [LMPHE, associé au CNRST (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble cedex 9 (France); Benyoussef, A. [Institute of Nanomaterials and Nanotechnology, MAScIR, Rabat (Morocco); LMPHE, associé au CNRST (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Rabat (Morocco)

    2014-11-25

    Highlights: • Simple doping, (Sn,Fe)O{sub 2} exhibits a soft ferromagnetism at low temperature. • High blocking temperature was observed for Cu doped (Sn,Fe)O{sub 2} nanocrystalline. • Experimental results are confirmed by ab initio calculations. - Abstract: (Fe,Cu)-doped SnO{sub 2} nanocrystals was synthesized using the co-precipitation method. Magnetic Properties Measurement System (MPMS) revealed that for simple doping, Fe-doped SnO{sub 2} soft ferromagnetism at low temperature appears, while the ferromagnetic phase is stable at temperature higher than room temperature for Cu co-doping element. The ferromagnetism is significantly enhanced by the Cu addition to Fe-doped SnO{sub 2}, according to the ZFC and FC magnetizations and the hysteresis loops. The evidences for the existence of superparamagnetism are characterized and high blocking temperature super-paramagnetism in (Fe,Cu)-doped SnO{sub 2} nanocrystals was observed. Based on first-principles calculations, we have investigated electronic structures and magnetic properties of Fe-doped SnO{sub 2} and (Fe,Cu)-doped SnO{sub 2} with and without defect with LDA and LDA-SIC approximations. The results suggest that the oxygen vacancies (V{sub O}) play a critical role in the activation of ferromagnetism in Fe doped SnO{sub 2}. For (Fe,Cu)-doped SnO{sub 2} the results exhibit that Cu strongly influences on the magnetic properties of these doped systems which are in good agreement with the experimental observations. Electronic structure show that the presence of Cu promote the ferromagnetic bound magnetic polaron interaction through the carriers introduce by d (Cu)

  2. Magnetic properties of Np2T2Sn compounds

    International Nuclear Information System (INIS)

    Sanchez, J.P.; Colineau, E.; Jeandey, C.; Oddou, J.L.; Rebizant, J.; Seret, A.; Spirlet, J.C.

    1994-01-01

    The magnetic properties of the Np 2 T 2 Sn series investigated by 237 Np Moessbauer spectroscopy are reported. Magnetic ordering is shown to occur for T = Ni, Pd, Pt, whereas the Np ions do not carry a local moment when T = Co, Ru, Rh. Comparison is made with the corresponding Np 2 T 2 In and U 2 T 2 Sn compounds. (authors). 5 refs., 3 figs

  3. Complex magnetic properties and large magnetocaloric effects in RCoGe (R=Tb, Dy compounds

    Directory of Open Access Journals (Sweden)

    Yan Zhang

    2018-05-01

    Full Text Available Complicated magnetic phase transitions and Large magnetocaloric effects (MCEs in RCoGe (R=Tb, Dy compounds have been reported in this paper. Results show that the TbCoGe compounds have a magnetic phase transition from antiferromagnetic to paramagnetic (AFM-PM at TN∼16 K, which is close to the value reported by neutron diffraction. The DyCoGe compound undergoes complicated phase changes from 2 K up to 300 K. The peak at 10 K displays a phase transition from antiferromagnetic to ferromagnetic (AFM-FM. In particular, a significant ferromagnetic to paramagnetic (FM-PM phase transition was found at the temperature as high as 175 K and the cusp becomes more abrupt with the magnetic field increasing from 0.01 T to 0.1 T. The maximum value of magnetic entropy change of TbCoGe and DyCoGe compounds achieve 14.5 J/kg K and 11.5 J/kg K respectively for a field change of 0-5 T. Additionally, the correspondingly considerable refrigerant capacity value of 260 J/kg and 242 J/kg are also obtained respectively, suggesting that both TbCoGe and DyCoGe compounds could be considered as good candidates for low temperature magnetic refrigerant.

  4. Electronic, magnetic properties and phase diagrams of system with Fe4N compound: An ab initio calculations and Monte Carlo study

    Science.gov (United States)

    Masrour, R.; Jabar, A.; Hlil, E. K.

    2018-05-01

    Self-consistent ab initio calculations, based on Density Functional Theory (DFT) approach and using Full potential Linear Augmented Plane Wave (FLAPW) method, are performed to investigate the electronic and magnetic properties of the Fe4N compound. Polarized spin and spin-orbit coupling are included in calculations within the framework of the ferromagnetic state between Fe(I) and Fe(II) in Fe4N compound. We have used the obtained data from abinitio calculations as an input in Monte Carlo simulation to calculate the magnetic properties of this compounds such as the ground state phase diagrams, total and partial magnetization of Fe(I) and Fe(II) as well as the transition temperatures are computed. The variation of magnetization with the crystal field are also studied. The magnetic hysteresis cycle of the same Fe4N compound are determined for different values of temperatures and crystal field values. The two-step hysteresis loop are evidenced, which is typical for Fe4N structure. The ferromagnetic and superparamagnetic phase is observed as well.

  5. Magnetic anisotropy of (Sm, Y)2Fe17Ny compounds

    International Nuclear Information System (INIS)

    Lu, Y.; Tegus, O.; Li, Q.A.; Tang, N.; Yu, M.J.; Zhao, R.W.; Kuang, J.P.; Yang, F.M.; Zhou, G.F.; Li, X.; Boer, F.R. de

    1992-01-01

    A study of the crystal structure and the magnetic properties, especially the magnetocrystalline anisotropy of (Sm 1-x Y x ) 2 Fe 17 N y compounds (x = 0, 0.2, 0.4, 0.6, 0.8, and 1.0, 2 2 Zn 17 - or Th 2 Ni 17 -type structure as the original compounds. The Curie temperatures decrease from 750 to 700 K as x increases from 0 to 1. The anisotropy field decreases linearly with increasing yttrium content. The spin reorientation has been investigated by means of high field magnetization measurements, AC-susceptibility measurements and thermomagnetic analysis, combined with X-ray diffraction. The anisotropy constants K 1 , K 2 and K 3 were derived by a phenomenological analysis, using magnetization curves measured in high fields, applied perpendicular to the alignment direction of the powder samples. A tentative spin phase diagram of the series is presented. (orig.)

  6. Development of stable isotope dilution assays for the quantitation of Amadori compounds in foods.

    Science.gov (United States)

    Meitinger, Michael; Hartmann, Sandra; Schieberle, Peter

    2014-06-04

    During thermal processing of foods, reducing carbohydrates and amino acids may form 1-amino-1-desoxyketoses named Amadori rearrangement products after the Italian chemist Mario Amadori. Although these compounds are transient intermediates of the Maillard reaction, they are often used as suitable markers to measure the extent of a thermal food processing, such as for spray-dried milk or dried fruits. Several methods are already available in the literature for their quantitation, but measurements are often done with external calibration without addressing losses during the workup procedure. To cope with this challenge, stable isotope dilution assays in combination with LC-MS/MS were developed for the glucose-derived Amadori products of the seven amino acids valine, leucine, isoleucine, phenylalanine, tyrosine, methionine, and histidine using the respective synthesized [(13)C6]-labeled isotopologues as internal standards. The quantitation of the analytes added to a model matrix showed a very good sensitivity with the lowest limits of detection for the Amadori compound of phenylalanine of 0.1 μg/kg starch and 0.2 μg/kg oil, respectively. Also, the standard deviation measured in, for example, wheat beer was only ±2% for this analyte. Application of the method to several foods showed the highest concentrations of the Amadori product of valine in unroasted cocoa (342 mg/kg) as well as in dried bell pepper (3460 mg/kg). In agreement with literature data, drying of foods led to the formation of Amadori products, whereas they were degraded during roasting of, for example, coffee or cocoa. The study presents for the first time results on concentrations of the Amadori compounds of tyrosine and histidine in foods.

  7. Rare-earth-free high energy product manganese-based magnetic materials.

    Science.gov (United States)

    Patel, Ketan; Zhang, Jingming; Ren, Shenqiang

    2018-06-14

    The constant drive to replace rare-earth metal magnets has initiated great interest in an alternative. Manganese (Mn) has emerged to be a potential candidate as a key element in rare-earth-free magnets. Its five unpaired valence electrons give it a large magnetocrystalline energy and the ability to form several intermetallic compounds. These factors have led Mn-based magnets to be a potential replacement for rare-earth permanent magnets for several applications, such as efficient power electronics, energy generators, magnetic recording and tunneling applications, and spintronics. For past few decades, Mn-based magnets have been explored in many different forms, such as bulk magnets, thin films, and nanoparticles. Here, we review the recent progress in the synthesis and structure-magnetic property relationships of Mn-based rare-earth-free magnets (MnBi, MnAl and MnGa). Furthermore, we discuss their potential to replace rare-earth magnetic materials through the control of their structure and composition to achieve the theoretically predicted magnetic properties.

  8. Magnetic structure of two- and three-dimensional supramolecular compounds

    Energy Technology Data Exchange (ETDEWEB)

    Decurtins, S.; Schmalle, H.W.; Pellaux, R. [Zurich Univ. (Switzerland); Fischer, P.; Fauth, F. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Ouladdiaf, B. [Institut Max von Laue - Paul Langevin, 75 - Paris (France)

    1997-09-01

    Supramolecular chiral networks of oxalato-bridged transition metals show either two- or three-dimensional structural features. The magnetic structures of such compounds have been investigated by means of elastic neutron powder diffraction. (author) 2 figs., 2 refs.

  9. Valence, magnetism and conduction in the intermediate valence compounds: the case SmB6

    International Nuclear Information System (INIS)

    Derr, J.

    2006-09-01

    In some rare earth based compounds, the 4f level is situated so close to the Fermi level that the valence of the compound can become intermediate between two integer values. The so called 'intermediate valence' compound of Samarium hexaboride (SmB 6 ) is one typical example of the exciting physics which can result from this quantum equilibrium between two valence configurations. The first configuration (Sm 2+ ) corresponds to an insulating and non magnetic state whereas the second one (Sm 3+ ) would theoretically give a magnetic and metallic ground state. This dissertation deals with the influence of pressure on this equilibrium. Specific heat measurements under pressure evidenced a new long range magnetic ordering for pressures higher than p c ∼ 10 GPa. On another hand, transport measurements measured for the first time in good conditions of hydrostatics found a reliable and reproducible critical pressure for the insulator to metal transition equal to p c . The phase diagram of SmB 6 is now well known and the observation for the first time of a magnetic anomaly in the high pressure resistivity curves certifies that the onset of the magnetic phase really coincide with the closure of the gap. This change at the critical pressure p c is discussed in a general frame taking into account the Kondo lattice temperature as a key parameter for the renormalization of the wavefunction from one integer configuration to the other whereas the valence itself is still intermediate. This general idea seems to be valid also for other systems studied in this dissertation like SmS or TmSe and could even be valid for more general cases (Ytterbium, Cerium). In the same time, resistivity measurements under uniaxial stress were undertaken. The result is a strong anisotropy effect observed on the pressure dependence of the residual resistivity in the compound SmB 6 . The comparison with the transport under hydrostatic conditions enables us to consider a new idea for the nature of the gap

  10. The effect of spin dilution on magnetism of the linear chain system β ...

    Indian Academy of Sciences (India)

    one-dimensional alternating exchange Heisenberg antiferromagnetism (HAF) is observed ... is seen in the magnetic chains for all Zn concentrations (x ≤ 0.3). ... ion (3d8) while a lot of attention has been focussed on compounds of copper and ... but they attributed the gap to arise from the dimerization of the Cu ions. Pom-.

  11. Characterization of the major aroma-active compounds in mango (Mangifera indica L.) cultivars Haden, White Alfonso, Praya Sowoy, Royal Special, and Malindi by application of a comparative aroma extract dilution analysis.

    Science.gov (United States)

    Munafo, John P; Didzbalis, John; Schnell, Raymond J; Schieberle, Peter; Steinhaus, Martin

    2014-05-21

    The aroma-active compounds present in tree-ripened fruits of the five mango (Mangifera indica L.) cultivars Haden, White Alfonso, Praya Sowoy, Royal Special, and Malindi were isolated by solvent extraction followed by solvent-assisted flavor evaporation (SAFE) and analyzed by gas chromatography-olfactometery (GC-O). Application of a comparative aroma extract dilution analysis (cAEDA) afforded 54 aroma-active compounds in the flavor dilution (FD) factor range from 4 to ≥2048, 16 of which are reported for the first time in mango. The results of the identification experiments in combination with the FD factors revealed 4-hydroxy-2,5-dimethyl-3(2H)-furanone as an important aroma compound in all cultivars analyzed. Twenty-seven aroma-active compounds were present in at least one mango cultivar at an FD factor ≥128. Clear differences in the FD factors of these odorants between each of the mango cultivars suggested that they contributed to the unique sensory profiles of the individual cultivars.

  12. Magnetic properties of nearly stoichiometric CeAuBi2 heavy fermion compound

    International Nuclear Information System (INIS)

    Adriano, C.; Jesus, C. B. R.; Pagliuso, P. G.; Rosa, P. F. S.; Grant, T.; Fisk, Z.; Garcia, D. J.

    2015-01-01

    Motivated by the interesting magnetic anisotropy found in the heavy fermion family CeTX 2 (T = transition metal and X = pnictogen), here, we study the novel parent compound CeAu 1−x Bi 2−y by combining magnetization, pressure dependent electrical resistivity, and heat-capacity measurements. The magnetic properties of our nearly stoichiometric single crystal sample of CeAu 1−x Bi 2−y (x = 0.92 and y = 1.6) revealed an antiferromagnetic ordering at T N  = 12 K with an easy axis along the c-direction. The field dependent magnetization data at low temperatures reveal the existence of a spin-flop transition when the field is applied along the c-axis (H c  ∼ 7.5 T and T = 5 K). The heat capacity and pressure dependent resistivity data suggest that CeAu 0.92 Bi 1.6 exhibits a weak heavy fermion behavior with strongly localized Ce 3+ 4f electrons. Furthermore, the systematic analysis using a mean field model including anisotropic nearest-neighbors interactions and the tetragonal crystalline electric field (CEF) Hamiltonian allows us to extract a CEF scheme and two different values for the anisotropic J RKKY exchange parameters between the Ce 3+ ions in this compound. Thus, we discuss a scenario, considering both the anisotropic magnetic interactions and the tetragonal CEF effects, in the CeAu 1−x Bi 2−y compounds, and we compare our results with the isostructural compound CeCuBi 2

  13. Phase diagrams of site diluted ferromagnetic thin film

    International Nuclear Information System (INIS)

    Hamedoun, M.; Bouslykhane, K.; Bakrim, H.; Hourmatallah, A.; Benzakour, N.; Masrour, R.

    2006-01-01

    The phase transition properties of Ising, classical XY and Heisenberg of diluted ferromagnetic thin film are studied by the method of exact high-temperature series expansions extrapolated with the Pade approximants method. The reduced critical temperature τ c of the diluted ferromagnetic thin films is studied as a function of film thickness L and the exchange interactions in the bulk J b , in the surface J s and between surface and nearest-neighbour layer J - bar . It is found that τ c increases with the exchange interactions of surface and L. The magnetic phase diagram (τ c versus dilution x) is obtained. A critical value of the surface exchange interaction above which the surface magnetism appears is obtained. The dependence of the critical parameter of surface reduced coupling R 2 c as a function of the dilution x and the ratio of the exchange interaction between the surface and nearest-neighbour layer to the bulk one R 1 for the three studied models has been investigated. The percolation threshold is defined as the concentration x p at which τ c =0. The obtained values are x p ∼0.2 in the bulk and x p ∼0.4 at the surface

  14. Analysis of magnetic compounds of Kosice meteorite using Moessbauer spectrometry

    International Nuclear Information System (INIS)

    Dekan, J.; Sitek, J.; Sedlackova, K.

    2013-01-01

    Meteorite fall was observed by the town Kosice in Slovakia in February 2010. The fall itself was imaged by three security video cameras from Hungary. Detailed bolide light curves were obtained through clouds by radiometers on seven cameras of the European Fireball Network. Records of sonic waves were found on six seismic and four infrasonic stations. chondrites in various works. Due to the high abundance of iron in the solar system and its chemical and physical properties, we can gain insight into the formation and evolution of planets through the study of iron compounds in the planetary bodies. These kinds of analyses can bring important knowledge about phases and compounds formed in extraterrestrial conditions, which have another features than their terrestrial analogues. The "5"7Fe Moessbauer spectroscopy is one of the most sensitive methods for such studies. In this work Moessbauer spectroscopy will be used for phase analysis of iron bearing compounds with the aim to identify magnetic fractions using magnetic separation. (authors)

  15. Different magnetic behaviour of the Kondo compounds Al3Ce and Al11Ce3

    International Nuclear Information System (INIS)

    Benoit, A.; Flouquet, J.; Palleau, J.; Buevoz, J.L.

    1979-08-01

    Neutron diffraction experiments on the Al 3 Ce and Al 11 Ce 3 compounds have been performed on the multidetector of the I.L.L. high flux reactor. No magnetic structure has been detected on the Al 3 Ce compound down to 20 mK. This confirms the non magnetic ground state of Al 3 Ce. For Al 11 Ce 3 , two magnetic structures have been observed: a ferromagnetic one at 4.2 K and an antiferromagnetic one at 2 K. The antiferromagnetic structure, which corresponds to a propagation vector (0,0,1/3), implies a strong reduction of the magnetic moment of determined sites; this reflects the Kondo character of the compounds

  16. Special Heusler compounds for spintronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Balke, B.

    2007-07-01

    This work emphasizes the potential of Heusler compounds in a wide range of spintronic applications. Using electronic structure calculations it is possible to design compounds for specific applications. Examples for GMR and TMR applications, for spin injection into semiconductors, and for spin torque transfer applications will be shown. After a detailed introduction about spintronics and related materials chapter 5 reports about the investigation of new half-metallic compounds where the Fermi energy is tuned in the middle of the gap to result in more stable compounds for GMR and TMR applications. The bulk properties of the quaternary Heusler alloy Co{sub 2}Mn{sub 1-x}Fe{sub x}Si with the Fe concentration ranging from x=0 to 1 are reported and the results suggest that the best candidate for applications may be found at an iron concentration of about 50%. Due to the effect that in the Co{sub 2}Mn{sub 1-x}Fe{sub x}Si series the transition metal carrying the localized moment is exchanged and this might lead to unexpected effects on the magnetic properties if the samples are not completely homogeneous chapter 6 reports about the optimization of the Heusler compounds for GMR and TMR applications. The structural and magnetic properties of the quaternary Heusler alloy Co{sub 2}FeAl{sub 1-x}Si{sub x} with varying Si concentration are reported. From the combination of experimental (better order for high Si content) and theoretical findings (robust gap at x=0.5) it is concluded that a compound with an intermediate Si concentration close to x=0.5-0.7 would be best suited for spintronic applications, especially for GMR and TMR applications. In chapter 7 the detailed investigation of compounds for spin injection into semiconductors is reported. It is shown that the diluted magnetic semiconductors based on CoTiSb with a very low lattice mismatch among each other are interesting materials for spintronics applications like Spin-LEDs or other spin injection devices. Chapter 8 refers

  17. Thermodynamics of a dilute XX chain in a field

    Energy Technology Data Exchange (ETDEWEB)

    Timonin, P. N., E-mail: pntim@live.ru [Southern Federal University, Physics Research Institute (Russian Federation)

    2016-06-15

    Gapless phases in ground states of low-dimensional quantum spin systems are rather ubiquitous. Their peculiarity is a remarkable sensitivity to external perturbations due to permanent criticality of such phases manifested by a slow (power-low) decay of pair correlations and the divergence of the corresponding susceptibility. A strong influence of various defects on the properties of the system in such a phase can then be expected. Here, we consider the influence of vacancies on the thermodynamics of the simplest quantum model with a gapless phase, the isotropic spin-1/2 XX chain. The existence of the exact solution of this model gives a unique opportunity to describe in detail the dramatic effect of dilution on the gapless phase—the appearance of an infinite series of quantum phase transitions resulting from level crossing under the variation of a longitudinal magnetic field. We calculate the jumps in the field dependences of the ground-state longitudinal magnetization, susceptibility, entropy, and specific heat appearing at these transitions and show that they result in a highly nonlinear temperature dependence of these parameters at low T. Also, the effect of enhancement of the magnetization and longitudinal correlations in the dilute chain is established. The changes of the pair spin correlators under dilution are also analyzed. The universality of the mechanism of the quantum transition generation suggests that similar effects of dilution can also be expected in gapless phases of other low-dimensional quantum spin systems.

  18. Ferrimagnetic Properties of Bond Dilution Mixed Blume-Capel Model with Random Single-Ion Anisotropy

    International Nuclear Information System (INIS)

    Liu Lei; Yan Shilei

    2005-01-01

    We study the ferrimagnetic properties of spin 1/2 and spin-1 systems by means of the effective field theory. The system is considered in the framework of bond dilution mixed Blume-Capel model (BCM) with random single-ion anisotropy. The investigation of phase diagrams and magnetization curves indicates the existence of induced magnetic ordering and single or multi-compensation points. Special emphasis is placed on the influence of bond dilution and random single-ion anisotropy on normal or induced magnetic ordering states and single or multi-compensation points. Normal magnetic ordering states take on new phase diagrams with increasing randomness (bond and anisotropy), while anisotropy induced magnetic ordering states are always occurrence no matter whether concentration of anisotropy is large or small. Existence and disappearance of compensation points rely strongly on bond dilution and random single-ion anisotropy. Some results have not been revealed in previous papers and predicted by Neel theory of ferrimagnetism.

  19. High field magnetization process of (Sm, Nd)2Fe17Ny compounds

    International Nuclear Information System (INIS)

    Yu, M.J.; Tang, N.; Liu, Y.L.; Tegus, O.; Lu, Y.; Kuang, J.P.; Yang, F.M.; Li, X.; Zhou, G.F.; Boer, F.R. de

    1992-01-01

    The crystal structure and high-field magnetization process of (Sm 1-x Nd x ) 2 Fe 17 N y compounds (x = 0.0, 0.1, ..., 1.0, 2 1-x Nd x ) 2 Fe 17 N y compounds were found to crystallize in the rhombohedral Th 2 Zn 17 structure. As x increases, the Curie temperature decreases. The anisotropy fields and easy magnetization direction were investigated from 1.5 K to room temperature by means of high-field magnetization measurements and AC-susceptibility measurements, combined with X-ray diffraction on random and magnetically aligned powder samples. The anisotropy field decreases with increasing x and approaches a minimum value at about x = 0.6, then increases again. A tentative spin phase diagram for the (Sm 1-x Nd x ) 2 Fe 17 N y series is presented. At room temperature, the easy magnetization direction remains along the c-axis up to x = 0.6. (orig.)

  20. The phase diagrams and the order parameters of the diluted superlattice with antiferromagnetic interface coupling

    International Nuclear Information System (INIS)

    Oubelkacem, A.; El Aouad, N.; Bentaleb, M.; Laaboudi, B.; Saber, M.

    2004-01-01

    Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation functions, the magnetic properties of the diluted Ising superlattice consisting of two ferromagnetic materials A and B, with L a layers of diluted spins S a =((1)/(2)) and L b layers of diluted spins S b =1 with antiferromagnetic interface coupling are examined. For fixed values of the reduced exchange interactions and the concentration c of magnetic atoms, the phase diagrams, the two sublattice magnetizations and the total magnetization for the superlattice with the same spin S a =S b =((1)/(2)) and for S a =((1)/(2)), S b =1 are studied as a function of the temperature. We find a number of characteristic phenomena. In particular, the effect of the concentration c of magnetic atoms, the interlayer coupling and the layer thickness on both the compensation temperature and the magnetization profiles are clarified

  1. Assessment of off-stoichiometric Zr33-xFe52+xSi15 C14 Laves phase compounds as permanent magnet materials

    Science.gov (United States)

    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.

  2. Single-chain magnet features in 1D [MnR4TPP][TCNE] compounds

    International Nuclear Information System (INIS)

    Balanda, Maria; Tomkowicz, Zbigniew; Rams, Michal; Haase, Wolfgang

    2011-01-01

    Molecular chains of antiferrimagnetically coupled Mn III -ion (S = 2) and TCNE (tetracyanoethylene) radical moments (s = 1/2 ) show different behaviour depending on group R substituted to TPP (tetraphenylporphyrin) and on the substitution site. The compound with R = F in Ortho position is a Single-Chain Magnet (SCM) with blocking temperature T b = 6.6K, while that with R = F in Meta position shows both blocking (T b = 5.4 K) and magnetic ordering transition (T c = 10 K). For bulky groups R = OC n H 2n+1 , the magnetically ordered phase is observed (T c ∼ 22 K), which does not however prevent slow relaxation at T c of 2 T at 2.3 K is like that of SCM. The frequency dependent AC susceptibility in the superimposed DC field reveals common features of all systems. The energy of intrachain ferromagnetic coupling between effective spin units 3/2, relevant at low temperatures, is determined for all compounds and the interchain dipolar coupling is estimated. It is concluded that slow relaxation is inherent for all quasi one-dimensional compounds and for the magnetically ordered ones shows up in the high enough magnetic field.

  3. Determination of photooxygenation products of rotenone with isotope dilution method

    International Nuclear Information System (INIS)

    Chubachi, Mitsuo; Hamada, Masayuki

    1975-01-01

    When rotenone dissolved in certain solvent was photochemically oxidized, rotenolones, dehydrorotenone and rotenonone were obtained as main products. In order to determine the quantitative yields of these compounds in photooxygenation products, four compounds mentioned above were labeled with carbon-14 and the isotope dilution method by these labeled compounds was applied to the product analysis. (auth.)

  4. Dilution rate and microstructure of TIG arc Ni-Al powder surfacing layer

    Institute of Scientific and Technical Information of China (English)

    SHAN Jiguo; DONG Wei; TAN Wenda; ZHANG Di; PEN Jialie

    2007-01-01

    Surfacing beads are prepared by a direct current tungsten inert gas arc nickel-aluminum (Ni-Al) powder surfacing process. With the aim of controlling the dilution rate and obtaining surfacing beads rich in intermetallic compounds, the effects of surfacing parameters on geometric parameters, dilution rate, composition, and microstructure of the bead are investigated. An assistant cooler, which can potentially reduce the temperature of the base metal, is used in the surfacing process and its effect on dilution rate and microstructure is studied. The result indicates that with the surfacing parameter combination of low current and speed, the width and penetration of the bead decrease, reinforcement increases, and dilution rate drops markedly. With the reduc- tion of the parameter combination, the intergranular phase T-(Fe, Ni) is formed in the grain boundaries of Ni-Al interme- tallic matrix instead of the intergranular phase α-Fe, and large amount of intermetallics are obtained. With the use of an assistant cooler on a selected operation condition during the surfacing process, the reinforcement of the bead increases, penetration decreases, and dilution rate declines. The use of an assistant cooler helps obtain a surfacing bead composed of only intermetallics.

  5. Point defects in dilute nitride III-N-As and III-N-P

    International Nuclear Information System (INIS)

    Chen, W.M.; Buyanova, I.A.; Tu, C.W.; Yonezu, H.

    2006-01-01

    We provide a brief review of our recent results from optically detected magnetic resonance studies of grown-in non-radiative defects in two most important dilute nitride systems-Ga(In)NAs grown on GaAs substrates and Ga(Al,In)NP grown on Si and GaP substrates. These results have led to the identification of defect complexes in the alloys, involving intrinsic defects such as As Ga antisites and Ga i self-interstitials. They have also shed light on formation mechanisms of the defects and on their role in non-radiative carrier recombination that is harmful to the performance of potential optoelectronic and photonic devices based on these dilute nitrides

  6. Compositional Tuning, Crystal Growth, and Magnetic Properties of Iron Phosphate Oxide

    Science.gov (United States)

    Tarne, Michael

    Iron phosphate oxide, Fe3PO4O 3, is a crystalline solid featuring magnetic Fe3+ ions on a complex lattice composed of closely-spaced triangles. Previous work from our research group on this compound has proposed a helical magnetic structure below T = 163 K attributed to J1 - J2 competing interactions between nearest-neighbor and next-nearest-neighbor iron atoms. This was based on neutron powder diffraction featuring unique broad, flat-topped magnetic reflections due to needle-like magnetic domains. In order to confirm the magnetic structure and origins of frustration, this thesis will expand upon the research focused on this compound. The first chapter focuses on single crystal growth of Fe3PO 4O3. While neutron powder diffraction provides insight to the magnetic structure, powder and domain averaging obfuscate a conclusive structure for Fe3PO4O3 and single crystal neutron scattering is necessary. Due to the incongruency of melting, single crystal growth has proven challenging. A number of techniques including flux growth, slow cooling, and optical floating zone growth were attempted and success has been achieved via heterogenous chemical vapor transport from FePO 4 using ZrCl4 as a transport agent. These crystals are of sufficient size for single crystal measurements on modern neutron diffractometers. Dilution of the magnetic sublattice in frustrated magnets can also provide insight into the nature of competing spin interactions. Dilution of the Fe 3+ lattice in Fe3PO4O3 is accomplished by substituting non-magnetic Ga3+ to form the solid solution series Fe3-xGaxPO4O3 with x = 0, 0.012, 0.06, 0.25, 0.5, 1.0, 1.5. The magnetic susceptibility and neutron powder diffraction data of these compounds are presented. A dramatic decrease of the both the helical pitch length and the domain size is observed with increasing x; for x > 0.5, the compounds lack long range magnetic order. The phases that do exhibit magnetic order show a decrease in helical pitch with increasing x

  7. Electronic and magnetic properties of rare earth-Sn3 compounds for 119Sn Moessbauer spectroscopy

    International Nuclear Information System (INIS)

    Sanchez, J.P.; Friedt, J.M.; Shenoy, G.K.; Percheron, A.; Achard, J.C.

    1975-01-01

    The electronic and magnetic properties of RESn 3 compounds (RE=La, Ce, Pr, Nd, Sm, Eu, Gd, Yb) have been investigated using the 23.8keV Moessbauer resonance of 119 Sn. The isomer shifts and quadrupole interactions are nearly the same in all compounds. The transferred magnetic fields and their orientation with respect to the principal electric field gradient axis at various Sn sites in the magnetically ordered state of RESn 3 (RE=Pr, Nd, Sm, Eu, Gd) have been utilized to get information about the magnetic structure. An evaluation of the transferred fields in PrSn 3 and NdSn 3 shows that the spin density at the Sn nucleus is nearly the same in both compounds [fr

  8. Water-based adhesives with tailored hydrophobic association: dilution resistance and improved setting behavior.

    Science.gov (United States)

    Dundua, Alexander; Landfester, Katharina; Taden, Andreas

    2014-11-01

    Hydrophobic association and stimuli-responsiveness is a powerful tool towards water-based adhesives with strongly improved properties, which is demonstrated based on the example of hydrophobically modified alkali-soluble latexes (HASE) with modulated association. Their rheological properties are highly tunable due to the hydrophobic domains that act as physical crosslinking sites of adjustable interaction strength. Ethanol, propanol, and butanol are used as water-soluble model additives with different hydrophobicity in order to specifically target the association sites and impact the viscoelastic properties and stimuli-responsiveness. The rheological and mechanical property response upon dilution with water can be tailored, and dilution-resistant or even dilution-thickening systems are obtained. The investigations are of high importance for water-based adhesives, as our findings provide insight into general structure-property relationships to improve their setting behavior, especially upon contact with wet substrates. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Magnetic and transport properties of EuNi(Si1-xGex)3 compounds

    International Nuclear Information System (INIS)

    Uchima, K; Takaesu, Y; Akamine, H; Kakihana, M; Tomori, K; Uejo, T; Teruya, A; Nakamura, A; Hedo, M; Nakama, T; Yagasaki, K; Matsubayashi, K; Uwatoko, Y

    2014-01-01

    The magnetization M, electrical resistivity ρ, thermopower S and specific heat C of EuNi(Si 1-x Ge x ) 3 compounds have been measured at temperatures from 2 to 300 K. For the compounds of EuNi(Si 1-x Ge x ) 3 , we obtained an effective magnetic moment of μ eff ∼ 7.7 μ B , which is close to the divalent Eu value of μ eff =7.94 μ B . All compounds of EuNi(Si 1-x Ge x ) 3 order antiferromagnetically. The Néel temperature T N decreases monotonously with increasing the Ge concentration x from T N =49 K for EuNiSi 3 to T N =14 K for EuNiGe 3 . In the low temperature region below T N , anomalies corresponding to an additional magnetic phase transition into ferromagnetic state for compounds with x < 0.3, and into another antiferromagnetic for x > 0.3 were observed. The Curie temperature T C rapidly decreases with increasing x and vanishes at x ≈ 0.3. It is found that the magnetic phase transition temperatures of T N and T C in EuNi(Si 1-x Ge x ) 3 are strongly connected with the change of volume induced by the atomic substitution of Si by Ge

  10. Magnetic properties for the Mn{sub 2}GeTe{sub 4} compound

    Energy Technology Data Exchange (ETDEWEB)

    Quintero, M. [Departamento de Fisica, Facultad de Ciencias, Centro de Estudios de Semiconductores, Universidad de los Andes, Merida 5101 (Venezuela, Bolivarian Republic of)], E-mail: mquinter@ula.ve; Quintero, E.; Caldera, D.; Moreno, E.; Morocoima, M.; Grima, P.; Ferrer, D.; Marchan, N.; Bocaranda, P. [Departamento de Fisica, Facultad de Ciencias, Centro de Estudios de Semiconductores, Universidad de los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Delgado, G.E. [Laboratorio de Cristalografia, Departamento de Quimica, Facultad de Ciencias, Universidad de Los Andes, Merida 5101 (Venezuela, Bolivarian Republic of); Henao, J.A.; Macias, M.A.; Pinto, J.L. [Grupo de Investigacion en Quimica Estructural (GIQUE), Centro de Investigacion en Biomoleculas (CIBIMOL), Facultad de Ciencias, Escuela de Quimica, Universidad Industrial de Santander, Apartado aereo 678, Bucaramanga (Colombia); Ponce, C.A. [Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Corrientes 3400 (Argentina)

    2009-02-15

    Measurements of magnetic susceptibility {chi}, in the temperature range from 2 to 300 K, and of magnetization M vs. applied magnetic field B, up to 5 T, at various temperatures were made on polycrystalline samples of the Mn{sub 2}GeTe{sub 4} compound. It was found that Mn{sub 2}GeTe{sub 4} has a Neel temperature T{sub N} of about 135 K, shows mainly antiferromagnetic behavior with a very weak superimposed ferromagnetic component that is attributed to spin canting. Also, the magnetic results suggest that a possible spin-glass transition takes place at T{sub f}{approx}45 K. The spin-glass order parameter q(T), determined from the susceptibility data, was found to be in agreement with the prediction of conventional spin-glass theory. The M vs. B results indicated that bound magnetic polarons (BMPs) occur in the compound, and that the effects from BMPs disappear at approximately 80 K. The M vs. B curves were well fitted by a Langevin type of equation, and the variation of the fitting parameters determined as a function of temperature. Using a simple spherical model, the radius of the BMP in the material was found to be about 27 A; this value is similar to the effective Bohr radius for an acceptor in the II-IV-V{sub 2} and I-III-VI{sub 2} ternary semiconductor compounds.

  11. Influence of Al on the magnetic properties of TmCo{sub 4}Al compound, a magnetic and neutron diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Laslo, A. [CNRS, Inst. Néel, F-38042 Grenoble (France); Univ. Grenoble Alpes, Inst. Néel, F-38042 Grenoble (France); Babes-Bolyai University, Faculty of Physics, 400084 Cluj-Napoca (Romania); Pop, V. [Babes-Bolyai University, Faculty of Physics, 400084 Cluj-Napoca (Romania); Isnard, O. [CNRS, Inst. Néel, F-38042 Grenoble (France); Univ. Grenoble Alpes, Inst. Néel, F-38042 Grenoble (France)

    2015-03-25

    Highlights: • The existence of a compensation temperature is found for TmCo{sub 4}Al. • The crystal structure and its thermal evolution are analysed by X-ray and neutron diffraction. • The ferrimagnetic magnetic structure of TmCo{sub 4}Al is established. • Magnetic properties are determined. • Significant coercivity is reported for TmCo{sub 4}Al. - Abstract: The structural and magnetic properties of the TmCo{sub 4}Al compound are presented as deduced from magnetic measurements, X-ray and neutron powder diffraction. The crystal structure is obtained in the light of Rietveld refinement of the neutron powder diffraction pattern. The symmetry of the CaCu{sub 5} structure is preserved and the Al atom is found to substitute the Co one exclusively on the 3g atomic position. Thermal expansion of the crystal lattice is reported, the temperature variation occurring mostly along the basal hexagonal plane. This compound exhibits a ferrimagnetic structure, the Tm and Co magnetic moments being coupled antiparallel. An ordering temperature of 511 K is found. The thermal dependence of the Tm magnetic moment is obtained down to 4 K. A compensation of the two sublattice magnetization is found at 75 K, a feature induced by the Al for Co substitution and not observed in the corresponding TmCo{sub 5} compound. Magnetization curves reveal large coercivity values at low temperature such as 2.48 T at 2 K.

  12. Magnetic structure and physical properties of the multiferroic compound PrMn{sub 2}O{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Doubrovsky, C. [Laboratoire de Physique des Solides, Universite Paris-Sud, CNRS-UMR 8502, 91405 Orsay Cedex (France); Andre, G. [Laboratoire Leon Brillouin, CEA-CNRS UMR 12, 91191 Gif-sur-Yvette Cedex (France); Bouquet, F. [Laboratoire de Physique des Solides, Universite Paris-Sud, CNRS-UMR 8502, 91405 Orsay Cedex (France); Elkaim, E. [Soleil Synchrotron, 91191 Gif-sur-Yvette Cedex (France); Li, M.; Greenblatt, M. [Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); Foury-Leylekian, P., E-mail: pascale.foury@u-psud.fr [Laboratoire de Physique des Solides, Universite Paris-Sud, CNRS-UMR 8502, 91405 Orsay Cedex (France)

    2012-06-01

    RMn{sub 2}O{sub 5} (R=lanthanide, Bi, Y) multiferroic compounds are intensively studied for their potential application in the spintronic field. In these systems, the key issue is to understand the origin of the strong coupling between the ferroelectric and magnetic orders and to investigate the influence of the nature of the R ions in this coupling. While the phase diagram of RMn{sub 2}O{sub 5} compounds with small R size is well established, this of large R size compounds is missing due to the lack of samples originating with difficulties of synthesis. We present in this paper the first investigation of the thermodynamic, structural and magnetic properties of high quality polycrystalline PrMn{sub 2}O{sub 5} samples. Our work shows that PrMn{sub 2}O{sub 5} presents two magnetic transitions corresponding to commensurate magnetic orderings. We also evidence a weak lattice effect coupled to the magnetic order. Our results point out that the physical properties of PrMn{sub 2}O{sub 5} differ from those of the parent compounds with magnetic R ions.

  13. Magnetism and superconductivity in Eu-based iron pnictides

    Energy Technology Data Exchange (ETDEWEB)

    Zapf, Sina [1. Physikalisches Institut, Universitaet Stuttgart (Germany)

    2015-07-01

    EuFe{sub 2}As{sub 2} is an extraordinary parent compound of the iron pnictides, as it exhibits at low temperatures - additional to the Fe spin density wave - long-range magnetic order of the Eu{sup 2+} local moments. Nevertheless, bulk superconductivity around 30 K can be induced by mechanical pressure or chemical substitution. In this talk we review the remarkable interplay of unconventional superconductivity, itinerant and local magnetism in Eu based iron pnictides. We focus on the appearance of a re-entrant spin glass phase that coexists with superconductivity and an indirect magneto-elastic coupling, enabling the persistent magnetic detwinning by small magnetic fields.

  14. Electronic paramagnetic resonance in the Mn In X (X:Te,S) diluted magnetic semiconductor system

    International Nuclear Information System (INIS)

    Vincent, Bernardo; Betancourt, Luis; Sagredo, Vicente; Alcala, Rafael

    1996-01-01

    Semiconductor compounds wit the II-III-VI stoichiometry are very interesting materials since they present very good semiconducting characteristics and, along with strong magnetic properties, these II Mn In VI compounds have a great potential as opt and magneto-electronic devices. Among the possible magnetic properties of the materials is the presence of the spin-glass phase. Electron paramagnetic resonance is one of the techniques used to confirm this phase. The chosen crystals were chosen by chemical vapor transport. The absorption lines of these two families with 0.1 x 1 were all Lorentzian in shape and centred at g=2. A large broadening of the resonance line width was observed when lowering the temperature to below 80 K. This behaviour was fitted to the known existing models, and good values of the calculated parameters were obtained (author)

  15. Magnetic behaviour of a new compound, Eu{sub 2}CuSi{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Majumdar, Subham; Mallik, R; Sampathkumaran, E V [Tata Institute of Fundamental Research, Mumbai (India)

    1999-07-01

    As a part of our program to synthesize new ternary Eu compounds, we report here the formation of Eu{sub 2}CuSi{sub 3} for the first time and its magnetic behaviour by magnetic susceptibility, electrical-resistivity and heat-capacity measurements. This compound is found to crystallize in an AlB{sub 2}-derived hexagonal structure. The results establish that Eu ions are divalent, undergoing long-range ferromagnetic-ordering below 38 K. (author)

  16. Dilution Confusion: Conventions for Defining a Dilution

    Science.gov (United States)

    Fishel, Laurence A.

    2010-01-01

    Two conventions for preparing dilutions are used in clinical laboratories. The first convention defines an "a:b" dilution as "a" volumes of solution A plus "b" volumes of solution B. The second convention defines an "a:b" dilution as "a" volumes of solution A diluted into a final volume of "b". Use of the incorrect dilution convention could affect…

  17. Finite Element Analysis of the Rotor System of a Magnetically Suspended Compound Molecule Pump

    International Nuclear Information System (INIS)

    Liu Pingfan; Zhao Lei; Shi Zhengang; Yang Guojun

    2014-01-01

    A novel magnetically suspended compound molecule pump has been designed, which has been supported by the active magnetic bearings (AMBs) system with 5 degrees of freedom. According to the characteristics of the high speed and AMBs, the rotor system of the magnetically suspended compound molecule pump has been analyzed by the finite element method. Modal analysis has been performed for the rotor, thus modal frequencies and corresponding modal shapes have been obtained. For the high rotating speed the blades usually have tended to be destroyed as the results of the centrifugal deformation and vibration. So several static parameters have been analyzed, such as stress distributions and deformations. Simulation results provide a theoretical foundation for the design of the magnetically suspended compound molecule pump’s controllers. The reliability and safety of the structure have been verified completely. Furthermore, this paper is of great significance for the pumps’ future developments. (author)

  18. Universal features underlying the magnetism in diluted magnetic semiconductors

    Science.gov (United States)

    Andriotis, Antonis N.; Menon, Madhu

    2018-04-01

    Investigation of a diverse variety of wide band gap semiconductors and metal oxides that exhibit magnetism on substitutional doping has revealed the existence of universal features that relate the magnetic moment of the dopant to a number of physical properties inherent to the dopants and the hosts. The investigated materials consist of ZnO, GaN, GaP, TiO2, SnO2, Sn3N4, MoS2, ZnS and CdS doped with 3d-transition metal atoms. The primary physical properties contributing to magnetism include the orbital hybridization and charge distribution, the d-band filling, d-band center, crystal field splitting, electron pairing energy and electronegativity. These features specify the strength of the spin-polarization induced by the dopants on their first nearest neighboring anions which in turn specify the long range magnetic coupling among the dopants through successively induced spin polarizations (SSP) on neighboring dopants. The proposed local SSP process for the establishment of the magnetic coupling among the TM-dopants appears as a competitor to other classical processes (superexchange, double exchange, etc). Furthermore, these properties can be used as a set of descriptors suitable for developing statistical predictive theories for a much larger class of magnetic materials.

  19. Universal features underlying the magnetism in diluted magnetic semiconductors.

    Science.gov (United States)

    Andriotis, Antonis N; Menon, Madhu

    2018-04-04

    Investigation of a diverse variety of wide band gap semiconductors and metal oxides that exhibit magnetism on substitutional doping has revealed the existence of universal features that relate the magnetic moment of the dopant to a number of physical properties inherent to the dopants and the hosts. The investigated materials consist of ZnO, GaN, GaP, TiO 2 , SnO 2 , Sn 3 N 4 , MoS 2 , ZnS and CdS doped with 3d-transition metal atoms. The primary physical properties contributing to magnetism include the orbital hybridization and charge distribution, the d-band filling, d-band center, crystal field splitting, electron pairing energy and electronegativity. These features specify the strength of the spin-polarization induced by the dopants on their first nearest neighboring anions which in turn specify the long range magnetic coupling among the dopants through successively induced spin polarizations (SSP) on neighboring dopants. The proposed local SSP process for the establishment of the magnetic coupling among the TM-dopants appears as a competitor to other classical processes (superexchange, double exchange, etc). Furthermore, these properties can be used as a set of descriptors suitable for developing statistical predictive theories for a much larger class of magnetic materials.

  20. Electronic structure, magnetism and disorder in the Heusler compound Co2TiSn

    International Nuclear Information System (INIS)

    Kandpal, Hem Chandra; Ksenofontov, Vadim; Wojcik, Marek; Seshadri, Ram; Felser, Claudia

    2007-01-01

    Polycrystalline samples of the Heusler compound Co 2 TiSn have been prepared and studied using bulk techniques (x-ray diffraction and magnetization) as well as local probes ( 119 Sn Moessbauer spectroscopy and 59 Co nuclear magnetic resonance spectroscopy) in order to determine how disorder affects the half-metallic behaviour and also to establish the joint use of Moessbauer and NMR spectroscopies as a quantitative probe of local atom ordering in these compounds. Additionally, density functional electronic structure calculations on ordered and partially disordered Co 2 TiSn compounds have been carried out at a number of different levels of theory in order to simultaneously understand how the particular choice of DFT scheme as well as disorder affects the computed magnetization. Our studies suggest that a sample which seems well ordered by x-ray diffraction and magnetization measurements can possess up to 10% of antisite (Co/Ti) disordering. Computations similarly suggest that even 12.5% antisite Co/Ti disorder does not destroy the half-metallic character of this material. However, the use of an appropriate level of non-local DFT is crucial

  1. Uranium magnetism in UGa2 and U(Gasub(1-x)Alsub(x))2 compounds

    International Nuclear Information System (INIS)

    Ballou, R.

    1983-01-01

    Magnetism of intermetallic compounds of uranium is studied. A monocrystal of the highly anisotropic ferromagnetic material UGa 2 is studied by polarized neutron diffraction. Localisation of 5f electrons is evidenced. Magnetic structure of uranium in UGa 2 is determined. The pseudobinary compound U(Gasub(1-x)Alsub(x)) 2 is studied for crystal structure, ferromagnetism, paramagnetism, specific heat and resistivity [fr

  2. Investigations on Ce- and Yb-based intermetallic compounds

    International Nuclear Information System (INIS)

    Elenbaas, R.A.

    1980-01-01

    The author describes investigations on a number of cerium- and ytterbium-based intermetallic compounds and alloys, yielding a lot of experimental results which could not always be put in a quantitative picture. All experimental data are consistent with a single-ion behaviour, where the 4f state is more or less modified by the conduction electrons. In the investigated systems several different features of the magnetism of cerium atoms in metals were studied. (Auth.)

  3. Dilute Magnetic Semiconductor Cu2FeSnS4 Nanocrystals with a Novel Zincblende Structure

    Directory of Open Access Journals (Sweden)

    Xiaolu Liang

    2012-01-01

    Full Text Available Diluted magnetic semiconductor Cu2FeSnS4 nanocrystals with a novel zincblende structure have been successfully synthesized by a hot-injection approach. Cu+, Fe2+, and Sn4+ ions occupy the same position in the zincblende unit cell, and their occupancy possibilities are 1/2, 1/4, and 1/4, respectively. The nanocrystals were characterized by means of X-ray diffraction (XRD, transmission electron microscopy (TEM, selected area electron diffraction (SAED, energy-dispersive spectroscopy (EDS, and UV-vis-NIR absorption spectroscopy. The nanocrystals have an average size of 7.5 nm and a band gap of 1.1 eV and show a weak ferromagnetic behavior at low temperature.

  4. Calculations of the magnetic properties of R{sub 2}M{sub 14}B intermetallic compounds (R=rare earth, M=Fe, Co)

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Masaaki, E-mail: masaaki.ito@neel.cnrs.fr [CNRS, Institut Néel, 25 rue des Martyrs, BP166, 38042 Grenoble (France); University Grenoble Alpes, Institut Néel, 38042 Grenoble (France); Advanced Material Engineering Division, Toyota Motor Corporation, Susono 410-1193 (Japan); Yano, Masao [Advanced Material Engineering Division, Toyota Motor Corporation, Susono 410-1193 (Japan); Dempsey, Nora M. [CNRS, Institut Néel, 25 rue des Martyrs, BP166, 38042 Grenoble (France); University Grenoble Alpes, Institut Néel, 38042 Grenoble (France); Givord, Dominique [CNRS, Institut Néel, 25 rue des Martyrs, BP166, 38042 Grenoble (France); University Grenoble Alpes, Institut Néel, 38042 Grenoble (France); Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro (Brazil)

    2016-02-15

    The hard magnetic properties of “R–M–B” (R=rare earth, M=mainly Fe) magnets derive from the specific intrinsic magnetic properties encountered in Fe-rich R{sub 2}M{sub 14}B compounds. Exchange interactions are dominated by the 3d elements, Fe and Co, and may be modeled at the macroscopic scale with good accuracy. Based on classical formulae that relate the anisotropy coefficients to the crystalline electric field parameters and exchange interactions, a simple numerical approach is used to derive the temperature dependence of anisotropy in various R{sub 2}Fe{sub 14}B compounds (R=Pr, Nd, Dy). Remarkably, a unique set of crystal field parameters give fair agreement with the experimentally measured properties of all compounds. This implies reciprocally that the properties of compounds that incorporate a mixture of different rare-earth elements may be predicted accurately. This is of special interest for material optimization that often involves the partial replacement of Nd with another R element and also the substitution of Co for Fe. - Highlights: • Anisotropy constants derived from CEF parameters of R{sub 2}M{sub 14}B compounds (M=Fe, Co). • Anisotropy constants of all R{sub 2}Fe{sub 14}B compounds using unique set of CEF parameters. • Moment non-collinearity in magnetization processes under B{sub app} along hard axis.

  5. Dzyaloshinskii-Moriya interaction and magnetic anisotropies in Uranium compounds

    Science.gov (United States)

    Sandratskii, L. M.

    2018-05-01

    We report on the first-principles study of complex noncollinear magnetic structures in Uranium compounds. We contrast two cases. The first is the periodic magnetic structure of U2Pd2In with exactly orthogonal atomic moments, the second is an incommensurate plane spiral structure of UPtGe where the angle between atomic moments of nearest neighbors is also close to 90°. We demonstrate that the hierarchy of magnetic interactions leading to the formation of the magnetic structure is opposite in the two cases. In U2Pd2In, the magnetic anisotropy plays the leading role, followed by the Dzyaloshinskii-Moriya interaction (DMI) interaction specifying the chirality of the structure. Here, the interatomic exchange interaction does not play important role. In UPtGe the hierarchy of the interactions is opposite. The leading interaction is the interatomic exchange interaction responsible for the formation of the incommensurate spiral structure followed by the DMI responsible for the selected chirality of the helix. The magnetic anisotropy is very weak that is a prerequisite for keeping the distortion of the helical structure weak.

  6. Noncollinear magnetism in Mn{sub 2}RhSn Heusler compound

    Energy Technology Data Exchange (ETDEWEB)

    Meshcheriakova, Olga

    2014-09-15

    Heusler compounds is a large class of materials, which exhibits diverse fundamental phenomena, together with the possibility of their specific tailoring for various engineering demands. Present work discusses the magnetic noncollinearity in the family of noncentrosymmetric ferrimagnetic Mn{sub 2}-based Heusler compounds. Based on the obtained experimental and theoretical results, Mn{sub 2}YZ Heusler family is suspected to provide promising candidates for the formation of the skyrmion lattice. The work is focused on Mn{sub 2}RhSn bulk polycrystalline sample, which serves as a prototype. It crystallizes in the tetragonal noncentrosymmetric structure (No. 119, I anti 4m2), which enables the anisotropic Dzyaloshinskii-Moriya (DM) exchange coupling. Additional short-range modulation, induced by the competing nearest and next-nearest interplanes Heisenberg exchange, is suppressed above the 80 K. This allows to develop the long-range modulations in the ideal ferrimagnetic structure within the ab crystallographic planes, and thus, favors to the occurrence of the skyrmion lattice within the temperature range of (80≤T≤ 270) K. The studies of Mn{sub 2}RhSn were expanded to the broad composition range and continued on thin film samples.

  7. Effect of low severity dilute-acid pretreatment of barley straw and decreased enzyme loading hydrolysis on the production of fermentable substrates and the release of inhibitory compounds

    NARCIS (Netherlands)

    Panagiotopoulos, I.A.; Lignos, G.D.; Bakker, R.R.C.; Koukios, E.G.

    2012-01-01

    The objective of this work was to investigate the feasibility of combining low severity dilute-acid pretreatment of barley straw and decreased enzyme loading hydrolysis for the high production of fermentable substrates and the low release of inhibitory compounds. For most of the pretreatments at 160

  8. Magnetic properties of the LaCu5-xCox compounds

    International Nuclear Information System (INIS)

    Crisan, V.; Popescu, V.; Vernes, A.; Andreica, D.; Cristea, S.; Koepe, B.

    1996-01-01

    Magnetic moments and Curie temperatures of the intermetallic compounds LaCu 5-x Co x (x = 5) are calculated using a recursion method in the framework of the spin-fluctuation theory of Mohn and Wohlfarth. (orig.)

  9. Extended aroma extract dilution analysis profile of Shiikuwasha (Citrus depressa Hayata pulp essential oil

    Directory of Open Access Journals (Sweden)

    Yonathan Asikin

    2018-01-01

    Full Text Available Shiikuwasha pulp is an important raw material for producing citrus essential oils. The volatile aroma composition of pulp essential oil was evaluated using gas chromatography (GC methods, and its aroma profile was assessed using GC-olfactometry with an extended aroma extract dilution analysis (AEDA technique in regard to alterations of odor strength and sensorial perception throughout serial dilution steps. The essential oil comprised a mixture of 55 aroma compounds, including monoterpene hydrocarbon, sesquiterpene hydrocarbon, alcohol, aldehyde, ester, and oxide compounds. The predominant compounds were limonene [57.36% (4462.80 mg/100 g of pulp] and γ-terpinene [25.14% (1956.21 mg/100 g of pulp]. However, linalool was identified as one of the key aroma components providing the highest flavor dilution factor in AEDA, whilst three sesquiterpene hydrocarbons (δ-elemene, germacrene B, and bicyclosesquiphellandrene and two esters (heptyl acetate and decyl acetate had superior relative flavor activities. The extended AEDA profile identified variations in assessed odor perceptions, intensity, and duration of aroma components over dilution, whereas the 12 most odor-active compounds showed comparable odor strengths.

  10. Study of magnetism in Ni-Cr hardface alloy deposit on 316LN stainless steel using magnetic force microscopy

    Science.gov (United States)

    Kishore, G. V. K.; Kumar, Anish; Chakraborty, Gopa; Albert, S. K.; Rao, B. Purna Chandra; Bhaduri, A. K.; Jayakumar, T.

    2015-07-01

    Nickel base Ni-Cr alloy variants are extensively used for hardfacing of austenitic stainless steel components in sodium cooled fast reactors (SFRs) to avoid self-welding and galling. Considerable difference in the compositions and melting points of the substrate and the Ni-Cr alloy results in significant dilution of the hardface deposit from the substrate. Even though, both the deposit and the substrate are non-magnetic, the diluted region exhibits ferromagnetic behavior. The present paper reports a systematic study carried out on the variations in microstructures and magnetic behavior of American Welding Society (AWS) Ni Cr-C deposited layers on 316 LN austenitic stainless steels, using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The phase variations of the oscillations of a Co-Cr alloy coated magnetic field sensitive cantilever is used to quantitatively study the magnetic strength of the evolved microstructure in the diluted region as a function of the distance from the deposit/substrate interface, with the spatial resolution of about 100 nm. The acquired AFM/MFM images and the magnetic property profiles have been correlated with the variations in the chemical compositions in the diluted layers obtained by the energy dispersive spectroscopy (EDS). The study indicates that both the volume fraction of the ferromagnetic phase and its ferromagnetic strength decrease with increasing distance from the deposit/substrate interface. A distinct difference is observed in the ferromagnetic strength in the first few layers and the ferromagnetism is observed only near to the precipitates in the fifth layer. The study provides a better insight of the evolution of ferromagnetism in the diluted layers of Ni-Cr alloy deposits on stainless steel.

  11. Magnetic properties of Pr1-xGdxMn2Ge2 compounds

    International Nuclear Information System (INIS)

    Kilic, A.; Kervan, S.; Oezcan, S.; Gencer, A.

    2004-01-01

    The structure and magnetic properties of the Pr 1-x Gd x Mn 2 Ge 2 (0.0≤x≤1.0) compounds have been investigated by means of X-ray diffraction (XRD), differential scanning calorimetry (DSC) techniques and AC magnetic susceptibility measurements. All compounds crystallize in the ThCr 2 Si 2 -type structure with the space group I4/mmm. The lattice constants and the unit cell volume obey Vegard's law. Samples in this alloy system exhibit a crossover from ferromagnetic ordering for PrMn 2 Ge 2 to antiferromagnetic ordering for GdMn 2 Ge 2 as a function of Gd concentration x. At low temperatures, the rare earth sublattice also orders and reconfigures the ordering in the Mn sublattice. The results are summarized in the x-T magnetic phase diagram

  12. A scanning tunneling microscope for a dilution refrigerator.

    Science.gov (United States)

    Marz, M; Goll, G; Löhneysen, H v

    2010-04-01

    We present the main features of a home-built scanning tunneling microscope that has been attached to the mixing chamber of a dilution refrigerator. It allows scanning tunneling microscopy and spectroscopy measurements down to the base temperature of the cryostat, T approximately 30 mK, and in applied magnetic fields up to 13 T. The topography of both highly ordered pyrolytic graphite and the dichalcogenide superconductor NbSe(2) has been imaged with atomic resolution down to T approximately 50 mK as determined from a resistance thermometer adjacent to the sample. As a test for a successful operation in magnetic fields, the flux-line lattice of superconducting NbSe(2) in low magnetic fields has been studied. The lattice constant of the Abrikosov lattice shows the expected field dependence proportional to 1/square root of B and measurements in the scanning tunneling spectroscopy mode clearly show the superconductive density of states with Andreev bound states in the vortex core.

  13. Single-chain magnet features in 1D [MnR{sub 4}TPP][TCNE] compounds

    Energy Technology Data Exchange (ETDEWEB)

    Balanda, Maria [Institute of Nuclear Physics PAN, Radzikowskiego 152, 31-342 Krakow (Poland); Tomkowicz, Zbigniew; Rams, Michal [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland); Haase, Wolfgang, E-mail: Maria.Balanda@ifj.edu.pl [Institute of Physical Chemistry, Darmstadt University of Technology, 64287 Darmstadt (Germany)

    2011-07-06

    Molecular chains of antiferrimagnetically coupled Mn{sup III}-ion (S = 2) and TCNE (tetracyanoethylene) radical moments (s = 1/2 ) show different behaviour depending on group R substituted to TPP (tetraphenylporphyrin) and on the substitution site. The compound with R = F in Ortho position is a Single-Chain Magnet (SCM) with blocking temperature T{sub b} = 6.6K, while that with R = F in Meta position shows both blocking (T{sub b} = 5.4 K) and magnetic ordering transition (T{sub c} = 10 K). For bulky groups R = OC{sub n}H{sub 2n+1}, the magnetically ordered phase is observed (T{sub c} {approx} 22 K), which does not however prevent slow relaxation at T <8 K. Magnetic hysteresis with coercive field H{sub c} of 2 T at 2.3 K is like that of SCM. The frequency dependent AC susceptibility in the superimposed DC field reveals common features of all systems. The energy of intrachain ferromagnetic coupling between effective spin units 3/2, relevant at low temperatures, is determined for all compounds and the interchain dipolar coupling is estimated. It is concluded that slow relaxation is inherent for all quasi one-dimensional compounds and for the magnetically ordered ones shows up in the high enough magnetic field.

  14. A family of rare-earth-based single chain magnets: playing with anisotropy.

    Science.gov (United States)

    Bernot, Kevin; Bogani, Lapo; Caneschi, Andrea; Gatteschi, Dante; Sessoli, Roberta

    2006-06-21

    The first family of rare-earth-based single chain magnets is presented. Compounds of general formula [M(hfac)3(NITPhOPh)], where M = Eu, Gd, Tb, Dy, Ho, Er, or Yb, and PhOPh is the nitronyl-nitroxide radical (2,4'-benzoxo-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), have been structurally characterized and found to be isostructural. The characterization of both static and dynamic magnetic properties of the whole family is reported. Dy, Tb, and Ho compounds display slow relaxation of the magnetization, and ac susceptibility shows a thermally activated regime with energy barriers of 69, 45, and 34 K for Dy, Tb, and Ho compounds, respectively, while only a frequency-dependent susceptibility is observed for Er below 2.0 K. In Gd and Yb derivatives, antiferromagnetic interactions dominate. The pre-exponential factors differ by about 4 orders of magnitude. Finite size effects, due to naturally occurring defects, affect the static and dynamic properties of the compounds differently.

  15. Tailoring magnetic nanoparticle for transformers application.

    Science.gov (United States)

    Morais, P C; Silva, A S; Leite, E S; Garg, V K; Oliveira, A C; Viali, W R; Sartoratto, P P C

    2010-02-01

    In this study photoacoustic spectroscopy was used to investigate the effect of dilution of an oil-based magnetic fluid sample on the magnetic nanoparticle surface-coating. Changes of the photoacoustic signal intensity on the band-L region (640 to 830 nm) upon dilution of the stock magnetic fluid sample were discussed in terms of molecular surface desorption. The model proposed here assumes that the driving force taking the molecules out from the nanoparticle surface into the bulk solvent is the gradient of osmotic pressure. This gradient of osmotic pressure is established between the nanoparticle surface and the bulk suspension. It is further assumed that the photoacoustic signal intensity (area under the photoacoustic spectra) scales linearly with the number of coating molecules (surface grafting) at the nanoparticle surface. This model picture provides a non-linear analytical description for the reduction of the surface grafting coefficient upon dilution, which was successfully-used to curve-fit the photoacoustic experimental data.

  16. Magnetic and magnetocaloric properties of amorphous Y{sub 3}Fe{sub 5}O{sub 12} compound

    Energy Technology Data Exchange (ETDEWEB)

    Nóbrega, E.P., E-mail: pilad@cbpf.br; Costa, S.S.; Alvarenga, T.S.T.; Alho, B.P.; Caldas, A.; Ribeiro, P.O.; Sousa, V.S.R de; Oliveira, N.A. de; Ranke, P.J. von

    2017-01-15

    We report a theoretical model formed by two coupled magnetic sublattices of localized spins in the presence of an applied magnetic field to investigate the magnetic characteristics and magnetocaloric properties of amorphous yttrium iron garnet. The magnetic state equation is based on Handrich–Kobe´s theory, where the amorphization is taken into account by introducing fluctuations in the exchange parameters. Experimental results report that Y{sub 3}Fe{sub 5}O{sub 12} presents a structural phase transition from crystalline to amorphous caused by a variation of external pressure. This phase transition on Y{sub 3}Fe{sub 5}O{sub 12} leads to interesting results in the magnetic properties and magnetocaloric quantities. - Highlights: • Study of magnetic and magnetocaloric properties of amorphous Y{sub 3}Fe{sub 5}O{sub 12} compound. • Theoretical model formed by two coupled magnetic sublattices of localized spins in the presence of an applied magnetic field. • The influence of crystalline/amorphous transition on the magnetocaloric effect.

  17. Characterization of the key aroma compounds in beef and pork vegetable gravies á la chef by application of the aroma extract dilution analysis.

    Science.gov (United States)

    Christlbauer, Monika; Schieberle, Peter

    2009-10-14

    By application of the aroma extract dilution analysis (AEDA) on an aroma distillate isolated from a freshly prepared, stewed beef/vegetable gravy, 52 odor-active compounds were detected in the flavor dilution (FD) factor range of 4-4096. On the basis of high FD factors in combination with the results of the identification experiments, 3-(methylthio)propanal (cooked potato), 3-mercapto-2-methylpentan-1-ol (gravy-like), (E,E)-2,4-decadienal (deep-fried, fatty), 3-hydroxy-4,5-dimethyl-2(5H)-furanone (lovage-like), vanillin (vanilla-like), (E,E)-2,4-nonadienal (deep-fried), and (E)-2-undecenal (metallic) are suggested as key contributors to the aroma of the gravy. To get an insight into the role of the vegetables as sources of gravy odorants, a beef gravy was prepared without vegetables. The AEDA results revealed that, in particular, onions and leek are important sources of gravy aroma compounds, adding particularly the very potent, gravy-like smelling 3-mercapto-2-methylpentan-1-ol to the overall aroma profile. Further compounds that were clearly derived from the vegetables and, thus, are important modifiers of the overall aroma were 4-vinyl-2-methoxyphenol, (E)-beta-damascenone, beta-ionone, 2-isopropyl-3-methoxypyrazine, and 2-(sec-butyl)-3-methoxypyrazine. Interestingly, none of the key odorants detected in the gravy can be assumed to be formed from a reaction between beef and vegetable constituents. A comparison of the odorants in the beef/vegetable gravy with a gravy prepared according to the same procedure, but substituting beef by pork meat, indicated that most of the aroma compounds were identical-although different in FD factors-but the tallowy smelling 12-methyltridecanal was detected as key odorant only in the beef/vegetable gravy.

  18. Computer predictions on Rh-based double perovskites with unusual electronic and magnetic properties

    Science.gov (United States)

    Halder, Anita; Nafday, Dhani; Sanyal, Prabuddha; Saha-Dasgupta, Tanusri

    2018-03-01

    In search for new magnetic materials, we make computer prediction of structural, electronic and magnetic properties of yet-to-be synthesized Rh-based double perovskite compounds, Sr(Ca)2BRhO6 (B=Cr, Mn, Fe). We use combination of evolutionary algorithm, density functional theory, and statistical-mechanical tool for this purpose. We find that the unusual valence of Rh5+ may be stabilized in these compounds through formation of oxygen ligand hole. Interestingly, while the Cr-Rh and Mn-Rh compounds are predicted to be ferromagnetic half-metals, the Fe-Rh compounds are found to be rare examples of antiferromagnetic and metallic transition-metal oxide with three-dimensional electronic structure. The computed magnetic transition temperatures of the predicted compounds, obtained from finite temperature Monte Carlo study of the first principles-derived model Hamiltonian, are found to be reasonably high. The prediction of favorable growth condition of the compounds, reported in our study, obtained through extensive thermodynamic analysis should be useful for future synthesize of this interesting class of materials with intriguing properties.

  19. Gluconeogenesis from labeled carbon: estimating isotope dilution

    International Nuclear Information System (INIS)

    Kelleher, J.K.

    1986-01-01

    To estimate the rate of gluconeogenesis from steady-state incorporation of labeled 3-carbon precursors into glucose, isotope dilution must be considered so that the rate of labeling of glucose can be quantitatively converted to the rate of gluconeogenesis. An expression for the value of this isotope dilution can be derived using mathematical techniques and a model of the tricarboxylic acid (TCA) cycle. The present investigation employs a more complex model than that used in previous studies. This model includes the following pathways that may affect the correction for isotope dilution: 1) flux of 3-carbon precursor to the oxaloacetate pool via acetyl-CoA and the TCA cycle; 2) flux of 4- or 5-carbon compounds into the TCA cycle; 3) reversible flux between oxaloacetate (OAA) and pyruvate and between OAA and fumarate; 4) incomplete equilibrium between OAA pools; and 5) isotope dilution of 3-carbon tracers between the experimentally measured pool and the precursor for the TCA-cycle OAA pool. Experimental tests are outlined which investigators can use to determine whether these pathways are significant in a specific steady-state system. The study indicated that flux through these five pathways can significantly affect the correction for isotope dilution. To correct for the effects of these pathways an alternative method for calculating isotope dilution is proposed using citrate to relate the specific activities of acetyl-CoA and OAA

  20. Magnetic structure and phase formation of magnetocaloric Mn-Fe-P-X compounds

    NARCIS (Netherlands)

    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

  1. Pressure effect on magnetic and magnetotransport properties of intermetallic and colossal magnetoresistance oxide compounds

    Czech Academy of Sciences Publication Activity Database

    Arnold, Zdeněk; Ibarra, M. R.; Algarabel, P. A.; Marquina, C.; De Teresa, J. M.; Morellon, L.; Blasco, J.; Magen, C.; Prokhnenko, Olexandr; Kamarád, Jiří; Ritter, C.

    2005-01-01

    Roč. 17, - (2005), S3035-S3055 ISSN 0953-8984 Institutional research plan: CEZ:AV0Z10100521 Keywords : pressure effect * intermetallic compounds * magnetic properties * magnetic phase transitions * magnetotransport properties * oxides Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.145, year: 2005

  2. The physical mechanism of magnetic field controlled magnetocaloric effect and magnetoresistance in bulk PrGa compound

    Science.gov (United States)

    Zheng, X. Q.; Wu, H.; Chen, J.; Zhang, B.; Li, Y. Q.; Hu, F. X.; Sun, J. R.; Huang, Q. Z.; Shen, B. G.

    2015-01-01

    The PrGa compound shows excellent performance on the magnetocaloric effect (MCE) and magnetoresistance (MR). The physical mechanism of MCE and MR in PrGa compound was investigated and elaborated in detail on the basis of magnetic measurement, heat capacity measurement and neutron powder diffraction (NPD) experiment. New types of magnetic structure and magnetic transition are found. The results of the NPD along with the saturation magnetic moment (MS) and magnetic entropy (SM) indicate that the magnetic moments are randomly distributed within the equivalent conical surface in the ferromagnetic (FM) temperature range. PrGa compound undergoes an FM to FM transition and an FM to paramagnetic (PM) transition as temperature increases. The magnetizing process was discussed in detail and the physical mechanism of the magnetic field controlled magnetocaloric effect (MCE) and the magnetoresistance (MR) was studied. The formation of the plateau on MCE curve was explained and MR was calculated in detail on the basis of the magnetic structure and the analysis of the magnetizing process. The experimental results are in excellent agreement with the calculations. Finally, the expression of MR = β(T)X2 and its application conditions were discussed, where X is M(H)/Meff, and Meff is the paramagnetic effective moment. PMID:26455711

  3. Lattice and magnetic anisotropies in uranium intermetallic compounds

    DEFF Research Database (Denmark)

    Havela, L.; Mašková, S.; Adamska, A.

    2013-01-01

    Examples of UNiAlD and UCoGe illustrate that the soft crystallographic direction coincides quite generally with the shortest U-U links in U intermetallics. Added to existing experimental evidence on U compounds it leads to a simple rule, that the easy magnetization direction and the soft crystall...... crystallographic direction (in the sense of highest compressibility under hydrostatic pressure) must be mutually orthogonal....

  4. Capsize of polarization in dilute photonic crystals.

    Science.gov (United States)

    Gevorkian, Zhyrair; Hakhoumian, Arsen; Gasparian, Vladimir; Cuevas, Emilio

    2017-11-29

    We investigate, experimentally and theoretically, polarization rotation effects in dilute photonic crystals with transverse permittivity inhomogeneity perpendicular to the traveling direction of waves. A capsize, namely a drastic change of polarization to the perpendicular direction is observed in a one-dimensional photonic crystal in the frequency range 10 ÷ 140 GHz. To gain more insights into the rotational mechanism, we have developed a theoretical model of dilute photonic crystal, based on Maxwell's equations with a spatially dependent two dimensional inhomogeneous dielectric permittivity. We show that the polarization's rotation can be explained by an optical splitting parameter appearing naturally in Maxwell's equations for magnetic or electric fields components. This parameter is an optical analogous of Rashba like spin-orbit interaction parameter present in quantum waves, introduces a correction to the band structure of the two-dimensional Bloch states, creates the dynamical phase shift between the waves propagating in the orthogonal directions and finally leads to capsizing of the initial polarization. Excellent agreement between theory and experiment is found.

  5. Exchange interactions and magnetic properties of hexagonal rare-earth-cobalt compounds

    Science.gov (United States)

    Burzo, E.

    2018-03-01

    The magnetic properties of some GdxY1-xCo4A compounds with A = Co, Si or B are analysed including the pressure effects. Isomorphous structure transitions, parallelly with changes of cobalt moments from high spin states to low spin states, were shown as pressure increases. The magnetic data, obtained from band structures, were compared with those predicted by the mean field model.

  6. Weak ferromagnetism and temperature dependent dielectric properties of Zn{sub 0.9}Ni{sub 0.1}O diluted magnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Raju [Department of Electrical and Electronic Engineering, Shahjalal University of Science and Technology, Sylhet 3114 (Bangladesh); Department of Applied Physics, Electronics and Communication Engineering, University of Dhaka, Dhaka 1000 (Bangladesh); Moslehuddin, A.S.M.; Mahmood, Zahid Hasan [Department of Applied Physics, Electronics and Communication Engineering, University of Dhaka, Dhaka 1000 (Bangladesh); Hossain, A.K.M. Akther, E-mail: akmhossain@phy.buet.ac.bd [Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000 (Bangladesh)

    2015-03-15

    Highlights: • Single phase wurtzite structure was confirmed from XRD analysis. • Weak ferromagnetic behaviour at room temperature. • Pure semiconducting properties confirmed from temperature dependent conductivity. • Smaller dielectric properties at higher frequency. • Possible potential application in high frequency spintronic devices. - Abstract: In this study the room temperature ferromagnetic behaviour and dielectric properties of ZnO based diluted magnetic semiconductor (DMS) have been investigated using nominal chemical composition Zn{sub 0.9}Ni{sub 0.1}O. The X-ray diffraction analysis confirmed formation of single phase hexagonal wurtzite structure. An increase in grain size with increasing sintering temperature was observed from scanning electron microscopy. Field dependent DC magnetization values indicated dominant paramagnetic ordering along with a slight ferromagnetic behaviour at room temperature. Frequency dependent complex initial permeability showed some positive values around 12 at room temperature. In dielectric measurement, an increasing trend of complex permittivity, loss tangent and ac conductivity with increasing temperature were observed. The temperature dependent dispersion curves of dielectric properties revealed clear relaxation at higher temperature. Frequency dependent ac conductivity was found to increase with frequency whereas complex permittivity and loss tangent showed an opposite trend.

  7. 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.)

  8. Dilute Potts chain in a magnetic field

    International Nuclear Information System (INIS)

    Chaves, C.M.; Riera, R.

    1983-03-01

    The Potts lattice gas in presence of a uniform magnetic field is solved exactly in one dimension. For negative values of the exchange parameter, the magnetization curve exhibits two or three steps, depending on the concentration of vacancies. These steps arise as a result of the competition between the exchange interaction and the magnetic field, being associated to different structural distribution of vacancies and to the magnetic ordering of one or both sublattices. (Author) [pt

  9. Magnetism in ordered metallic perovskite compound GdPd{sub 3}B{sub x}C{sub 1-x}

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Abhishek [S.N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)], E-mail: abhishek.phy@gmail.com; Mazumdar, Chandan [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)], E-mail: chandan.mazumdar@saha.ac.in; Ranganathan, R. [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Dattagupta, S. [Indian Institute of Science Education and Research, Block-HC, Sector-III, Salt Lake, Kolkata 700106 (India)

    2009-08-15

    We report results of dc-magnetization, ac-susceptibility and magnetoresistance measurements on crystalline metallic-perovskite compounds GdPd{sub 3}B{sub x}C{sub 1-x} (x=0.25, 0.50, 0.75 and 1.00) and the parent cubic compound GdPd{sub 3}. The interest in these materials stems from the observation of negative temperature coefficient of resistance and negative thermal expansion in some of the members of this series. In the present study, we show that by substitution of non-magnetic elements, boron and carbon, the nature of the magnetic interaction can be varied from dominating ferromagnetic to antiferromagnetic and finally to a canted magnetic structure without altering the crystal symmetry of the compounds. The variation of magnetic interaction by modifying the lattice parameter resembles Ruderman-Kittel-Kasuya-Yosida (RKKY) oscillations.

  10. Temperature and magnetic field dependence of magnetic correlations in the heavy fermion compound CeCu6

    International Nuclear Information System (INIS)

    Regnault, L.P.; Rossat-Mignod, J.; Jacoud, J.L.; Erkelens, W.A.C.; Rijksuniversiteit Leiden

    1988-01-01

    Inelastic neutron scattering experiments have been performed on the heavy fermion compound CeCu 6 at very low temperatures (T > 20 mK) and under magnetic fields up to 50 kOe. The analysis of the data shows that the magnetic scattering is the superposition of a single site contribution of Lorentzian type and of a broadened inelastic contribution associated with AF correlations. These correlations saturate below 1.5 - 2 K and are completely destroyed above 40 kOe

  11. Study of magnetism in Ni–Cr hardface alloy deposit on 316LN stainless steel using magnetic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Kishore, G.V.K.; Kumar, Anish, E-mail: anish@igcar.gov.in; Chakraborty, Gopa; Albert, S.K; Rao, B. Purna Chandra; Bhaduri, A.K.; Jayakumar, T.

    2015-07-01

    Nickel base Ni–Cr alloy variants are extensively used for hardfacing of austenitic stainless steel components in sodium cooled fast reactors (SFRs) to avoid self-welding and galling. Considerable difference in the compositions and melting points of the substrate and the Ni–Cr alloy results in significant dilution of the hardface deposit from the substrate. Even though, both the deposit and the substrate are non-magnetic, the diluted region exhibits ferromagnetic behavior. The present paper reports a systematic study carried out on the variations in microstructures and magnetic behavior of American Welding Society (AWS) Ni Cr–C deposited layers on 316 LN austenitic stainless steels, using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The phase variations of the oscillations of a Co–Cr alloy coated magnetic field sensitive cantilever is used to quantitatively study the magnetic strength of the evolved microstructure in the diluted region as a function of the distance from the deposit/substrate interface, with the spatial resolution of about 100 nm. The acquired AFM/MFM images and the magnetic property profiles have been correlated with the variations in the chemical compositions in the diluted layers obtained by the energy dispersive spectroscopy (EDS). The study indicates that both the volume fraction of the ferromagnetic phase and its ferromagnetic strength decrease with increasing distance from the deposit/substrate interface. A distinct difference is observed in the ferromagnetic strength in the first few layers and the ferromagnetism is observed only near to the precipitates in the fifth layer. The study provides a better insight of the evolution of ferromagnetism in the diluted layers of Ni–Cr alloy deposits on stainless steel. - Highlights: • Study of evolution of ferromagnetism in Comonoy-6 deposit on austenitic steel. • Magnetic force microscopy (MFM) exhibited ferromagnetic matrix in first two layers. • The maximum MFM

  12. μSR-studies of magnetic properties of metallic rare earth compounds

    International Nuclear Information System (INIS)

    Asch, L.; Kalvius, G.M.; Chappert, J.; Yaouanc, A.; Hartmann, O.; Karlsson, E.; Wappling, R.

    1984-01-01

    Positive muons can probe the magnitude and the time dependence of the magnetic field at interstitial sites in condensed matter. Thus the relatively new techniques of muons spin rotation and muon spin relaxation have become unique tools for studying magnetism. After a brief introduction into the experimental method we then discuss measurements on the elemental rare earth metals and on intermetallic compounds, in particular on the cubic Laves phases REAl 2

  13. Magneto-optical and transport studies of ZnO-based dilute magnetic semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Behan, A.J. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Neal, J.R. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)]. E-mail: J.R.Neal@Sheffield.ac.uk; Ibrahim, R.M. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Mokhtari, A. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Ziese, M. [Universitaet Leipzig, Fakultaet fuer Physik und Geowissenschaften, Abteilung Supra leitung und Magnetismus, Linnestrasse 5, 04103 Leipzig (Germany); Blythe, H.J. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Fox, A.M. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Gehring, G.A. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)

    2007-03-15

    Thin film samples of ZnO doped with V were grown on sapphire substrates by pulsed laser deposition (PLD). The magnetization was measured by SQUID magnetometry and the films were found to be ferromagnetic at room temperature. The transmission, Faraday rotation and magnetic circular dichroism were measured as a function of frequency at room temperature over an energy range of 1.5-4.0 eV and carrier concentrations were determined from Hall effect measurements. Clear magneto-optical signals that are ferromagnetic in origin were observed at the ZnO band edge and the optimal conditions for observing large ferromagnetic magneto-optic signals are discussed.

  14. Comparison of dilution factors for German wastewater treatment plant effluents in receiving streams to the fixed dilution factor from chemical risk assessment.

    Science.gov (United States)

    Link, Moritz; von der Ohe, Peter C; Voß, Katharina; Schäfer, Ralf B

    2017-11-15

    Incomplete removal during wastewater treatment leads to frequent detection of compounds such as pharmaceuticals and personal care products in municipal effluents. A fixed standard dilution factor of 10 for effluents entering receiving water bodies is used during the exposure assessment of several chemical risk assessments. However, the dilution potential of German receiving waters under low flow conditions is largely unknown and information is sparse for other European countries. We calculated dilution factors for two datasets differing in spatial extent and wastewater treatment plant (WWTP) size: a national dataset comprising 1225 large WWTPs in Central and Northern Germany and a federal dataset for 678 WWTPs of a single state in Southwest Germany. We found that the fixed factor approach overestimates the dilution potential of 60% and 40% of receiving waters in the national and the federal dataset, with median dilution factors of 5 and 14.5, respectively. Under mean flow conditions, 8% of calculated dilution factors were below 10, with a median dilution factor of 106. We also calculated regional dilution factors that accounted for effluent inputs from upstream WWTPs. For the national and the federal dataset, 70% and 60% of calculated regional dilution factors fell below 10 under mean low flow conditions, respectively. Decrease of regional dilution potential in small receiving streams was mainly driven by the next WWTP upstream with a 2.5 fold drop of median regional dilution factors. Our results show that using the standard dilution factor of 10 would result in the underestimation of environmental concentrations for authorised chemicals by a factor of 3-5 for about 10% of WWTPs, especially during low flow conditions. Consequently, measured environmental concentrations might exceed predicted environmental concentrations and ecological risks posed by effluents could be much higher, suggesting that a revision of current risk assessment practices may be required

  15. Kinetic-sound propagation in dilute gas mixtures

    International Nuclear Information System (INIS)

    Campa, A.; Cohen, E.G.D.

    1989-01-01

    Kinetic sound is predicted in dilute disparate-mass binary gas mixtures, propagating exclusively in the light compound and much faster than ordinary sound. It should be detectable by light-scattering experiments, as an extended shoulder in the scattering cross section for large frequencies. As an example, H 2 -Ar mixtures are discussed

  16. Phase formation and magnetic properties of YFe12-xNbx (x=0.70-0.90) compounds

    International Nuclear Information System (INIS)

    Fuquan, B.; Wang, J.L.; Tegus, O.; Dagula, W.; Tang, N.; Yang, F.M.; Wu, G.H.; Brueck, E.; Boer, F.R. de; Buschow, K.H.J.

    2005-01-01

    The phase formation and the magnetic properties of YFe 12-x Nb x (x=0.70-0.90) compounds have been investigated by means of X-ray diffraction and magnetization measurements. The powder X-ray diffraction patterns show that all compounds investigated crystallize single phase in the tetragonal ThMn 12 -type of structure. The lattice parameters and the unit-cell volume increase slightly with increasing Nb content, but the Curie temperature does not change. The X-ray-diffraction patterns of aligned powders of the samples show that all the compounds investigated have uniaxial anisotropy at room temperature. At 1.5K, the spontaneous magnetization, the anisotropy field and the anisotropy constant K 1 decrease with increasing Nb content

  17. Pressure effects on the magnetic behaviour of copper (II) compounds: magnetic ordering of layered organic/inorganic magnets

    International Nuclear Information System (INIS)

    Levchenko, G; Varyukhin, V N; Berezhnaya, L V; Rusakov, V F

    2012-01-01

    The high hydrostatic pressure effect on the magnetic properties of the layered hybrid compounds Cu 2 (OH) 3 (C n H 2n+1 CO 2 )⋅mH 2 O with distance between magnetic layers of up to 40 Å is studied. It is shown that the temperature of the ferromagnetic ordering decreases linearly with pressure increase. From measurements of susceptibility in the paramagnetic region, using both quantum Heisenberg and Ising exchange coupling models in layers and dipole interaction between layers, the in- and interlayer interactions are deduced. The dipole interactions are calculated and are shown to coincide with the model of Ising interactions in the layers. The value and decrease of T c under pressure are mainly driven by the value and decrease of the in-plane interactions. The formation of the long range ordering in the layered sample with dipolar interaction between layers is analysed. As a conclusion it is suggested that for designing high temperature ferromagnetism in layer compounds it is enough to have large in-plane interactions of ions with specific symmetry in layers and weak dipole interactions between layers. (paper)

  18. Vibrations on pulse tube based Dry Dilution Refrigerators for low noise measurements

    Energy Technology Data Exchange (ETDEWEB)

    Olivieri, E. [CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, 91405 Orsay (France); Billard, J.; De Jesus, M.; Juillard, A. [Univ Lyon, Université Lyon 1, CNRS/IN2P3, IPN-Lyon, F-69622 Villeurbanne (France); Leder, A. [Massachussets Institute of Technology, Laboratory for Nuclear Science, 77 Massachusetts Avenue Cambridge, MA 02139-4307 (United States)

    2017-06-21

    Dry Dilution Refrigerators (DDR) based on pulse tube cryo-coolers have started to replace Wet Dilution Refrigerators (WDR) due to the ease and low cost of operation. However these advantages come at the cost of increased vibrations, induced by the pulse tube. In this work, we present the vibration measurements performed on three different commercial DDRs. We describe in detail the vibration measurement system we assembled, based on commercial accelerometers, conditioner and DAQ, and examined the effects of the various damping solutions utilized on three different DDRs, both in the low and high frequency regions. Finally, we ran low temperature, pseudo-massive (30 and 250 g) germanium bolometers in the best vibration-performing system under study and report on the results.

  19. Magnetic field induced low temperature upturn of magnetization in highly Ca-doped La{sub 0.1875}Ca{sub 0.8125}MnO{sub 3} polycrystalline compound

    Energy Technology Data Exchange (ETDEWEB)

    Das, Kalipada, E-mail: kalipadadasphysics@gmail.com [Indian Association for the Cultivation of Science, 2A and 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032 (India); Dasgupta, P.; Poddar, A. [CMP Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700 064 (India)

    2017-06-15

    Highlights: • Magnetic field induced super paramagnetic nanoclusters formation. • Magnetic field dependent change of the curvature of the magnetization. • We report the training effect in polycrystalline La{sub 0.1875}Ca{sub 0.8125}MnO{sub 3} compound. - Abstract: In our present study we have reported the magnetic properties of highly Ca-doped polycrystalline compound La{sub 0.1875}Ca{sub 0.8125}MnO{sub 3}. Along with the conventional charge ordered antiferromagnetic ground state, a small ferromagnetic phase fraction is present at the low temperature. The effect of the external magnetic field markedly modifies the ground state of the compound. Our experimental results indicate that in addition to the ferromagnetic phase fraction, another field induced super paramagnetic phase grow at low temperature (T < 50 K) above H = 10 kOe magnetic field within the charge ordered antiferromagnetic matrix. The nature of the temperature dependent magnetization curves influenced by the external applied magnetic field was observed and analyzed using Langevin theory of super paramagnetism.

  20. Characterization of the major odor-active compounds in Thai durian ( Durio zibethinus L. 'Monthong') by aroma extract dilution analysis and headspace gas chromatography-olfactometry.

    Science.gov (United States)

    Li, Jia-Xiao; Schieberle, Peter; Steinhaus, Martin

    2012-11-14

    An aroma extract dilution analysis applied on the volatile fraction isolated from Thai durian by solvent extraction and solvent-assisted flavor evaporation resulted in 44 odor-active compounds in the flavor dilution (FD) factor range of 1-16384, 41 of which could be identified and 24 that had not been reported in durian before. High FD factors were found for ethyl (2S)-2-methylbutanoate (fruity; FD 16384), ethyl cinnamate (honey; FD 4096), and 1-(ethylsulfanyl)ethanethiol (roasted onion; FD 1024), followed by 1-(ethyldisulfanyl)-1-(ethylsulfanyl)ethane (sulfury, onion), 2(5)-ethyl-4-hydroxy-5(2)-methylfuran-3(2H)-one (caramel), 3-hydroxy-4,5-dimethylfuran-2(5H)-one (soup seasoning), ethyl 2-methylpropanoate (fruity), ethyl butanoate (fruity), 3-methylbut-2-ene-1-thiol (skunky), ethane-1,1-dithiol (sulfury, durian), 1-(methylsulfanyl)ethanethiol (roasted onion), 1-(ethylsulfanyl)propane-1-thiol (roasted onion), and 4-hydroxy-2,5-dimethylfuran-3(2H)-one (caramel). Among the highly volatile compounds screened by static headspace gas chromatography-olfactometry, hydrogen sulfide (rotten egg), acetaldehyde (fresh, fruity), methanethiol (rotten, cabbage), ethanethiol (rotten, onion), and propane-1-thiol (rotten, durian) were found as additional potent odor-active compounds. Fourteen of the 41 characterized durian odorants showed an alkane-1,1-dithiol, 1-(alkylsulfanyl)alkane-1-thiol, or 1,1-bis(alkylsulfanyl)alkane structure derived from acetaldehyde, propanal, hydrogen sulfide, and alkane-1-thiols. Among these, 1-(propylsulfanyl)ethanethiol, 1-{[1-(methylsulfanyl)ethyl]sulfanyl}ethanethiol, and 1-{[1-(ethylsulfanyl)ethyl]sulfanyl}ethanethiol were reported for the first time in a natural product.

  1. Magnetic properties of Nd3(Fe,Mo)29 compound and its nitride

    International Nuclear Information System (INIS)

    Pan Hongge

    1998-01-01

    The iron-rich ternary intermetallic compound Nd 3 (Fe,Mo) 29 with the Nd 3 (Fe,Ti) 29 -type monoclinic structure and its nitride were prepared. After nitrogenation, the nitride retains the structure of the parent compound, but the unit-cell volume of the nitride is 5.9% greater than that of the parent compound. The Curie temperature of Nd 3 (Fe,Mo) 29 nitride is 70.9% higher than that of the parent compound and the saturation magnetization of the nitride is about 6.6% (at 4.2 K) and 23.7% (at 300 K) higher than that of the parent compound. The anisotropy of the nitride is similar to that of parent compound, which exhibits plane anisotropy. (orig.)

  2. MnFe(PGe) compounds: Preparation, structural evolution, and magnetocaloric effects

    International Nuclear Information System (INIS)

    Yue Ming; Zhang Hong-Guo; Zhang Jiu-Xing; Liu Dan-Min

    2015-01-01

    The interdependences of preparation conditions, magnetic and crystal structures, and magnetocaloric effects (MCE) of the MnFePGe-based compounds are reviewed. Based upon those findings, a new method for the evaluation of the MCE in these compounds, based on differential scanning calorimetry (DSC), is proposed. The MnFePGe-based compounds are a group of magnetic refrigerants with giant magnetocaloric effect (GMCE), and as such, have drawn tremendous attention, especially due to their many advantages for practical applications. Structural evolution and phase transformation in the compounds as functions of temperature, pressure, and magnetic field are reported. Influences of preparation conditions upon the homogeneity of the compounds’ chemical composition and microstructure, both of which play a key role in the MCE and thermal hysteresis of the compounds, are introduced. Lastly, the origin of the “virgin effect” in the MnFePGe-based compounds is discussed. (paper)

  3. InSb semiconductors and (In,Mn)Sb diluted magnetic semiconductors: Growth and properties

    International Nuclear Information System (INIS)

    Tran, Lien

    2011-01-01

    This dissertation describes investigations of the growth by molecular beam epitaxy and the characterization of the semiconductor InSb as well as the diluted magnetic semiconductor (DMS) In 1-x Mn x Sb. The InSb films were grown on GaAs (001) substrate and Si (001) offcut by 4 toward (110) substrate up to a thickness of about 2 μm, in spite of a large lattice mismatch between the epi-layer and substrate (14.6% between InSb and GaAs, and 19.3% between InSb and Si). After optimizing the growth conditions, the best InSb films grown directly on GaAs without any special technique results in a high crystal quality, low noise, and an electron mobility of 41100 cm 2 /V s Vs with associated electron concentration of 2.9.10 6 cm -3 at 300 K. Such structures could be used, for example, for infrared detector structures. The growth of InSb on Si, however, is a challenge. In order to successfully grow InSb on Si, tilted substrates and the insertion of buffer layers were used, which helps to reduce the lattice mismatch as well as the formation of defects, and hence to improve the crystal quality. An electron mobility of 24000 cm 2 /V s measured at 300 K, with an associated carrier concentration of 2.6.10 1 6 cm -3 is found for the best sample that was grown at 340 C with a 0.06 μm-thick GaSb/AlSb superlattice buffer layer. The smaller value of electron mobility (compared to the best GaAsbased sample) is related to a higher density of microtwins and stacking faults as well as threading dislocations in the near-interface region as shown by transmission electron microscopy. Deep level noise spectra indicate the existence of deep levels in both GaAs and Si-based samples. The samples grown on Si exhibit the lowest Hooge factor at 300 K, lower than the samples grown on GaAs. Taking the optimized growth conditions of InSb/GaAs, the diluted magnetic semiconductor In 1-x Mn x Sb/GaAs (001) is prepared by adding a few percent of Mn into the host material InSb during growth. I have

  4. Crystallographic and magnetic structure of the novel compound ErGe 1.83

    Science.gov (United States)

    Oleksyn, O.; Schobinger-Papamantellos, P.; Ritter, C.; de Groot, C. H.; Buschow, K. H. J.

    1997-02-01

    The crystal structure and the magnetic ordering of the novel orthorhombic compound ErGe 2-x has been studied by neutron powder diffraction and magnetic measurements. The crystal structure belongs to the DyGe 1.85-type (space group Cmc2 1)·ErGe 2-x ( x = 0.17 (2)) orders antiferromagnetically below TN = 6 K and displays a metamagnetic behaviour. The magnetic cell has the same size as the chemical unit cell ( q = 0 ). The magnetic space group is Cmc2 1 (Sh 36173). At T = 1.5 K the magnetic moments of the two erbium sites have the same ordered magnetic moment values of 7.63 (6) μB/Er and are antiferromagnetically coupled leading to an uniaxial structure along the a direction.

  5. Magnetic properties of Sm2Co17-xCrx (0 ≤ x ≤ 3.0) compounds

    International Nuclear Information System (INIS)

    Fuquan, B.; Wang, J.L.; Tegus, O.; Dagula, W.; Tang, N.; Wang, W.Q.; Yang, F.M.; Brueck, E.; Boer, F.R. de; Buschow, K.H.J.

    2004-01-01

    The structural and magnetic properties of Sm 2 Co 17-x Cr x (0≤x≤3.0) compounds have been investigated by means of X-ray diffraction and magnetization measurements. The powder X-ray diffraction patterns show that all samples crystallize as a single phase with the rhombohedral Th 2 Zn 17 -type structure. The lattice parameters a and V increase monotonically with increasing Cr content, but the lattice parameter c increases very slowly with increasing Cr content. The X-ray diffraction patterns of the aligned powder of the samples have confirmed that all the compounds investigated have uniaxial anisotropy. The Curie temperature of the compounds decreases rapidly the spontaneous magnetization M 0 , the anisotropy field B a , and the anisotropy constant K 1 of Sm 2 Co 17-x Cr x (0≤x≤3.0) compounds decrease strongly with increasing Cr content

  6. Magnetism: a supramolecular function

    International Nuclear Information System (INIS)

    Decurtins, S.; Pellaux, R.; Schmalle, H.W.

    1996-01-01

    The field of molecule-based magnetism has developed tremendously in the last few years. Two different extended molecular - hence supramolecular -systems are presented. The Prussian-blue analogues show some of the highest magnetic ordering temperature of any class of molecular magnets, T c = 315 K, whereas the class of transition-metal oxalate-bridged compounds exhibits a diversity of magnetic phenomena. Especially for the latter compounds, the elastic neutron scattering technique has successfully been proven to trace the magnetic structure of these supramolecular and chiral compounds. (author) 18 figs., 25 refs

  7. Magnetism: a supramolecular function

    Energy Technology Data Exchange (ETDEWEB)

    Decurtins, S; Pellaux, R; Schmalle, H W [Zurich Univ., Inst. fuer Anorganische Chemie, Zurich (Switzerland)

    1996-11-01

    The field of molecule-based magnetism has developed tremendously in the last few years. Two different extended molecular - hence supramolecular -systems are presented. The Prussian-blue analogues show some of the highest magnetic ordering temperature of any class of molecular magnets, T{sub c} = 315 K, whereas the class of transition-metal oxalate-bridged compounds exhibits a diversity of magnetic phenomena. Especially for the latter compounds, the elastic neutron scattering technique has successfully been proven to trace the magnetic structure of these supramolecular and chiral compounds. (author) 18 figs., 25 refs.

  8. The role of iron(II) dilution in the magnetic and photomagnetic properties of the series [Fe(x)Zn(1-x)(bpp)₂](NCSe)₂.

    Science.gov (United States)

    Baldé, Chérif; Desplanches, Cédric; Le Gac, Fréderic; Guionneau, Philippe; Létard, Jean-François

    2014-06-07

    The effects of metal dilution on the spin-crossover behavior of iron(II) in the mixed crystal series [Fe(x)Zn(1-x)(bpp)2](NCSe)2 (bpp = 2,6-bis(pyrazol-3-yl)pyridine) have been studied using magnetic susceptibility, photomagnetism and diffuse reflectivity measurements. For each mixed-crystal system, the thermal spin transition temperature, T(1/2), and the relaxation temperature of the photo-induced high-spin state, T(LIESST), have been systematically determined. It appears that T(1/2) decreases with the metal dilution while T(LIESST) remains unchanged. Dilution also tends to decrease the hysteresis width and smooth the transition curves. These effects were discussed first qualitatively and then quantitatively on the basis of a kinetic study governing the photo-induced back conversion taking into account the relative sizes of Zn(II) and Fe(II) ions. Interestingly, single crystals were obtained for [Fe(0.6)Zn(0.4)(bpp)2](NCSe)2 allowing the X-ray diffraction crystal-structure determination.

  9. Measurement parameter selection for quantitative isotope dilution gas chromatography/mass spectrometry

    International Nuclear Information System (INIS)

    Colby, B.N.; Rosecrance, A.E.; Colby, M.E.

    1981-01-01

    By use of the two-isotope model of isotope dilution, selection criteria were developed for identifying optimum m/z's for quantitation of compounds by gas chromatography/mass spectrometry. In addition, it was possible to predict the optimum ratio of naturally abundant to labeled compound and to identify appropriate data reduction methods. The validity of these predictions was confirmed by using experimental GC/MS data for several organic compounds

  10. Lattice specific heat for the RMIn5 (R=Gd, La, Y; M=Co, Rh) compounds: Non-magnetic contribution subtraction

    International Nuclear Information System (INIS)

    Facio, Jorge I.; Betancourth, D.; Cejas Bolecek, N.R.; Jorge, G.A.; Pedrazzini, Pablo; Correa, V.F.; Cornaglia, Pablo S.; Vildosola, V.; García, D.J.

    2016-01-01

    We analyze theoretically a common experimental process used to obtain the magnetic contribution to the specific heat of a given magnetic material. In the procedure, the specific heat of a non-magnetic analog is measured and used to subtract the non-magnetic contributions, which are generally dominated by the lattice degrees of freedom in a wide range of temperatures. We calculate the lattice contribution to the specific heat for the magnetic compounds GdMIn 5 (M=Co, Rh) and for the non-magnetic YMIn 5 and LaMIn 5 (M=Co, Rh), using density functional theory based methods. We find that the best non-magnetic analog for the subtraction depends on the magnetic material and on the range of temperatures. While the phonon specific heat contribution of YRhIn 5 is an excellent approximation to the one of GdCoIn 5 in the full temperature range, for GdRhIn 5 we find a better agreement with LaCoIn 5 , in both cases, as a result of an optimum compensation effect between masses and volumes. We present measurements of the specific heat of the compounds GdMIn 5 (M=Co, Rh) up to room temperature where it surpasses the value expected from the Dulong–Petit law. We obtain a good agreement between theory and experiment when we include anharmonic effects in the calculations.

  11. Slow relaxation of the magnetization observed in an antiferromagnetically ordered phase for SCM-based two-dimensional layered compounds.

    Science.gov (United States)

    Kagesawa, Koichi; Nishimura, Yuki; Yoshida, Hiroki; Breedlove, Brian K; Yamashita, Masahiro; Miyasaka, Hitoshi

    2017-03-07

    Two-dimensional layered compounds with different counteranions, [{Mn(salen)} 4 C6](BF 4 ) 2 ·2(CH 3 OH) (1) and [{Mn(salen)} 4 C6](PF 6 ) 2 ·2(CH 3 OH) (2) (salen 2- = N,N'-bis(salicylideneiminato), C6 2- = C 6 H 12 (COO) 2 2- ), were synthesized by assembling [Mn(salen)(H 2 O)]X (X - = BF 4 - and PF 6 - ) and C 6 H 12 (CO 2 - ) 2 (C6 2- ) in a methanol/2-propanol medium. The compounds have similar structures, which are composed of Mn(salen) out-of-plane dimers bridged by μ 4 -type C6 2- ions, forming a brick-wall-type network of [-{Mn 2 }-OCO-] chains alternately connected via C 6 H 12 linkers of C6 2- moieties. The counteranions for 1 and 2, i.e., BF 4 - and PF 6 - , respectively, are located between layers. Since the size of BF 4 - is smaller than that of PF 6 - , intra-layer inter-chain and inter-plane nearest-neighbor MnMn distances are shorter in 1 than in 2. The zigzag chain moiety of [-{Mn 2 }-OCO-] leads to a canted S = 2 spin arrangement with ferromagnetic coupling in the Mn III out-of-plane dimer moiety and antiferromagnetic coupling through -OCO- bridges. Due to strong uniaxial anisotropy of the Mn III ion, the [-{Mn 2 }-OCO-] chains could behave as a single-chain magnet (SCM), which exhibits slow relaxation of magnetization at low temperatures. Nevertheless, these compounds fall into an antiferromagnetic ground state at higher temperatures of T N = 4.6 and 3.8 K for 1 and 2, respectively, than active temperatures for SCM behavior. The spin flip field at 1.8 K is 2.7 and 1.8 kOe for 1 and 2, respectively, which is attributed to the inter-chain interactions tuned by the size of the counteranions. The relaxation times of magnetization become longer at the boundary between the antiferromagnetic phase and the paramagnetic phase.

  12. Hubbard U calculations for gap states in dilute magnetic semiconductors.

    Science.gov (United States)

    Fukushima, T; Katayama-Yoshida, H; Sato, K; Bihlmayer, G; Mavropoulos, P; Bauer, D S G; Zeller, R; Dederichs, P H

    2014-07-09

    On the basis of constrained density functional theory, we present ab initio calculations for the Hubbard U parameter of transition metal impurities in dilute magnetic semiconductors, choosing Mn in GaN as an example. The calculations are performed by two methods: (i) the Korringa-Kohn-Rostoker (KKR) Green function method for a single Mn impurity in GaN and (ii) the full-potential linearized augmented plane-wave (FLAPW) method for a large supercell of GaN with a single Mn impurity in each cell. By changing the occupancy of the majority t2 gap state of Mn, we determine the U parameter either from the total energy differences E(N + 1) and E(N - 1) of the (N ± 1)-electron excited states with respect to the ground state energy E(N), or by using the single-particle energies for n(0) ± 1/2 occupancies around the charge-neutral occupancy n0 (Janak's transition state model). The two methods give nearly identical results. Moreover the values calculated by the supercell method agree quite well with the Green function values. We point out an important difference between the 'global' U parameter calculated using Janak's theorem and the 'local' U of the Hubbard model.

  13. Phase-Transition and Magnetic Moment of the Gd3+ Ion in the Gd2Fe17 Compound

    Institute of Scientific and Technical Information of China (English)

    HAO Yan-Ming; FU Bin; ZHOU Yan; ZHAO Miao

    2009-01-01

    The structure and magnetic phase transitions of the Gd2Fe17 compound are investigated by using a differential thermal/thermogravimetric analyzer, x-ray diffraction, and magnetization measurements. The result shows that there are two phase structures for the Gd2Fe17 compound: the hexagonal Th2Ni17-type structure at high tem-peratures (above 1243℃), and the rhombohedrai Th2Zn17-type structure, respectively. A method to measure the magnetic moments of the Gd-sublattice and the Fe-sublattice in the Gd2Fe17 compound is presented. The moments of the Gd-sublattice and the Fe-sublattice in the Gd2Fe17 compound from 77 to 500 K are measured in this way with a vibrating sample magnetometer. A detailed discussion is presented.

  14. Crystal structure and magnetic properties of PrCo6.8-xCuxHf0.2 compounds

    International Nuclear Information System (INIS)

    Luo, J; Liang, J K; Guo, Y Q; Liu, Q L; Liu, F S; Yang, L T; Zhang, Y; Rao, G H

    2004-01-01

    The effects of Cu substitution on the crystal structure and magnetic properties of PrCo 6.8-x Cu x Hf 0.2 (x = 0-1.0) compounds were investigated by means of x-ray powder diffraction and magnetic measurements. The as-cast PrCo 6.8-x Cu x Hf 0.2 compounds crystallize in the TbCu 7 -type structure with the space group P6/mmm. The Curie temperature and magnetic anisotropy field decrease with increasing Cu content. A spin reorientation behaviour has been observed in the PrCo 6.8-x Cu x Hf 0.2 compounds. The addition of Cu weakens the anisotropy of the Co sublattice, leading to an increase in the spin reorientation temperature with increasing content of Cu

  15. Characterization and comparison of key aroma compounds in raw and dry porcini mushroom (Boletus edulis) by aroma extract dilution analysis, quantitation and aroma recombination experiments.

    Science.gov (United States)

    Zhang, Huiying; Pu, Dandan; Sun, Baoguo; Ren, Fazheng; Zhang, Yuyu; Chen, Haitao

    2018-08-30

    A study was carried out to determine and compare the key aroma compounds in raw and dry porcini mushroom (Boletus edulis). The volatile fractions were prepared by solvent-assisted flavor evaporation (SAFE), and aroma extract dilution analysis (AEDA) combined with gas chromatography-mass spectrometry (GC-MS) was employed to identify the odorants. Selected aroma compounds were quantitated and odor activity values (OAVs) were calculated revealing OAVs ≥ 1 for 12 compounds in raw porcini, among which 1-octen-3-one showed the highest OAV. In addition to compounds with eight carbon atoms, 3-methylbutanal, (E,E)-2,4-decadienal and (E,E)-2,4-nonadienal were also responsible for the unique aroma profile. In dry mushroom OAVs ≥ 1 were obtained for 20 odorants. Among them, 3-(methylthio)propanal, 1-octen-3-one and pyrazines were determined as predominant odorants. Overall, drying increased complexity of volatile compounds, thus significantly changing the aroma profile of porcini, providing more desirable roasted and seasoning-like flavor and less grass-like and earthy notes. Copyright © 2018 Elsevier Ltd. All rights reserved.

  16. Complex magnetic behaviour and evidence of a superspin glass state in the binary intermetallic compound Er5Pd2

    Science.gov (United States)

    Sharma, Mohit K.; Yadav, Kavita; Mukherjee, K.

    2018-05-01

    The binary intermetallic compound Er5Pd2 has been investigated using dc and ac magnetic susceptibilities, magnetic memory effect, isothermal magnetization, non-linear dc susceptibility, heat capacity and magnetocaloric effect studies. Interestingly, even though the compound does not show geometrical frustration it undergoes glassy magnetic phase transition below 17.2 K. Investigation of dc magnetization and heat capacity data divulged absence of long-ranged magnetic ordering. Through the magnetic memory effect, time dependent magnetization and ac susceptibility studies it was revealed that the compound undergoes glass-like freezing below 17.2 K. Analysis of frequency dependence of this transition temperature through scaling and Arrhenius law; along with the Mydosh parameter indicate, that the dynamics in Er5Pd2 are due to the presence of strongly interacting superspins rather than individual spins. This phase transition was further investigated by non-linear dc susceptibility and was characterized by static critical exponents γ and δ. Our results indicate that this compound shows the signature of superspin glass at low temperature. Additionally, both conventional and inverse magnetocaloric effect was observed with a large value of magnetic entropy change and relative cooling power. Our results suggest that Er5Pd2 can be classified as a superspin glass system with large magnetocaloric effect.

  17. Unexpected magnetism, and transport properties in mixed lanthanide compound

    Science.gov (United States)

    Pathak, Arjun; Gschneidner, Karl, Jr.; Pecharsky, Vitalij; Ames Laboratory Team

    For intelligent materials design it is desirable to have compounds which have multiple functionalities such as a large magnetoresistance, ferromagnetic and ferrimagnetic states, and field-induced first-order metamagnetic transitions. Here, we discuss one such example where we have combined two lanthanide elements Pr and Er in Pr0.6Er0.4Al2. This compound exhibits multiple functionalities in magnetic fields between 1 and 40 kOe. It undergoes only a trivial ferrimagnetism to paramagnetism transition in a zero magnetic field, but Pr0.6Er0.4Al2 exhibits a large positive magnetoresistance (MR) for H >=40 kOe, a small but non negligible negative MR for H field cooling from the paramagnetic state. These phenomena are attributed to the competition between single-ion anisotropies of Pr and Er ions coupled with the opposite nearest-neighbor and next-nearest-neighbor exchange interactions. This work was supported by the US Department of Energy, Office of Basic Energy Science, Division of Material Sciences and Engineering. The research was performed at the Ames Laboratory. The Ames Laboratory is operated by Iowa State University for the US D.

  18. A Cold Cycle Dilution Refrigerator for Space Applications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The cold cycle dilution refrigerator is a continuous refrigerator capable of cooling to temperatures below 100 mK that makes use of a novel thermal magnetic pump....

  19. Beam Halo on the LHC TCDQ Diluter System and Thermal Load on the Downstream Superconducting Magnets

    CERN Document Server

    Goddard, B; Presland, A; Redaelli, S; Robert-Démolaize, G; Sarchiapone, L; Weiler, T; Weterings, W

    2006-01-01

    The moveable single-jawed graphite TCDQ diluter must be positioned very close to the circulating LHC beam in order to prevent damage to downstream components in the event of an unsynchronised beam abort. A two-jawed graphite TCS.IR6 collimator forms part of the TCDQ system. The requirement to place the jaws close to the beam means that the system can intercept a substantial beam halo load. Initial investigations indicated a worryingly high heat load on the Q4 coils. This paper presents the updated load cases, shielding and simulation geometry, and the results of simulations of the energy deposition in the TCDQ system and in the downstream superconducting Q4 magnet. The implications for the operation of the LHC are discussed.

  20. Magnetostriction of some cubic rare earth-Co2 compounds in high magnetic fields

    International Nuclear Information System (INIS)

    Moral, A. del; Melville, D.

    1975-01-01

    Magnetostriction measurements have been carried out in the cubic Laves phase compounds DyCo 2 , HoCo 2 and ErCo 2 from 10 K to well above their respective Neel temperatures Tsub(N). Pulsed magnetic fields up to 15 T (150kOe) were applied. The observed magnetostrictions are very large (approximately 10 -3 ) being similar to those found in the RFe 2 compounds. The measurements confirm the extremely high anisotropy of these materials. At the highest fields the polycrystalline samples are still undergoing rotational magnetization processes. The expected values of the saturation magnetostriction at O K are similar in sign and magnitude to those found in the corresponding rare earth metals. This fact and the scaling of magnetostriction with rare earth sublattice magnetization indicates that the rare earth ion is the main source of the magnetostriction. The metamagnetic transition above Tsub(N) has been studied, the relation between critical field and temperature being nonlinear for HoCo 2 and ErCo 2 . The compounds are highly anisotropic above Tsub(N) and all the features indicate that the field-induced phases are likely to be ferrimagnetic. (author)

  1. Nearly constant magnetic entropy change involving two closely spaced transitions in the compound LaFe11.375Al1.625

    International Nuclear Information System (INIS)

    Hu, F X; Qian, X L; Wang, G J; Wang, J; Sun, J R; Zhang, X X; Cheng, Z H; Shen, B G

    2003-01-01

    A large change in the magnetic entropy, |ΔS|, was observed in the Fe-based NaZn 13 -type compound LaFe 11.375 Al 1.625 , which was nearly temperature independent over a wide temperature range (an about 70 K span from ∼ 140 to 210 K). This behaviour of the magnetic entropy change is associated with two closely spaced magnetic transitions. X-ray diffraction investigation at different temperatures indicates that the crystal structure remains cubic, of NaZn 13 type, when the magnetic state changes with temperature, but the cell parameter changes dramatically at the first-order transition point

  2. Pr-magnetism in the quasi-skutterudite compound PrFe2Al8.

    Science.gov (United States)

    Nair, Harikrishnan S; Ogunbunmi, Michael O; Kumar, C M N; Adroja, D T; Manuel, P; Fortes, D; Taylor, J; Strydom, A M

    2017-08-31

    The intermetallic compound PrFe 2 Al 8 that possesses a three-dimensional network structure of Al polyhedra centered at the transition metal element Fe and the rare earth Pr is investigated through neutron powder diffraction and inelastic neutron scattering in order to elucidate the magnetic ground state of Pr and Fe and the crystal field effects of Pr. Our neutron diffraction study confirms long-range magnetic order of Pr below [Formula: see text] K in this compound. Subsequent magnetic structure estimation reveals a magnetic propagation vector [Formula: see text] with a magnetic moment value of [Formula: see text]/Pr along the orthorhombic c-axis and evidence the lack of ordering in the Fe sublattice. The inelastic neutron scattering study reveals one crystalline electric field excitation near 19 meV at 5 K in PrFe 2 Al 8 . The energy-integrated intensity of the 19 meV excitation as a function of [Formula: see text] follows the square of the magnetic form factor of [Formula: see text] thereby confirming that the inelastic excitation belongs to the Pr sublattice. The second sum rule applied to the dynamic structure factor indicates only 1.6(2) [Formula: see text] evolving at the 19 meV peak compared to the 3.58 [Formula: see text] for free [Formula: see text], indicating that the crystal field ground state is magnetic and the missing moment is associated with the resolution limited quasi-elastic line. The magnetic order occurring in Pr in PrFe 2 Al 8 is counter-intuitive to the symmetry-allowed crystal field level scheme, hence, is suggestive of exchange-mediated mechanisms of ordering stemming from the magnetic ground state of the crystal field levels.

  3. Generation of shock/discontinuity compound structures through magnetic reconnection in the geomagnetic tail

    Energy Technology Data Exchange (ETDEWEB)

    Weng, C. J. [Department of Physics, National Cheng Kung University, Tainan 701, Taiwan (China); Institute of Space Science, National Central University, Jungli 320, Taiwan (China); Lin, C. C. [Chemical Systems Research Division, Chung-Shan Institute of Science and Technology, Longtan 325, Taiwan (China); Lee, L. C. [Institute of Earth Science, Academia Sinica, Nankang 115, Taiwan (China); Institute of Space Science, National Central University, Jungli 320, Taiwan (China); Chao, J. K. [Institute of Space Science, National Central University, Jungli 320, Taiwan (China)

    2012-12-15

    We use 1-D hybrid code to simulate the generation and evolution of MHD discontinuities associated with magnetic reconnection in a current sheet. It is found that the leakage of slow shock (SS) downstream particles to upstream region tends to increase the ion parallel temperature and temperature anisotropy with {beta}{sub i||}/{beta}{sub i Up-Tack } Much-Greater-Than 1, where {beta}{sub i||}({beta}{sub i Up-Tack }) is the ion parallel (perpendicular) beta. As a result, the propagation speed of rotational discontinuity (RD) is highly reduced and RD becomes attached to SS, leading to formation of various compound structures in the reconnection outflow region. Four types of compound structure are found in our simulations: (a) RD-SS compound structure: the RD is attached to the leading part of SS, (b) SS-RD (DD) compound structure: RD is attached to the rear part of SS, (c) SS-RD-SS compound structure: RD is trapped inside SS, and (d) switch-off slow shock (SSS) with a rotational wave train. The type of compound structure generated depends on initial ion beta {beta}{sub i0} and magnetic shear angle {phi}. RD tends to move in front of SS to form an RD-SS compound structure for cases with low {beta}{sub i0}. RD stays behind SS and form an SS-RD (DD) compound structure for large {beta}{sub i0}. The SS-RD-SS compound structure is formed for intermediate values of {beta}{sub i0}. When the shear angle is 180 Degree-Sign , SSS with a wave train is formed.

  4. Tuning the Origin of Magnetic Relaxation by Substituting the 3d or Rare-Earth Ions into Three Isostructural Cyano-Bridged 3d-4f Heterodinuclear Compounds.

    Science.gov (United States)

    Zhang, Yan; Guo, Zhen; Xie, Shuang; Li, Hui-Li; Zhu, Wen-Hua; Liu, Li; Dong, Xun-Qing; He, Wei-Xun; Ren, Jin-Chao; Liu, Ling-Zhi; Powell, Annie K

    2015-11-02

    Three isostructural cyano-bridged 3d-4f compounds, [YFe(CN)6(hep)2(H2O)4] (1), [DyFe(CN)6(hep)2(H2O)4] (2), and [DyCo(CN)6(hep)2(H2O)4] (3), were successfully assembled by site-targeted substitution of the 3d or rare-earth ions. All compounds have been structurally characterized to display slightly distorted pentagonal-bipyramidal local coordination geometry around the rare-earth ions. Magnetic analyses revealed negligible magnetic coupling in compound 1, antiferromagnetic intradimer interaction in 2, and weak ferromagnetic coupling through dipolar-dipolar interaction in 3. Under an applied direct-current (dc) field, 1 (Hdc = 2.5 kOe, τ0 = 1.3 × 10(-7) s, and Ueff/kB = 23 K) and 3 (Hdc = 2.0 kOe, τ0 = 7.1 × 10(-11) s, and Ueff/kB = 63 K) respectively indicated magnetic relaxation behavior based on a single [Fe(III)]LS ion and a Dy(III) ion; nevertheless, 2 (Hdc = 2.0 kOe, τ0 = 9.7 × 10(-8) s, and Ueff/kB = 23 K) appeared to be a single-molecule magnet based on a cyano-bridged DyFe dimer. Compound 1, which can be regarded as a single-ion magnet of the [Fe(III)]LS ion linked to a diamagnetic Y(III) ion in a cyano-bridged heterodimer, represents one of the rarely investigated examples based on a single Fe(III) ion explored in magnetic relaxation behavior. It demonstrated that the introduction of intradimer magnetic interaction of 2 through a cyano bridge between Dy(III) and [Fe(III)]LS ions negatively affects the energy barrier and χ″(T) peak temperature compared to 3.

  5. Effect of γ-lactones and γ-lactams compounds on Streptococcus mutans biofilms

    Directory of Open Access Journals (Sweden)

    Mariane Beatriz Sordi

    2018-02-01

    Full Text Available Abstract Considering oral diseases, antibiofilm compounds can decrease the accumulation of pathogenic species such as Streptococcus mutans at micro-areas of teeth, dental restorations or implant-supported prostheses. Objective To assess the effect of thirteen different novel lactam-based compounds on the inhibition of S. mutans biofilm formation. Material and methods We synthesized compounds based on γ-lactones analogues from rubrolides by a mucochloric acid process and converted them into their corresponding γ-hydroxy-γ-lactams by a reaction with isobutylamine and propylamine. Compounds concentrations ranging from 0.17 up to 87.5 μg mL-1 were tested against S. mutans. We diluted the exponential cultures in TSB and incubated them (37°C in the presence of different γ-lactones or γ-lactams dilutions. Afterwards, we measured the planktonic growth by optical density at 630 nm and therefore assessed the biofilm density by the crystal violet staining method. Results Twelve compounds were active against biofilm formation, showing no effect on bacterial viability. Only one compound was inactive against both planktonic and biofilm growth. The highest biofilm inhibition (inhibition rate above 60% was obtained for two compounds while three other compounds revealed an inhibition rate above 40%. Conclusions Twelve of the thirteen compounds revealed effective inhibition of S. mutans biofilm formation, with eight of them showing a specific antibiofilm effect.

  6. II-VI semiconductor compounds

    CERN Document Server

    1993-01-01

    For condensed matter physicists and electronic engineers, this volume deals with aspects of II-VI semiconductor compounds. Areas covered include devices and applications of II-VI compounds; Co-based II-IV semi-magnetic semiconductors; and electronic structure of strained II-VI superlattices.

  7. Superconductivity and magnetic order in the noncentrosymmetric half-Heusler compound ErPdBi

    NARCIS (Netherlands)

    Pan, Y.; Nikitin, A.M.; Bay, T.V.; Huang, Y.K.; Paulsen, C.; Yan, B.H.; de Visser, A.

    2013-01-01

    We report superconductivity at Tc = 1.22 K and magnetic order at TN = 1.06\\ K in the semimetallic noncentrosymmetric half-Heusler compound ErPdBi. The upper critical field, Bc2, has an unusual quasi-linear temperature variation and reaches a value of 1.6 T for T - 0 . Magnetic order is found below

  8. 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

  9. Interface magnetization effect in heterojunctions based on semimagnetic compounds

    International Nuclear Information System (INIS)

    Malkova, N.

    1998-07-01

    The electronic states of stressed heterojunctions formed from narrow-gap semimagnetic semiconductors showing antiferromagnetic ordering are studies. The model Hamiltonian is constructed in the framework of the two-band envelope function approximation including far-band corrections. Heterojunctions both with normal and inverted band arrangements in the initial semiconductors are investigated. The interface Tamm-like states have been shown recently toe appear in these heterojunctions and they are spin-split with the magnetic axis perpendicular to the interface plane. The effect of far-band corrections is shown to be conditioned by the mutual movement of the constituent bands, resulting in changes and in some cases in full disappearance of the energy interval in which the interface state exists. The interface magnetization effect is expected when the Fermi level lies in one of the spin-polarized interface bands. Using the appropriate parameters, the value of the relative interface magnetization is calculated. (author)

  10. Collective spin fluctuations in diluted magnetic semiconductors

    Czech Academy of Sciences Publication Activity Database

    König, J.; Schliemann, J.; Jungwirth, Tomáš; MacDonald, A. H.

    2002-01-01

    Roč. 12, - (2002), s. 379-382 ISSN 1386-9477 Institutional research plan: CEZ:AV0Z1010914 Keywords : spin fluctuation * magnetic semiconductors Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.107, year: 2002

  11. Magnetic measurements and neutron diffraction study of the layered hybrid compounds Mn(C8H4O4)(H2O)2 and Mn2(OH)2(C8H4O4)

    International Nuclear Information System (INIS)

    Sibille, Romain; Mesbah, Adel; Mazet, Thomas; Malaman, Bernard; Capelli, Silvia; François, Michel

    2012-01-01

    Mn(C 8 H 4 O 4 )(H 2 O) 2 and Mn 2 (OH) 2 (C 8 H 4 O 4 ) layered organic–inorganic compounds based on manganese(II) and terephthalate molecules (C 8 H 4 O 4 2− ) have been studied by DC and AC magnetic measurements and powder neutron diffraction. The dihydrated compound behaves as a 3D antiferromagnet below 6.5 K. The temperature dependence of its χT product is typical of a 2D Heisenberg system and allows determining the in-plane exchange constant J≈−7.4 K through the carboxylate bridges. The magnetic structure confirms the in-plane nearest neighbor antiferromagnetic interactions and the 3D ordering. The hydroxide based compound also orders as a 3D antiferromagnet with a higher Néel temperature (38.5 K). Its magnetic structure is described from two antiferromagnetically coupled ferromagnetic sublattices, in relation with the two independent metallic sites. The isothermal magnetization data at 2 K are consistent with the antiferromagnetic ground-state of these compounds. However, in both cases, a slope change points to field-induced modification of the magnetic structure. - Graphical abstract: The macroscopic magnetic properties and magnetic structures of two metal-organic frameworks based on manganese (II) and terephthalate molecules are presented. Highlights: ► Magnetic study of Mn(C 8 H 4 O 4 )(H 2 O) 2 and Mn 2 (OH) 2 (C 8 H 4 O 4 ). ► Two compounds with common features (interlayer linker/distance, S=5/2 spin). ► Magnetic measurements quantitatively analyzed to deduce exchange constants. ► Magnetic structures determined from neutron powder diffraction experiments.

  12. Prediction of activity coefficients at infinite dilution for organic solutes in ionic liquids by artificial neural network

    Energy Technology Data Exchange (ETDEWEB)

    Nami, Faezeh [Department of Chemistry, Shahid Beheshti University, G.C., Evin-Tehran 1983963113 (Iran, Islamic Republic of); Deyhimi, Farzad, E-mail: f-deyhimi@sbu.ac.i [Department of Chemistry, Shahid Beheshti University, G.C., Evin-Tehran 1983963113 (Iran, Islamic Republic of)

    2011-01-15

    To our knowledge, this work illustrates for the first time the ability of artificial neural network (ANN) to predict activity coefficients at infinite dilution for organic solutes in ionic liquids (ILs). Activity coefficient at infinite dilution ({gamma}{sup {infinity}}) is a useful parameter which can be used for the selection of effective solvent in the separation processes. Using a multi-layer feed-forward network with Levenberg-Marquardt optimization algorithm, the resulting ANN model generated activity coefficient at infinite dilution data over a temperature range of 298 to 363 K. The unavailable input data concerning softness (S) of organic compounds (solutes) and dipole moment ({mu}) of ionic liquids were calculated using GAMESS suites of quantum chemistry programs. The resulting ANN model and its validation are based on the investigation of up to 24 structurally different organic compounds (alkanes, alkenes, alkynes, cycloalkanes, aromatics, and alcohols) in 16 common imidazolium-based ionic liquids, at different temperatures within the range of 298 to 363 K (i.e. a total number of 914 {gamma}{sub Solute}{sup {infinity}}for each IL data point). The results show a satisfactory agreement between the predicted ANN and experimental data, where, the root mean square error (RMSE) and the determination coefficient (R{sup 2}) of the designed neural network were found to be 0.103, 0.996 for training data and 0.128, 0.994 for testing data, respectively.

  13. Prediction of activity coefficients at infinite dilution for organic solutes in ionic liquids by artificial neural network

    International Nuclear Information System (INIS)

    Nami, Faezeh; Deyhimi, Farzad

    2011-01-01

    To our knowledge, this work illustrates for the first time the ability of artificial neural network (ANN) to predict activity coefficients at infinite dilution for organic solutes in ionic liquids (ILs). Activity coefficient at infinite dilution (γ ∞ ) is a useful parameter which can be used for the selection of effective solvent in the separation processes. Using a multi-layer feed-forward network with Levenberg-Marquardt optimization algorithm, the resulting ANN model generated activity coefficient at infinite dilution data over a temperature range of 298 to 363 K. The unavailable input data concerning softness (S) of organic compounds (solutes) and dipole moment (μ) of ionic liquids were calculated using GAMESS suites of quantum chemistry programs. The resulting ANN model and its validation are based on the investigation of up to 24 structurally different organic compounds (alkanes, alkenes, alkynes, cycloalkanes, aromatics, and alcohols) in 16 common imidazolium-based ionic liquids, at different temperatures within the range of 298 to 363 K (i.e. a total number of 914 γ Solute ∞ for each IL data point). The results show a satisfactory agreement between the predicted ANN and experimental data, where, the root mean square error (RMSE) and the determination coefficient (R 2 ) of the designed neural network were found to be 0.103, 0.996 for training data and 0.128, 0.994 for testing data, respectively.

  14. Topological phase, electronic, magnetic and optical properties of ScPdBi compound with Gd, Np and Cm impurities

    Energy Technology Data Exchange (ETDEWEB)

    Narimani, Mitra; Nourbakhsh, Zahra, E-mail: z.nourbakhsh@sci.ui.ac.ir

    2017-07-15

    Highlights: • Gd, Np and Cm impurities induce the magnetic moment in ScPdBi compound. • ScPdBi compound with Gd, Np and Cm impurities has normal band order. • The ε(0) and R(0) increase by increasing the atomic number of X atom. - Abstract: The electronic, magnetic and optical properties of X-doped ScPdBi (X = Gd, Np, Cm) are investigated in the framework of density functional theory. The exchange-correlation potential is treated using generalized gradient approximation with Coulomb interaction parameter. The band order and energy band gap of X-doped ScPdBi are investigated by calculation of band structure. The effect of doping impurity on magnetic properties of ScPdBi compound is studied by calculation of total and partial magnetic moments of X-doped ScPdBi compound. Furthermore, the optical properties of X-doped ScPdBi are calculated and compared in the energy range of 0–25 eV.

  15. A Linear Tetranuclear Dysprosium(III) Compound Showing Single-Molecule Magnet Behavior

    Energy Technology Data Exchange (ETDEWEB)

    Ke, Hongshan; Xu, Gong Feng; Guo, Yun-Nan; Gamez, Patrick; Beavers, Christine M; Teat, Simon J; Tang, Jinkui

    2010-04-20

    Although magnetic measurements reveal a single-relaxation time for a linear tetranuclear Dy(III) compound, the wide distribution of the relaxation time observed clearly suggests the presence of two slightly different anisotropic centres, therefore opening new avenues for investigating the relaxation dynamics of lanthanide aggregates.

  16. Magnetic and magnetocaloric properties of HoCr0.75Fe0.25O3 compound

    Science.gov (United States)

    Kotnana, Ganesh; Babu, P. D.; Jammalamadaka, S. Narayana

    2018-05-01

    We report on the magnetic and magnetocaloric properties of HoCr0.75Fe0.25O3 compound around the Néel temperature (TN), which is due to Cr3+ ordering. Susceptibility (χ) vs. temperature (T) graph of HoCr0.75Fe0.25O3 compound infer two transitions due to the ordering of Cr3+ moments (TN ˜ 155 K) and Ho3+ moments (TNHo ˜ 8 K). Magnetic entropy (-ΔSM) value of 1.14 J kg-1 K-1 around 157.5 K with a magnetic field (H) of 90 kOe is attributed to antiferromagnetic (AFM) ordering of Cr3+ moments. A maximum value of adiabatic temperature (ΔTad) ˜ 0.41 K around TN is obtained and is found to increases with applied magnetic field. Negative slope for H/M vs. M2 graph is evident for HoCr0.75Fe0.25O3 compound below TN, which indicates the first order phase transition. Quantified values of -ΔSM and ΔTad open the way to explore rare earth orthochromites for the MCE properties and refrigeration applications.

  17. Estimation of the volatility distribution of organic aerosol combining thermodenuder and isothermal dilution measurements

    Directory of Open Access Journals (Sweden)

    E. E. Louvaris

    2017-10-01

    Full Text Available A method is developed following the work of Grieshop et al. (2009 for the determination of the organic aerosol (OA volatility distribution combining thermodenuder (TD and isothermal dilution measurements. The approach was tested in experiments that were conducted in a smog chamber using organic aerosol (OA produced during meat charbroiling. A TD was operated at temperatures ranging from 25 to 250 °C with a 14 s centerline residence time coupled to a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS and a scanning mobility particle sizer (SMPS. In parallel, a dilution chamber filled with clean air was used to dilute isothermally the aerosol of the larger chamber by approximately a factor of 10. The OA mass fraction remaining was measured as a function of temperature in the TD and as a function of time in the isothermal dilution chamber. These two sets of measurements were used together to estimate the volatility distribution of the OA and its effective vaporization enthalpy and accommodation coefficient. In the isothermal dilution experiments approximately 20 % of the OA evaporated within 15 min. Almost all the OA evaporated in the TD at approximately 200 °C. The resulting volatility distributions suggested that around 60–75 % of the cooking OA (COA at concentrations around 500 µg m−3 consisted of low-volatility organic compounds (LVOCs, 20–30 % of semivolatile organic compounds (SVOCs, and around 10 % of intermediate-volatility organic compounds (IVOCs. The estimated effective vaporization enthalpy of COA was 100 ± 20 kJ mol−1 and the effective accommodation coefficient was 0.06–0.07. Addition of the dilution measurements to the TD data results in a lower uncertainty of the estimated vaporization enthalpy as well as the SVOC content of the OA.

  18. Estimation of the volatility distribution of organic aerosol combining thermodenuder and isothermal dilution measurements

    Science.gov (United States)

    Louvaris, Evangelos E.; Karnezi, Eleni; Kostenidou, Evangelia; Kaltsonoudis, Christos; Pandis, Spyros N.

    2017-10-01

    A method is developed following the work of Grieshop et al. (2009) for the determination of the organic aerosol (OA) volatility distribution combining thermodenuder (TD) and isothermal dilution measurements. The approach was tested in experiments that were conducted in a smog chamber using organic aerosol (OA) produced during meat charbroiling. A TD was operated at temperatures ranging from 25 to 250 °C with a 14 s centerline residence time coupled to a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a scanning mobility particle sizer (SMPS). In parallel, a dilution chamber filled with clean air was used to dilute isothermally the aerosol of the larger chamber by approximately a factor of 10. The OA mass fraction remaining was measured as a function of temperature in the TD and as a function of time in the isothermal dilution chamber. These two sets of measurements were used together to estimate the volatility distribution of the OA and its effective vaporization enthalpy and accommodation coefficient. In the isothermal dilution experiments approximately 20 % of the OA evaporated within 15 min. Almost all the OA evaporated in the TD at approximately 200 °C. The resulting volatility distributions suggested that around 60-75 % of the cooking OA (COA) at concentrations around 500 µg m-3 consisted of low-volatility organic compounds (LVOCs), 20-30 % of semivolatile organic compounds (SVOCs), and around 10 % of intermediate-volatility organic compounds (IVOCs). The estimated effective vaporization enthalpy of COA was 100 ± 20 kJ mol-1 and the effective accommodation coefficient was 0.06-0.07. Addition of the dilution measurements to the TD data results in a lower uncertainty of the estimated vaporization enthalpy as well as the SVOC content of the OA.

  19. Magneto-transport in CdTe/CdMnTe dilute magnetic semiconductor single barrier structures

    International Nuclear Information System (INIS)

    Lyons, V.R.

    1999-03-01

    This thesis presents work done on electrical transport through dilute magnetic semiconductor (DMS) single barriers in both zero and non-zero magnetic fields. The fields are applied either perpendicular or parallel to the DMS layers. The main samples under investigation consist of 100 A and 200 A CdTe/Cd 0.8 Mn 0.2 Te/CdTe single barrier heterostructures. In addition electrical characterisation of the non magnetic layers is performed. Current through the barrier is measured as a function of voltage, magnetic field and temperature. A theoretical model is derived in order to calculate the current as a function of barrier height, barrier width, emitting layer carrier concentration, applied bias and temperature. These variables are then treated as fitting parameters and comparisons are made between the calculated and the experimental currents. The barriers are shown to produce non-Ohmic transport. The roles of quantum mechanical tunnelling and thermal activation across the barrier are investigated and shown to be highly mixed. An unexpectedly high degree of tunnelling is found to occur at high temperatures, within the region previously assumed to be dominated by thermal activation. Moreover the barrier height is found to be lower and the width greater than expected. These observations suggest that a high level of Mn diffusion occurs, possibly due to In dopant related effects. This suggestion is validated by the high emitting layer carrier concentration suggested by the fitting. At low temperatures and voltages the thicker barrier sample is shown to contain a parasitic leak path which short-circuits the barrier. This leak may exist in both samples but only becomes dominant where the barriers are sufficiently opaque to the incident carriers. Changes in a magnetic field are expected to be due to sp-d exchange induced giant Zeeman splitting in the barrier and either normal spin splitting or sp-d exchange effects in the emitter regions. The application of a magnetic field is

  20. Hole doping and pressure effects on the II-II-V-based diluted magnetic semiconductor (Ba1-xKx)(Zn1-yMny)2As2

    International Nuclear Information System (INIS)

    Sun, F.; Zhao, G. Q.; Escanhoela, C. A. Jr.

    2017-01-01

    We investigate doping- and pressure-induced changes in the electronic state of Mn 3d and As 4p orbitals in II-II-V based diluted magnetic semiconductor (Ba_1_-_x,K_x)(Zn_1_-_y,Mn_y)_2As_2 to shed light into the mechanism of indirect exchange interactions leading to high ferromagnetic ordering temperature (T_c = 230 K in optimally doped samples). A suite of x-ray spectroscopy experiments (emission, absorption and dichroism) show that the emergence, and further enhancement of ferromagnetic interactions with increased hole doping into the As 4p band is accompanied by a decrease in local 3d spin density at Mn sites. This is a result of increasing Mn 3d - As 4p hybridization with hole doping which enhances indirect exchange interactions between Mn dopants and gives rise to induced magnetic polarization in As 4p states. On the contrary, application of pressure suppresses exchange interactions. While Mn Kβ emission spectra show a weak response of 3d state to pressure, clear As 4p band broadening (hole delocalization) is observed under pressure ultimately leading to loss of ferromagnetism concomitant with a semiconductor to metal transition. The pressure response of As 4p and Mn 3d states is intimately connected with the evolution of the As-As interlayer distance and the geometry of the MnAs_4 tetrahedral units, which we probed with X-ray diffraction. Our results indicate that hole doping increases the degree of covalency between the anion (As) p states and cation (Mn) d states in the MnA_s_4 tetrahedron, a crucial ingredient to promote indirect exchange interactions between Mn dopants and high T_c ferromagnetism. As a result, the instability of ferromagnetism and semiconducting state against pressure is mainly dictated by delocalization of anion p states.

  1. Intramolecular charge separation in spirobifluorene-based donor–acceptor compounds adsorbed on Au and indium tin oxide electrodes

    International Nuclear Information System (INIS)

    Heredia, Daniel; Otero, Luis; Gervaldo, Miguel; Fungo, Fernando; Dittrich, Thomas; Lin, Chih-Yen; Chi, Liang-Chen; Fang, Fu-Chuan; Wong, Ken-Tsung

    2013-01-01

    Surface photovoltage (SPV) measurements were performed with a Kelvin-probe in spirobifluorene-based donor (diphenylamine)–acceptor (dicyano or cyanoacrylic acid moieties) compounds adsorbed from highly diluted solutions onto Au and indium tin oxide electrode surfaces. Strong intramolecular charge separation (negative SPV signals up to more than 0.1 V) due to directed molecule adsorption was observed only for spirobifluorene donor–acceptor compounds with carboxylic acid moiety. SPV signals and onset energies of electronic transitions depended on ambience conditions. - Highlights: ► Fluorene donor–acceptor derivatives were adsorbed at Au and indium tin oxide. ► Surface photovoltage measurements were performed with a Kelvin-probe. ► Strong intra-molecular charge separation was observed. ► SPV signals depended on ambience conditions

  2. Comparision between ab-initio and phenomenological modeling of the exchange couplings in diluted magnetic semiconductors: the case of Zn.sub.1-x./sub.Cr.sub.x./sub.Te

    Czech Academy of Sciences Publication Activity Database

    Bouzerar, G.; Bouzerar, R.; Kudrnovský, Josef; Ziman, T.

    2006-01-01

    Roč. 203, č. 11 (2006), s. 2989-2994 ISSN 0031-8965 Institutional research plan: CEZ:AV0Z10100520 Keywords : ab-intio * exchange interactions * Curie temperatures * diluted systems * RPA Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.221, year: 2006

  3. State of atoms and interatomic interactions in complex perovskite-like oxides. Communication XVIII. Magnetic dilution in the LaCrO3-LaGaO3 system

    International Nuclear Information System (INIS)

    Chezhina, N.V.; Zolotukhina, N.V.; Bodritskaya, Eh.V.

    2005-01-01

    Solid solutions LaCr x Ga 1-x O 3 (0.01 ≤ x ≤ 0.10) were synthesized using the ceramic technique and characterized by X-ray powder diffraction and chemical analysis. Magnetic susceptibility of dilute solid solutions of lanthanum chromate in lanthanum gallate was studied in the temperature range 77-400 K. The calculated antiferromagnetic exchange parameter and distribution of chromium atoms over the diamagnetic matrix gave evidence for enhanced chromium aggregation and weakened magnetic exchange in lanthanum gallate compared to lanthanum aluminate [ru

  4. Magnetic properties and magnetocaloric effect of MnFeP0.5Ge0.5-xSix compounds

    International Nuclear Information System (INIS)

    Song, L.; Wang, G.F.; Ou, Z.Q.; Haschaolu, O.; Tegus, O.; Brueck, E.; Buschow, K.H.J.

    2009-01-01

    We have studied the magnetic properties and magnetic-entropy changes of the MnFeP 0.5 Ge 0.5-x Si x compounds with x = 0.1, 0.2, 0.3, 0.4 and 0.45. X-ray diffraction shows that the compounds crystallize in the Fe 2 P-type hexagonal structure. The lattice parameter a and the Curie temperature decreases with increasing x. The maximal magnetic-entropy changes for x = 0.4 and 0.45 derived from the magnetization data are about 6.0 J/kg K and 5.8 J/kg K, respectively, for a field change from 0 to 1.5 T

  5. Dilute antiferromagnetism in magnetically doped phosphorene

    Directory of Open Access Journals (Sweden)

    Andrew Allerdt

    2017-11-01

    Full Text Available We study the competition between Kondo physics and indirect exchange on monolayer black phos-phorous using a realistic description of the band structure in combination with the density matrixrenormalization group (DMRG method. The Hamiltonian is reduced to a one-dimensional problemvia an exact canonical transformation that makes it amenable to DMRG calculations, yielding exactresults that fully incorporate the many-body physics. We find that a perturbative description of theproblem is not appropriate and cannot account for the slow decay of the correlations and the completelack of ferromagnetism. In addition, at some particular distances, the impurities decouple formingtheir own independent Kondo states. This can be predicted from the nodes of the Lindhard function.Our results indicate a possible route toward realizing dilute anti-ferromagnetism in phosphorene. Received: 19 September 2017, Accepted: 12 October 2017; Edited by: K. Hallberg; DOI: http://dx.doi.org/10.4279/PIP.090008 Cite as: A Allerdt, A E Feiguin, Papers in Physics 9, 090008 (2017

  6. Magnetic properties of FeZr{sub 2} and Fe{sub 2}Zr intermetallic compounds

    Energy Technology Data Exchange (ETDEWEB)

    Prajapat, C. L., E-mail: prajapat@barc.gov.in; Singh, M. R.; Mishra, P. K. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai, INDIA-400085 (India); Chattaraj, D. [Product Development Division, Bhabha Atomic Research Centre, Mumbai, INDIA-400085 (India); Mishra, R. [Chemistry Division, Bhabha Atomic Research Centre, Mumbai, INDIA-400085 (India); Ravikumar, G. [Scientific Information Resources Division, Bhabha Atomic Research Centre, Mumbai, INDIA-400085 (India)

    2016-05-23

    Magnetic properties of Fe-Zr system, viz., FeZr{sub 2} and Fe{sub 2}Zr have been studied. Both the compounds show soft ferromagnetic behavior. Curie temperature is well above the room temperature. Lower saturation magnetization for the zirconium rich sample, FeZr{sub 2}, could be due to possible donation of electrons from the Zr-rich neighbors to Fe atoms or diminution of long range magnetic order by defects.

  7. Magnetocaloric effect of polycrystalline Sm0.5Ca0.5MnO3 compound: Investigation of low temperature magnetic state

    Science.gov (United States)

    Das, Kalipada; Banu, Nasrin; Das, I.; Dev, B. N.

    2018-06-01

    An attempt has been made to probe low temperature magnetic state of the polycrystalline Sm0.5Ca0.5MnO3 compound via magnetization and magnetocaloric studies. In the context of the earlier debatable reports on the above mentioned compound between the existence of glassy magnetic state and small ferromagnetic domains from the 'ac' susceptibility measurements, our experimental observation from magnetocaloric effect study clearly indicates the existence of ferromagnetic droplets along with certain amount of superparamagnetic component at low temperature (magnetization (even at H = 0.01 T) data do not exhibit the spin freezing nature at the low temperature which is almost a generic tendency of glassy magnetic state. Our study also highlights the competence of magnetocaloric effect as a tool to distinguish between different magnetic states of a compound.

  8. Impact of dilution on the microstructure and properties of Ni-based 625 alloy coatings

    Directory of Open Access Journals (Sweden)

    Tiago Jose Antoszczyszyn

    2014-06-01

    Full Text Available Nickel-based alloy IN 625 is used to protect components of aircrafts, power generation and oil refinery due to an association of toughness and high corrosion resistance. These properties are associated with the chemical composition and microstructure of coatings which depend on the processing parameters and the composition of the component being protected. This paper assessed impact of dilution on the microstructure and properties of the Ni alloy IN 625 deposited by Plasma Transferred Arc (PTA on two substrates: carbon steel API 5L and stainless steel AISI 316L. Differences due to the interaction with the substrate were maximized analyzing single layer coatings, processed with three deposition current: 120, 150 and 180 A. Correlation with a cast Nickel-based alloy sample contributed to assess the impact of dilution on coatings. Dilution was determined by the area ratio and Vickers hardness measured on the transverse section of coatings. Scanning electron and Laser confocal microscopy and X-ray diffraction analysis were carried out to characterize the microstructure. Results indicated the increasing dilution with the deposition current was deeply influenced by the substrate. Dilution ranging from 5 to 29% was measured on coatings processed on the API 5L steel and from 22 to 51% on the low thermal conductivity AISI 316L steel substrate. Differences on the microstructure and properties of coatings can be associated with the interaction with each substrate. Higher fraction of carbides account for the higher coating hardness when processing on API 5L whereas the low thermal conductivity of AISI 316L and the higher Fe content in solid solution contributed to the lower hardness of coatings.

  9. Magnetic Study of the Novel Polynuclear Compound [Cu(II)(6-Mercaptopurinolate 2-)] n

    Science.gov (United States)

    Acevedo-Chávez, Rodolfo; Costas, María. Eugenia; Escudero, Roberto

    1997-08-01

    Chemical reactions between Cu(II) and 6-mercaptopurine, both in aqueous and in methanolic media, yield the novel amorphous polynuclear compound [Cu(II)(6-mercaptopurinolate)2-]n, which is also obtained from diverse Cu(II)-heterocyclic ligand competitive reactions. The kinetic and thermodynamic stabilities associated with the formation of this compound are inferred as remarkable. The spectroscopic data let us suggest the involvement of the exocyclic S(6) donor site and the N atoms in the imidazolic moiety of the deprotonated heterocyclic ligand in the coordination to Cu(II) atoms, forming a distorted bidimensional metallic network. The magnetic studies show the existence of very weak antiferromagnetic coupling in the solid sample. This system represents the first example of a 1 : 1 metal : 6-mercaptopurinolate2-system with ad-type open shell metallic center. The magnetic study carried out also represents the first example of magnetic characterization for this type of polynuclear Cu(II) systems with the dianionic 6-mercaptopurine ligand.

  10. Incorporation of Mg and Ca into nanostructured Fe2O3 improves Fe solubility in dilute acid and sensory characteristics in foods.

    Science.gov (United States)

    Hilty, Florentine M; Knijnenburg, Jesper T N; Teleki, Alexandra; Krumeich, Frank; Hurrell, Richard F; Pratsinis, Sotiris E; Zimmermann, Michael B

    2011-01-01

    Iron deficiency is one of the most common micronutrient deficiencies worldwide. Food fortification can be an effective and sustainable strategy to reduce Fe deficiency but selection of iron fortificants remains a challenge. Water-soluble compounds, for example, FeSO(4), usually demonstrate high bioavailability but they often cause unacceptable sensory changes in foods. On the other hand, poorly acid-soluble Fe compounds, for example FePO(4), may cause fewer adverse sensory changes in foods but are usually not well bioavailable since they need to be dissolved in the stomach prior to absorption. The solubility and the bioavailability of poorly acid-soluble Fe compounds can be improved by decreasing their primary particle size and thereby increasing their specific surface area. Here, Fe oxide-based nanostructured compounds with added Mg or Ca were produced by scalable flame aerosol technology. The compounds were characterized by nitrogen adsorption, X-ray diffraction, transmission electron microscopy, and Fe solubility in dilute acid. Sensory properties of the Fe-based compounds were tested in 2 highly reactive, polyphenol-rich food matrices: chocolate milk and fruit yoghurt. The Fe solubility of nanostructured Fe(2)O(3) doped with Mg or Ca was higher than that of pure Fe(2)O(3). Since good solubility in dilute acid was obtained despite the inhomogeneity of the powders, inexpensive precursors, for example Fe- and Ca-nitrates, can be used for their manufacture. Adding Mg or Ca lightened powder color, while sensory changes when added to foods were less pronounced than for FeSO(4). The combination of high Fe solubility and low reactivity in foods makes these flame-made nanostructured compounds promising for food fortification. Practical Application: The nanostructured iron-containing compounds presented here may prove useful for iron fortification of certain foods; they are highly soluble in dilute acid and likely to be well absorbed in the gut but cause less severe

  11. Design of a Dry Dilution Refrigerator for MMC Gamma Detector Arrays

    Energy Technology Data Exchange (ETDEWEB)

    Friedrich, Stephan [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Boyd, Stephen [Univ. of New Mexico, Albuquerque, NM (United States); Cantor, Robin

    2017-04-03

    The goal of this LCP is to develop an ultra-high resolution gamma detector based on magnetic microcalorimeters (MMCs) for accurate non-destructive analysis (NDA) of nuclear materials. For highest energy resolution, we will introduce erbium-doped silver (Ag:Er) as a novel sensor material to replace current Au:Er sensors. The detector sensitivity will be increased by developing arrays of 32 Ag:Er pixels read out by 16 SQUID preamplifiers. MMC detectors require operating temperatures of ~15 mK and thus the use of a dilution refrigerator, and the desire for user-friendly operation without cryogenic liquids requires that this refrigerator use pulse-tube pre-cooling to ~4 K. For long-term reliability, we intend to re-design the heat switch that is needed to apply the magnetizing current to the Ag:Er sensor and that used to fail in earlier designs after months of operation. A cryogenic Compton veto will be installed to reduce the spectral background of the MMC, especially at low energies where ultra-high energy resolution is most important. The goals for FY16 were 1) to purchase a liquid-cryogen-free dilution refrigerator and adapt it for MMC operation, and 2) to fabricate Ag:Er-based MMC γ-detectors with improved performance and optimize their response. This report discusses the design of the instruments, and progress in MMC detector fabrication. Details of the MMC fabrication have been discussed in an April 2016 report to DOE.

  12. Magnetic entropy of the mixed and sintered compound of the RAl/sub 2/ system

    International Nuclear Information System (INIS)

    Kuzuhara, T.; Wakabayashi, H.; Matsumoto, K.; Hashimoto, T.; Sahashi, M.; Inomata, K.; Tomokiyo, A.; Yayama, H.

    1986-01-01

    The magnetic refrigerant for the Ericsson type magnetic refrigerator should have a constant magnetic entropy difference ΔS/sub J/ between two constant magnetic field processes. However, the magnetic entropy change of an homogeneous ferromagnet exhibits a sharp peak at the Curie temperature. In the present investigation the authors succeeded to make the layer structural sintered composite composed of several kinds of RAl/sub 2/ compounds having large entropy change near their Curie temperatures and made clear that this composite has the constant πS/sub J/ in the wide temperature range suitable for the Ericsson cycle

  13. Muon and other studies of magnetic ordering in cuprate layer-compounds

    International Nuclear Information System (INIS)

    Portis, A.M.; Celio, M.

    1989-01-01

    Muon spin rotation studies of magnetic ordering in the planar cuprates are reviewed. Particular attention is given to doped La 2 CuO 4 and oxygen-depleted YBa 2 Cu 3 O 7-δ and to related experimental investigations. Studies of transition element substituted compounds are also reviewed. (orig.)

  14. Magnetic, electrical and structural properties of the Re-doped ruthenocuprate Ru1−xRexSr2GdCu2Oy

    International Nuclear Information System (INIS)

    Corredor, L.T.; Albino Aguiar, J.; Landínez Téllez, D.A.; Pureur, P.; Mesquita, F.; Roa-Rojas, J.

    2015-01-01

    Highlights: • We investigated the effect of the dilution of magnetic Ru sub-lattice of RuSr 2 GdCu 2 O 8 . • We synthesized the doped compound Rui x Re x Sr 2 GdCu 2 O y , for 3%, 6%, 9% and 12% Re. • Re would affect the electron coupling: just 3 and 6% samples were superconductor. • Superconductivity emergence strongly affects magnetic properties of 3 and 6% samples. • A weak ferromagnetic component is consistent with a globally antiferromagnetic system. - Abstract: Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependant effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the Ru 1−x Re x Sr 2 GdCu 2 O y ruthenocuprate-type family, adapting the known two-step process (double perovskite + CuO) by directly doping the double perovskite, thus obtaining the perovskite compound Sr 2 GdRu 1−x Re x O y , which represents a new synthesis process to the best of our knowledge. Our samples were structurally characterized through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterization as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO 2 (magnetic) and CuO 2 (superconductor) sub-lattices can clearly be observed

  15. Interplay between effects of external pressure and dilution of the U sublattice in UCoAl-based materials

    International Nuclear Information System (INIS)

    Andreev, A.V.; Koyama, K.; Mushnikov, N.V.; Sechovsky, V.; Shiokawa, Y.; Satoh, I.; Watanabe, K.

    2007-01-01

    Substitution of Y for U in the itinerant 5f-electron metamagnet, UCoAl, transforms the system to a ferromagnetic state. Application of external hydrostatic pressure above 0.3 GPa suppresses the ferromagnetism and restores the 'UCoAl-type' metamagnetism back. However, the metamagnetic transition becomes of the second order instead of the first order one in parent UCoAl. This is attributed to enhancement of fluctuations of the U magnetic moment upon dilution of the U sublattice

  16. Investigation on magnetic field dependent modulus of epoxidized natural rubber based magnetorheological elastomer

    International Nuclear Information System (INIS)

    Yunus, N. A.; Mazlan, S. A.; Ubaidillah; Aziz, S. A. A.; Khairi, M. H. Ahmad; Wahab, N. A. A.; Shilan, S. T.

    2016-01-01

    This paper presents an investigation on the use of epoxidized natural rubber (ENR) as a matrix of magnetorheological elastomers (MREs). Isotropic ENR-based MRE samples were synthesized by homogeneously mixed the ENR compound with carbonyl iron particles (CIPs). The microstructure of the sample was observed, and the magnetic field-dependent moduli were analyzed using rheometer. The influences of excitation frequency, CIPs content and magnetic field on the field-dependent moduli of ENR-based MREs were evaluated through dynamic shear test. The microstructure of MRE samples demonstrated the dispersed CIPs in the ENR matrix. The remarkable increment of storage and loss moduli of the ENR-based MREs has exhibited the magnetically controllable storage and loss moduli of the samples when exposed to the magnetic field. Consequently, the CIPs content, frequency and magnetic field were significantly influenced the dynamic moduli of the ENR-based MREs. (paper)

  17. Key Aroma Compounds in Lippia dulcis (Dushi Button).

    Science.gov (United States)

    Schmitt, Rainer; Cappi, Michael; Pollner, Gwendola; Greger, Veronika

    2018-03-14

    An aroma extract dilution analysis (AEDA) applied on aroma extracts prepared from the edible flower Dushi Button ( Lippia dulcis) resulted in the detection of 34 odor-active compounds. The highest flavor dilution (FD) factors were determined for methyl 2-methylbutanoate, ethyl 2-methylbutanoate, 4-mercapto-4-methyl-2-pentanone, an unknown caramel-like compound, and vanillin. Quantitative measurements performed by application of stable isotope dilution assays (SIDA), followed by a calculation of odor activity values (OAVs), resulted in the revelation of 4-mercapto-4-methyl-2-pentanone, linalool, myrcene, ethyl 2-methylbutanoate, methyl 2-methylbutanoate, and ( Z)-3-hexenal as important contributors to the flavor of Dushi Buttons.

  18. Application of a General Computer Algorithm Based on the Group-Additivity Method for the Calculation of Two Molecular Descriptors at Both Ends of Dilution: Liquid Viscosity and Activity Coefficient in Water at Infinite Dilution

    Directory of Open Access Journals (Sweden)

    Rudolf Naef

    2017-12-01

    Full Text Available The application of a commonly used computer algorithm based on the group-additivity method for the calculation of the liquid viscosity coefficient at 293.15 K and the activity coefficient at infinite dilution in water at 298.15 K of organic molecules is presented. The method is based on the complete breakdown of the molecules into their constituting atoms, further subdividing them by their immediate neighborhood. A fast Gauss–Seidel fitting method using experimental data from literature is applied for the calculation of the atom groups’ contributions. Plausibility tests have been carried out on each of the calculations using a ten-fold cross-validation procedure which confirms the excellent predictive quality of the method. The goodness of fit (Q2 and the standard deviation (σ of the cross-validation calculations for the viscosity coefficient, expressed as log(η, was 0.9728 and 0.11, respectively, for 413 test molecules, and for the activity coefficient log(γ∞ the corresponding values were 0.9736 and 0.31, respectively, for 621 test compounds. The present approach has proven its versatility in that it enabled the simultaneous evaluation of the liquid viscosity of normal organic compounds as well as of ionic liquids.

  19. Field-dependent dynamic responses from dilute magnetic nanoparticle dispersions

    DEFF Research Database (Denmark)

    Fock, Jeppe; Balceris, Christoph; Costo, Rocio

    2018-01-01

    The response of magnetic nanoparticles (MNPs) to an oscillating magnetic field outside the linear response region is important for several applications including magnetic hyperthermia, magnetic resonance imaging and biodetection. The size and magnetic moment are two critical parameters for the pe...

  20. On the role of diluted magnetic cobalt-doped ZnO electrodes in efficiency improvement of InGaN light emitters

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hong-Ru; Wang, Shih-Yin [Department of Materials Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan (China); Ou, Sin-Liang [Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan (China); Wuu, Dong-Sing, E-mail: dsw@dragon.nchu.edu.tw [Department of Materials Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan (China); Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan (China); Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 70101, Taiwan (China)

    2016-07-11

    The 120-nm-thick cobalt-doped ZnO (Co-doped ZnO, CZO) dilute magnetic films deposited by pulsed laser deposition were employed as the n-electrodes for both lateral-type blue (450 nm) and green (520 nm) InGaN light emitters. In comparison to the conventional blue and green emitters, there were 15.9% and 17.7% enhancements in the output power (@350 mA) after fabricating the CZO n-electrode on the n-GaN layer. Observations on the role of CZO n-electrodes in efficiency improvement of InGaN light emitters were performed. Based on the results of Hall measurements, the carrier mobilities were 176 and 141 cm{sup 2}/V s when the electrons passed through the n-GaN and the patterned-CZO/n-GaN, respectively. By incorporating the CZO n-electrode into the InGaN light emitters, the electrons would be scattered because of the collisions between the magnetic atoms and the electrons as the device is driven, leading to the reduction of the electron mobility. Therefore, the excessively large mobility difference between electron and hole carriers occurred in the conventional InGaN light emitter can be efficiently decreased after preparing the CZO n-electrode on the n-GaN layer, resulting in the increment of carrier recombination rate and the improvement of light output power.

  1. On the role of diluted magnetic cobalt-doped ZnO electrodes in efficiency improvement of InGaN light emitters

    International Nuclear Information System (INIS)

    Liu, Hong-Ru; Wang, Shih-Yin; Ou, Sin-Liang; Wuu, Dong-Sing

    2016-01-01

    The 120-nm-thick cobalt-doped ZnO (Co-doped ZnO, CZO) dilute magnetic films deposited by pulsed laser deposition were employed as the n-electrodes for both lateral-type blue (450 nm) and green (520 nm) InGaN light emitters. In comparison to the conventional blue and green emitters, there were 15.9% and 17.7% enhancements in the output power (@350 mA) after fabricating the CZO n-electrode on the n-GaN layer. Observations on the role of CZO n-electrodes in efficiency improvement of InGaN light emitters were performed. Based on the results of Hall measurements, the carrier mobilities were 176 and 141 cm"2/V s when the electrons passed through the n-GaN and the patterned-CZO/n-GaN, respectively. By incorporating the CZO n-electrode into the InGaN light emitters, the electrons would be scattered because of the collisions between the magnetic atoms and the electrons as the device is driven, leading to the reduction of the electron mobility. Therefore, the excessively large mobility difference between electron and hole carriers occurred in the conventional InGaN light emitter can be efficiently decreased after preparing the CZO n-electrode on the n-GaN layer, resulting in the increment of carrier recombination rate and the improvement of light output power.

  2. Band metamagnetism and peculiarities of magnetic structure of (Er1-xYx)Co2 compounds

    International Nuclear Information System (INIS)

    Baranov, N.V.; Kozlov, A.I.; Pirogov, A.N.; Sinitsyn, E.V.

    1989-01-01

    A study of the magnetization, electric resistance, and thermal expansion as well as neutron diffraction data are used to show that in Er 1-x Y x Co 2 compounds the splitting of the d=zone of cobalt disappears as yttrium concentration grows up to x=0.4 and that simultaneously disordering of the Er subssystem sets in due to a phase transition of the first kind. It is discovered that at x∼0.45 the introduction of a weak external magnetic field with μ 0 H∼0.4 T causes the magnetization of the partially disordered Er subsystem to grow, which is accompanied by an irreversible splitting of the d-zone and an increase in the magnetic moment of cobalt from 0.3μ B to 0.9μ B . The presence of minima on the temperature curves for the electric resistance, observed in Er 1-x Y x Co 2 compounds (.2≤x≤0.6) at temperatures above the magnetic ordering temperature, is related to spin density fluctuations in the Co subsystem

  3. Lattice specific heat for the RMIn{sub 5} (R=Gd, La, Y; M=Co, Rh) compounds: Non-magnetic contribution subtraction

    Energy Technology Data Exchange (ETDEWEB)

    Facio, Jorge I., E-mail: jorge.facio@cab.cnea.gov.ar [Centro Atómico Bariloche and Instituto Balseiro, CNEA, 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Betancourth, D.; Cejas Bolecek, N.R. [Centro Atómico Bariloche and Instituto Balseiro, CNEA, 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Jorge, G.A. [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina); Pedrazzini, Pablo; Correa, V.F.; Cornaglia, Pablo S. [Centro Atómico Bariloche and Instituto Balseiro, CNEA, 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Vildosola, V. [Centro Atómico Constituyentes, CNEA, 1650 San Martín, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); García, D.J. [Centro Atómico Bariloche and Instituto Balseiro, CNEA, 8400 Bariloche (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina)

    2016-06-01

    We analyze theoretically a common experimental process used to obtain the magnetic contribution to the specific heat of a given magnetic material. In the procedure, the specific heat of a non-magnetic analog is measured and used to subtract the non-magnetic contributions, which are generally dominated by the lattice degrees of freedom in a wide range of temperatures. We calculate the lattice contribution to the specific heat for the magnetic compounds GdMIn{sub 5} (M=Co, Rh) and for the non-magnetic YMIn{sub 5} and LaMIn{sub 5} (M=Co, Rh), using density functional theory based methods. We find that the best non-magnetic analog for the subtraction depends on the magnetic material and on the range of temperatures. While the phonon specific heat contribution of YRhIn{sub 5} is an excellent approximation to the one of GdCoIn{sub 5} in the full temperature range, for GdRhIn{sub 5} we find a better agreement with LaCoIn{sub 5}, in both cases, as a result of an optimum compensation effect between masses and volumes. We present measurements of the specific heat of the compounds GdMIn{sub 5} (M=Co, Rh) up to room temperature where it surpasses the value expected from the Dulong–Petit law. We obtain a good agreement between theory and experiment when we include anharmonic effects in the calculations.

  4. Rare earth-based quaternary Heusler compounds MCoVZ (M = Lu, Y; Z = Si, Ge with tunable band characteristics for potential spintronic applications

    Directory of Open Access Journals (Sweden)

    Xiaotian Wang

    2017-11-01

    Full Text Available Magnetic Heusler compounds (MHCs have recently attracted great attention since these types of material provide novel functionalities in spintronic and magneto-electronic devices. Among the MHCs, some compounds have been predicted to be spin-filter semiconductors [also called magnetic semiconductors (MSs], spin-gapless semiconductors (SGSs or half-metals (HMs. In this work, by means of first-principles calculations, it is demonstrated that rare earth-based equiatomic quaternary Heusler (EQH compounds with the formula MCoVZ (M = Lu, Y; Z = Si, Ge are new spin-filter semiconductors with total magnetic moments of 3 µB. Furthermore, under uniform strain, there are physical transitions from spin-filter semiconductor (MS → SGS → HM for EQH compounds with the formula LuCoVZ, and from HM → SGS → MS → SGS → HM for EQH compounds with the formula YCoVZ. Remarkably, for YCoVZ EQH compounds there are not only diverse physical transitions, but also different types of spin-gapless feature that can be observed with changing lattice constants. The structural stability of these four EQH compounds is also examined from the points of view of formation energy, cohesive energy and mechanical behaviour. This work is likely to inspire consideration of rare earth-based EQH compounds for application in future spintronic and magneto-electronic devices.

  5. First-principles theory of dilute magnetic semiconductors

    Czech Academy of Sciences Publication Activity Database

    Sato, K.; Bergqvist, L.; Kudrnovský, Josef; Dederichs, P. H.; Eriksson, O.; Turek, Ilja; Sanyal, B.; Bouzerar, G.; Katayama-Yoshida, H.; Dinh, V. A.; Fukushima, T.; Kizaki, H.; Zeller, R.

    2010-01-01

    Roč. 82, č. 2 (2010), s. 1633-1690 ISSN 0034-6861 R&D Projects: GA AV ČR IAA100100616; GA ČR GA202/07/0456 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z20410507 Keywords : magnetic semiconductors * electronic structure * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 51.695, year: 2010

  6. Determination of the maximum inhibitory dilution of cetylpyridinium chloride-based mouthwashes against staphylococcus aureus: an in vitro study

    Directory of Open Access Journals (Sweden)

    Evandro Watanabe

    2008-08-01

    Full Text Available The aim of this in vitro study was to determine the maximum inhibitory dilution (MID of four cetylpyridinium chloride (CPC-based mouthwashes: CPC+Propolis, CPC+Malva, CPC+Eucaliptol+Juá+Romã+Propolis (Natural Honey® and CPC (Cepacol®, against 28 Staphylococcus aureus field strains, using the agar dilution method. Decimal dilutions ranging from 1/10 to 1/655,360 were prepared and added to Mueller Hinton Agar. Strains were inoculated using Steers multipoint inoculator. The inocula were seeded onto the surface of the culture medium in Petri dishes containing different dilutions of the mouthwashes. The dishes were incubated at 37ºC for 24 h. For readings, the MID was considered as the maximum dilution of mouthwash still capable of inhibiting microbial growth. The obtained data showed that CPC+Propolis had antimicrobial activity against 27 strains at 1/320 dilution and against all 28 strains at 1/160 dilution, CPC+Malva inhibited the growth of all 28 strains at 1/320 dilution, CPC+Eucaliptol+Juá+Romã+Propolis inhibited the growth of 2 strains at 1/640 dilution and all 28 strains at 1/320 dilution, and Cepacol® showed antimicrobial activity against 3 strains at 1/320 dilution and against all 28 strains at 1/160 dilution. Data were submitted to Kruskal-Wallis test, showing that the MID of Cepacol® was lower than that determined for the other products (p<0.05. In conclusion, CPC-mouthwashes showed antimicrobial activity against S. aureus and the addition of other substances to CPC improved its antimicrobial effect.

  7. Magnetic anisotropy of some R2CO17 compounds

    International Nuclear Information System (INIS)

    Khan, W.I.; Melville, D.

    1978-01-01

    The singular-point detection technique, in which the second derivative of the magnetization with respect to field is examined, has been used to determine the anisotropy field Bsub(A) = (2/Msub(s)) (K 1 + 2K 2 ) for Sm 2 Co 17 , Er 2 Co 17 , and Tm 2 Co 17 over the temperature range 77 - 300 K. Exrapolation of the initial part of the hard-direction magnetization curve for aligned powders enables K 1 and K 2 to be estimated. For Er 2 Co 17 and Tm 2 Co 17 the rare-earth (R) and cobalt sublattices are oppositely aligned, so that the onset of ordering of the R sublattice leads to a decrease in saturation magnetization as the temperature is lowered. This is in sharp contrast to the rapid increase in K 1 at low temperatures. By subtracting the corresponding Msub(s) values from that of Y 2 Co 17 the temperature dependence of the R sublattice can be determined. It is found that K 1 is directly proportional to the cube of this quantity, indicating the dominance of the rare-earth sublattice in determining the anisotropic properties of these compounds. For Sm 2 Co 17 the anisotropy constant varies very strongly with the reduced magnetization. (author)

  8. Magnetic Properties of linear chain compounds formed by lanthanide (III) ions and nitronyl-nitroxide radicals

    Energy Technology Data Exchange (ETDEWEB)

    Benelli, C.; Caneschi, A.; Gatteschi, D.; Pardi, L. (Florence Univ. (IT)); Rey, P. (CEA Centre d' Etudes Nucleaires de Grenoble, 38 (FR). Dept. de Recherche Fondamentale)

    1988-12-01

    The magnetic properties of novel linear chain compounds containing lanthanide (III) ions (gadolinium, europium) coupled to stable nitronyl-nitroxide radicals are reported. The metal ions and the radicals are regularly alternating along the chain. The magnetic behaviors appears to be dominated by antiferromagnetic interactions between the radicals.

  9. Magnetic Properties of linear chain compounds formed by lanthanide (III) ions and nitronyl-nitroxide radicals

    International Nuclear Information System (INIS)

    Benelli, C.; Caneschi, A.; Gatteschi, D.; Pardi, L.; Rey, P.

    1988-01-01

    The magnetic properties of novel linear chain compounds containing lanthanide (III) ions (gadolinium, europium) coupled to stable nitronyl-nitroxide radicals are reported. The metal ions and the radicals are regularly alternating along the chain. The magnetic behaviors appears to be dominated by antiferromagnetic interactions between the radicals

  10. Magnetofluidic concentration and separation of non-magnetic particles using two magnet arrays

    Science.gov (United States)

    Hejazian, Majid

    2016-01-01

    The present paper reports the use of diluted ferrofluid and two arrays of permanent magnets for the size-selective concentration of non-magnetic particles. The micro magnetofluidic device consists of a straight channels sandwiched between two arrays of permanent magnets. The permanent magnets create multiple capture zones with minimum magnetic field strength along the channel. The complex interaction between magnetic forces and hydrodynamic force allows the device to operate in different regimes suitable for concentration of non-magnetic particles with small difference in size. Our experimental results show that non-magnetic particles with diameters of 3.1 μm and 4.8 μm can be discriminated and separated with this method. The results from this study could be used as a guide for the design of size-sensitive separation devices for particle and cell based on negative magnetophoresis. PMID:27478527

  11. Spectroscopic and magnetic studies of tetravalent Pa and trivalent Th compounds

    International Nuclear Information System (INIS)

    Edelstein, N.M.; Kot, W.K.

    1992-06-01

    At the beginning of the actinide series, the 5f and 6d configurations are very close in energy. Consequently, both the 5f and 6d energy level splittings may be observed experimentally in Pa 4+ and Th 3+ compounds. The available magnetic and optical data on these systems are reviewed

  12. Separation and enrichment of enantiopure from racemic compounds using magnetic levitation.

    Science.gov (United States)

    Yang, Xiaochuan; Wong, Shin Yee; Bwambok, David K; Atkinson, Manza B J; Zhang, Xi; Whitesides, George M; Myerson, Allan S

    2014-07-18

    Crystallization of a solution with high enantiomeric excess can generate a mixture of crystals of the desired enantiomer and the racemic compound. Using a mixture of S-/RS-ibuprofen crystals as a model, we demonstrated that magnetic levitation (MagLev) is a useful technique for analysis, separation and enantioenrichment of chiral/racemic products.

  13. Magnetic structure of post-perovskite compound CaIrO3

    International Nuclear Information System (INIS)

    Ohgushi, Kenya; Ohsumi, Hiroyuki; Yamaura, Jun-ichi; Arima, Taka-hisa

    2014-01-01

    We have performed resonant X-ray diffraction experiments at the Ir L absorption edges for a post-perovskite compound CaIrO 3 with a Ir 4+ : (t 2g ) 5 electronic configuration. By observing the magnetic signals, we could clearly see that the magnetic structure was a striped ordering with antiferromagnetic moments along the c axis and that the wave function of a t 2g hole is strongly spin-orbit entangled, the J eff = 1/2 state. The observed spin arrangement is consistent with a theoretical work predicting a unique superexchange interaction called the quantum compass model. Our studies stimulate further studies for developing novel quantum states in iridium oxides. (author)

  14. Magnetic quantum tunneling: insights from simple molecule-based magnets.

    Science.gov (United States)

    Hill, Stephen; Datta, Saiti; Liu, Junjie; Inglis, Ross; Milios, Constantinos J; Feng, Patrick L; Henderson, John J; del Barco, Enrique; Brechin, Euan K; Hendrickson, David N

    2010-05-28

    This perspectives article takes a broad view of the current understanding of magnetic bistability and magnetic quantum tunneling in single-molecule magnets (SMMs), focusing on three families of relatively simple, low-nuclearity transition metal clusters: spin S = 4 Ni(II)(4), Mn(III)(3) (S = 2 and 6) and Mn(III)(6) (S = 4 and 12). The Mn(III) complexes are related by the fact that they contain triangular Mn(III)(3) units in which the exchange may be switched from antiferromagnetic to ferromagnetic without significantly altering the coordination around the Mn(III) centers, thereby leaving the single-ion physics more-or-less unaltered. This allows for a detailed and systematic study of the way in which the individual-ion anisotropies project onto the molecular spin ground state in otherwise identical low- and high-spin molecules, thus providing unique insights into the key factors that control the quantum dynamics of SMMs, namely: (i) the height of the kinetic barrier to magnetization relaxation; and (ii) the transverse interactions that cause tunneling through this barrier. Numerical calculations are supported by an unprecedented experimental data set (17 different compounds), including very detailed spectroscopic information obtained from high-frequency electron paramagnetic resonance and low-temperature hysteresis measurements. Comparisons are made between the giant spin and multi-spin phenomenologies. The giant spin approach assumes the ground state spin, S, to be exact, enabling implementation of simple anisotropy projection techniques. This methodology provides a basic understanding of the concept of anisotropy dilution whereby the cluster anisotropy decreases as the total spin increases, resulting in a barrier that depends weakly on S. This partly explains why the record barrier for a SMM (86 K for Mn(6)) has barely increased in the 15 years since the first studies of Mn(12)-acetate, and why the tiny Mn(3) molecule can have a barrier approaching 60% of this

  15. Dilute-and-shoot coupled to nanoflow liquid chromatography high resolution mass spectrometry for the determination of drugs of abuse and sport drugs in human urine.

    Science.gov (United States)

    Alcántara-Durán, Jaime; Moreno-González, David; Beneito-Cambra, Miriam; García-Reyes, Juan F

    2018-05-15

    In this work, a sensitive nanoflow liquid chromatography high-resolution mass spectrometry screening method has been developed for the determination of multiclass drugs of abuse and sport drugs in human urine. 81 drugs belonging to different multiclass pharmaceuticals were targeted. The method is based on the use of a nanoLC column (75 µm × 150 mm, 3 µm particle size and 100 Å pore) with the nanospray emitter tip integrated so that dead volumes are significantly minimized. Data acquisition method included both full-scan and all ion fragmentation experiments using an Orbitrap analyser (Q-Exactive) operated in the positive ionization mode. To increase laboratory throughput, a dilute-and-shoot methodology has been tested and proposed, based solely on direct urine dilution without further sample workup. Matrix effects were evaluated, showing a negligible effect for all studied compounds when a dilution 1:50 was implemented. Despite this high-dilution factor, limits of quantification were still satisfactory, with values below 5 µg L -1 in most cases, being lower than their minimum required performance limits correspond established by the World Anti-Doping Agency. Therefore, the use of the dilute-and-shoot method with the enhanced sensitivity provided by nanoflow LC setup could be useful tool for the determination of studied compounds in drug testing, thus increasing laboratory performance, because a minimum sample treatment steps are required. Copyright © 2018 Elsevier B.V. All rights reserved.

  16. Dilution-triggered SMM behavior under zero field in a luminescent Zn2Dy2 tetranuclear complex incorporating carbonato-bridging ligands derived from atmospheric CO2 fixation.

    Science.gov (United States)

    Titos-Padilla, Silvia; Ruiz, José; Herrera, Juan Manuel; Brechin, Euan K; Wersndorfer, Wolfgang; Lloret, Francesc; Colacio, Enrique

    2013-08-19

    The synthesis, structure, magnetic, and luminescence properties of the Zn2Dy2 tetranuclear complex of formula {(μ3-CO3)2[Zn(μ-L)Dy(NO3)]2}·4CH3OH (1), where H2L is the compartmental ligand N,N',N″-trimethyl-N,N″-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine, are reported. The carbonate anions that bridge two Zn(μ-L)Dy units come from the atmospheric CO2 fixation in a basic medium. Fast quantum tunneling relaxation of the magnetization (QTM) is very effective in this compound, so that single-molecule magnet (SMM) behavior is only observed in the presence of an applied dc field of 1000 Oe, which is able to partly suppress the QTM relaxation process. At variance, a 1:10 Dy:Y magnetic diluted sample, namely, 1', exhibits SMM behavior at zero applied direct-current (dc) field with about 3 times higher thermal energy barrier than that in 1 (U(eff) = 68 K), thus demonstrating the important role of intermolecular dipolar interactions in favoring the fast QTM relaxation process. When a dc field of 1000 Oe is applied to 1', the QTM is almost fully suppressed, the reversal of the magnetization slightly slows, and U(eff) increases to 78 K. The dilution results combined with micro-SQUID magnetization measurements clearly indicate that the SMM behavior comes from single-ion relaxation of the Dy(3+) ions. Analysis of the relaxation data points out that a Raman relaxation process could significantly affect the Orbach relaxation process, reducing the thermal energy barrier U(eff) for slow relaxation of the magnetization.

  17. Properties of nanoparticles prepared from NdFeB-based compound for magnetic hyperthermia application.

    Science.gov (United States)

    Périgo, E A; Silva, S C; de Sousa, E M B; Freitas, A A; Cohen, R; Nagamine, L C C M; Takiishi, H; Landgraf, F J G

    2012-05-04

    Nanoparticles were prepared from a NdFeB-based alloy using the hydrogen decrepitation process together with high-energy ball milling and tested as heating agent for magnetic hyperthermia. In the milling time range evaluated (up to 10 h), the magnetic moment per mass at H = 1.59 MA m(-1) is superior than 70 A m(2) kg(-1); however, the intrinsic coercivity might be inferior than 20 kA m(-1). The material presents both ferromagnetic and superparamagnetic particles constituted by a mixture of phases due to the incomplete disproportionation reaction of Nd(2)Fe(14)BH(x) during milling. Solutions prepared with deionized water and magnetic particles exposed to an AC magnetic field (H(max) ~ 3.7 kA m(-1) and f = 228 kHz) exhibited 26 K ≤ ΔT(max) ≤ 44 K with a maximum estimated specific absorption rate (SAR) of 225 W kg(-1). For the pure magnetic material milled for the longest period of time (10 h), the SAR was estimated as ~2500 W kg(-1). In vitro tests indicated that the powders have acceptable cytotoxicity over a wide range of concentration (0.1-100 µg ml(-1)) due to the coating applied during milling.

  18. Thin film Heusler compounds manganese nickel gallium

    Science.gov (United States)

    Jenkins, Catherine Ann

    Multiferroic Heusler compounds Mn3--xNi xGa (x=0,1,2) have a tetragonal unit cell that can variously be used for magneto-mechanically coupled shape memory ( x=1,2) and spin-mechanical applications (x=0). The first fabrication of fully epitaxial thin films of these and electronically related compounds by sputtering is discussed. Traditional and custom lab characterization of the magnetic and temperature driven multiferroic behavior is augmented by more detailed synchrotron-based high energy photoemission spectroscopic techniques to describe the atomic and electronic structure. Integration of the MnNi2Ga magnetic shape memory compound in microwave patch antennas and active free-standing structures represents a fraction of the available and promising applications for these compounds. Prototype magnetic tunnel junctions are demonstrated by Mn3Ga electrodes with perpendicular anisotropy for spin torque transfer memory structures. The main body of the work concentrates on the definition and exploration of the material series Mn3--xNi xGa (x=0,1,2) and the relevant multiferroic phenomena exhibited as a function of preparation and external stimuli. Engineering results on each x=0,1,2 are presented with device prototypes where relevant. In the appendices the process of the materials design undertaken with the goal of developing new ternary intermetallics with enhanced properties is presented with a full exploration of the road from band structure calculations to device implementation. Cobalt based compounds in single crystal and nanoparticle form are fabricated with an eye to developing the production methods for new cobalt- and iron-based magnetic shape memory compounds for device applications in different forms. Mn2CoSn, a compound isolectronic and with similar atomic ordering to Mn2NiGa is experimentally determined to be a nearly half-metallic ferromagnet in contrast to the metallic ferrimagnetism in the parent compound. High energy photoemission spectroscopy is shown to

  19. Magnetic and structural characterization of the semiconductor FeIn2Se4

    International Nuclear Information System (INIS)

    Torres, T.; Sagredo, V.; Chalbaud, L.M. de; Attolini, G.; Bolzoni, F.

    2006-01-01

    Plate-like single crystals of magnetic semiconductor FeIn 2 Se 4 were grown with a chemical vapour transport technique. The X-ray powder diffraction analyses suggest that the compound crystallize in the hexagonal structure with space group P3m1. We have performed dc magnetization measurements at different magnetic fields on the diluted magnetic semiconductor FeIn 2 Se 4 . Low field magnetizations measurements shows irreversibility in the DC magnetization, as evidenced by field cooled and zero field cooled measurements below 17 K, suggesting a spin-glass like behaviour. The high-temperature susceptibility data follow a typical Curie-Weiss law with θ=-183±2 K which suggest the presence of predominant antiferromagnetic interactions with high degree of frustration. The randomness and frustration necessary for spin-glass behaviour are explained in a manner compatible with the cation and charge ordering present in the material

  20. Calculation of the magnetic properties of pseudo-ternary R2M14B intermetallic compounds (R = rare earth, M = Fe, Co

    Directory of Open Access Journals (Sweden)

    Gabriel Gómez Eslava

    2016-06-01

    Full Text Available The extrinsic properties of NdFeB-based magnets can be tuned through partial substitution of Nd by another rare-earth element and Fe by Co, as such substitution leads to a modification in the intrinsic properties of the main phase. Optimisation of a magnet's composition through trial and error is time consuming and not straightforward, since the interplay existing between magnetocrystalline anisotropy and coercivity is not completely understood. In this paper we present a model to calculate the intrinsic magnetic properties of pseudo-ternary Nd2Fe14B-based compounds. As concrete examples, which are relevant for the optimisation of NdFeB-based high-performance magnets used in (hybrid electric vehicles and wind turbines, we consider partial substitution of Nd by Dy or Tb, and Fe by Co.

  1. Magnetic characteristics of M2FeV3O11 (M = Mg, Zn, Pb, Co, Ni) compounds

    Science.gov (United States)

    Groń, T.; Blonska-Tabero, A.; Filipek, E.; Stokłosa, Z.; Duda, H.; Sawicki, B.

    2018-02-01

    The unusual physical characteristics of the multicomponent oxide systems renewed the interest as the potential cathode materials in high-energy cells. Since the earlier magnetic characteristics were not entirely conclusive, we report the results of dc magnetic measurements including higher harmonics of ac magnetic susceptibility of the M2FeV3O11 (M = Mg, Zn, Pb, Co, Ni) compounds. Ferrimagnetic long-range and antiferromagnetic short-range interactions for all compounds under study at low temperatures as well as superparamagnetic-like behavior with the blocking temperature of 29 K and the freezing parameter of 0.013 were observed. These effects are discussed within the framework of superexchange and double exchange magnetic interactions as well as the mixed valence band of iron ions.

  2. Manipulation of incoherent and coherent spin ensembles in diluted magnetic semiconductors via ferromagnetic fringe fields; Manipulation inkohaerenter und kohaerenter Spinensembles in verduennt-magnetischen Halbleitern mittels ferromagnetischer Streufelder

    Energy Technology Data Exchange (ETDEWEB)

    Halm, Simon

    2009-05-19

    In this thesis it is demonstrated that fringe fields of nanostructured ferromagnets provide the opportunity to manipulate both incoherent and coherent spin ensembles in a dilute magnetic semiconductor (DMS). Fringe fields of Fe/Tb ferromagnets with a remanent out-of-plane magnetization induce a local magnetization in a (Zn,Cd,Mn)Se DMS. Due to the sp-d exchange interaction, optically generated electron-hole pairs align their spin along the DMS magnetization. One obtains a local, remanent spin polarization which was probed by spatially resolved, polarization sensitive photoluminescence spectroscopy. Fringe fields from in-plane magnetized Co ferromagnets allow to locally modify the precession frequency of the Manganese magnetic moments of the DMS in an external magnetic field. This was probed by time-resolved Kerr rotation technique. The inhomogeneity of the fringe field leads to a shortening of the ensemble decoherence time and to the effect of a time-dependent ensemble precession frequency. (orig.)

  3. Synthesis and study of the magnetic properties of thallium-based over-doped superconducting compounds

    International Nuclear Information System (INIS)

    Opagiste, C.

    1994-07-01

    The synthesis, structure and magnetic properties of the normal and superconducting states of over-doped Tl 2 Ba 2 Cu O 6±x and Tl 2 Ba 2 Ca Cu 2 O 8±x superconducting compounds, are presented. Synthesis under high pressure using Tl 2 Ba 2 O 5 as a precursor avoids thallium losses and Ba Cu O 2 formation. The entire over-doped region has been investigated (Tc ranging from 0 to 92 K) and the different stability zones for the two crystallographic structures have been explored. The orthorhombic structure is shown to be stoichiometric in cations, while the tetragonal one could present thallium deficiency. Clear correlations have been established between Tc and the lattice parameters for the two phases. It has been observed that the Meissner fraction increased with Tc and that the reversibility domain was more extended for samples having a Tc near the maximal value, which must be linked to the decrease of the anisotropy with over-doping. In the reversible regime, the mixed state is affected by thermal fluctuations around Tc. Evolution of the penetration depth with Tc is examined; it shows that the optimum doped compound (maximal Tc) behaves as a BCS type superconductor. The over-doping results in a penetration depth behaviour which strongly deviates from the standard model (BCS, two fluids). The zero temperature, obtained by extrapolation, seems to be independent of the over-doping. 54 figs., 3 tabs., 168 refs

  4. Magnetic properties and magnetocaloric effect in the HoNi1−xCuxIn (x=0, 0.1, 0.3, 0.4) intermetallic compounds

    International Nuclear Information System (INIS)

    Mo, Zhao-Jun; Shen, Jun; Yan, Li-Qin; Tang, Cheng-Chun; He, Xiao-Nan; Zheng, Xinqi; Wu, Jian-Feng; Sun, Ji-Rong; Shen, Bao-Gen

    2014-01-01

    The magnetic properties and magnetocaloric effect (MCE) in HoNi 1−x Cu x In (x=0, 0.1, 0.3, 0.4) compounds have been investigated. With the substitution of Cu for Ni, the Ho magnetic moment will cant from the c-axis, and form a complicated magnetic structure. These compounds exhibit two successive magnetic transitions with the increase in temperature. The large reversible magnetocaloric effects have been observed in HoNi 1−x Cu x In compounds around T ord , with no thermal and magnetic hysteresis loss. The large reversible isothermal magnetic entropy change (−ΔS M ) is 20.2 J/kg K and the refrigeration capacity (RC) reaches 356.7 J/kg for field changes of 5 T for HoNi 0.7 Cu 0.3 In. Especially, the value of −ΔS M (12.5 J/kg K) and the large RC (132 J/kg) are observed for field changes of 2 T for HoNi 0.9 Cu 0.1 In. Additionally, the values of RC are improved to 149 J/K for the field changes of 2 T due to a wide temperature span for the mix of HoNi 0.9 Cu 0.1 In and HoNi 0.7 Cu 0.3 In compounds with the mass ratio of 1:1. These compounds with excellent MCE are expected to have effective applications in magnetic refrigeration around 20 K. - Highlights: • For magnetic-field changes of 2 T, the values of RC are improved to 149 J/K. • MCEs of these compounds show no thermal and magnetic hysteresis. • Compounds show two successive magnetic transitions with the increase in temperature. • With the substitution of Cu for Ni, compounds form a complicated magnetic structure

  5. Magnetization, Magnetocrystalline Anisotropy and the Crystalline Electric Field in Rare-Earth Al2 Compounds

    DEFF Research Database (Denmark)

    Purwins, H. -G.; Walker, E.; Barbara, B.

    1974-01-01

    a quantitative quantum mechanical description of the magnetization and the related magnetocrystalline anisotropy in terms of a cubic crystalline electric field and an isotropic exchange interaction. The parameters used in this description can be unified to good approximation to all REAl2 intermetallic compounds......Magnetization measurements are reported for single crystals of PrAl2 in the range from 4.2K to 30K for magnetic fields up to 150 kOe applied in the (100), (110) and (111) directions. For these measurements, together with the magnetization results obtained earlier for TbAl2 the authors give...

  6. Magnetic separation from superparamagnetic particle suspensions

    International Nuclear Information System (INIS)

    Sinha, Ashok; Ganguly, Ranjan; Puri, Ishwar K.

    2009-01-01

    We investigate the magnetophoretic separation of magnetic microparticles from a non-dilute flow in a microfluidic channel and their subsequent field-induced aggregation under the influence of an externally applied magnetic force. This force induces dipolar interactions between the particles that aid in their separation from the flow. Existing analytical models for dilute suspensions cannot be extended to non-dilute suspensions in which interparticle magnetic interactions play an important role. We therefore conduct a parametric investigation of the mechanics of this problem in a microcapillary flow through simulations and experimental visualization. When a magnetic field is applied, the magnetic microparticles form an aggregate on the channel wall that is influenced by the competition between the holding magnetic force and the aggregate-depleting flow shear force. Microparticle collection in the aggregate increases linearly with increasing magnetic field strength and is characterized by distinct buildup and washaway phases. The collected microparticle volume fraction in an aggregate is found to depend on a single dimensional group that depends upon characteristic system parameters.

  7. Coherence and stiffness of spin waves in diluted ferromagnets

    Czech Academy of Sciences Publication Activity Database

    Turek, Ilja; Kudrnovský, Josef; Drchal, Václav

    2016-01-01

    Roč. 94, č. 17 (2016), č. článku 174447. ISSN 2469-9950 R&D Projects: GA ČR GA15-13436S Institutional support: RVO:68081723 ; RVO:68378271 Keywords : spin wave s * diluted ferromagnets * disordered systems Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016

  8. Structure and magnetic properties of Gd2Co17-xCr x (1.17 ≤ x ≤ 3.0) compounds

    International Nuclear Information System (INIS)

    Fuquan, B.; Tegus, O.; Dagula, W.; Brueck, E.; Klaasse, J.C.P.; Buschow, K.H.J.

    2007-01-01

    The structure and magnetic properties of Gd 2 Co 17-x Cr x (1.17 ≤ x ≤ 3.0) compounds have been investigated by means of X-ray diffraction (XRD) and magnetization measurements. The powder X-ray diffraction patterns show that all samples crystallize as a single phase with the rhombohedral Th 2 Zn 17 -type structure. The lattice parameters a and the unit cell volume V increases slightly with increasing Cr content, but the c parameter varies in a less simple way with increasing Cr content. The X-ray diffraction patterns of the magnetically aligned samples show that all compounds investigated have uniaxial anisotropy. Spin reorientation phenomena occur in all of the compounds. The Curie temperature T C , the spin reorientation temperature T sr , the spontaneous magnetization M 0 and the saturation magnetization M s decrease with the increasing Cr content. The anisotropy constant K 1 and the anisotropy field B a of the compounds at room temperature reach a maximum for x = 1.76. The M 0 and M s increase with increasing temperature from 5 K to 300 K. The easy-axis anisotropy of all compounds changes to easy-plane anisotropy at low temperatures and the spin reorientation phenomena are more pronounced for low Cr concentration

  9. The relation between lattice parameters of NaCl type U, Np and Pu compounds and their magnetic and binding properties

    International Nuclear Information System (INIS)

    Ohmichi, Toshihiko; Arai, Yasuo

    1992-01-01

    The lattice parameters of NaCl type uranium, neptunium and plutonium compounds are analyzed using Pauling equation. The numbers of bonding electrons and localized electrons of the compounds are calculated using the single bond radius by Pauling for metalloids and assumed ones for the actinides. The number of bonding electrons per unit bonding length can be correlated linearly with the uranium compounds. The number of localized electrons is found to have a speculative relation with magnetic properties, in particular magnetic moments in ordered state; excluding some compounds, the magnetic moments increase at a gradient of 45 degrees with increasing localized electrons in the range up to about 2.5 and then decrease to zero value roughly at a same gradient with increasing localized electrons. (author)

  10. Crystal growth and magnetic property of a new compound CeAu4Si2

    International Nuclear Information System (INIS)

    Nakashima, Hiroshi; Thamizhavel, Arumugam; Matsuda, Tatsuma D.; Haga, Yoshinori; Takeuchi, Tetsuya; Sugiyama, Kiyohiro; Settai, Rikio; Onuki, Yoshichika

    2006-01-01

    We have succeeded in growing a new ternary Ce compound CeAu 4 Si 2 . This compound crystallizes in the tetragonal crystal structure P4-bar m2 (-bar 1-bar 1-bar 5) with lattice parameters a=4.3304 -bar A and c=27.409 -bar A. The local environment around Ce atoms is similar to that of the well-known ThCr 2 Si 2 -type tetragonal structure in CeAu 2 Si 2 . Single crystals of CeAu 4 Si 2 were grown by the flux method using an Au 4.37 Si eutectic alloy as flux. Electrical resistivity, specific heat and magnetization measurements revealed a ferromagnetic ordering at T C =5.3 -bar K with a saturation moment of 1.7-bar μ B /Ce. Anisotropic features in the magnetic susceptibility and magnetization were well explained by a crystalline electric field (CEF) model. Estimated excitation energies from the ground state doublet to two excited doublets are 284 and 340-bar K, respectively

  11. Magnetic, transport and magnetocaloric properties in the Laves phase intermetallic Ho (Co1−xAlx)2 compounds

    International Nuclear Information System (INIS)

    Ivanova, T.I.; Nikitin, S.A.; Tskhadadze, G.A.; Koshkid’ko, Yu.S.; Suski, W.; Iwasieczko, W.; Badurski, D.

    2014-01-01

    Highlights: • The Al influence on magnetic properties of the Ho (Co 1-x Al x ) 2 compounds is analyzed. • The first-order magnetic transition appears in sample with Al concentrations x ≤ 0.06. • The MCE and Curie temperature TC demonstrate complex Al concentration dependences. • The magnetoresistance for sample with Al concentration x = 0.06 (58%) is maximum. • High magnetic fields changes the Curie temperature T c of the Ho (Co 1−x Al x ) 2 compounds. - Abstract: The magnetization, magnetoresistivity and magnetocaloric effect (MCE) of the Ho (Co 1−x Al x ) 2 Laves phase intermetallic compounds for x ⩽ 0.2 have been investigated. Complex measurements have been carried out in order to determine the influence of substitution in the Co sublattice by Al on the Co moment, type of the magnetic transition and related properties of these compounds. A comparative analysis of the magnetic, transport and magnetocaloric properties of Ho (Co 1−x Al x ) 2 alloys under various Al concentration is represented. Substitutions at the Co site by Al are found to result in the appearance of itinerant electron metamagnetism (IEM) at the small Al concentrations and in positive magnetovolume effect, leading to an initial increase in the ordering temperature; on the other hand the magnetic phase transition temperature as well as ΔT (MCE) do not depend in direct way on the Al concentration. The 16% increase of magnetocaloric effect for the alloy with x = 0.02 is detected in relation to maternal HoCo 2 . A giant value of magnetoresistivity (58%) is observed for the alloy with the same Al concentration

  12. Phase diagrams of diluted transverse Ising nanowire

    International Nuclear Information System (INIS)

    Bouhou, S.; Essaoudi, I.; Ainane, A.; Saber, M.; Ahuja, R.; Dujardin, F.

    2013-01-01

    In this paper, the phase diagrams of diluted Ising nanowire consisting of core and surface shell coupling by J cs exchange interaction are studied using the effective field theory with a probability distribution technique, in the presence of transverse fields in the core and in the surface shell. We find a number of characteristic phenomena. In particular, the effect of concentration c of magnetic atoms, the exchange interaction core/shell, the exchange in surface and the transverse fields in core and in surface shell of phase diagrams are investigated. - Highlights: ► We use the EFT to investigate the phase diagrams of Ising transverse nanowire. ► Ferrimagnetic and ferromagnetic cases are investigated. ► The effects of the dilution and the transverse fields in core and shell are studied. ► Behavior of the transition temperature with the exchange interaction is given

  13. Magnetic properties of magnetic Co1-xMgxFe2O4 spinel by HTSE method

    International Nuclear Information System (INIS)

    Hamedoun, M.; Benyoussef, A.; Bousmina, M.

    2011-01-01

    Magnetic properties and exchange-coupling interactions of diluted magnetic spinels A 1-x A' x B 2 X 4 , where A and B are magnetic ions, namely Co 1-x Mg x Fe 2 O 4 , were investigated using the high-temperature series expansion method (HTSE) and the distribution method of magnetic cations in the range 0≤x≤1. The magnetic phase diagram and transition temperature versus dilution x were determined using the Pade approximants method along with HTSE. The critical exponent associated with the magnetic susceptibility γ was then deduced. The obtained results are in good agreement with experimental results and critical exponent values are consistent with those suggested by the universality hypothesis.

  14. Geometrically frustrated magnetic structures of the heavy-fermion compound CePdAl studied by powder neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Doenni, A.; Fischer, P.; Zolliker, M. [Laboratory for Neutron Scattering, ETH Zuerich and Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Ehlers, G.; Maletta, H. [Hahn Meitner Institute Berlin, Glienicker Strasse 100, D-14092 Berlin (Germany); Kitazawa, H. [National Research Institute for Metals, Tsukuba, Ibaraki 305 (Japan)

    1996-12-09

    The heavy-fermion compound CePdAl with ZrNiAl-type crystal structure (hexagonal space group P6-bar2m) was investigated by powder neutron diffraction. The triangular coordination symmetry of magnetic Ce atoms on site 3f gives rise to geometrical frustration. CePdAl orders below T{sub N} = 2.7 K with an incommensurate antiferromagnetic propagation vector k=[1/2, 0, {tau}], {tau} approx. 0.35, and a longitudinal sine-wave (LSW) modulated spin arrangement. Magnetically ordered moments at Ce(1) and Ce(3) coexist with frustrated disordered moments at Ce(2). The experimentally determined magnetic structure is in agreement with group theoretical symmetry analysis considerations, calculated by the program MODY, which confirm that for Ce(2) an ordered magnetic moment parallel to the magnetically easy c-axis is forbidden by symmetry. Further low-temperature experiments give evidence for a second magnetic phase transition in CePdAl between 0.6 and 1.3 K. Magnetic structures of CePdAl are compared with those of the isostructural compound TbNiAl, where a non-zero ordered magnetic moment for the geometrically frustrated Tb(2) atoms is allowed by symmetry. (author)

  15. X-ray magnetic circular dichroism experiments and theory of transuranium Laves phase compounds

    Czech Academy of Sciences Publication Activity Database

    Wilhelm, F.; Eloirdi, R.; Rusz, Ján; Springell, R.; Colineau, E.; Griveau, J.C.; Oppeneer, P. M.; Caciuffo, R.; Rogalev, A.; Lander, G.H.

    2013-01-01

    Roč. 88, č. 2 (2013), "024424-1"-"024424-14" ISSN 1098-0121 Institutional support: RVO:68378271 Keywords : electronic-structure * uranium-compounds * self -absorption * moments Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.664, year: 2013

  16. Magnetic and Random Anisotropy Studies in some Amorphous Fe-Based Compounds

    Science.gov (United States)

    Tlemçani, Mohamed; Benbachir, Khadija; Sayouri, Salaheddine; Meknassi, K.; Kadiri, H.

    2000-12-01

    We have studied the magnetization of melt spun amorphous Fe100-x-yCrx(PCSi)y alloys with 4≤x≤11 and 19≤y≤22 under magnetic fields up to 18 kOe, and have analyzed the results at 10 K in the framework of the phenomenological model of Chudnovsky and Serota. Behaviour of magnetic moment and exchange and anisotropy constants has been compared to that of the same parameters in amorphous FeNi(BSi), FeNiCr(BSi) and FeV(BSi).

  17. 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

  18. Magnetic compound refractive lens for focusing and polarizing cold neutron beams

    International Nuclear Information System (INIS)

    Littrell, K. C.; Velthuis, S. G. E. te; Felcher, G. P.; Park, S.; Kirby, B. J.; Fitzsimmons, M. R.

    2007-01-01

    Biconcave cylindrical lenses are used to focus beams of x rays or neutrons using the refractive properties of matter. In the case of neutrons, the refractive properties of magnetic induction can similarly focus and simultaneously polarize the neutron beam without the concomitant attenuation of matter. This concept of a magnetic refractive lens was tested using a compound lens consisting of 99 pairs of cylindrical permanent magnets. The assembly successfully focused the intensity of a white beam of cold neutrons of one spin state at the detector, while defocusing the other. This experiment confirmed that a lens of this nature may boost the intensity locally by almost an order of magnitude and create a polarized beam. An estimate of the performance of a more practically dimensioned device suitable for incorporation in reflectometers and slit-geometry small angle scattering instruments is given

  19. Magnetic compound refractive lens for focusing and polarizing cold neutron beams.

    Science.gov (United States)

    Littrell, K C; te Velthuis, S G E; Felcher, G P; Park, S; Kirby, B J; Fitzsimmons, M R

    2007-03-01

    Biconcave cylindrical lenses are used to focus beams of x rays or neutrons using the refractive properties of matter. In the case of neutrons, the refractive properties of magnetic induction can similarly focus and simultaneously polarize the neutron beam without the concomitant attenuation of matter. This concept of a magnetic refractive lens was tested using a compound lens consisting of 99 pairs of cylindrical permanent magnets. The assembly successfully focused the intensity of a white beam of cold neutrons of one spin state at the detector, while defocusing the other. This experiment confirmed that a lens of this nature may boost the intensity locally by almost an order of magnitude and create a polarized beam. An estimate of the performance of a more practically dimensioned device suitable for incorporation in reflectometers and slit-geometry small angle scattering instruments is given.

  20. Magnetic Properties of the S=2 Heisenberg Antiferromagnetic Chain Compound MnCl3(bpy)

    International Nuclear Information System (INIS)

    Hagiwara, M; Idutsu, Y; Honda, Z; Yamamoto, S

    2012-01-01

    We report the results of magnetic susceptibilities at temperatures between 2 and 300 K, and magnetization in magnetic fields of up to 52 T on polycrystalline samples of MnCl 3 (bpy) (bpy=2, 2'-bipyridine) and the comparison with numerical calculations. This compound is one of the rare examples of the spin 2 quasi-one-dimensional Heisenberg antiferromagnet, and the magnetic properties of tiny single crystal samples were reported previously. The temperature dependence of magnetic susceptibility and the magnetization curve after subtracting the contribution of magnetic impurity are well fitted to those calculated by a quantum Monte Carlo method with the intrachain exchange constant J/k B =31.2 K and the g-value g=2.02 which are comparable to reported values (J/k B =34.8±1.6 K and g=2.04±0.04).

  1. The phase diagrams and the order parameters of the diluted transverse superlattice with antiferromagnetic interface coupling

    International Nuclear Information System (INIS)

    Oubelkacem, A.; El Aouad, N.; Benaboud, A.; Saber, M.

    2004-01-01

    Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation functions, the magnetic properties of the Ising superlattice consisting of two ferromagnetic materials A and B, with L a layers of diluted spins S a =((1)/(2)) and L b layers of diluted spins S b =1 in an applied transverse field Ω with antiferromagnetic interface coupling are examined. For fixed values of the reduced exchange interactions and the concentration c of magnetic atoms, the phase diagrams and the total magnetization for the superlattice are studied as a function of the transverse field and the temperature. We find a number of characteristic phenomena. In particular, the effect of the concentration c of magnetic atoms, the interlayer coupling and the transverse field on both the compensation temperature and the magnetization profiles are clarified. Some of them may be related to the experimental works of rare-earth (RE)/transition metal (TM) multilayer films

  2. Study of magnetic structure of neptunium compounds: Np As, Np Sb, Np Se et Np Ru2 Si2

    International Nuclear Information System (INIS)

    Bonnisseau, D.

    1987-11-01

    Magnetic behavior and localization of 5f electrons in actinide compounds is studied experimentally by Moessbauer spectroscopy and neutron diffraction. Binary actinide compounds with a NaCl structure are examined and properties of U, Pu and Np monopnictides and monochalcogenides are recalled. Results of neutron diffraction by NpAs and NpSb are discussed and results of magnetic susceptibility, magnetization, Moessbauer spectroscopy and neutron diffraction measurements on NpSe and NpTe are presented. Magnetic properties of NpRu 2 Si 2 are also presented. Heavy fermion system electronic and magnetic properties are described and theory is discussed. Electronic and magnetic properties of CeCu 2 Si 2 , CeRu 2 Si 2 and URu 2 Si 2 are compared to NpRu 2 Si 2 which has the same crystal structure [fr

  3. X-ray magnetic circular dichroism in (Ge,Mn) compounds: Experiments and modeling

    International Nuclear Information System (INIS)

    Tardif, Samuel; Titov, Andrey; Arras, Emmanuel; Slipukhina, Ivetta; Hlil, El-Kébir; Cherifi, Salia; Joly, Yves; Jamet, Matthieu; Barski, André; Cibert, Joël; Kulatov, Erkin; Uspenskii, Yurii A.; Pochet, Pascal

    2014-01-01

    X-ray absorption (XAS) and x-ray magnetic circular dichroism (XMCD) spectra at the L 2,3 edges of Mn in (Ge,Mn) compounds have been measured and are compared to the results of first principles calculation. Early ab initio studies show that the Density Functional Theory (DFT) can very well describe the valence band electronic properties but fails to reproduce a characteristic change of sign in the L 3 XMCD spectrum of Mn in Ge 3 Mn 5 , which is observed in experiments. In this work we demonstrate that this disagreement is partially related to an underestimation of the exchange splitting of Mn 2p core states within the local density approximation. It is shown that the change in sign experimentally observed is reproduced if the exchange splitting is accurately calculated within the Hartree–Fock approximation, while the final states can be still described by the DFT. This approach is further used to calculate the XMCD in different (Ge,Mn) compounds. It demonstrates that the agreement between experimental and theoretical spectra can be improved by combining state of the art calculations for the core and valence states respectively. - Highlights: • X-ray absorption and magnetic circular dichroism spectra are measured and compared to first principles calculations in (Ge,Mn) compounds. • Standard density functional theory fails in properly describing peculiar features observed in the experiment. • A new approach to calculate theoretical X-ray absorption and magnetic circular dichroism spectra is proposed. • Improved modeling of the core levels splitting using the Hartree–Fock approximation allows for a better matching with the experiment. • This new method could be generalized to any 3d metallic-like system

  4. Effects of Ga substitution on the structural and magnetic properties of half metallic Fe{sub 2}MnSi Heusler compound

    Energy Technology Data Exchange (ETDEWEB)

    Pedro, S. S., E-mail: sandrapedro@uerj.br; Caraballo Vivas, R. J.; Andrade, V. M.; Cruz, C.; Paixão, L. S.; Contreras, C.; Costa-Soares, T.; Rocco, D. L.; Reis, M. S. [Instituto de Física, Universidade Federal Fluminense, Niterói-RJ (Brazil); Caldeira, L. [IF Sudeste MG, Campus Juiz de Fora - Núcleo de Física, Juiz de Fora-MG (Brazil); Coelho, A. A. [Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas - Unicamp, Campinas-SP (Brazil); Carvalho, A. Magnus G. [Laboratório Nacional de Luz Sincrotron, CNPEM, Campinas-SP (Brazil)

    2015-01-07

    The so-called half-metallic magnets have been proposed as good candidates for spintronic applications due to the feature of exhibiting a hundred percent spin polarization at the Fermi level. Such materials follow the Slater-Pauling rule, which relates the magnetic moment with the valence electrons in the system. In this paper, we study the bulk polycrystalline half-metallic Fe{sub 2}MnSi Heusler compound replacing Si by Ga to determine how the Ga addition changes the magnetic, the structural, and the half-metal properties of this compound. The material does not follow the Slater-Pauling rule, probably due to a minor structural disorder degree in the system, but a linear dependence on the magnetic transition temperature with the valence electron number points to the half-metallic behavior of this compound.

  5. A new wire fabrication processing using high Ga content Cu-Ga compound in V3Ga compound superconducting wire

    International Nuclear Information System (INIS)

    Hishinuma, Yoshimitsu; Nishimura, Arata; Kikuchi, Akihiro; Iijima, Yasuo; Takeuchi, Takao

    2007-01-01

    A superconducting magnet system is also one of the important components in an advanced magnetic confinement fusion reactor. Then it is required to have a higher magnetic field property to confine and maintain steady-sate burning deuterium (D)-tritium (T) fusion plasma in the large interspace during the long term operation. Burning plasma is sure to generate 14 MeV fusion neutrons during deuterium-tritium reaction, and fusion neutrons will be streamed and penetrated to superconducting magnet through large ports with damping neutron energy. Therefore, it is necessary to consider carefully not only superconducting property but also neutron irradiation property in superconducting materials for use in a future fusion reactor, and a 'low activation and high field superconducting magnet' will be required to realize the fusion power plant beyond International Thermonuclear Experimental Reactor (ITER). V-based superconducting material has a much shorter decay time of induced radioactivity compared with the Nb-based materials. We thought that the V 3 Ga compound was one of the most promising materials for the 'low activation and higher field superconductors' for an advanced fusion reactor. However, the present critical current density (J c ) property of V 3 Ga compound wire is insufficient for apply to fusion magnet applications. We investigated a new route PIT process using a high Ga content Cu-Ga compound in order to improve the superconducting property of the V 3 Ga compound wire. (author)

  6. Band magnetism due to f-electrons

    International Nuclear Information System (INIS)

    Brodsky, M.B.; Trainor, R.J.

    1976-01-01

    Specific heat data illustrate several types of itinerant or band magnetism in actinide intermetallic compounds. The results show ferromagnetic spin fluctuations in UAl 2 with T/sub sf/ equals 25K, itinerant antiferromagnetism in NpSn 3 with T/sub N/ equals 9.5K and itinerant ferromagnetism in NpOs 2 with T/sub C/ equals 7.9K. Specific heat studies of dilute U/sub 1-x/Th/sub x/Al 2 show the theoretically predicted modifications due to impurity scattering in a spin fluctuation system. For NpSn 3 it is possible to show the BCS nature of the transition due to the gap formation

  7. Theoretical investigation of the electronic and magnetic properties of TM (TM=Ti, V, and Cr)-doped w-BN compound

    Energy Technology Data Exchange (ETDEWEB)

    Jiménez, Gladys Casiano; López, César Ortega [Grupo Avanzado de Materiales y Sistemas Complejos GAMASCO, Universidad de Córdoba, Montería (Colombia); Espitia R, Miguel J., E-mail: mespitiar@udistrital.edu.co [Grupo GEFEM, Universidad Distrital Francisco José de Caldas, Bogotá (Colombia)

    2016-03-15

    The electronic and magnetic properties of w-BN compound doped with Ti, V, and Cr atoms are calculated by means of the pseudopotential method, employed exactly as implemented in computational Quantum ESPRESSO code. For the description of the electron-electron interaction, generalized gradient approximation (GGA) was used. A half-metallic behavior is predicted for the concentrations B{sub 0.9375}Ti{sub 0.0625}N, B{sub 0.9375}V{sub 0.0625}N, and B{sub 0.9375}Cr{sub 0.0625}N, because of the fact that the majority spins are metallic and the minority spins are semiconducting. We found magnetic moments of 1.0, 2.0 and 3.0 µ{sub β} per supercell, respectively. The main contribution to the magnetic moment mainly comes from the transition metals Ti, V, and Cr, with partialmoments of 0.88 µ{sub β}, 1.75 µ{sub β}, and 2.65 µ{sub β}, respectively. These compounds are good candidates for potential applications in spintronic and as spin injectors. - Highlights: • The B{sub 0.9375}Ti{sub 0.0625}N, B{sub 0.9375}V{sub 0.0625}N, and B{sub 0.9375}Cr{sub 0.0625}N compounds has a magnetic properties. • The magnetic moment for compounds are 1.0, 2.0 and 3.0 µ{sub β} per supercell, respectively. • The magnetic moment mainly comes from the transition metals Ti, V, and Cr, with local moments of 0.88 µ{sub β}, 1.75 µ{sub β}, and 2.65 µ{sub β}, respectively. • The compounds have a half-metallic behavior.

  8. Pressure effects on crystal structures and magnetic properties of RCo{sub 5} (R = Y or Gd) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Burzo, E. [Faculty of Physics, Babes-Bolyai University Cluj-Napoca 400084 (Romania); Vlaic, P. [Faculty of Physics, Babes-Bolyai University Cluj-Napoca 400084 Romania and University of Medicine and Pharmacy Iuliu Hatieganu, Physics and Biophysics Department Cluj-Napoca (Romania)

    2013-11-13

    The pressure dependences of crystal structures and magnetic properties of YCo{sub 5} and GdCo{sub 5} compounds are analysed based on band structure calculations. Isomorphic transitions were evidenced for relative volumes v/v{sub 0} = 0.91 and 0.86, for YCo{sub 5} and GdCo{sub 5}, respectively. At the transition, there is a higher decrease of cobalt moments at 3g sites as compared to those located in 2c ones. The induced polarizations on Y4d and Gd5d bands, by short range interactions, are linearly dependent on the magnetizations of cobalt atoms situated in their neighborhood. The isomorphic transitions are analysed in correlations with band structures.

  9. Fe based amorphous and compounds metallic alloys for magnetic and structural use

    International Nuclear Information System (INIS)

    Lavorato, G; Bassi, F; De Rosa, H; Moya, J

    2008-01-01

    Massive amorphous metals (thicker than 1mm) are new types of material that could have a wide range of future applications due to a unique combination of their physical properties, mechanics and magnetics. Among these are the elevated tension of fracture and hardness, and excellent soft magnetic properties. Since 1960, when an amorphous metallic alloy was first discovered, progress has continued on the application possibilities for these materials. One of their main limitations, maximum obtainable thickness, has continued to increase, since at first thicknesses of a few microns were obtained. Now amorphous alloys more than 70 mm thick are obtained using different metallic elements. Since 1995 massive amorphous metals can be produced using Fe as the base element. At first they were made in order to achieve good soft magnetic properties (thicknesses of ∼5 mm) and later a renewed interest in their use as structural material led to the development of materials with thicknesses of 16 mm and paramagnetics at room temperature. Increasing the toughness of these materials is also a challenge and investigators have proposed several solutions, among them is the development of composite materials where dendrites from a solid solution act as crack stoppers of fissures that are spread by an amorphous matrix. This work presents the results of studies with two types of synthesized materials using the rapid cooling technique from injection copper mold casting at air temperature: 1) a massive amorphous metallic alloy with composition (Fe 0.375 Co 0 .375 B 0.2 Si 0.05 )96Nb 4 (at.%) and 2) a composite of solid solution dendrites α-(FeCo) scattered in an amorphous matrix with a composition similar to alloy 1. Using the samples obtained structural studies were made (optic and electronic microscopy SEM, XRD, EDAX, DTA), magnetic studies (coercive field and saturation magnetization) and mechanical studies (Vickers microhardness). The fully amorphous alloy could be obtained with a

  10. Acetone and acetaldehyde determination in tomato juice by isotopic dilution

    International Nuclear Information System (INIS)

    Piva, M.-T.; Crouzet, J.

    1977-01-01

    Acetone and acetaldehyde content of tomato juice were determined by isotope dilution techniques. The juice is added to 14 C labelled compounds, carried along by nitrogen at low pressure. The mixture of 2.4 dinitrophenylhydrazones obtained from volatile compounds is separated by thin layer chromatography on silica gel and then on alumina. A determination of radioactivity and concentration of acetone and acetaldehyde 2,4 dinitrophenylhydrazones obtained after separation and elution allow to calculate the content of these two compounds in the initial product with the same sample. This technique could be used for determination of methanol and ethanol after transformation in 3,5 dinitrobenzoates [fr

  11. Prediction of compounds with electric and magnetic ordering

    Energy Technology Data Exchange (ETDEWEB)

    Nikiforov, L G [Rybinskij Aviatsionnyj Tekhnologicheskij Inst. (USSR)

    1979-03-01

    The possibility of polymorphic transformations from the structure of the pyrochlore type into that of the perovskite type for nine lead-containing compounds has been forecast. Some of them (PbTaO/sub 3/, Pb/sub 2/NiTaO/sub 6/, Pb/sub 2/MnTaO/sub 6/, Pb/sub 2/SmTaO/sub 6/) are expected to have, in addition to common for all lead-containing perovskites ferro-or antiferro-electric properties, specific magnetic properties. The periods of elementary cells of new perovskites are forecast. The possibility of considerable reduction of the number of errors when searching thermodynamical parameters of transformation has been shown.

  12. Synthesis and magnetic structure of the YbMn{sub 2}Sb{sub 2} compound

    Energy Technology Data Exchange (ETDEWEB)

    Morozkin, A.V. [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation)]. E-mail: morozkin@general.chem.msu.ru; Isnard, O. [Institute Laue-Langevin, 6 Rue J. Horowitz, 38042 Grenoble (France); Henry, P. [Institute Laue-Langevin, 6 Rue J. Horowitz, 38042 Grenoble (France); Granovsky, S. [Physics Department, Moscow State University, GSP-2, 119899 Moscow (Russian Federation); Nirmala, R. [Indian Institute of Science, Bangalore (India); Manfrinetti, P. [Dipartimento di Chimica, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy)

    2006-08-31

    A neutron diffraction investigation has been carried out on the trigonal La{sub 2}O{sub 3}-type (hP5, space group P3-bar ml, No. 164; also CaAl{sub 2}Si{sub 2}-type) YbMn{sub 2}Sb{sub 2} intermetallic. A two-step synthesis route has been tried in this work, and successfully utilised to prepare single phase samples of this compound. This study shows that YbMn{sub 2}Sb{sub 2} presents antiferromagnetic ordering below 120K. The magnetic structure of this intermetallic consists of antiferromagnetically coupled magnetic moments of the manganese atoms, in the Mn1 (1/3, 2/3, Z{sub Mn}) and Mn2 (2/3, 1/3, 1-Z{sub Mn}) sites; the direction of magnetic moments of manganese atoms forming a {phi} and a {theta} angle, respectively with the X- and the Z-axis. At 4K the magnetic moment of the Mn1 atom is {mu}{sub Mn}=3.6(1) {mu}{sub B}, with {phi}=0{sup o} and {theta}=62(4){sup o}, whilst the Mn2 atom has a magnetic moment {mu}{sub Mn}=3.6(1) {mu}{sub B}, with {phi}=0{sup o} and {theta}=242(4){sup o}. On the other hand, in this compound no local moment was detected on the Yb site.

  13. Magnetic anisotropy of pure and doped YbInCu sub 4 compounds at ambient and high pressures

    CERN Document Server

    Mushnikov, N V; Rozenfeld, E V; Yoshimura, K; Zhang, W; Yamada, M; Kageyama, H

    2003-01-01

    The susceptibility and high-field magnetization of single-crystalline Yb sub 1 sub - sub x Y sub x InCu sub 4 (x = 0, 0.2 and 0.3) samples have been measured for different field orientations at ambient and high pressures. The compounds with x = 0 and 0.2 undergo a first-order valence transition from the intermediate-valence state to the trivalent state on increasing either temperature or magnetic field. The magnetization and susceptibility of these compounds have appreciable anisotropy in both states. The magnetic phase diagram of Yb sub 1 sub - sub x Y sub x InCu sub 4 determined at ambient pressure is also anisotropic, which is explained by the crystal-field calculations for the free Yb ion in the high-temperature phase. Moreover, the low-temperature magnetization process for x = 0.2 and 0.3 has been measured in low fields under high pressure; it shows anisotropic ferromagnetic ordering.

  14. Magnetic structure of the YbMn2SbBi compound

    International Nuclear Information System (INIS)

    Morozkin, A.V.; Manfrinetti, P.

    2011-01-01

    Graphical abstract: Display Omitted Research highlights: → A neutron diffraction investigation in zero applied field of La 2 O 2 S-type YbMn 2 SbBi shows antiferromagnetic ordering below 138(3) K and ferrimagnetic ordering below 112(3) K. → Between 138 and 112 K, the magnetic structure of YbMn 2 SbBi consists of antiferromagnetically coupled ab-plane magnetic moments of the manganese atoms (D 1d magnetic point group). → Below 112(3) K, the magnetic structure of YbMn 2 SbBi becames the sum antiferromagnetic component with D 1d magnetic point group and ferromagnetic one with C 2 magnetic point group. → The magnitude of Yb and Mn magnetic moments in YbMn 2 SbBi at 2 K (M Yb = 3.6(2) μ B , M Mn = 3.5(2) μ B ) correspond to the trivalent state of the Yb ions and tetravalent state of the Mn ions. - Abstract: A neutron diffraction investigation has been carried out on the trigonal La 2 O 2 S-type (hP5, space group P3-bar ml, No. 164; also CaAl 2 Si 2 -type) YbMn 2 SbBi intermetallic compound. The YbMn 2 SbBi presents antiferromagnetic ordering below 138(3) K and ferrimagnetic ordering below 112(3) K. Between 138 and 112 K, the magnetic structure of YbMn 2 SbBi consists of antiferromagnetically coupled ab-plane magnetic moments of the manganese atoms (D 1d magnetic point group). Below 112(3) K, the ferromagnetic components of Yb and Mn begin to develop, and the magnetic structure of YbMn 2 SbBi becames the sum antiferromagnetic component with D 1d magnetic point group and ferromagnetic one with C 2 magnetic point group. The magnitude of Yb and Mn magnetic moments in YbMn 2 SbBi at 2 K (M Yb = 3.6(2) μ B , M Mn = 3.5(2) μ B ) correspond to the trivalent state of the Yb ions and tetravalent state of the Mn ions.

  15. Electronically- and crystal-structure-driven magnetic structures and physical properties of RScSb (R = rare earth) compounds. A neutron diffraction, magnetization and heat capacity study

    Energy Technology Data Exchange (ETDEWEB)

    Ritter, C [Institut Lauer-Langevin, Grenoble (France); Dhar, S K [TIFR, Mumbai (India); Kulkarni, R [TIFR, Mumbai (India); Provino, A [Inst. SPIN-CNR, Genova (Italy); Univ. of Genova (Italy); Ames Lab., Ames, IA (United States); Paudyal, Durga [Ames Lab., Ames, IA (United States); Manfrinetti, Pietro [Inst. SPIN-CNR, Genova (Italy); Univ. of Genova (Italy); Ames Lab., Ames, IA (United States); Gschneidner, Karl A [Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States)

    2014-08-14

    The synthesis of the new equiatomic RScSb ( R = La-Nd, Sm, Gd-Tm, Lu, Y) compounds has been recently reported. These rare earth compounds crystallize in two different crystal structures, adopting the CeScSi-type ( I 4/ mmm) for the lighter R (La-Nd, Sm) and the CeFeSi-type (P4 /nmm) structure for the heavier R ( R = Gd-Tm, Lu, Y). Here we report the results of neutron diffraction, magnetization and heat capacity measurements on some of these compounds ( R = Ce, Pr, Nd, Gd and Tb). Band structure calculations have also been performed on CeScSb and GdScGe (CeScSi-type), and on GdScSb and TbScSb (CeFeSi-type) to compare and understand the exchange interactions in CeScSi and CeFeSi structure types. The neutron diffraction investigation shows that all five compounds order magnetically, with the highest transition temperature of 66 K in TbScSb and the lowest of about 9 K in CeScSb. The magnetic ground state is simple ferromagnetic (τ = [0 0 0]) in CeScSb, as well in NdScSb for 32 >T > 22 K. Below 22 K a second magnetic transition, with propagation vector τ = [¼ ¼ 0], appears in NdScSb. PrScSb has a magnetic structure within, determined by mostly ferromagnetic interactions and antiferromagnetic alignment of the Pr-sites connected through the I-centering ( τ = [1 0 0]). A cycloidal spiral structure with a temperature dependent propagation vector τ = [δ δ ½] is found in TbScSb. The results of magnetization and heat capacity lend support to the main conclusions derived from neutron diffraction. As inferred from a sharp peak in magnetization, GdScSb orders antiferromagnetically at 56 K. First principles calculations show lateral shift of spin split bands towards lower energy from the Fermi level as the CeScSi-type structure changes to the CeFeSi-type structure. This rigid shift may force the system to transform from exchange split ferromagnetic state to the antiferromagnetic state in RScSb compounds (as seen for example in GdScSb and TbScSb) and is proposed to

  16. Method for preparing high cure temperature rare earth iron compound magnetic material

    Science.gov (United States)

    Huang, Yuhong; Wei, Qiang; Zheng, Haixing

    2002-01-01

    Insertion of light elements such as H,C, or N in the R.sub.2 Fe.sub.17 (R=rare earth metal) series has been found to modify the magnetic properties of these compounds, which thus become prospective candidates for high performance permanent magnets. The most spectacular changes are increases of the Curie temperature, T.sub.c, of the magnetization, M.sub.s, and of coercivity, H.sub.c, upon interstitial insertion. A preliminary product having a component R--Fe--C,N phase is produced by a chemical route. Rare earth metal and iron amides are synthesized followed by pyrolysis and sintering in an inert or reduced atmosphere, as a result of which, the R--Fe--C,N phases are formed. Fabrication of sintered rare earth iron nitride and carbonitride bulk magnet is impossible via conventional process due to the limitation of nitridation method.

  17. Dilution effects on combined magnetic and electric dipole interactions: A study of ferromagnetic cobalt nanoparticles with tuneable interactions

    Science.gov (United States)

    Hod, M.; Dobroserdova, A.; Samin, S.; Dobbrow, C.; Schmidt, A. M.; Gottlieb, M.; Kantorovich, S.

    2017-08-01

    Improved understanding of complex interactions between nanoparticles will facilitate the control over the ensuing self-assembled structures. In this work, we consider the dynamic changes occurring upon dilution in the self-assembly of a system of ferromagnetic cobalt nanoparticles that combine magnetic, electric, and steric interactions. The systems examined here vary in the strength of the magnetic dipole interactions and the amount of point charges per particle. Scattering techniques are employed for the characterization of the self-assembly aggregates, and zeta-potential measurements are employed for the estimation of surface charges. Our experiments show that for particles with relatively small initial number of surface electric dipoles, an increase in particle concentration results in an increase in diffusion coefficients; whereas for particles with relatively high number of surface dipoles, no effect is observed upon concentration changes. We attribute these changes to a shift in the adsorption/desorption equilibrium of the tri-n-octylphosphine oxide (TOPO) molecules on the particle surface. We put forward an explanation, based on the combination of two theoretical models. One predicts that the growing concentration of electric dipoles, stemming from the addition of tri-n-octylphosphine oxide (TOPO) as co-surfactant during particle synthesis, on the surface of the particles results in the overall repulsive interaction. Secondly, using density functional theory, we explain that the observed behaviour of the diffusion coefficient can be treated as a result of the concentration dependent nanoparticle self-assembly: additional repulsion leads to the reduction in self-assembled aggregate size despite the shorter average interparticle distances, and as such provides the growth of the diffusion coefficient.

  18. Electronic response of rare-earth magnetic-refrigeration compounds GdX2 (X = Fe and Co)

    Science.gov (United States)

    Bhatt, Samir; Ahuja, Ushma; Kumar, Kishor; Heda, N. L.

    2018-05-01

    We present the Compton profiles (CPs) of rare-earth-transition metal compounds GdX2 (X = Fe and Co) using 740 GBq 137Cs Compton spectrometer. To compare the experimental momentum densities, we have also computed the CPs, electronic band structure, density of states (DOS) and Mulliken population (MP) using linear combination of atomic orbitals (LCAO) method. Local density and generalized gradient approximations within density functional theory (DFT) along with the hybridization of Hartree-Fock and DFT (B3LYP and PBE0) have been considered under the framework of LCAO scheme. It is seen that the LCAO-B3LYP based momentum densities give a better agreement with the experimental data for both the compounds. The energy bands and DOS for both the spin-up and spin-down states show metallic like character of the reported intermetallic compounds. The localization of 3d electrons of Co and Fe has also been discussed in terms of equally normalized CPs and MP data. Discussion on magnetization using LCAO method is also included.

  19. Enhancement of two photon absorption with Ni doping in the dilute magnetic semiconductor ZnO crystalline nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Rana, Amit Kumar; Kumar, Yogendra; Arjunan, M.S.; Sen, Somaditya; Shirage, Parasharam M., E-mail: pmshirage@iiti.ac.in, E-mail: paras.shirage@gmail.com [Department of Physics, Indian Institute of Technology Indore, Simrol Campus, Khandwa Road, Indore 452020 (India); Centre of Materials Science and Engineering, Indian Institute of Technology Indore, Simrol Campus, Khandwa Road, Indore 452020 (India); J, Aneesh; Adarsh, K. V. [Department of Physics, Indian Institute of Science Education and Research, Bhopal 462023 (India)

    2015-12-07

    In this letter, we have investigated the third-order optical nonlinearities of high-quality Ni doped ZnO nanorods crystallized in wurtzite lattice, prepared by the wet chemical method. In our experiments, we found that the two photon absorption coefficient (β) increases by as much as 14 times, i.e., 7.6 ± 0.4 to 112 ± 6 cm/GW, when the Ni doping is increased from 0% to 10%. The substantial enhancement in β is discussed in terms of the bandgap scaling and Ni doping. Furthermore, we also show that the optical bandgap measured by UV-Vis and photoluminescence spectroscopies, continuously redshift with increasing Ni doping concentration. We envision that the strong nonlinear optical properties together with their dilute magnetic effects, they form an important class of materials for potential applications in magneto-optical and integrated optical chips.

  20. Enhancement of two photon absorption with Ni doping in the dilute magnetic semiconductor ZnO crystalline nanorods

    International Nuclear Information System (INIS)

    Rana, Amit Kumar; Kumar, Yogendra; Arjunan, M.S.; Sen, Somaditya; Shirage, Parasharam M.; J, Aneesh; Adarsh, K. V.

    2015-01-01

    In this letter, we have investigated the third-order optical nonlinearities of high-quality Ni doped ZnO nanorods crystallized in wurtzite lattice, prepared by the wet chemical method. In our experiments, we found that the two photon absorption coefficient (β) increases by as much as 14 times, i.e., 7.6 ± 0.4 to 112 ± 6 cm/GW, when the Ni doping is increased from 0% to 10%. The substantial enhancement in β is discussed in terms of the bandgap scaling and Ni doping. Furthermore, we also show that the optical bandgap measured by UV-Vis and photoluminescence spectroscopies, continuously redshift with increasing Ni doping concentration. We envision that the strong nonlinear optical properties together with their dilute magnetic effects, they form an important class of materials for potential applications in magneto-optical and integrated optical chips

  1. Atomic and magnetic structure of MnF3

    International Nuclear Information System (INIS)

    Hunter, B.A.; Kennedy, B.J.; Vogt, T.

    2003-01-01

    Full text: The magnetic and atomic structure of MnF 3 has been determined from 4K to 300K using neutron powder diffraction. The MnF 3 compound is the archetypical Mn-based colossal magnetoresistive compound. A Neel temperature of approximately 40K was observed from the temperature variation of the magnetic moment. Below the Neel temperature a large negative thermal expansion was observed, in striking similarity to other Mn-based colossal magnetoresistive compounds. The variation in structure is discussed in relation to other Mn-based compounds, particularly as this compound cannot support charge ordering

  2. High-throughput ab-initio dilute solute diffusion database.

    Science.gov (United States)

    Wu, Henry; Mayeshiba, Tam; Morgan, Dane

    2016-07-19

    We demonstrate automated generation of diffusion databases from high-throughput density functional theory (DFT) calculations. A total of more than 230 dilute solute diffusion systems in Mg, Al, Cu, Ni, Pd, and Pt host lattices have been determined using multi-frequency diffusion models. We apply a correction method for solute diffusion in alloys using experimental and simulated values of host self-diffusivity. We find good agreement with experimental solute diffusion data, obtaining a weighted activation barrier RMS error of 0.176 eV when excluding magnetic solutes in non-magnetic alloys. The compiled database is the largest collection of consistently calculated ab-initio solute diffusion data in the world.

  3. On-chip broadband magnetic resonance spectroscopy down to ultralow temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Clauss, Conrad

    2014-12-03

    This thesis presents a novel technical realization to perform electron paramagnetic resonance (EPR) based on superconducting coplanar waveguides (CPWs) and superconducting CPW resonators. This technique allows for the investigation of magnetic properties of the material under study at basically any arbitrary frequency. The compact design radically facilitates the implementation into dilution refrigerators to probe the samples at temperatures in the milli Kelvin regime. The working principle of the devices is explained and further substantiated by analytical calculations and 3D-electromagnetic (EM) simulations of the microwave EM fields of the given chip structures. The proof of principle was demonstrated on an organic radical with spin 1/2 and on a ruby single crystal with S=3/2, as a more complex spin system. The technique was then utilized to characterize a Gd-based single-ion magnet and to investigate the magnetic properties of the ground states of a heavy-fermion metal. Both materials were studied in detail at temperatures as low as 40 mK, far below the typical low-temperature limit of conventional EPR equipment at around 1 K. The results of the heavy-fermion compound reveal intriguing behavior of the spin-relaxation mechanisms and local magnetic fields at the lowest achievable temperatures and at the phase transitions and crossover regimes of the phase diagram. The thesis is a pioneering work outlining the great potential regarding the range of applicability of the introduced technique and provides a starting point for future improvements and further functional enhancements.

  4. Electron paramagnetic resonance studies of defects in dilute magnetic alloys

    International Nuclear Information System (INIS)

    Suss, J.T.; Raizman, A.

    1980-01-01

    The EPR spectrum of erbium was used to study the effects of cold-working (rolling and mechanical polishing) in dilute gold-erbium alloys. Variation in the EPR linewidth, intensity and asymmetry parameter (A/B ratio) were investigated. Most of the results could be interpreted in terms of segregation of erbium ions to subgrain boundaries (dislocations) in a surface layer of a few thousand Angstroms. (author)

  5. Extended Le Chatelier's formula for carbon dioxide dilution effect on flammability limits.

    Science.gov (United States)

    Kondo, Shigeo; Takizawa, Kenji; Takahashi, Akifumi; Tokuhashi, Kazuaki

    2006-11-02

    Carbon dioxide dilution effect on the flammability limits was measured for various flammable gases. The obtained values were analyzed using the extended Le Chatelier's formula developed in a previous study. As a result, it has been found that the flammability limits of methane, propane, propylene, methyl formate, and 1,1-difluoroethane are adequately explained by the extended Le Chatelier's formula using a common set of parameter values. Ethylene, dimethyl ether, and ammonia behave differently from these compounds. The present result is very consistent with what was obtained in the case of nitrogen dilution.

  6. Powder metallurgical processing of magnetostrictive materials based on rare earth-iron intermetallic compounds

    International Nuclear Information System (INIS)

    Malekzadeh, M.

    1978-01-01

    Procedures are described for fabrication of high density rare earth-iron magnetostrictive compounds by powder metallurgical techniques. The fabrication involves a sequence of steps which includes preparing the pre-alloyed compounds, pulverizing them into a fine powder, compacting in suitable sizes and shapes, and sintering. Samples prepared by these procedures are carefully characterized by scanning electron microscopy, x-ray diffraction, dilatometry, and magnetic measurements. Process steps are found to exert important influences upon densities, microstructure and magnetic properties attained after densification. Investigations on a number of these process steps, including milling time and medium, sintering, and magnetic powder alignment are described

  7. Viability and fertility of cooled equine semen diluted with skimmed milk or glycine egg yolk-based extenders

    Directory of Open Access Journals (Sweden)

    Guilherme Pugliesi

    2012-12-01

    Full Text Available Two semen extenders were compared for their ability to maintain viability of horse semen during 24 hours of cold preservation, and for the pregnancy rate after artificial insemination. In the experiment 1, five ejaculates from three stallions were split-diluted in either a skimmed milk-based extender (Kenney extender or a glycine egg yolk-based extender (Foote extender and cooled at 6-8 ºC for 24 hours. Semen samples stored in Kenney extender for 24 hours had higher motility and spermatic vigor compared with those stored in Foote extender. However, samples stored in Foote extender had higher number of reactive sperm by hypoosmotic test and greater viability by epifluorescence test compared with those in Kenney extender. In the experiment 2, 17 and 23 ejaculates from two stallions were split-diluted with Kenney extender and Foote extender. The sperm concentration in each extender was adjusted to 500 million viable sperms per insemination dose. Semen was cooled to 6-8 ºC and stored for 24 hours. Seventy-four cycles of crossbred mares were inseminated with either semen diluted in Kenney extender or semen diluted in Foote extender. The pregnancy rate was higher from semen diluted in Kenney extender than that from semen in Foote extender (0.553 vs. 0.306. The Kenney extender is effective in preserving the motility, vigor and fertility of stallion semen after 24 hours of cold storage, whereas the Foote extender is not acceptable.

  8. Phase diagrams of diluted transverse Ising nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Bouhou, S.; Essaoudi, I. [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Ainane, A., E-mail: ainane@pks.mpg.de [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Max-Planck-Institut für Physik Complexer Systeme, Nöthnitzer Str. 38 D-01187 Dresden (Germany); Saber, M. [Laboratoire de Physique des Matériaux et Modélisation, des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Max-Planck-Institut für Physik Complexer Systeme, Nöthnitzer Str. 38 D-01187 Dresden (Germany); Ahuja, R. [Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala (Sweden); Dujardin, F. [Laboratoire de Chimie et Physique des Milieux Complexes (LCPMC), Institut de Chimie, Physique et Matériaux (ICPM), 1 Bd. Arago, 57070 Metz (France)

    2013-06-15

    In this paper, the phase diagrams of diluted Ising nanowire consisting of core and surface shell coupling by J{sub cs} exchange interaction are studied using the effective field theory with a probability distribution technique, in the presence of transverse fields in the core and in the surface shell. We find a number of characteristic phenomena. In particular, the effect of concentration c of magnetic atoms, the exchange interaction core/shell, the exchange in surface and the transverse fields in core and in surface shell of phase diagrams are investigated. - Highlights: ► We use the EFT to investigate the phase diagrams of Ising transverse nanowire. ► Ferrimagnetic and ferromagnetic cases are investigated. ► The effects of the dilution and the transverse fields in core and shell are studied. ► Behavior of the transition temperature with the exchange interaction is given.

  9. Magnetic and Electrical Transport Properties of Dirac Compound BaMnSb2*

    Science.gov (United States)

    Huang, Silu; Kim, Jisun; Shelton, William. A.; Plummer, Ward; Jin, Rongying

    BaMnSb2 is a layered compound containing Sb square nets that is theoretically predicted to host Dirac fermions. We have carried out experimental investigations on electrical transport and magnetic properties of BaMnSb2 single crystals. Both in-plane (ρab) and c-axis (ρc) resistivities show metallic behavior with a small bump in ρc located near 40 K, while there is large anisotropy ρc / ρab ( 100 at 300 K) that increases with decreasing temperature to 1500 at 2 K. Interestingly, Shubnikov-de Hass (SdH) oscillations are observed for both ρab and ρc over a wide temperature and magnetic field range. Quantitative analysis indicates that large amplitude SdH oscillations result from nearly massless Dirac Fermions. Furthermore, our magnetic measurements indicate an A-type antiferromagnetic magnetic ordering below 286 K where ferromagnetic ordering is observed in the ab plane with antiferromagnetic coupling along the c direction. These results indicate that BaMnSb2 is a 2D magnetic Dirac material. This work is supported by NSF through Grant Number DMR-1504226.

  10. Calculations of magnetic x-ray dichroism in the 3d absorption spectra of rare-earth compounds

    NARCIS (Netherlands)

    GOEDKOOP, JB; THOLE, BT; VANDERLAAN, G; SAWATZKY, GA; DEGROOT, FMF; FUGGLE, JC; de Groot, Frank|info:eu-repo/dai/nl/08747610X

    1988-01-01

    We present atomic calculations for the recently discovered magnetic x-ray dichroism (MXD) displayed by the 3d x-ray-absorption spectra of rare-earth compounds. The spectral shapes expected at T=0 K for linear polarization parallel and normal to the local magnetic field is given, together with the

  11. The origin of magnetism in anatase Co-doped TiO2 magnetic semiconductors

    NARCIS (Netherlands)

    Lee, Y.J.

    2010-01-01

    Dilute magnetic semiconductors (DMS) can be tailored by doping a small amount of elements containing a magnetic moment into host semiconductors, which leads to a new class of semiconductors with the functionality of tunable magnetic properties. Recently, oxide semiconductors have attained interests

  12. The phase diagrams of the site-diluted spin-1/2 Ising superlattice

    International Nuclear Information System (INIS)

    Saber, A.; Essaoudi, I.; Ainane, A.; Dujardin, F.; Saber, M.; Stebe, B.

    1998-08-01

    Using the effective field theory with a probability distribution technique that accounts for the single-site spin correlations, the critical behavior of a diluted spin-1/2 Ising superlattice consisting of two different ferromagnet materials is examined. The critical temperature of the system is studied as a function of the thickness of the constituents in a unit cell, the concentration of magnetic atoms, and the exchange interactions in each material. It is shown that the properties of the diluted system are different from those of the corresponding pure system. (author)

  13. Local magnetic moments in dilute Cr-Nb alloys: the effects of applied magnetic field and Nb concentration

    International Nuclear Information System (INIS)

    Souza, P E N de; Oliveira, L M de; Ortiz, W A; Camargo, P C de; Oliveira, A J A de

    2005-01-01

    In this work we present magnetic susceptibility results for Cr-x at.% Nb alloys (x = 0.2, 0.6, 0.7, 1.4, and 2.0), showing that a local short-range order spin-density wave (L-SDW) appears at a characteristic temperature (T loc ) above the Neel temperature. The evidence for L-SDW is based on a Curie-Weiss-like behaviour, which is suppressed when large magnetic fields are applied or for alloys with Nb concentration above x = 2.0 at.%

  14. Magnetic properties of the filled skutterudite-type structure compounds GdRu4P12 and TbRu4P12 synthesized under high pressure

    OpenAIRE

    Sekine, C; Uchiumi, T; Shirotani, I; Matsuhira, kazuyuki; Sakakibara, T; Goto, T; Yagi, T

    2000-01-01

    We have succeeded in synthesizing filled skutterudite-type structure compounds GdRu4P12 and TbRu4P12 under high pressure. The magnetic properties of GdRu4P12 and TbRu4P12 have been studied by means of electrical resistivity, magnetic susceptibility, and magnetization measurements. Magnetic experiments suggest that the Gd and Tb ions in the compounds have trivalent state. The compound GdRu4P12 displays features that suggest the occurrence of antiferromagnetic ordering below TN=22 K. In TbRu4P1...

  15. Newly engineered magnetic erythrocytes for sustained and targeted delivery of anti-cancer therapeutic compounds.

    Directory of Open Access Journals (Sweden)

    Caterina Cinti

    Full Text Available Cytotoxic chemotherapy of cancer is limited by serious, sometimes life-threatening, side effects that arise from toxicities to sensitive normal cells because the therapies are not selective for malignant cells. So how can they be selectively improved? Alternative pharmaceutical formulations of anti-cancer agents have been investigated in order to improve conventional chemotherapy treatment. These formulations are associated with problems like severe toxic side effects on healthy organs, drug resistance and limited access of the drug to the tumor sites suggested the need to focus on site-specific controlled drug delivery systems. In response to these concerns, we have developed a new drug delivery system based on magnetic erythrocytes engineered with a viral spike fusion protein. This new erythrocyte-based drug delivery system has the potential for magnetic-controlled site-specific localization and highly efficient fusion capability with the targeted cells. Here we show that the erythro-magneto-HA virosomes drug delivery system is able to attach and fuse with the target cells and to efficiently release therapeutic compounds inside the cells. The efficacy of the anti-cancer drug employed is increased and the dose required is 10 time less than that needed with conventional therapy.

  16. Newly Engineered Magnetic Erythrocytes for Sustained and Targeted Delivery of Anti-Cancer Therapeutic Compounds

    Science.gov (United States)

    Taranta, Monia; Naldi, Ilaria

    2011-01-01

    Cytotoxic chemotherapy of cancer is limited by serious, sometimes life-threatening, side effects that arise from toxicities to sensitive normal cells because the therapies are not selective for malignant cells. So how can they be selectively improved? Alternative pharmaceutical formulations of anti-cancer agents have been investigated in order to improve conventional chemotherapy treatment. These formulations are associated with problems like severe toxic side effects on healthy organs, drug resistance and limited access of the drug to the tumor sites suggested the need to focus on site-specific controlled drug delivery systems. In response to these concerns, we have developed a new drug delivery system based on magnetic erythrocytes engineered with a viral spike fusion protein. This new erythrocyte-based drug delivery system has the potential for magnetic-controlled site-specific localization and highly efficient fusion capability with the targeted cells. Here we show that the erythro-magneto-HA virosomes drug delivery system is able to attach and fuse with the target cells and to efficiently release therapeutic compounds inside the cells. The efficacy of the anti-cancer drug employed is increased and the dose required is 10 time less than that needed with conventional therapy. PMID:21373641

  17. Evaluation and validation of a single-dilution potency assay based upon serology of vaccines containing diphtheria toxoid: statistical analysis

    NARCIS (Netherlands)

    Marsman FR; Akkermans AM; Hendriksen CFM; de Jong WH

    1993-01-01

    This document presents the results of a validation study to the use of a single dilution assay in potency testing of the diphtheria component of DPT-polio vaccines. Based on historical data of multi-dilution assays on 27 consecutive batches a simulation study was performed to test the actual

  18. A comparative study of magnetic field induced meta-magnetic transition in nanocrystalline and bulk Pr0.65(Ca0.7Sr0.3)0.35MnO3 compound

    Science.gov (United States)

    Saha, Suvayan; Das, Kalipada; Bandyopadhyay, Sudipta; Das, I.

    2017-06-01

    In our present study we highlight the observations of external magnetic field induced sharp meta-magnetic transition in polycrystalline bulk as well as nanocrystalline form of Pr0.65(Ca0.7Sr0.7)0.35MnO3 compound. Interestingly, such behavior persists in the nanoparticles regardless of the disorder broadened transition. However, higher magnetic field is required for nanoparticles having average particle size ∼40 nm for such meta-magnetic transition, which differs from the general trends of the pure charge ordered nano materials. The interfacial strain between the different magnetic domains plays the important role in magnetic isothermal properties of nanoparticles, when the samples are cooled down in different cooling field. Additionally, both the bulk and nanoparticle compounds exhibit spontaneous phase separation and significantly large magnetoresistance at the low temperature region due to the melting of charge ordered fraction.

  19. Electronic and magnetic properties of R0.5A0.5MnO3 compounds (R=Gd, Dy, Ho, Er; A=Sr, Ca)

    International Nuclear Information System (INIS)

    Terai, T.; Sasaki, T.; Kakeshita, T.; Fukuda, T.; Saburi, T.; Kitagawa, H.; Kindo, K.; Honda, M.

    2000-01-01

    Electronic and magnetic properties of the perovskitelike compounds of R 0.5 A 0.5 MnO 3 (R=Gd, Dy, Ho, Er; A=Sr, Ca) have been studied by measuring lattice parameter, electrical resistivity, magnetic susceptibility, and magnetization. All the Sr-doped compounds show a transition from a paramagnetic insulator to a spin-glass-like insulator at T g , even though the manganite La 0.5 Ca 0.5 MnO 3 , with nearly the same tolerance factor t, have been shown by others, to have different transitions. On the other hand, all the Ca-doped compounds show a charge-ordering transition at T CO and show a transition from a paramagnetic insulator to a canted antiferromagnetic insulator and/or a spin-glass-like insulator at T CA below T CO . These transition temperatures decrease with decreasing t. In the compound of Gd 0.5 Ca 0.5 MnO 3 , the collapse of the charge ordering has been observed under a pulsed high magnetic field of 45 T at 4.2 K. On the other hand, in the compound of Gd 0.5 Sr 0.5 MnO 3 , the magnetization process depends on the strength of magnetic field. These electronic and magnetic properties depend not only on the tolerance factor but also the variance (second moment) of the A-site ion radii distribution

  20. Theoretical and experimental study of high-magnetic-field XMCD spectra at the L2,3 absorption edges of mixed-valence rare-earth compounds

    International Nuclear Information System (INIS)

    Kotani, Akio; Matsuda, Yasuhiro H; Nojiri, Hiroyuki

    2009-01-01

    X-ray magnetic circular dichroism(XMCD) spectra at the L 2,3 edges of mixed-valence rare-earth compounds in high magnetic fields are studied both theoretically and experimentally. The theoretical study is based on a new framework proposed recently by Kotani. The Zeeman splitting of 4f states, the mixed-valence character of 4f states, and the 4f-5d exchange interaction are incorporated into a single impurity Anderson model. New XMCD experiments in high magnetic fields up to 40 T are carried out for the mixed-valence compounds EuNi 2 (Si 0.18 Ge 0.82 ) 2 and YbInCu 4 by using a miniature pulsed magnet, which was developed recently by Matsuda et al. The XMCD data are taken at 5 K by transmission measurements for incident X-rays with ± helicities at BL39XU in SPring-8. After giving a survey on recent developments in the theory of XMCD spectra for mixed-valence Ce and Yb compounds, we calculate the XMCD spectra of YbInCu 4 at the field-induced valence transition around 32 T by applying the recent theoretical framework and by newly introducing at 32 T a discontinuous change in the Yb 4f level and that in the hybridization strength between the Yb 4f and conduction electrons. The calculated results are compared with the experimental ones.

  1. Quinoline-Based Hybrid Compounds with Antimalarial Activity

    Directory of Open Access Journals (Sweden)

    Xhamla Nqoro

    2017-12-01

    Full Text Available The application of quinoline-based compounds for the treatment of malaria infections is hampered by drug resistance. Drug resistance has led to the combination of quinolines with other classes of antimalarials resulting in enhanced therapeutic outcomes. However, the combination of antimalarials is limited by drug-drug interactions. In order to overcome the aforementioned factors, several researchers have reported hybrid compounds prepared by reacting quinoline-based compounds with other compounds via selected functionalities. This review will focus on the currently reported quinoline-based hybrid compounds and their preclinical studies.

  2. Syntheses and Characterization of Some Tetradentate Schiff-Base Complexes and Their Heteroleptic Analogues

    Directory of Open Access Journals (Sweden)

    A. A. Osowole

    2008-01-01

    Full Text Available VO(IV, Ni(II and Cu(II complexes of the asymmetric Schiff base [(HOC6H3(OCH3C(C6H5:N(CH2CH2N:C(CH3CH:C(C6H5OH], and their heteroleptic analogues with triphenyl phosphine and 2,2’-bipyridine have been synthesized and characterized by elemental analyses, conductance, magnetic, infrared and electronic spectral measurements. The ligand is tetradentate coordinating via the imine N and enolic O atoms. The Ni(II and Cu(II complexes adopt a four coordinate square planar geometry, the VO(IV complex is five coordinate square-pyramidal and the heteroleptic complexes are 6-coordinate, octahedral. The assignment of geometry is collaborated by magnetic moments and electronic spectra measurements. The compounds are non-electrolyte in nitromethane and are magnetically dilute.

  3. Magnetic structure of the magnetocaloric compound AlFe{sub 2}B{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Cedervall, Johan, E-mail: johan.cedervall@kemi.uu.se [Department of Chemistry – Ångström Laboratory, Uppsala University, Box 538, 751 21 Uppsala (Sweden); Andersson, Mikael Svante; Sarkar, Tapati [Department of Engineering Sciences, Uppsala University, Box 534, 751 21 Uppsala (Sweden); Delczeg-Czirjak, Erna K. [Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala (Sweden); Bergqvist, Lars [Department of Materials and Nano Physics and Swedish e-Science Research Centre (SeRC), Royal Institute of Technology (KTH), Electrum 229, SE-164 40 Kista (Sweden); Hansen, Thomas C. [Institut Laue-Langevin, B.P. 156, Grenoble Cedex 9, 38042 France (France); Beran, Premysl [Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Rez, 25068 Czech Republic (Czech Republic); Nordblad, Per [Department of Engineering Sciences, Uppsala University, Box 534, 751 21 Uppsala (Sweden); Sahlberg, Martin [Department of Chemistry – Ångström Laboratory, Uppsala University, Box 538, 751 21 Uppsala (Sweden)

    2016-04-15

    The crystal and magnetic structures of AlFe{sub 2}B{sub 2} have been studied with a combination of X-ray and neutron diffraction and electronic structure calculations. The magnetic and magnetocaloric properties have been investigated by magnetisation measurements. The samples have been produced using high temperature synthesis and subsequent heat treatments. The compound crystallises in the orthorhombic crystal system Cmmm and it orders ferromagnetically at 285 K through a second order phase transition. At temperatures below the magnetic transition the magnetic moments align along the crystallographic a-axis. The magnetic entropy change from 0 to 800 kA/m was found to be −1.3 J/K kg at the magnetic transition temperature. - Graphical abstract: The magnetic structure of AlFe{sub 2}B{sub 2} has been investigated using neutron diffraction and the magnetic spins have been found to align ferromagnetically along the crystallographic a-axis. - Highlights: • The crystal and magnetic structures of AlFe{sub 2}B{sub 2} have been studied. • Orders ferromagnetically at 285 K via a second order phase transition. • The magnetic moments are found to be aligned along the crystallographic a-axis. • The magnetic entropy change from 0 to 800 kA/m was found to be −1.3 J/K kg.

  4. Moessbauer spectroscopic studies of the chemical effects associated with 57Co(electron capture)57Fe decay in tris-β-diketonatocobalt(III) compounds

    International Nuclear Information System (INIS)

    Sakai, Yoichi; Endo, Kazutoyo; Sano, Hirotoshi

    1980-01-01

    Magnetic hyperfine structures (hfs) were found in the absorption Moessbauer spectra at 78 K of a paramagnetic iron(III) complex diluted in a diamagnetic cobalt(III) or aluminium(III) complex such as 57 Fe(acac) 3 in Co(acac) 3 , 57 Fe(oxin) 3 in Al(oxin) 3 , and 57 Fe(dbm) 3 in Co(dbm) 3 (acac=acetylacetonato, oxin=8-quinolinolato, and dbm=dibenzoylmethanato), showing that the magnetic hfs is caused by the spin-spin relaxation through the surrounding diamagnetic species. In the emission Moessbauer experiments, magnetic hfs was observed at 78 K in 57 Co-labelled Co(dbm) 3 , Co(oxin) 3 , and polystyrene-diluted Co(acac) 3 , while it was not observed in 57 Co-labelled Co(acac) 3 and Co(dpm) 3 (dpm=dipivaloylmethanato). The former possess pi -conjugated systems to a greater extent than the latter, either in the ligands or in the vicinity of the 57 Co-labelled Co(III) species. These results were explained in terms of the radiolytic stabilities of the matrices as well as those of 57 Co-labelled compounds by showing that the paramagnetic radicals produced in a diamagnetic matrix quench the magnetic hfs because of the increased spin-spin interaction, as a consequence of the local radiolysis by EC-decay. (author)

  5. Tuning the magnetic phase transition and the magnetocaloric properties of La0.7Ca0.3MnO3 compounds through Sm-doping

    Science.gov (United States)

    Thanh, Tran Dang; Dung, Nguyen Thi; Van Dang, Nguyen; Bau, Le Viet; Piao, Hong-Guang; Phan, The Long; Huyen Yen, Pham Duc; Hau, Kieu Xuan; Kim, Dong-Hyun; Yu, Seong-Cho

    2018-05-01

    In this work, we point out that the width and the nature of the magnetic phase transition, TC value, and as well as magnetocaloric effect in La0.7-xSmxCa0.3MnO3 compounds can be easily modified through Sm-doped into La-site. With an increasing Sm concentration, a systematic decrease in the magnetization, TC, and magnetic entropy change (ΔSm) are observed. The Arrott-plot proveds that the samples with x = 0 and 0.1 undergoing a first-order phase transition. Meanwhile, sample x = 0.2 undergoes a second-order phase transition, which exhibits a high value of the relative cooling power (81.5 J/kg at ΔH = 10 kOe). An analysis of the critical behavior based on the modified Arrott plots method has been done for sample x = 0.2. The results proved a coexistence of the long- and short-range interactions in La0.5Sm0.2Ca0.3MnO3 compound.

  6. High-field magnetization studies of U2T2Sn (T=Co, Ir, Pt) compounds

    International Nuclear Information System (INIS)

    Prokes, K.; Nakotte, H.; de Boer, F.R.

    1995-01-01

    High-field magnetization measurements at 4.2 K on U 2 T 2 Sn (T = Co, Ir and Pt) compounds have been performed on free and fixed powders up to 57 T. An antiferromagnetic ground state of U 2 Pt 2 Sn is corroborated by a metamagnetic transition at 22 T with very small hysteresis going up and down with field. U 2 Co 2 Sn and U 2 Ir 2 Sn show no metamagnetic transition up to 57 T which is in agreement with the non-magnetic ground state of these compounds. In all cases, the maximum applied field is not sufficient to achieve saturation. The short-pulse measurements presented here are compared with previous results obtained in quasi-static fields up to 35 T

  7. Magnetic structure of the quasi-two-dimensional compound CoTa{sub 2}O{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Kinast, E.J. [Universidade Estadual do Rio Grande do Sul, Rua 7 de Setembro, 1156, 90010-191 Porto Alegre (Brazil); Santos, C.A. dos [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, C.P. 15051, 91501-970 Porto Alegre (Brazil); Schmitt, D. [Laboratoire de Geophysique Interne et Tectonophysique, Universite Joseph Fourier, B. P. 53, 38041 Grenoble Cedex 9 (France); Isnard, O., E-mail: olivier.isnard@grenoble.cnrs.f [Institut Neel, CNRS/Universite Jospeh Fourier, avenue des martyrs B. P. 166, 38042 Grenoble Cedex 9 (France); Gusmao, M.A.; Cunha, J.B.M. da [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, C.P. 15051, 91501-970 Porto Alegre (Brazil)

    2010-02-18

    We report on a detailed investigation of magnetic properties of CoTa{sub 2}O{sub 6} using several techniques: neutron and X-ray diffraction, specific-heat, magnetic susceptibility, and magnetization measurements. The compound shows quasi-two-dimensional behavior due to its layered structure of alternating Co-O and Ta-O planes. We find that all magnetic moments lie entirely in the Co-O planes, along easy axes determined by the orientations of oxygen octahedra that surround the Co ions. The easy axes in successive magnetic planes have relative orientations that differ by 90{sup o}. Antiferromagnetic ordering is observed below 6.6 K, with propagation vectors ({+-}1/4,1/4,1/4) associated to the two non-equivalent sets of Co{sup 2+} ions, whose magnetic moments are perpendicularly oriented.

  8. Electronic structure of chromium-doped lead telluride-based diluted magnetic semiconductors

    International Nuclear Information System (INIS)

    Skipetrov, E.P.; Pichugin, N.A.; Slyn'ko, E.I.; Slyn'ko, V.E.

    2011-01-01

    The crystal structure, composition, galvanomagnetic and oscillatory properties of the Pb 1-x-y Sn x Cr y Te (x = 0, 0.05-0.30, y ≤ 0.01) alloys have been investigated with varying matrix composition and chromium impurity concentration. It is shown that the chromium impurity atoms dissolve in the crystal lattice at least up to 1 mol.%. The following increase of the chromium concentration leads to the appearance of microscopic regions enriched with chromium and inclusions of Cr-Te compounds. A decrease of the hole concentration, a p-n-conversion of the conductivity type and a pinning of the Fermi level by the chromium resonant level are observed with increasing chromium content. Initial rates of changes in the free carrier concentration on doping are determined. The dependences of electron concentration and Fermi level on tin content are calculated by the two-band Kane dispersion relation. A diagram of electronic structure rearrangement for the chromium-doped alloys with varying the matrix composition is proposed.

  9. Magnetoviscous effect in ferrofluids diluted with sheep blood

    Science.gov (United States)

    Nowak, J.; Borin, D.; Haefner, S.; Richter, A.; Odenbach, S.

    2017-11-01

    Suspensions of magnetic nanoparticles in suitable carrier liquids, denoted as ferrofluids, are in the focus of current research in the biomedical area. Those fluids can be potentially used for the treatment of cancer by coupling chemotherapeutic agents and accumulating them in the diseased region with the help of external magnetic fields or by artificially local induced heating. Those applications rely on the help of external magnetic fields, which are well known to drastically influence the physical behaviour of ferrofluids. This study investigates the changing viscosity of a biocompatible ferrofluid in a flow situation close to the situation found in a biomedical application. For this purpose blood as diluting agent and thin capillaries have been utilised. The strong magnetoviscous effects found lead to the assumption of quite big changes of the microstructure due to the external magnetic fields, which was investigated and quantified using a microscopic setup. In the result an increases of the structure size as well as faster structure formation in the stronger magnetic fields were observed. Moreover, with increasing duration of the applied magnetic field the size of the structures increases too. The observed process of the structure formation is reversible.

  10. Magnetic hyperfine field in Tb Zn compound measured by PAC spectroscopy using {sup 111}Cd and {sup 140}Ce

    Energy Technology Data Exchange (ETDEWEB)

    Bosch-Santos, B.; Cabrera-Pasca, G.A.; Carbonari, A.W.; Costa, M.S.; Saxena, R.N., E-mail: brianna@usp.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    The ferromagnetic compound Tb Zn has been investigated by perturbed {gamma}-{gamma} angular correlation (PAC) spectroscopy using {sup 111}In{yields}{sup 111}Cd (t{sub 1/2} = 85 ns) and {sup 140}La{yields}{sup 140}Ce (t{sub 1/2} = 3,4 ns) as probe nuclei. Measurements were carried out in the temperature range of 10 - 295K for the {sup 111}Cd probe and below Curie temperature (T{sub C}) for the {sup 140}Ce probe. The study of magnetic properties of rare earth (R) and zinc compounds of the type RZn is interesting because Zn ion is a closed shell atom and the rare earth elements present a localized magnetism associated with 4f electrons, which do not participate in chemical bonds. Therefore, the magnetic properties of these compounds are only originated from the 4f electrons of rare earth. Furthermore, the compounds exhibit the highly symmetric cubic structure of the CsCl prototype and have a Curie temperature of TbZn is T{sub C} {approx} 204 K. (author)

  11. Correlation between magnetostriction and magnetic structure in pseudobinary compounds Tb(Co1-xFex2

    Directory of Open Access Journals (Sweden)

    Yue Wang

    2017-07-01

    Full Text Available Giant low-field magnetostriction has been achieved in pseudobinary Laves phase compounds RR’T2 (R and R’: rare earth elements; T: transition metal elements around the ferromagnetic - ferromagnetic (ferro.-ferro. transition temperature. Evolution of the magnetic structure across such transition requires comprehensive investigation. In this work, pseudobinary system Tb(Co1-xFex2 is selected to investigate the evolution of local magnetic moment, for which two end terminals TbCo2 and TbFe2 possess the rhombohedral (R structure at the ferromagnetic state but with different magnetic ordering temperatures (TC. Magnetometry measurements reveal that a composition independent ferromagnetic - ferromagnetic transition occurs at ∼100 K despite the increased Curie temperature TC with raised Fe concentration in the Tb(Co1-xFex2. Synchrotron XRD data reveal that both the lattice parameter and the lattice strain along the direction are abnormally temperature dependent, accompanied with experimentally observed magnetostriction abnormality at 100 K. In-situ neutron powder diffraction (NPD results show that the local magnetic moments of T2 (9e site atoms are also abnormally temperature dependent, which is larger at 100 K than that at a lower temperature 50 K. Such findings indicate close correlations between the magnetic structure and the magnetostrictive effect in the pseudobinary RT2 compounds.

  12. Magnetic and electrical transport properties of delta-doped amorphous Ge:Mn magnetic semiconductors

    International Nuclear Information System (INIS)

    Li, H.L.; Lin, H.T.; Wu, Y.H.; Liu, T.; Zhao, Z.L.; Han, G.C.; Chong, T.C.

    2006-01-01

    We report on the growth and characterization of delta-doped amorphous Ge:Mn diluted magnetic semiconductor thin films on GaAs (0 0 1) substrates. The fabricated samples exhibit different magnetic behaviors, depending on the Mn doping concentration. The Curie temperature was found to be dependent on both the Mn doping concentration and spacing between the doping layers. A sharp drop in magnetization and rise in resistivity are observed at low temperature in samples with high Mn doping concentrations, which is also accompanied by a negative thermal remanent magnetization (TRM) in the higher temperature range. The temperature at which the magnetization starts to drop and the negative TRM appears show a correlation with the Mn doping concentration. The experimental results are discussed based on the formation of ferromagnetic regions at high temperature and antiferromagnetic coupling between these regions at low temperature

  13. Effect of disorder on the magnetic properties of cubic Mn2RuxGa compounds: A first-principles study

    International Nuclear Information System (INIS)

    Galanakis, I.; Özdoğan, K.; Şaşıoğlu, E.; Blügel, S.

    2014-01-01

    We perform first-principles electronic structure calculations to explain the anomalous magnetic behavior of the Mn 2 Ru x Ga compounds upon Ru doping as shown experimentally recently by Kurt et al. [Phys. Rev. Lett. 112, 027201 (2014)]. Our results suggest that disorder caused by the distribution of the Mn and Ru atoms at various sites reproduces the experimental data. All compounds present antiparallel alignment of the neighboring Mn magnetic moments and, with the exception of Mn 2 RuGa, none of them presents half metallic behavior.

  14. Effects of alloying element and temperature on the stacking fault energies of dilute Ni-base superalloys.

    Science.gov (United States)

    Shang, S L; Zacherl, C L; Fang, H Z; Wang, Y; Du, Y; Liu, Z K

    2012-12-19

    A systematic study of stacking fault energy (γ(SF)) resulting from induced alias shear deformation has been performed by means of first-principles calculations for dilute Ni-base superalloys (Ni(23)X and Ni(71)X) for various alloying elements (X) as a function of temperature. Twenty-six alloying elements are considered, i.e., Al, Co, Cr, Cu, Fe, Hf, Ir, Mn, Mo, Nb, Os, Pd, Pt, Re, Rh, Ru, Sc, Si, Ta, Tc, Ti, V, W, Y, Zn, and Zr. The temperature dependence of γ(SF) is computed using the proposed quasistatic approach based on a predicted γ(SF)-volume-temperature relationship. Besides γ(SF), equilibrium volume and the normalized stacking fault energy (Γ(SF) = γ(SF)/Gb, with G the shear modulus and b the Burgers vector) are also studied as a function of temperature for the 26 alloying elements. The following conclusions are obtained: all alloying elements X studied herein decrease the γ(SF) of fcc Ni, approximately the further the alloying element X is from Ni on the periodic table, the larger the decrease of γ(SF) for the dilute Ni-X alloy, and roughly the γ(SF) of Ni-X decreases with increasing equilibrium volume. In addition, the values of γ(SF) for all Ni-X systems decrease with increasing temperature (except for Ni-Cr at higher Cr content), and the largest decrease is observed for pure Ni. Similar to the case of the shear modulus, the variation of γ(SF) for Ni-X systems due to various alloying elements is traceable from the distribution of (magnetization) charge density: the spherical distribution of charge density around a Ni atom, especially a smaller sphere, results in a lower value of γ(SF) due to the facility of redistribution of charges. Computed stacking fault energies and the related properties are in favorable accord with available experimental and theoretical data.

  15. Spin reorientation and magnetic anisotropy in Y2Co17-xCr x (x 1.17-3.0) compounds

    International Nuclear Information System (INIS)

    Fuquan, B.; Tegus, O.; Dagula, W.; Brueck, E.; Boer, F.R. de; Buschow, K.H.J.

    2005-01-01

    Spin reorientation transitions and magnetic anisotropy in Y 2 Co 17-x Cr x (x = 1.17-3.0) compounds have been investigated by means of X-ray diffraction and magnetization measurements. The powder X-ray diffraction patterns show that most samples crystallize as a single phase with the rhombohedral Th 2 Zn 17 -type structure. However, in the compound Y 2 Co 14 Cr 3 the Th 2 Zn 17 phase coexist with the hexagonal Th 2 Ni 17 -type phase. The lattice parameters a and c hardly change and the unit cell volume V increases slightly with increasing Cr content. The X-ray diffraction patterns of the aligned powder of the samples have confirmed that at room temperature the compound with x = 1.17 has planar anisotropy, but the compounds with x = 1.76, 2.34 and 3.00 have uniaxial anisotropy. Spin reorientation phenomena occur in all of the compounds. With increasing Cr content, the Curie temperature, the spin reorientation temperature, the spontaneous magnetization, and the anisotropy constant K 2 of the Y 2 Co 17-x Cr x (x = 1.17-3.0) compounds decrease strongly while the anisotropy constant K 1 increases in the range of x from 1.17 to 2.34 and then decreases in the range of x from 2.34 to 3.00

  16. Probing the magnetic profile of diluted magnetic semiconductors using polarized neutron reflectivity.

    Science.gov (United States)

    Luo, X; Tseng, L T; Lee, W T; Tan, T T; Bao, N N; Liu, R; Ding, J; Li, S; Lauter, V; Yi, J B

    2017-07-24

    Room temperature ferromagnetism has been observed in the Cu doped ZnO films deposited under an oxygen partial pressure of 10 -3 and 10 -5 torr on Pt (200 nm)/Ti (45 nm)/Si (001) substrates using pulsed laser deposition. Due to the deposition at relatively high temperature (873 K), Cu and Ti atoms diffuse to the surface and interface, which significantly affects the magnetic properties. Depth sensitive polarized neutron reflectometry method provides the details of the composition and magnetization profiles and shows that an accumulation of Cu on the surface leads to an increase in the magnetization near the surface. Our results reveal that the presence of the copper at Zn sites induces ferromagnetism at room temperature, confirming intrinsic ferromagnetism.

  17. The bond diluted spin-1 Blume-Emery-Griffiths model in a transverse field

    International Nuclear Information System (INIS)

    Ez Zahraouy, H.

    1993-09-01

    The effect of Bond-dilution on the magnetic properties of a quantum transverse spin-1 Blume-Emery-Griffiths model is investigated within an expansion technique for cluster identities of a spin-1 localized spin system. The longitudinal and transverse magnetizations and quadrupolar moments are studied for several values of the bond concentration. A general formula, applicable to structures with arbitrary coordination number N, are given. (author). 41 refs, 6 figs

  18. Collection of Ni-bearing material from electroless plating waste by magnetic separation with HTS bulk magnet

    International Nuclear Information System (INIS)

    Oka, T.; Fukazawa, H.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M.; Tsujimura, M.; Yokoyama, K.

    2014-01-01

    Highlights: ► The magnetic separation for Ni compounds was conducted by HTS bulk magnet. ► The coarse Ni-sulfate crystals were formed from the Ni-phosphite precipitates. ► Ni-sulfate crystals was separated from the mixture of Ni-sulfate and Ni-phosphite compounds. -- Abstract: The magnetic separation experiment to collect the Ni compounds from the waste liquid of electroless plating processes was conducted in the open-gradient magnetic separation process with the high temperature superconducting bulk magnet system. The magnetic pole containing Gd-based bulk superconductors was activated to 3.45 T at 35 K in the static magnetic field of 5 T with use of a superconducting solenoid magnet. The coarse Ni-sulfate crystals were formed by adding the concentrated sulfuric acid to the Ni-phosphite precipitates which yielded from the plating waste liquid by controlling the temperature and the pH value. The open-gradient magnetic separation technique was employed to separate the Ni-sulfate crystals from the mixture of the Ni-sulfate and Ni-phosphite compounds by the difference between their magnetic properties. And we succeeded in collecting Ni-sulfate crystals preferentially to the Ni-phosphite by attracting them to the magnetic pole soon after the Ni-sulfate crystals began to grow

  19. Collection of Ni-bearing material from electroless plating waste by magnetic separation with HTS bulk magnet

    Energy Technology Data Exchange (ETDEWEB)

    Oka, T., E-mail: okat@eng.niigata-u.ac.jp [Niigata University, 8050 Ikarashi-Ninocho, Nishi-ku, Niigata 950-2181 (Japan); Fukazawa, H.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M. [Niigata University, 8050 Ikarashi-Ninocho, Nishi-ku, Niigata 950-2181 (Japan); Tsujimura, M. [Aichi Giken Co., 50-1 Takeshita, Hitotugi-cho, Kariya, Aichi 448-0003 (Japan); Yokoyama, K. [Ashikaga Institute of Technology, 268-1 Ohmae-cho, Ashikaga, Tochigi 326-8558 (Japan)

    2014-01-15

    Highlights: ► The magnetic separation for Ni compounds was conducted by HTS bulk magnet. ► The coarse Ni-sulfate crystals were formed from the Ni-phosphite precipitates. ► Ni-sulfate crystals was separated from the mixture of Ni-sulfate and Ni-phosphite compounds. -- Abstract: The magnetic separation experiment to collect the Ni compounds from the waste liquid of electroless plating processes was conducted in the open-gradient magnetic separation process with the high temperature superconducting bulk magnet system. The magnetic pole containing Gd-based bulk superconductors was activated to 3.45 T at 35 K in the static magnetic field of 5 T with use of a superconducting solenoid magnet. The coarse Ni-sulfate crystals were formed by adding the concentrated sulfuric acid to the Ni-phosphite precipitates which yielded from the plating waste liquid by controlling the temperature and the pH value. The open-gradient magnetic separation technique was employed to separate the Ni-sulfate crystals from the mixture of the Ni-sulfate and Ni-phosphite compounds by the difference between their magnetic properties. And we succeeded in collecting Ni-sulfate crystals preferentially to the Ni-phosphite by attracting them to the magnetic pole soon after the Ni-sulfate crystals began to grow.

  20. Yb-based heavy fermion compounds and field tuned quantum chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Mun, Eundeok [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    The motivation of this dissertation was to advance the study of Yb-based heavy fermion (HF) compounds especially ones related to quantum phase transitions. One of the topics of this work was the investigation of the interaction between the Kondo and crystalline electric field (CEF) energy scales in Yb-based HF systems by means of thermoelectric power (TEP) measurements. In these systems, the Kondo interaction and CEF excitations generally give rise to large anomalies such as maxima in ρ(T) and as minima in S(T). The TEP data were use to determine the evolution of Kondo and CEF energy scales upon varying transition metals for YbT2Zn20 (T = Fe, Ru, Os, Ir, Rh, and Co) compounds and applying magnetic fields for YbAgGe and YbPtBi. For YbT2Zn20 and YbPtBi, the Kondo and CEF energy scales could not be well separated in S(T), presumably because of small CEF level splittings. A similar effect was observed for the magnetic contribution to the resistivity. For YbAgGe, S(T) has been successfully applied to determine the Kondo and CEF energy scales due to the clear separation between the ground state and thermally excited CEF states. The Kondo temperature, TK, inferred from the local maximum in S(T), remains finite as magnetic field increases up to 140 kOe. In this dissertation we have examined the heavy quasi-particle behavior, found near the field tuned AFM quantum critical point (QCP), with YbAgGe and YbPtBi. Although the observed nFL behaviors in the vicinity of the QCP are different between YbAgGe and YbPtBi, the constructed H-T phase diagram including the two crossovers are similar. For both YbAgGe and YbPtBi, the details of the quantum criticality turn out to be complicated. We expect that YbPtBi will provide an additional example of field tuned quantum criticality, but clearly there are further experimental investigations left and more ideas needed to understand the basic physics of field-induced quantum

  1. Evaluation of the key aroma compounds in beef and pork vegetable gravies a la chef by stable isotope dilution assays and aroma recombination experiments.

    Science.gov (United States)

    Christlbauer, Monika; Schieberle, Peter

    2011-12-28

    Although the aroma compounds of meat processed as such have been studied previously, data on complete homemade dishes containing beef and pork meat were scarcely studied. Recently, 38 odor-active compounds were characterized in beef and pork vegetable gravies using GC-olfactometry. In the present investigation, the most odor-active compounds were quantitated in a freshly prepared stewed beef vegetable gravy (BVG) as well as a stewed pork vegetable gravy (PVG) by means of stable isotope dilution assays. Calculation of odor activity values (OAVs; ratio of concentration to odor threshold) revealed 3-mercapto-2-methylpentan-1-ol, (E,E)-2,4-decadienal, (E,Z)-2,6-nonadienal, (E)-2-decenal, (E)-2-undecanal, and 3-hydroxy-4,5-dimethyl-2(5H)-furanone as the most potent odorants in both gravies. However, significantly different OAVs were found for 12-methyltridecanal, which was much higher in the BVG, whereas (E,Z)-2,4-decadienal showed a clearly higher OAV in the PVG. Aroma recombination experiments performed on the basis of the actual concentrations of the odorants in both gravies revealed a good similarity of the aromas of both model mixtures containing all odorants with OAVs > 1 with those of the original gravies.

  2. Novel Dilute Bismide, Epitaxy, Physical Properties and Device Application

    Directory of Open Access Journals (Sweden)

    Lijuan Wang

    2017-02-01

    Full Text Available Dilute bismide in which a small amount of bismuth is incorporated to host III-Vs is the least studied III-V compound semiconductor and has received steadily increasing attention since 2000. In this paper, we review theoretical predictions of physical properties of bismide alloys, epitaxial growth of bismide thin films and nanostructures, surface, structural, electric, transport and optic properties of various binaries and bismide alloys, and device applications.

  3. Developments on drug discovery and on new therapeutics: highly diluted tinctures act as biological response modifiers.

    Science.gov (United States)

    de Oliveira, Carolina C; Abud, Ana Paula R; de Oliveira, Simone M; Guimarães, Fernando de S F; de Andrade, Lucas F; Di Bernardi, Raffaello P; Coletto, Ediely L de O; Kuczera, Diogo; Da Lozzo, Eneida J; Gonçalves, Jenifer P; Trindade, Edvaldo da S; Buchi, Dorly de F

    2011-10-26

    In the search for new therapies novel drugs and medications are being discovered, developed and tested in laboratories. Highly diluted substances are intended to enhance immune system responses resulting in reduced frequency of various diseases, and often present no risk of serious side-effects due to its low toxicity. Over the past years our research group has been investigating the action of highly diluted substances and tinctures on cells from the immune system. We have developed and tested several highly diluted tinctures and here we describe the biological activity of M1, M2, and M8 both in vitro in immune cells from mice and human, and in vivo in mice. Cytotoxicity, cytokines released and NF-κB activation were determined after in vitro treatment. Cell viability, oxidative response, lipid peroxidation, bone marrow and lymph node cells immunophenotyping were accessed after mice in vivo treatment. None of the highly diluted tinctures tested were cytotoxic to macrophages or K562. Lipopolysaccharide (LPS)-stimulated macrophages treated with all highly diluted tinctures decreased tumour necrosis factor alpha (TNF-α) release and M1, and M8 decreased IFN-γ production. M1 has decreased NF-κB activity on TNF-α stimulated reporter cell line. In vivo treatment lead to a decrease in reactive oxygen species (ROS), nitric oxide (NO) production was increased by M1, and M8, and lipid peroxidation was induced by M1, and M2. All compounds enhanced the innate immunity, but M1 also augmented acquired immunity and M2 diminished B lymphocytes, responsible to acquired immunity. Based on the results presented here, these highly diluted tinctures were shown to modulate immune responses. Even though further investigation is needed there is an indication that these highly diluted tinctures could be used as therapeutic interventions in disorders where the immune system is compromised.

  4. First principles density functional calculation of magnetic moment and hyperfine fields of dilute transition metal impurities in Gd host

    International Nuclear Information System (INIS)

    Mohanta, S.K.; Mishra, S.N.; Srivastava, S.K.

    2014-01-01

    We present first principles calculations of electronic structure and magnetic properties of dilute transition metal (3d, 4d and 5d) impurities in a Gd host. The calculations have been performed within the density functional theory using the full potential linearized augmented plane wave technique and the GGA+U method. The spin and orbital contributions to the magnetic moment and the hyperfine fields have been computed. We find large magnetic moments for 3d (Ti–Co), 4d (Nb–Ru) and 5d (Ta–Os) impurities with magnitudes significantly different from the values estimated from earlier mean field calculation [J. Magn. Magn. Mater. 320 (2008) e446–e449]. The exchange interaction between the impurity and host Gd moments is found to be positive for early 3d elements (Sc–V) while in all other cases an anti-ferromagnetic coupling is observed. The trends for the magnetic moment and hyperfine field of d-impurities in Gd show qualitative difference with respect to their behavior in Fe, Co and Ni. The calculated total hyperfine field, in most cases, shows excellent agreement with the experimental results. A detailed analysis of the Fermi contact hyperfine field has been made, revealing striking differences for impurities having less or more than half filled d-shell. The impurity induced perturbations in host moments and the change in the global magnetization of the unit cell have also been computed. The variation within each of the d-series is found to correlate with the d–d hybridization strength between the impurity and host atoms. - Highlights: • Detailed study of transition metal impurities in ferromagnetic Gd has been carried out. • The trends in impurity magnetic moment are qualitatively different from Fe, Co and Ni. • The variation within each of the d-series is found to correlate with the d–d hybridization strength between the impurity and host atoms. • Experimental trend in a hyperfine field has been reproduced successfully

  5. Experimental investigation on blood magnetic contamination in the presence of drug molecules

    International Nuclear Information System (INIS)

    Creanga, D E; Nadejde, C; Iacob, G H

    2009-01-01

    The purpose of the present project was to study the interference of magnetic nanoparticles with drug molecules - rifampicin, used in lung infectious disease and respectively, sodium diclofenac, an antiinflammatory steroid. The controlled magnetic contamination was accomplished using colloidal nanoparticles supplied from diluted magnetic fluids. Various concentrations of diluted aqueous magnetic fluids, based on magnetite cores coated with citric acid and respectively sodium oleate, were tested. The experiment was focused on the capacity of the magnetic nanoparticles to form reversible complexes with the drug molecules, as well as on the monitoring of the nanoparticle-drug complex dynamics, under the action of external magnetic field. The level of released rifampicin ranged between 4 mg/100 ml and 7 mg/100 ml for the magnetic exposure of 20 mT, while the sodium diclofenac decomplexation level was not higher than 2.5 mg/100 ml under magnetic exposure of 60 mT. The experimental arrangement was proved to be an adequate model for the dynamical study of magnetite reversible complexation with drug molecules, evidencing certain specific values of drug concentration and magnetic field induction that favour such interactions.

  6. Experimental investigation on blood magnetic contamination in the presence of drug molecules

    Energy Technology Data Exchange (ETDEWEB)

    Creanga, D E; Nadejde, C [' Al. I. Cuza' University, Faculty of Physics, 11A Blvd. Carol I, RO-700506, Iasi (Romania); Iacob, G H [' Gr. T. Popa' University, Faculty of Biomedical Engineering, Kogalniceanu Street, No. 9-13, RO-700454, Iasi (Romania)], E-mail: nadej_dia@yahoo.com

    2009-05-01

    The purpose of the present project was to study the interference of magnetic nanoparticles with drug molecules - rifampicin, used in lung infectious disease and respectively, sodium diclofenac, an antiinflammatory steroid. The controlled magnetic contamination was accomplished using colloidal nanoparticles supplied from diluted magnetic fluids. Various concentrations of diluted aqueous magnetic fluids, based on magnetite cores coated with citric acid and respectively sodium oleate, were tested. The experiment was focused on the capacity of the magnetic nanoparticles to form reversible complexes with the drug molecules, as well as on the monitoring of the nanoparticle-drug complex dynamics, under the action of external magnetic field. The level of released rifampicin ranged between 4 mg/100 ml and 7 mg/100 ml for the magnetic exposure of 20 mT, while the sodium diclofenac decomplexation level was not higher than 2.5 mg/100 ml under magnetic exposure of 60 mT. The experimental arrangement was proved to be an adequate model for the dynamical study of magnetite reversible complexation with drug molecules, evidencing certain specific values of drug concentration and magnetic field induction that favour such interactions.

  7. The Toulouse pulsed magnet facility

    International Nuclear Information System (INIS)

    2006-01-01

    The 'Laboratoire National des Champs Magnetiques Pulses' (LNCMP) is an international user facility providing access to pulsed magnetic fields up to and beyond 60 T. The laboratory disposes of 10 magnet stations equipped with long-pulse magnets operating in the 35-60 T range and a short-pulse system reaching magnetic fields in excess of 70 T. The experimental infrastructure includes various high and low-temperature systems ranging from ordinary flow-type cryostats to dilution refrigerators reaching 50 mK, as well as different types of high-pressure cells. Experimental techniques include magnetization, transport, luminescence, IR-spectroscopy and polarimetry. The LNCMP pursues an extensive in-house research program focussing on all technological and scientific aspects of pulsed magnetic fields. Recent technical developments include the implementation of 60 T rapid-cooling coils, an 80 T prototype, a pulsed dipole magnet for optical investigations of dilute matter and a transportable horizontal access magnet for small angle x-ray scattering experiments. Scientific activities cover a variety of domains, including correlated electron systems, magnetism, semiconductors and nanoscience

  8. Structural and magnetic properties of transition metal substituted BaFe2As2 compounds studied by x-ray and neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Gyu [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    The purpose of my dissertation is to understand the structural and magnetic properties of the newly discovered FeAs-based superconductors and the interconnection between superconductivity, antiferromagnetism, and structure. X-ray and neutron scattering techniques are powerful tools to directly observe the structure and magnetism in this system. I used both x-ray and neutron scattering techniques on different transition substituted BaFe2As2 compounds in order to investigate the substitution dependence of structural and magnetic transitions and try to understand the connections between them.

  9. Different approaches to analyze the dipolar interaction effects on diluted and concentrated granular superparamagnetic systems

    Energy Technology Data Exchange (ETDEWEB)

    Moscoso-Londoño, O., E-mail: omoscoso@ifi.unicamp.br [Instituto de Física ‘Gleb Wataghin’, Universidade Estadual de Campinas (UNICAMP), CEP13083-859 Campinas, São Paulo (Brazil); Tancredi, P. [Laboratorio de Sólidos Amorfos, INTECIN, Facultad de Ingeniería, Universidad de Buenos Aires (UBA), CONICET, C1063ACV Buenos Aires (Argentina); Muraca, D. [Instituto de Física ‘Gleb Wataghin’, Universidade Estadual de Campinas (UNICAMP), CEP13083-859 Campinas, São Paulo (Brazil); Centro de Ciencias Naturais e Humanas, Universidade Federal do ABC (UFABC), Av. Dos Estados, 5001, Santo André, SP (Brazil); Mendoza Zélis, P.; Coral, D.; Fernández van Raap, M.B. [Instituto de Física, Universidad Nacional de La Plata (UNLP), CONICET, CC.67, 1900 La Plata, Buenos Aires (Argentina); Wolff, U.; Neu, V.; Damm, C. [IFW Dresden, Leibniz Institute for Solid State and Materials Research, Dresden, Helmholtzstrasse 20, 01069 Dresden (Germany); Oliveira, C.L.P. de [Instituto de Física, Universidade de São Paulo, São Paulo 05314970 (Brazil); Pirota, K.R. [Instituto de Física ‘Gleb Wataghin’, Universidade Estadual de Campinas (UNICAMP), CEP13083-859 Campinas, São Paulo (Brazil); and others

    2017-04-15

    Controlled magnetic granular materials with different concentrations of magnetite nanoparticles immersed in a non-conducting polymer matrix were synthesized and, their macroscopic magnetic observables analyzed in order to advance towards a better understanding of the magnetic dipolar interactions and its effects on the obtained magnetic parameters. First, by means of X-ray diffraction, transmission electron microscopy, small angle X-ray scattering and X-ray absorption fine structure an accurate study of the structural properties was carried out. Then, the magnetic properties were analyzed by means of different models, including those that consider the magnetic interactions through long-range dipolar forces as: the Interacting Superparamagnetic Model (ISP) and the Vogel-Fulcher law (V-F). In systems with larger nanoparticle concentrations, magnetic results clearly indicate that the role played by the dipolar interactions affects the magnetic properties, giving rise to obtaining magnetic and structural parameters without physical meaning. Magnetic parameters as the effective anisotropic constant, magnetic moment relaxation time and mean blocking temperature, extracted from the application of the ISP model and V-F Law, were used to simulate the zero-field-cooling (ZFC) and field-cooling curves (FC). A comparative analysis of the simulated, fitted and experimental ZFC/FC curves suggests that the current models depict indeed our dilute granular systems. Notwithstanding, for concentrated samples, the ISP model infers that clustered nanoparticles are being interpreted as single entities of larger magnetic moment and volume, effect that is apparently related to a collective and complex magnetic moment dynamics within the cluster. - Highlights: • Nanoparticle architecture into matrices determines the composite magnetic response. • Magnetically diluted or compacted systems are useful to study magnetism at nanoscale. • Particle aggregation into the matrices was examined

  10. X-Ray diffraction on rare earth-3d Laves phase compound ErCo2 in magnetic field

    International Nuclear Information System (INIS)

    Yagasaki, Katsuma; Notsu, Shiko; Takaesu, Yoshinao; Nakama, Takao; Sakai, Eijiro; Koyama, Keiichi; Watanabe, Kazuo; Burkov, Alexander T.

    2006-01-01

    X-Ray powder diffraction method is used to investigate the effect of magnetic ordering and external magnetic field on crystal structure of Laves phase intermetallic compound ErCo 2 . The diffraction patterns were recorded at temperatures from 300K down to 8.5K in magnetic field up to 5T. Distortion of the room-temperature cubic structure was found in magnetically ordered state below 32K. The symmetry at low temperature is rhombohedral in agreement with literature results, or lower symmetry than it. However the symmetry of the unit cell increases to cubic in external magnetic field of 5T

  11. Moessbauer investigation of magnetic hyperfine fields near bivalent Eu compounds under high pressure

    International Nuclear Information System (INIS)

    Abd Elmeguid, M.

    1979-01-01

    The paper deals with the pressure or volume dependence of hyperfine interactions of magnetically ordered, bivalent europium compounds. Emphasis is laid on the investigation of the pressure or volume dependence of magnetic hyperfine fields as they are found at the nuclear site of 151 Eu or of diamagnetic 119 Sn or 197 Au probe atoms. The measurements were carried out with the aid of the gamma resonance of 151 Eu (21.6 keV) 119 Sn (23.8 keV) and 167 Au (77.4 keV) at low temperatures and external pressures up to 65 kbar. (orig./WBU) [de

  12. Dilute chemical decontamination program review

    International Nuclear Information System (INIS)

    Anstine, L.D.; Blomgren, J.C.; Pettit, P.J.

    1980-01-01

    The objective of the Dilute Chemical Decontamination Program is to develop and evaluate a process which utilizes reagents in dilute concentrations for the decontamination of BWR primary systems and for the maintenance of dose rates on the out-of-core surfaces at acceptable levels. A discussion is presented of the process concept, solvent development, advantages and disadvantages of reagent systems, and VNC loop tests. Based on the work completed to date it is concluded that (1) rapid decontamination of BWRs using dilute reagents is feasible; (2) reasonable reagent conditions for rapid chemical decontamination are: 0.01M oxalic acid + 0.005M citric acid, pH3.0, 90/degree/C, 0.5 to 1.0 ppm dissolved oxygen; (3) control of dissolved oxygen concentration is important, since high levels suppress the rate of decontamination and low levels allow precipitation of ferrous oxalate. 4 refs

  13. Dynamical Properties of a Diluted Dipolar-Interaction Heisenberg Spin Glass

    International Nuclear Information System (INIS)

    Zhang Kai-Cheng; Liu Yong; Chi Feng

    2014-01-01

    Up to now the chirality is seldom studied in the diluted spin glass although many investigations have been performed on the site-ordered Edwards—Anderson model. By simulation, we investigate the dynamical properties of both the spin-glass and the chiral-glass phases in a diluted dipolar system, which was manifested to have a spin-glass transition by recent numerical study. By scaling we find that both phases have the same aging behavior and closer aging parameter μ. Similarly, the domains grow in the same way and both phases have a closer barrier exponent Ψ. It means that both the spins and the chirality have the same dynamical properties and they may freeze at the same temperature. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  14. Two stages of Kondo effect and competition between RKKY and Kondo in Gd-based intermetallic compound

    International Nuclear Information System (INIS)

    Vaezzadeh, Mehdi; Yazdani, Ahmad; Vaezzadeh, Majid; Daneshmand, Gissoo; Kanzeghi, Ali

    2006-01-01

    The magnetic behavior of Gd-based intermetallic compound (Gd 2 Al (1-x) Au x ) in the form of the powder and needle, is investigated. All the samples are an orthorhombic crystal structure. Only the compound with x=0.4 shows the Kondo effect (other compounds have a normal behavior). Although, for the compound in the form of powder, with x=0.4, the susceptibility measurement χ(T) shows two different stages. Moreover for (T>T K2 ) a fall of the value of χ(T) is observable, which indicates a weak presence of ferromagnetic phase. About the two stages of Kondo effect, we observe at the first (T K1 ) an increase of χ(T) and in the second stage (T K2 ) a new remarkable decrease of χ(T) (T K1 >T K2 ). For the sample in the form of needles, the first stage is observable only under high magnetic field. This first stage could be corresponds to a narrow resonance between Kondo cloud and itinerant electron. The second stage, which is remarkably visible for the sample in the form of the powder, can be attribute to a complete polarization of Kondo cloud. Observation of these two Kondo stages could be due to the weak presence of RKKY contribution

  15. Ferroelectric and magnetic properties in high-pressure synthesized BiFeO3 compound

    International Nuclear Information System (INIS)

    Zhai, L.; Shi, Y.G.; Gao, J.L.; Tang, S.L.; Du, Y.W.

    2011-01-01

    Highlights: → A high-density polycrystalline BiFeO 3 compound was synthesized by high-pressure annealing method. → The sample showed weak ferromagnetic at room temperature, which could be attributed to the lattice distortion induced by the high-pressure annealing. → Irregular domains were observed on the surface of the sample by piezoresponse force microscopy, and a typical hysteresis loop was obtained. - Abstract: High-density polycrystalline BiFeO 3 compound was synthesized by high-pressure annealing. Measurements of crystal structure, magnetic, and ferroelectric properties were made on the sample. It was found that the sample was almost single phase with a distorted R3c structure. The results of the X-ray photoelectron spectra demonstrate that the oxidation state of Fe in the sample is Fe 3+ . The room-temperature field dependence of magnetization for BiFeO 3 exhibits a hysteretic behavior. The observed weak ferromagnetism could be ascribed to the lattice distortion induced by the high-pressure annealing. In addition, the local ferroelectric performance of the sample was studied by piezoresponse force microscopy.

  16. Observation of the magnetization-step in Gd doped antiperovskite compounds Mn{sub 3}Cu{sub 1−x}Gd{sub x}N (0.15≤x≤0.25)

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Quan [Center for Composite Materials and structures, Harbin Institute of Technology, Harbin 150080 (China); Zhang, Xinghong, E-mail: zhangxh@hit.edu.cn [Center for Composite Materials and structures, Harbin Institute of Technology, Harbin 150080 (China); Gao, Tangling [Institute of Petrochemistry, Heilongjiang Academy of Sciences, Harbin 150040 (China); Zhao, Jinggeng [Department of Physics, Harbin Institute of Technology, Harbin 150080 (China); Academy of Fundamental and Interdisciplinary Sciences, Harbin 150080 (China); Han, Jiecai; Zhou, Shanbao [Center for Composite Materials and structures, Harbin Institute of Technology, Harbin 150080 (China); Hu, Chang; Wang, Xianjie [Department of Physics, Harbin Institute of Technology, Harbin 150080 (China); Zhang, Zhihua [School of Materials Science and Engineering, Dalian Jiaotong University, Dalian 116028 (China); Song, Bo, E-mail: songbo@hit.edu.cn [Center for Composite Materials and structures, Harbin Institute of Technology, Harbin 150080 (China); Department of Physics, Harbin Institute of Technology, Harbin 150080 (China); Academy of Fundamental and Interdisciplinary Sciences, Harbin 150080 (China)

    2017-04-15

    (Gadolinium) Gd-doped antiperovskite compounds Mn{sub 3}Cu{sub 1−x}Gd{sub x}N were synthesized by the conventional solid-state reaction. With increasing Gd concentration, two magnetic transitions appeared at a high Curie temperature (T{sub C1}) corresponding to paramagnetic (PM)-ferromagnetic (FM) transition and a low temperature (T{sub C2}) ascribed to the FM-antiferromagnetic (AFM) transition. The magnetic relaxation results show the formation of a magnetic metastable state after the FM-AFM transition at low temperature (lower than T{sub C2}), forming a novel magnetic-step feature in the process from AFM to FM under a certain magnetic field. - Highlights: • For the first time, a novel magnetization-step features were revealed in Mn-based antiperovskite compounds. • This study not only benefits us to understand the intrinsic origin of two magnetic transitions after Gd doped, but also paves the way for the design and fabrication of new antiperovskite nitrides with different magnetic state and transition temperature for practical applications. • Two-step magnetic transition were induced by doping Gd element. • The process from AFM to FM in the magnetization-step is irreversible, which is different from that observed in other materials.

  17. Ising-type magnetic anisotropy in a cobalt(II) nitronyl nitroxide compound: a key to understanding the formation of molecular magnetic nanowires.

    Science.gov (United States)

    Caneschi, A; Gatteschi, Dante; Lalioti, N; Sessoli, R; Sorace, L; Tangoulis, V; Vindigni, A

    2002-01-04

    The compound [Co(hfac)2-(NITPhOMe)2] (2) (hfac = hexafluoroacetylacetonate, NITPhOMe = 4'-methoxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) crystallizes in the triclinic P1 space group, a= 10.870(5), b = 11.520(5), c = 19.749(5) A, alpha = 78.05(5), beta = 84.20(5), gamma = 64.51(5) degrees, Z = 2. It can be considered a model system for studying the nature of the magnetic anisotropy of [Co(hfac)2(NITPhOMe)] (1), which was recently reported to behave as a molecular magnetic wire. The magnetic anisotropy of 2 was investigated by EPR spectroscopy and SQUID magnetometry both in the polycrystalline powder and in a single crystal. The experimental magnetic anisotropy was related to the anisotropy of the central ion and to the exchange interaction between the cobalt(II) ion and the radicals.

  18. Transport coefficients and orientational distributions of dilute colloidal dispersions composed of hematite particles (for an external magnetic field parallel to the angular velocity vector of simple shear flow)

    International Nuclear Information System (INIS)

    Satoh, Akira; Hayasaka, Ryo; Majima, Tamotsu

    2008-01-01

    We have treated a dilute dispersion composed of ferromagnetic rodlike particles with a magnetic moment normal to the particle axis, such as hematites, to investigate the influences of the magnetic field strength, shear rate, and random forces on the orientational distribution of rodlike particles and also on transport coefficients, such as viscosity and diffusion coefficient. In the present analysis, these rodlike particles are assumed to conduct the rotational Brownian motion in a simple shear flow as well as an external magnetic field. The results obtained here are summarized as follows. In the case of a strong magnetic field and a smaller shear rate, the rodlike particle can freely rotate in the xy-plane with the magnetic moment continuing to point the magnetic field direction. On the other hand, for a strong shear flow, the particle has a tendency to incline in the flow direction with the magnetic moment pointing to the magnetic field direction. In the case of the magnetic field applied normal to the direction of the sedimentation, the diffusion coefficient gives rise to smaller values than expected, since the rodlike particle sediments with the particle axis inclining toward directions normal to the movement direction and, of course, toward the direction along that direction

  19. Magnetization of Paraffin-Based Magnetic Nanocolloids

    Science.gov (United States)

    Dikanskii, Yu. I.; Ispiryan, A. G.; Kunikin, S. A.; Radionov, A. V.

    2018-01-01

    Using paraffin-based magnetic nanocolloids as an example, the reasons for maxima in the temperature dependence of the magnetic susceptibility of magnetic colloids have been discussed. The behavior of these dependences in a wide temperature interval has been analyzed for colloids in solid and liquid states. It has been concluded that the maximum observed at the melting point of paraffin can be attributed to freezing Brownian degrees of freedom in magnetite coarse particles, the magnetic moment of which is intimately related to the solid matrix. The second main maximum, which arises in the solid state, is explained by the superparamagnetic-magnetically hard transition of most fine particles at lower temperatures. It has been noted that the flatness of this maximum results from the polydispersity of the magnetic nanoparticle ensemble.

  20. Characterization of Key Aroma Compounds in Raw and Thermally Processed Prawns and Thermally Processed Lobsters by Application of Aroma Extract Dilution Analysis.

    Science.gov (United States)

    Mall, Veronika; Schieberle, Peter

    2016-08-24

    Application of aroma extract dilution analysis (AEDA) to an aroma distillate of blanched prawn meat (Litopenaeus vannamei) (BPM) revealed 40 odorants in the flavor dilution (FD) factor range from 4 to 1024. The highest FD factors were assigned to 2-acetyl-1-pyrroline, 3-(methylthio)propanal, (Z)-1,5-octadien-3-one, trans-4,5-epoxy-(E)-2-decenal, (E)-3-heptenoic acid, and 2-aminoacetophenone. To understand the influence of different processing conditions on odorant formation, fried prawn meat was investigated by means of AEDA in the same way, revealing 31 odorants with FD factors between 4 and 2048. Also, the highest FD factors were determined for 2-acetyl-1-pyrroline, 3-(methylthio)propanal, and (Z)-1,5-octadien-3-one, followed by 4-hydroxy-2,5-dimethyl-3(2H)-furanone, (E)-3-heptenoic acid, and 2-aminoacetophenone. As a source of the typical marine, sea breeze-like odor attribute of the seafood, 2,4,6-tribromoanisole was identified in raw prawn meat as one of the contributors. Additionally, the aroma of blanched prawn meat was compared to that of blanched Norway and American lobster meat, respectively (Nephrops norvegicus and Homarus americanus). Identification experiments revealed the same set of odorants, however, with differing FD factors. In particular, 3-hydroxy-4,5-dimethyl-2(5H)-furanone was found as the key aroma compound in blanched Norway lobster, whereas American lobster contained 3-methylindole with a high FD factor.

  1. Quantifying the dilution effect for models in ecological epidemiology.

    Science.gov (United States)

    Roberts, M G; Heesterbeek, J A P

    2018-03-01

    The dilution effect , where an increase in biodiversity results in a reduction in the prevalence of an infectious disease, has been the subject of speculation and controversy. Conversely, an amplification effect occurs when increased biodiversity is related to an increase in prevalence. We explore the conditions under which these effects arise, using multi species compartmental models that integrate ecological and epidemiological interactions. We introduce three potential metrics for quantifying dilution and amplification, one based on infection prevalence in a focal host species, one based on the size of the infected subpopulation of that species and one based on the basic reproduction number. We introduce our approach in the simplest epidemiological setting with two species, and show that the existence and strength of a dilution effect is influenced strongly by the choices made to describe the system and the metric used to gauge the effect. We show that our method can be generalized to any number of species and to more complicated ecological and epidemiological dynamics. Our method allows a rigorous analysis of ecological systems where dilution effects have been postulated, and contributes to future progress in understanding the phenomenon of dilution in the context of infectious disease dynamics and infection risk. © 2018 The Author(s).

  2. Magnetic ordering in TCNQ-based metal–organic frameworks with host–guest interactions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xuan; Saber, Mohamed R.; Prosvirin, Andrey P.; Reibenspies, Joseph H.; Sun, Lei; Ballesteros-Rivas, Maria; Zhao, Hanhua; Dunbar, Kim R. (MIT); (TAM)

    2015-09-03

    Host–guest interactions between the aromatic molecules benzene, toluene, aniline and nitrobenzene and the redox-active TCNQ-based metal–organic framework (MOF), Fe(TCNQ)(4,4'-bpy) (1) (TCNQ = 7,7,8,8-tetracyanoquinodimethane), have been found to modulate spontaneous magnetization behaviours at low temperatures. An analogous MOF, Mn(TCNQ)(4,4'-bpy) (2) with isotropic Mn(II) ions as well as the two-dimensional compound Fe(TCNQ)(DMF)2·2DMF (3·2DMF), were also prepared as models for studying the effects of single-ion magnetic anisotropy and structural distortion on spin canting. The results indicate guest-dependent long range magnetic ordering occurs at low temperatures, which correlates with the electrostatic and steric effects of the incorporated aromatic guests.

  3. Crystalline and Electronic Structures and Magnetic and Electrical Properties of La-Doped Ca2Fe2O5 Compounds

    Science.gov (United States)

    Phan, T. L.; Tho, P. T.; Tran, N.; Kim, D. H.; Lee, B. W.; Yang, D. S.; Thiet, D. V.; Cho, S. L.

    2018-01-01

    Brownmillerite Ca2Fe2O5 has been observed to exhibit many outstanding properties that are applicable to ecotechnology. However, very little work on doped Ca2Fe2O5 compounds has been carried out to widen their application scope. We present herein a detailed study of the crystalline/geometric and electronic structures and magnetic and electrical properties of Ca2- x La x Fe2O5 ( x = 0 to 1) prepared by conventional solid-state reaction. X-ray diffraction patterns indicated that the compounds with x = 0 to 0.05 exhibited brownmillerite-type single phase. La doping with higher content ( x ≥ 0.1) stimulated additive formation of Grenier- (LaCa2Fe3O8) and perovskite-type (LaFeO3) phases. Extended x-ray absorption fine structure spectroscopy at the Fe K-edge and electron spin resonance spectroscopy revealed presence of Fe3+ in the parent Ca2Fe2O5 ( x = 0) and both Fe3+ and Fe4+ in the doped compounds ( x ≥ 0.05). The Fe4+ content tended to increase with increasing x. This stimulates ferromagnetic exchange interactions between Fe3+ and Fe4+ ions and directly influences the magnetic properties of Ca2- x La x Fe2O5. Electrical resistivity ( ρ) measurements in the temperature range of T = 20 K to 400 K revealed that all the compounds exhibit insulator behavior; the ρ( T) data for x ≥ 0.1 could be described based on the adiabatic small polaron hopping model.

  4. Spin-dependent recombination processes in wide band gap II-Mn-VI compounds

    International Nuclear Information System (INIS)

    Godlewski, M.; Yatsunenko, S.; Khachapuridze, A.; Ivanov, V.Yu.

    2004-01-01

    Mechanisms of optical detection of magnetic resonance in wide band gap II-Mn-VI diluted magnetic semiconductor (DMS) are discussed based on the results of photoluminescence (PL), PL kinetics, electron spin resonance (ESR) and optically detected magnetic resonance (ODMR) and optically detected cyclotron resonance (ODCR) investigations. Spin-dependent interactions between localized spins of Mn 2+ ions and spins/magnetic moments of free, localized or bound carriers are responsible for the observed ODMR signals. We conclude that these interactions are responsible for the observed rapid shortening of the PL decay time of 4 T 1 → 6 A 1 intra-shell emission of Mn 2+ ions and also for the observed delocalization of excitons in low dimensional structures

  5. Mn concentration and quantum size effects on spin-polarized transport through CdMnTe based magnetic resonant tunneling diode.

    Science.gov (United States)

    Mnasri, S; Abdi-Ben Nasrallahl, S; Sfina, N; Lazzari, J L; Saïd, M

    2012-11-01

    Theoretical studies on spin-dependent transport in magnetic tunneling diodes with giant Zeeman splitting of the valence band are carried out. The studied structure consists of two nonmagnetic layers CdMgTe separated by a diluted magnetic semiconductor barrier CdMnTe, the hole is surrounded by two p-doped CdTe layers. Based on the parabolic valence band effective mass approximation and the transfer matrix method, the magnetization and the current densities for holes with spin-up and spin-down are studied in terms of the Mn concentration, the well and barrier thicknesses as well as the voltage. It is found that, the current densities depend strongly on these parameters and by choosing suitable values; this structure can be a good spin filter. Such behaviors are originated from the enhancement and suppression in the spin-dependent resonant states.

  6. Nuclear magnetic resonance of randomly diluted magnetic materials; Ressonancia nuclear magnetica em materiais magneticos diluidos aleatoriamente

    Energy Technology Data Exchange (ETDEWEB)

    Magon, C J

    1986-12-31

    The temperature dependence of the nuclear relaxation rates and line shapes of the F{sub O} resonance in the diluted antiferromagnet Fe{sub x} Zn{sub 1-x} F{sub 2} and Mn{sub x} Zn{sub 1-x} F{sub 2} are studied over a large temperature range T{sub N} < {approx} T {<=} 300 K. The high (room) temperature spin-lattice relaxation rates (1/T{sub 1}) of the F{sub O} nuclei, which are not transfer hyperfine coupled to the Fe (or Mn) spins, have been measured and calculated as a function of the concentration x. Good agreement with experiment is found for the theoretical results, which have been obtained in the range 0.1 {<=} x {<=} 0.8. The temperature dependence of 1/T{sub 1} for T{sub N}magnetization. (author).

  7. Magnetic, thermodynamic and transport properties of novel non-centrosymmetric RCoSi{sub 3} (R=Pr, Nd and Sm) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Nallamuthu, S. [Department of Physics, National Institute of Technology, Tiruchirappalli 620015, Tamil Nadu (India); Chandrasekaran, S. Selva; Murugan, P. [CSIR-Central Electrochemical Research Institute, Karaikudi 630006, Tamil Nadu (India); Reiffers, Marian [Faculty of Humanities and Natural Sciences, Presov University, Presov (Slovakia); Nagalakshmi, R., E-mail: nagaphys@yahoo.com [Department of Physics, National Institute of Technology, Tiruchirappalli 620015, Tamil Nadu (India)

    2016-10-15

    Novel non-centrosymmetric RCoSi{sub 3} (R = Pr, Nd and Sm) compounds crystallize in tetragonal BaNiSn{sub 3} type structure with space group I4 mm. The bulk magnetic ordering of all the compounds were confirmed from heat capacity data. Magnetization measurements indicate that PrCoSi{sub 3} orders ferromagnetically at 5.9 K, while NdCoSi{sub 3} and SmCoSi{sub 3} order antiferromagnetically at 4 K and 8 K respectively. The magnetic transitions were also manifested by the slope change of temperature dependent resistivity at low temperatures. The energy level schemes created by crystal electric field splitting are determined from Schottky contribution to specific heat. The existence of magnon gap like features at low temperatures are consistent in both heat capacity and resistivity for NdCoSi{sub 3} and SmCoSi{sub 3}. Large magnetoresistance is observed in NdCoSi{sub 3} and SmCoSi{sub 3}. First principles electronic structure calculation based on density functional theory framework have been performed and compared with experimental data. - Highlights: • Magnetic, transport and thermodynamic studies are investigated extensively. • PrCoSi{sub 3} orders T{sub C} = 5.9 K, NdCoSi{sub 3} and SmCoSi{sub 3} order T{sub N}=4 K and 8 K. • Large magnetoresistance is observed in NdCoSi{sub 3} and SmCoSi{sub 3}. • Density of states calculated at the Fermi levels [N(E{sub F})].

  8. Quenched bond-dilute Ising ferromagnet in square lattice: thermodynamical properties

    International Nuclear Information System (INIS)

    Honmura, R.; Sarmento, E.F.; Tsallis, C.

    1982-01-01

    Within an effective field framework which improves the Molecular Field Approximation, the phase diagram, magnetization, specific heat and susceptibility associated with the quenched bond-dilute Ising ferromagnet in square lattice is calculated. The results are qualitatively (and within certain extent quantitatively) satisfactory; in particular the effects, on the specific heat and susceptibility, of the (eventually) coexisting finite and infinite clusters are exhibited. (Author) [pt

  9. Spectral, magnetic, and thermal properties of some thiazolylazo complexes

    International Nuclear Information System (INIS)

    Masoud, M. S.; Mohamed, G. B.; Abdulrazek, Y. H.; Ali, A. E.; Khairy, F. N.

    2002-01-01

    The thiazolylazo compounds and their Co(II), Ni(II) and Cu(II) complexes of barbituric acid, uracil, thiouracil, citrazinic acid, chromotropic acid, gallic acid, pyrogallol and salicylic acid were prepared and characterized by 1 H NMR, IR and the effect of pH on the electronic absorption spectra. The mode of ionization, the electronic transitions and the dissociation constants were discussed. The stoichiometries of the complexed were of 1:1, 2:1 and 3:2 (M:L). The copper complexes are of isotropic ESR spectra (except that of gallic acid which showed a complicated one) and are of magnetically diluted behavior with orbital contribution. Detailed DTA data were obtained and discussed

  10. Determination of critical nitrogen dilution curve based on stem dry matter in rice.

    Directory of Open Access Journals (Sweden)

    Syed Tahir Ata-Ul-Karim

    Full Text Available Plant analysis is a very promising diagnostic tool for assessment of crop nitrogen (N requirements in perspectives of cost effective and environment friendly agriculture. Diagnosing N nutritional status of rice crop through plant analysis will give insights into optimizing N requirements of future crops. The present study was aimed to develop a new methodology for determining the critical nitrogen (Nc dilution curve based on stem dry matter (SDM and to assess its suitability to estimate the level of N nutrition for rice (Oryza sativa L. in east China. Three field experiments with varied N rates (0-360 kg N ha(-1 using three Japonica rice hybrids, Lingxiangyou-18, Wuxiangjing-14 and Wuyunjing were conducted in Jiangsu province of east China. SDM and stem N concentration (SNC were determined during vegetative stage for growth analysis. A Nc dilution curve based on SDM was described by the equation (Nc = 2.17W(-0.27 with W being SDM in t ha(-1, when SDM ranged from 0.88 to 7.94 t ha(-1. However, for SDM < 0.88 t ha(-1, the constant critical value Nc = 1.76% SDM was applied. The curve was dually validated for N-limiting and non-N-limiting growth conditions. The N nutrition index (NNI and accumulated N deficit (Nand of stem ranged from 0.57 to 1.06 and 51.1 to -7.07 kg N ha(-1, respectively, during key growth stages under varied N rates in 2010 and 2011. The values of ΔN derived from either NNI or Nand could be used as references for N dressing management during rice growth. Our results demonstrated that the present curve well differentiated the conditions of limiting and non-limiting N nutrition in rice crop. The SDM based Nc dilution curve can be adopted as an alternate and novel approach for evaluating plant N status to support N fertilization decision during the vegetative growth of Japonica rice in east China.

  11. Magnetic and structural properties of the magnetic shape memory compound Ni2Mn1.48Sb0.52

    International Nuclear Information System (INIS)

    Brown, P J; Gandy, A P; Neumann, K U; Sheikh, A; Ziebeck, K R A; Ishida, K; Oikawa, K; Ito, W; Kainuma, R; Kanomata, T; Ouladdiaf, B

    2010-01-01

    Magnetization and high resolution neutron powder diffraction measurements on the magnetic shape memory compound Ni 2 Mn 1.48 Sb 0.52 have confirmed that it is ferromagnetic below 350 K and undergoes a structural phase transition at T M ∼310 K. The high temperature phase has the cubic L2 1 structure with a = 5.958 A, with the excess manganese atoms occupying the 4(b) Sb sites. In the cubic phase above ∼310 K the manganese moments are ferromagnetically aligned. The magnetic moment at the 4(a) site is 1.57(12) μ B and it is almost zero (0.15(9) μ B ) at the 4(b) site. The low temperature orthorhombic phase which is only fully established below 50 K has the space group Pmma with a cell related to the cubic one by a Bain transformation a orth = (a cub + b cub )/2; b orth = c cub and c orth = (a cub - b cub ). The change in cell volume is ∼2.5%. The spontaneous magnetization of samples cooled in fields less than 0.5 T decreases at temperatures below T M and at 2 K the magnetic moment per formula unit in fields up to 5.5 T is 2.01(5) μ B . Neutron diffraction patterns obtained below ∼132 K gave evidence for a weak incommensurate magnetic modulation with propagation vector (2/3, 1/3, 0).

  12. A chiral-based magnetic memory device without a permanent magnet.

    Science.gov (United States)

    Ben Dor, Oren; Yochelis, Shira; Mathew, Shinto P; Naaman, Ron; Paltiel, Yossi

    2013-01-01

    Several technologies are currently in use for computer memory devices. However, there is a need for a universal memory device that has high density, high speed and low power requirements. To this end, various types of magnetic-based technologies with a permanent magnet have been proposed. Recent charge-transfer studies indicate that chiral molecules act as an efficient spin filter. Here we utilize this effect to achieve a proof of concept for a new type of chiral-based magnetic-based Si-compatible universal memory device without a permanent magnet. More specifically, we use spin-selective charge transfer through a self-assembled monolayer of polyalanine to magnetize a Ni layer. This magnitude of magnetization corresponds to applying an external magnetic field of 0.4 T to the Ni layer. The readout is achieved using low currents. The presented technology has the potential to overcome the limitations of other magnetic-based memory technologies to allow fabricating inexpensive, high-density universal memory-on-chip devices.

  13. Cryogen-free dilution refrigerators

    International Nuclear Information System (INIS)

    Uhlig, K

    2012-01-01

    We review briefly our first cryogen-free dilution refrigerator (CF-DR) which was precooled by a GM cryocooler. We then show how today's dry DRs with pulse tube precooling have developed. A few examples of commercial DRs are explained and noteworthy features pointed out. Thereby we describe the general advantages of cryogen-free DRs, but also show where improvements are still desirable. At present, our dry DR has a base temperature of 10 mK and a cooling capacity of 700 μW at a mixing chamber temperature of 100 mK. In our cryostat, in most recent work, an additional refrigeration loop was added to the dilution circuit. This 4 He circuit has a lowest temperature of about 1 K and a refrigeration capacity of up to 100 mW at temperatures slightly above 1 K; the dilution circuit and the 4 He circuit can be run separately or together. The purpose of this additional loop is to increase the cooling capacity for experiments where the cooling power of the still of the DR is not sufficient to cool cold amplifiers and cables, e.g. in studies on superconducting quantum circuits or astrophysical applications.

  14. Cryogen-free dilution refrigerators

    Science.gov (United States)

    Uhlig, K.

    2012-12-01

    We review briefly our first cryogen-free dilution refrigerator (CF-DR) which was precooled by a GM cryocooler. We then show how today's dry DRs with pulse tube precooling have developed. A few examples of commercial DRs are explained and noteworthy features pointed out. Thereby we describe the general advantages of cryogen-free DRs, but also show where improvements are still desirable. At present, our dry DR has a base temperature of 10 mK and a cooling capacity of 700 μW at a mixing chamber temperature of 100 mK. In our cryostat, in most recent work, an additional refrigeration loop was added to the dilution circuit. This 4He circuit has a lowest temperature of about 1 K and a refrigeration capacity of up to 100 mW at temperatures slightly above 1 K; the dilution circuit and the 4He circuit can be run separately or together. The purpose of this additional loop is to increase the cooling capacity for experiments where the cooling power of the still of the DR is not sufficient to cool cold amplifiers and cables, e.g. in studies on superconducting quantum circuits or astrophysical applications.

  15. Synthetic structural and biochemical studies of coordination compounds of Bismuth (III) with Schiff bases of sulpha drugs

    International Nuclear Information System (INIS)

    Khan, Shahina; Gupta, M.K.; Varshney, S; Varshney, A.K.

    2006-01-01

    The reactions of Bismuth trichloride with Schiff's bases derived from sulpha drugs in 1:1 molar ratio leads to the formation of a new series of coordination compound of Bismuth (III). Their structures have been confirmed on the basis of elemental analysis, ultraviolet, infrared and multinuclear magnetic resonance (1H 13C) spectral studies. The antimicrobial activities of the ligands and their coordination compound have been screened in vitro against the organism Escherichia coli, Stuplhylococus crureus, Prouteus mirabilis, Bacillus thuren giensis, penicilliurn cf.vsogenum, Aspergillns raiger and Fusarium Oxysporum. (author)

  16. Molecular analysis of two mouse dilute locus deletion mutations: Spontaneous dilute lethal20J and radiation-induced dilute prenatal lethal Aa2 alleles

    International Nuclear Information System (INIS)

    Strobel, M.C.; Seperack, P.K.; Copeland, N.G.; Jenkins, N.A.

    1990-01-01

    The dilute (d) coat color locus of mouse chromosome 9 has been identified by more than 200 spontaneous and mutagen-induced recessive mutations. With the advent of molecular probes for this locus, the molecular lesion associated with different dilute alleles can be recognized and precisely defined. In this study, two dilute mutations, dilute-lethal20J (dl20J) and dilute prenatal lethal Aa2, have been examined. Using a dilute locus genomic probe in Southern blot analysis, we detected unique restriction fragments in dl20J and Aa2 DNA. Subsequent analysis of these fragments showed that they represented deletion breakpoint fusion fragments. DNA sequence analysis of each mutation-associated deletion breakpoint fusion fragment suggests that both genomic deletions were generated by nonhomologous recombination events. The spontaneous dl20J mutation is caused by an interstitial deletion that removes a single coding exon of the dilute gene. The correlation between this discrete deletion and the expression of all dilute-associated phenotypes in dl20J homozygotes defines the dl20J mutation as a functional null allele of the dilute gene. The radiation-induced Aa2 allele is a multilocus deletion that, by complementation analysis, affects both the dilute locus and the proximal prenatal lethal-3 (pl-3) functional unit. Molecular analysis of the Aa2 deletion breakpoint fusion fragment has provided access to a previously undefined gene proximal to d. Initial characterization of this new gene suggests that it may represent the genetically defined pl-3 functional unit

  17. XMCD study of the local magnetic and structural properties of microcrystalline NdFeB-based alloys

    Science.gov (United States)

    Menushenkov, A. P.; Ivanov, V. G.; Shchetinin, I. V.; Zhukov, D. G.; Menushenkov, V. P.; Rudnev, I. A.; Ivanov, A. A.; Wilhelm, F.; Rogalev, A.; Savchenko, A. G.

    2017-01-01

    X-ray Magnetic Circular Dichroism (XMCD) technique was used to investigate local magnetic properties of microcrystalline Nd10.4Zr4.0Fe79.2B6.4 samples, oriented along either easy or hard magnetization direction. The Nd L 2,3 and Fe K edge XMCD spectra were measured at room temperature under a magnetic field of T. A very strong dependence of XMCD spectra on the sample orientation has been observed at the Nd L 2,3-edges, whereas the Fe K-edge XMCD spectra are found to be practically isotropic. This result indicates that magnetic anisotropy of NdFeB-based alloys originates from the Nd sublattice. In addition, element selective magnetization curves have been recorded by measuring the intensity of XMCD signals as a function of an applied magnetic field up to T. To find a correlation between local and macroscopic magnetic properties of studied samples we compared these data with magnetization curves, measured by vibrating sample magnetometer up to T. Results are important for understanding the origin of high-coercivity state in NdFeB-based intermetallic compounds.

  18. Selective Removal of the Genotoxic Compound 2-Aminopyridine in Water using Molecularly Imprinted Polymers Based on Magnetic Chitosan and β-Cyclodextrin

    Directory of Open Access Journals (Sweden)

    Wei Zhang

    2017-08-01

    Full Text Available To develop efficient materials with enhanced adsorption and selectivity for genotoxic 2-aminopyridine in water, based on magnetic chitosan (CTs and β-cyclodextrin (β-CD, the magnetic molecularly imprinted polymers (MMIPs of Fe3O4-CTs@MIP and Fe3O4-MAH-β-CD@MIP were synthesized by a molecular imprinting technique using 2-aminopyridine as a template. The selective adsorption experiments for 2-aminopyridine were performed by four analogues including pyridine, aniline, 2-amino-5-chloropyridine and phenylenediamine. Results showed the target 2-aminopyridine could be selectively adsorbed and quickly separated by the synthesized MMIPs in the presence of the above structural analogues. The coexisting ions including Na+, K+, Mg2+, Ca2+, Cl− and SO42− showed little effect on the adsorption of 2-aminopyridine. The maximum adsorption capacity of 2-aminopyridine on Fe3O4-CTs@MIP and Fe3O4-MAH-β-CD@MIP was 39.2 mg·g−1 and 46.5 mg·g−1, respectively, which is much higher than values in previous reports. The comparison result with commercial activated carbon showed the obtained MMIPs had higher adsorption ability and selectivity for 2-aminopyridine. In addition, the synthesized MMIPs exhibited excellent performance of regeneration, which was used at least five times with little adsorption capacity loss. Therefore, the synthesized MMIPs are potential effective materials in applications for selective removal and analysis of the genotoxic compound aminopyridine from environmental water.

  19. Organic- and molecule-based magnets

    Indian Academy of Sciences (India)

    The discovery of organic- and molecule-based magnets has led to design and synthesis of several families with magnetic ordering temperatures as high as ∼ 125° C. Examples of soft and hard magnets with coercivities as high as 27 kOe have also been reported. Examples from our laboratory of organic-based magnets ...

  20. Insertion of a single-molecule magnet inside a ferromagnetic lattice based on a 3D bimetallic oxalate network: towards molecular analogues of permanent magnets.

    Science.gov (United States)

    Clemente-León, Miguel; Coronado, Eugenio; Gómez-García, Carlos J; López-Jordà, Maurici; Camón, Agustín; Repollés, Ana; Luis, Fernando

    2014-02-03

    The insertion of the single-molecule magnet (SMM) [Mn(III)(salen)(H2O)]2(2+) (salen(2-) = N,N'-ethylenebis-(salicylideneiminate)) into a ferromagnetic bimetallic oxalate network affords the hybrid compound [Mn(III)(salen)(H2O)]2[Mn(II)Cr(III)(ox)3]2⋅(CH3OH)⋅(CH3CN)2 (1). This cationic Mn2 cluster templates the growth of crystals formed by an unusual achiral 3D oxalate network. The magnetic properties of this hybrid magnet are compared with those of the analogous compounds [Mn(III)(salen)(H2O)]2[Zn(II)Cr(III)(ox)3]2⋅(CH3OH)⋅(CH3CN)2 (2) and [In(III)(sal2-trien)][Mn(II)Cr(III)(ox)3]⋅(H2O)0.25⋅(CH3OH)0.25⋅(CH3CN)0.25 (3), which are used as reference compounds. In 2 it has been shown that the magnetic isolation of the Mn2 clusters provided by their insertion into a paramagnetic oxalate network of Cr(III) affords a SMM behavior, albeit with blocking temperatures well below 500 mK even for frequencies as high as 160 kHz. In 3 the onset of ferromagnetism in the bimetallic Mn(II) Cr(III) network is observed at Tc = 5 K. Finally, in the hybrid compound 1 the interaction between the two magnetic networks leads to the antiparallel arrangement of their respective magnetizations, that is, to a ferrimagnetic phase. This coupling induces also important changes on the magnetic properties of 1 with respect to those of the reference compounds 2 and 3. In particular, compound 1 shows a large magnetization hysteresis below 1 K, which is in sharp contrast with the near-reversible magnetizations that the SMMs and the oxalate ferromagnetic lattice show under the same conditions. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Magnetically Recoverable Supported Ruthenium Catalyst for Hydrogenation of Alkynes and Transfer Hydrogenation of Carbonyl Compounds

    Science.gov (United States)

    A ruthenium (Ru) catalyst supported on magnetic nanoparticles (NiFe2O4) has been successfully synthesized and used for hydrogenation of alkynes at room temperature as well as transfer hydrogenation of a number of carbonyl compounds under microwave irradiation conditions. The cata...

  2. Electronic structure and magnetic properties of the ThCo4B compound

    International Nuclear Information System (INIS)

    Benea, D.; Pop, V.; Isnard, O.

    2008-01-01

    Detailed theoretical investigations of the electronic and magnetic properties of the newly discovered ThCo 4 B compound have been performed. The influence of the local environment on the magnitude of the Co magnetic moments is discussed by comparing the magnetic and electronic properties in the ThCo 4 B, YCo 4 B and ThCo 5 systems. All theoretical investigations of the electronic and magnetic properties have been done using the Korringa-Kohn-Rostoker (KKR) band-structure method in the ferromagnetic state. Very good agreement of the calculated and the experimental magnetic moments is obtained. Larger exchange-splitting is observed on the 2c site which carries by far the largest magnetic moment. Comparison of the band structure calculation for ThCo 5 and ThCo 4 B reveals that the presence of boron in the Co 6i site environment induces a broadening of the electronic bands as well as a significant reduction of the exchange-splitting and a diminution of the DOS at the Fermi level. These differences are attributed to the hybridization of the boron electronic states to the cobalt 3d ones. The calculated magnetic moment is 1.94μ B /formula unit. A large difference on the magnetic moment magnitude of the two Co sites is observed since 1.30 and 0.27μ B /atom are calculated for the 2c and 6i sites, respectively. The orbital contribution is found to differ by almost an order of magnitude on both cobalt sites. The Co magnetic moment is much smaller in the ThCo 4 B than in the YCo 4 B or RCo 4 B (where R is a rare earth) isotypes evidencing the major role played by the Th-Co bands on the electronic properties

  3. Melt-Dilute Form of AI-Based Spent Nuclear Fuel Disposal Criticality Summary Report

    International Nuclear Information System (INIS)

    D. Vinson; A. Serika

    2002-01-01

    Criticality analysis of the proposed melt-dilute (MD) form of aluminum-based spent nuclear fuel (SNF), under geologic repository conditions, was performed [1] following the methodology documented in the Disposal Criticality Analysis Methodology Topical Report [2]. This methodology evaluates the potential for nuclear criticality for a waste form in a waste package. Criticality calculations show that even with waste package failure, followed by degradation of material within the waste package and potential loss of neutron absorber materials, sub-critical conditions can be readily demonstrated for the MD form of aluminum-based SNF

  4. First-principles study of ZnSnAs2-based dilute magnetic semiconductors

    Science.gov (United States)

    Kizaki, Hidetoshi; Morikawa, Yoshitada

    2018-02-01

    The electronic structure and magnetic properties of chalcopyrite Zn(Sn,TM)As2 and (Zn,TM)SnAs2 have been investigated by the Korringa-Kohn-Rostoker method combined with the coherent potential approximation within the local spin density approximation, where TM denotes a 3d transition metal element. We find that the half-metallic and high-spin ferromagnetic state can be obtained in Zn(Sn,V)As2, Zn(Sn,Cr)As2, Zn(Sn,Mn)As2, (Zn,V)SnAs2, and (Zn,Cr)SnAs2. The calculated result of Zn(Sn,Mn)As2 is in good agreement with the experimentally observed room-temperature ferromagnetism if we can control selective Mn doping at Sn sites. In addition, (Zn,V)SnAs2 and (Zn,Cr)SnAs2 are predicted to exhibit high-Curie-temperature ferromagnetism.

  5. Magnetic, electrical and structural properties of the Re-doped ruthenocuprate Ru{sub 1−x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y}

    Energy Technology Data Exchange (ETDEWEB)

    Corredor, L.T. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Programa de Pós-Graduação em Ciências de Materiais-CCEN, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, Bogotá D.C. (Colombia); Albino Aguiar, J. [Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Programa de Pós-Graduação em Ciências de Materiais-CCEN, Universidade Federal de Pernambuco, 50670-901 Recife, PE (Brazil); Landínez Téllez, D.A. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, Bogotá D.C. (Colombia); Pureur, P.; Mesquita, F. [Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, RS (Brazil); Roa-Rojas, J. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, Bogotá D.C. (Colombia)

    2015-06-15

    Highlights: • We investigated the effect of the dilution of magnetic Ru sub-lattice of RuSr{sub 2}GdCu{sub 2}O{sub 8}. • We synthesized the doped compound Rui{sub x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y}, for 3%, 6%, 9% and 12% Re. • Re would affect the electron coupling: just 3 and 6% samples were superconductor. • Superconductivity emergence strongly affects magnetic properties of 3 and 6% samples. • A weak ferromagnetic component is consistent with a globally antiferromagnetic system. - Abstract: Despite the discovery of new superconductors classes, high-Tc oxides continue to be a current topic, because of their complex phase diagrams and doping-dependant effects (allowing one to investigate the interaction between orbitals), as well as structural properties such as lattice distortion and charge ordering, among many others. Ruthenocuprates are magnetic superconductors in which the magnetic transition temperature is much higher than the critical superconducting temperature, making them unique compounds. With the aim of investigating the dilution of the magnetic Ru sub-lattice, we proposed the synthesis of the Ru{sub 1−x}Re{sub x}Sr{sub 2}GdCu{sub 2}O{sub y} ruthenocuprate-type family, adapting the known two-step process (double perovskite + CuO) by directly doping the double perovskite, thus obtaining the perovskite compound Sr{sub 2}GdRu{sub 1−x}Re{sub x}O{sub y}, which represents a new synthesis process to the best of our knowledge. Our samples were structurally characterized through X-ray diffraction, and the patterns were analysed via Rietveld refinement. A complete magnetic characterization as a function of temperature and applied field, as well as transport measurements were carried out. We discuss our results in the light of the two-lattice model for ruthenocuprates, and a relation between RuO{sub 2} (magnetic) and CuO{sub 2} (superconductor) sub-lattices can clearly be observed.

  6. Ferromagnetism in diluted magnetic semiconductor heterojunction systems

    Czech Academy of Sciences Publication Activity Database

    Lee, B.; Jungwirth, Tomáš; MacDonald, A. H.

    2002-01-01

    Roč. 17, - (2002), s. 393-403 ISSN 0268-1242 R&D Projects: GA ČR GA202/98/0085; GA MŠk OC P5.10 Institutional research plan: CEZ:AV0Z1010914 Keywords : ferromagnetic semiconductors * heterostructures Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.241, year: 2002

  7. Enhancing the magnetic properties of magnetic nanoparticles

    DEFF Research Database (Denmark)

    Ahlburg, Jakob; Saura-Múzquiz, Matilde; Stingaciu, Marian

    with a similar magnetic performance. There are several different ways of enhancing magnetic properties of 3d magnetic compounds. This includes, size control, core-shell particles or mixing hard and soft magnetic materials together to achieve an exchange coupling between the compounds and enhancing the magnetic...... energy product. In order to control the particle size, a hydrothermal synthesis is preferred. This followed by reduction or the oxides into either core shell particles, or a mixture of magnetic oxides and a metallic phase....

  8. Mobile Melt-Dilute Treatment for Russian Spent Nuclear Fuel

    International Nuclear Information System (INIS)

    Peacock, H.

    2002-01-01

    Treatment of spent Russian fuel using a Melt-Dilute (MD) process is proposed to consolidate fuel assemblies into a form that is proliferation resistant and provides critically safety under storage and disposal configurations. Russian fuel elements contain a variety of fuel meat and cladding materials. The Melt-Dilute treatment process was initially developed for aluminum-based fuels so additional development is needed for several cladding and fuel meat combinations in the Russian fuel inventory (e.g. zirconium-clad, uranium-zirconium alloy fuel). A Mobile Melt-Dilute facility (MMD) is being proposed for treatment of spent fuels at reactor site storage locations in Russia; thereby, avoiding the costs of building separate treatment facilities at each site and avoiding shipment of enriched fuel assemblies over the road. The MMD facility concept is based on laboratory tests conducted at the Savannah River Technology Center (SRTC), and modular pilot-scale facilities constructed at the Savannah River Site for treatment of US spent fuel. SRTC laboratory tests have shown the feasibility of operating a Melt-Dilute treatment process with either a closed system or a filtered off-gas system. The proposed Mobile Melt-Dilute process is presented in this paper

  9. The Lattice Compatibility Theory LCT: Physical and Chemical Arguments from the Growth Behavior of Doped Compounds in terms of Bandgap Distortion and Magnetic Effects

    Directory of Open Access Journals (Sweden)

    K. Boubaker

    2013-01-01

    Full Text Available Physical and chemical arguments for the recently discussed materials-related Lattice Compatibility Theory are presented. The discussed arguments are based on some differences of Mn ions incorporation kinetics inside some compounds. These differences have been evaluated and quantified in terms of alteration of bandgap edges, magnetic patterns, and Faraday effect.

  10. Synthesis of Zn{sub 0.95}Cr{sub 0.05}O DMS by co-precipitation and ceramic methods: Structural and magnetization studies

    Energy Technology Data Exchange (ETDEWEB)

    Paul Joseph, D. [Materials Science Centre, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600025 (India); Naveenkumar, S. [Materials Science Centre, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600025 (India); Sivakumar, N. [Materials Science Centre, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600025 (India); Venkateswaran, C. [Materials Science Centre, Department of Nuclear Physics, University of Madras, Guindy Campus, Chennai 600025 (India)]. E-mail: cvunom@hotmail.com

    2006-05-10

    Transitional metal ions-substituted ZnO are recently explored for SPINTRONICS applications. Synthesis of single-phase oxide 'diluted magnetic semiconductors' (DMS) is a must to explore the magnetic properties arising due to the strong sp-d exchange interaction. The synthesis route plays a vital role in this aspect. In this work, we have prepared Zn{sub 0.95}Cr{sub 0.05}O by using the co-precipitation method and also the standard ceramic method and optimized the conditions to obtain the single-phase compound. X-ray diffraction measurements were done on Zn{sub 0.95}Cr{sub 0.05}O annealed and sintered at various temperatures. Comparing these results, we conclude that the co-precipitation method is more convenient for obtaining single-phase compound by the relatively low temperature processing of the precipitated hydroxides. Pelleted sample examined for its magnetic property using a vibrating sample magnetometer (VSM) indicated ferromagnetic-like behavior at 300 K and a spin-glass state at 77 K.

  11. Moessbauer studies of SnO2 powders doped with dilute 57Fe, prepared by a sol-gel method

    International Nuclear Information System (INIS)

    Nomur, K.; Sakuma, J.; Takeda, M.

    2006-01-01

    Diluted magnetic semiconductor (DMS) is prospected as new materials with both semiconductor and magnetic properties. In order to confirm these phenomena, we prepared the powders of SnO 2 doped with various amount of 57 Fe by a sol-gel method. Various compositions of Sn 1-x 57 Fe x O 2 were obtained by mixing some ratio of Fe 3+ nitrate solution and acetylacetonate Sn 4+ complex in the ethylene glycol and citric acid solution. The solutions were evaporated, ashed at around 200 grad C, and finally annealed at 500 grad C, 600 grad C, and 650 grad C, respectively. These Sn 1-x 57 Fe x O 2 (x=0.005, 0.01, 0.03 and 0.05) were measured by XRD, VSM, and Moessbauer spectrometry. The prepared powder samples were confirmed to be a rutile structure, but iron compounds were not detected by XRD. Moessbauer spectra of Sn 1-x 57 Fe x O 2 prepared at 500 grad C were shown in Fig. 1. A small amount of broad sextets were observed in MS spectra of Sn 1-x 57 Fe x O 2 in addition to paramagnetic components. The relative intensity seems to be strong with the decrease of the amount of doped Fe. Moessbauer spectrum at 10 K shows clearly the magnetic components. The magnetic sextet was observed in MS spectra of samples prepared at 650 grad C, but the magnetic behavior weakened because of antiferromagnetic α-Fe 2 O 3 , produced due to the phase separation at high temperatures. (authors)

  12. Simultaneous determination of creatinine and creatine in human serum by double-spike isotope dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-mass spectrometry (GC-MS).

    Science.gov (United States)

    Fernández-Fernández, Mario; Rodríguez-González, Pablo; Añón Álvarez, M Elena; Rodríguez, Felix; Menéndez, Francisco V Álvarez; García Alonso, J Ignacio

    2015-04-07

    This work describes the first multiple spiking isotope dilution procedure for organic compounds using (13)C labeling. A double-spiking isotope dilution method capable of correcting and quantifying the creatine-creatinine interconversion occurring during the analytical determination of both compounds in human serum is presented. The determination of serum creatinine may be affected by the interconversion between creatine and creatinine during sample preparation or by inefficient chemical separation of those compounds by solid phase extraction (SPE). The methodology is based on the use differently labeled (13)C analogues ((13)C1-creatinine and (13)C2-creatine), the measurement of the isotopic distribution of creatine and creatinine by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and the application of multiple linear regression. Five different lyophilized serum-based controls and two certified human serum reference materials (ERM-DA252a and ERM-DA253a) were analyzed to evaluate the accuracy and precision of the proposed double-spike LC-MS/MS method. The methodology was applied to study the creatine-creatinine interconversion during LC-MS/MS and gas chromatography-mass spectrometry (GC-MS) analyses and the separation efficiency of the SPE step required in the traditional gas chromatography-isotope dilution mass spectrometry (GC-IDMS) reference methods employed for the determination of serum creatinine. The analysis of real serum samples by GC-MS showed that creatine-creatinine separation by SPE can be a nonquantitative step that may induce creatinine overestimations up to 28% in samples containing high amounts of creatine. Also, a detectable conversion of creatine into creatinine was observed during sample preparation for LC-MS/MS. The developed double-spike LC-MS/MS improves the current state of the art for the determination of creatinine in human serum by isotope dilution mass spectrometry (IDMS), because corrections are made for all the possible errors

  13. Hybridizing pines with diluted pollen

    Science.gov (United States)

    Robert Z. Callaham

    1967-01-01

    Diluted pollens would have many uses by the tree breeder. Dilutions would be particularly advantageous in making many controlled pollinations with a limited amount of pollen. They also would be useful in artificial mass pollinations of orchards or single trees. Diluted pollens might help overcome troublesome genetic barriers to crossing. Feasibility o,f using diluted...

  14. Development of a Hybrid Piezo Natural Rubber Piezoelectricity and Piezoresistivity Sensor with Magnetic Clusters Made by Electric and Magnetic Field Assistance and Filling with Magnetic Compound Fluid.

    Science.gov (United States)

    Shimada, Kunio; Saga, Norihiko

    2017-02-10

    Piezoelements used in robotics require large elasticity and extensibility to be installed in an artificial robot skin. However, the piezoelements used until recently are vulnerable to large forces because of the thin solid materials employed. To resolve this issue, we utilized a natural rubber and applied our proposed new method of aiding with magnetic and electric fields as well as filling with magnetic compound fluid (MCF) and doping. We have verified the piezoproperties of the resulting MCF rubber. The effect of the created magnetic clusters is featured in a new two types of multilayered structures of the piezoelement. By measuring the piezoelectricity response to pressure, the synergetic effects of the magnetic clusters, the doping and the electric polymerization on the piezoelectric effect were clarified. In addition, by examining the relation between the piezoelectricity and the piezoresistivity created in the MCF piezo element, we propose a hybrid piezoelement.

  15. Development of a Hybrid Piezo Natural Rubber Piezoelectricity and Piezoresistivity Sensor with Magnetic Clusters Made by Electric and Magnetic Field Assistance and Filling with Magnetic Compound Fluid

    Science.gov (United States)

    Shimada, Kunio; Saga, Norihiko

    2017-01-01

    Piezoelements used in robotics require large elasticity and extensibility to be installed in an artificial robot skin. However, the piezoelements used until recently are vulnerable to large forces because of the thin solid materials employed. To resolve this issue, we utilized a natural rubber and applied our proposed new method of aiding with magnetic and electric fields as well as filling with magnetic compound fluid (MCF) and doping. We have verified the piezoproperties of the resulting MCF rubber. The effect of the created magnetic clusters is featured in a new two types of multilayered structures of the piezoelement. By measuring the piezoelectricity response to pressure, the synergetic effects of the magnetic clusters, the doping and the electric polymerization on the piezoelectric effect were clarified. In addition, by examining the relation between the piezoelectricity and the piezoresistivity created in the MCF piezo element, we propose a hybrid piezoelement. PMID:28208625

  16. Development of a Hybrid Piezo Natural Rubber Piezoelectricity and Piezoresistivity Sensor with Magnetic Clusters Made by Electric and Magnetic Field Assistance and Filling with Magnetic Compound Fluid

    Directory of Open Access Journals (Sweden)

    Kunio Shimada

    2017-02-01

    Full Text Available Piezoelements used in robotics require large elasticity and extensibility to be installed in an artificial robot skin. However, the piezoelements used until recently are vulnerable to large forces because of the thin solid materials employed. To resolve this issue, we utilized a natural rubber and applied our proposed new method of aiding with magnetic and electric fields as well as filling with magnetic compound fluid (MCF and doping. We have verified the piezoproperties of the resulting MCF rubber. The effect of the created magnetic clusters is featured in a new two types of multilayered structures of the piezoelement. By measuring the piezoelectricity response to pressure, the synergetic effects of the magnetic clusters, the doping and the electric polymerization on the piezoelectric effect were clarified. In addition, by examining the relation between the piezoelectricity and the piezoresistivity created in the MCF piezo element, we propose a hybrid piezoelement.

  17. Two stages of Kondo effect and competition between RKKY and Kondo in Gd-based intermetallic compound

    Energy Technology Data Exchange (ETDEWEB)

    Vaezzadeh, Mehdi [Department of Physics, K.N.Toosi University of Technology, P.O. Box 15875-4416, Tehran (Iran, Islamic Republic of)]. E-mail: mehdi@kntu.ac.ir; Yazdani, Ahmad [Tarbiat Modares University, P.O. Box 14155-4838, Tehran (Iran, Islamic Republic of); Vaezzadeh, Majid [Department of Physics, K.N.Toosi University of Technology, P.O. Box 15875-4416, Tehran (Iran, Islamic Republic of); Daneshmand, Gissoo [Department of Physics, K.N.Toosi University of Technology, P.O. Box 15875-4416, Tehran (Iran, Islamic Republic of); Kanzeghi, Ali [Department of Physics, K.N.Toosi University of Technology, P.O. Box 15875-4416, Tehran (Iran, Islamic Republic of)

    2006-05-01

    The magnetic behavior of Gd-based intermetallic compound (Gd{sub 2}Al{sub (1-x)}Au{sub x}) in the form of the powder and needle, is investigated. All the samples are an orthorhombic crystal structure. Only the compound with x=0.4 shows the Kondo effect (other compounds have a normal behavior). Although, for the compound in the form of powder, with x=0.4, the susceptibility measurement {chi}(T) shows two different stages. Moreover for (T>T{sub K2}) a fall of the value of {chi}(T) is observable, which indicates a weak presence of ferromagnetic phase. About the two stages of Kondo effect, we observe at the first (T{sub K1}) an increase of {chi}(T) and in the second stage (T{sub K2}) a new remarkable decrease of {chi}(T) (T{sub K1}>T{sub K2}). For the sample in the form of needles, the first stage is observable only under high magnetic field. This first stage could be corresponds to a narrow resonance between Kondo cloud and itinerant electron. The second stage, which is remarkably visible for the sample in the form of the powder, can be attribute to a complete polarization of Kondo cloud. Observation of these two Kondo stages could be due to the weak presence of RKKY contribution.

  18. Antiferroquadrupolar ordering and anisotropic magnetic phase diagram of dysprosium palladium bronze, DyPd3S4

    International Nuclear Information System (INIS)

    Matsuoka, Eiichi; Tayama, Takashi; Sakakibara, Toshiro; Hiroi, Zenji; Takeda, Naoya; Ishikawa, Masayasu; Shirakawa, Naoki

    2007-01-01

    From the measurements of magnetization and specific heat, we constructed B-T phase diagrams of single-crystalline DyPd 3 S 4 which is known to exhibit antiferroquadrupolar (AFQ) and antiferromagnetic (AFM) ordering at low temperatures. The phase diagrams are found to be highly anisotropic and re-entrant, which are typical of rare-earth compounds exhibiting multipolar ordering. The crystalline electric field (CEF) scheme of Dy 3+ in DyPd 3S4 was deduced from the specific heat and magnetization measurements of the Y-diluted compounds Dy 1-x Y x Pd 3 S 4 (0.1≤x≤0.9) and discussed in detail. The CEF ground state was determined to be the orbitally-degenerated quartet Γ 67 (1) , and the overall splitting width was estimated to be about 104 K. No correlation was found between the anisotropy of T Q and that of the Zeeman splitting width of the ground quartet Γ 67 (1) . (author)

  19. Impact of hydrogen absorption on crystal structure and magnetic properties of RE{sub 2}T{sub 2}X compounds

    Energy Technology Data Exchange (ETDEWEB)

    Mašková, S., E-mail: maskova@mag.mff.cuni.cz [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic); Kolomiets, A. [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic); Department of Physics, Lviv Polytechnic National University, Lviv (Ukraine); Havela, L. [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic); Andreev, A.V. [Institute of Physics, AVCR, Prague 8 (Czech Republic); Svoboda, P. [Department of Condensed Matter Physics, Charles University, Prague 2 (Czech Republic)

    2015-10-05

    Highlights: • RE{sub 2}Pd{sub 2}In(Sn) compounds absorb, depending on RE, different amounts of hydrogen. • Compounds with the light rare earths become amorphous upon the hydrogenation. • Compounds with the heavy rare earths preserve the original tetragonal structure. • Magnetic ordering temperatures of RE{sub 2}Pd{sub 2}In compounds are reduced by the hydrogenation. - Abstract: RE{sub 2}Pd{sub 2}In, RE{sub 2}Pd{sub 2}Sn compounds (RE = rare earth) absorb, depending on the rare earth (RE) element, different amounts of hydrogen. The parent compounds RE{sub 2}Pd{sub 2}In show the linear decrease of both lattice parameters and the unit cell volume with the increasing atomic number of RE, attributed to the lanthanide contraction. All the compounds absorb at least 2 H/f.u.; the tetragonal structure is merely expanded. The expansion is anisotropic (Δc/c > Δa/a), and for RE = Tb, Dy, Ho, and Er the lattice even contracts along the a-axis (Δa/a < 0), whereas Δc/c still weakly increases. A higher H concentration can be achieved in the compounds with light rare earths (La, Nd, both for In and Sn), which then become amorphous. The magnetic ordering temperatures of all studied RE{sub 2}Pd{sub 2}In compounds are dramatically reduced by the hydrogenation, typically to the temperature range below 1.8 K.

  20. Optimization of the solvent-based dissolution method to sample volatile organic compound vapors for compound-specific isotope analysis.

    Science.gov (United States)

    Bouchard, Daniel; Wanner, Philipp; Luo, Hong; McLoughlin, Patrick W; Henderson, James K; Pirkle, Robert J; Hunkeler, Daniel

    2017-10-20

    The methodology of the solvent-based dissolution method used to sample gas phase volatile organic compounds (VOC) for compound-specific isotope analysis (CSIA) was optimized to lower the method detection limits for TCE and benzene. The sampling methodology previously evaluated by [1] consists in pulling the air through a solvent to dissolve and accumulate the gaseous VOC. After the sampling process, the solvent can then be treated similarly as groundwater samples to perform routine CSIA by diluting an aliquot of the solvent into water to reach the required concentration of the targeted contaminant. Among solvents tested, tetraethylene glycol dimethyl ether (TGDE) showed the best aptitude for the method. TGDE has a great affinity with TCE and benzene, hence efficiently dissolving the compounds during their transition through the solvent. The method detection limit for TCE (5±1μg/m 3 ) and benzene (1.7±0.5μg/m 3 ) is lower when using TGDE compared to methanol, which was previously used (385μg/m 3 for TCE and 130μg/m 3 for benzene) [2]. The method detection limit refers to the minimal gas phase concentration in ambient air required to load sufficient VOC mass into TGDE to perform δ 13 C analysis. Due to a different analytical procedure, the method detection limit associated with δ 37 Cl analysis was found to be 156±6μg/m 3 for TCE. Furthermore, the experimental results validated the relationship between the gas phase TCE and the progressive accumulation of dissolved TCE in the solvent during the sampling process. Accordingly, based on the air-solvent partitioning coefficient, the sampling methodology (e.g. sampling rate, sampling duration, amount of solvent) and the final TCE concentration in the solvent, the concentration of TCE in the gas phase prevailing during the sampling event can be determined. Moreover, the possibility to analyse for TCE concentration in the solvent after sampling (or other targeted VOCs) allows the field deployment of the sampling

  1. Developments on drug discovery and on new therapeutics: highly diluted tinctures act as biological response modifiers

    Directory of Open Access Journals (Sweden)

    de Oliveira Carolina C

    2011-10-01

    Full Text Available Abstract Background In the search for new therapies novel drugs and medications are being discovered, developed and tested in laboratories. Highly diluted substances are intended to enhance immune system responses resulting in reduced frequency of various diseases, and often present no risk of serious side-effects due to its low toxicity. Over the past years our research group has been investigating the action of highly diluted substances and tinctures on cells from the immune system. Methods We have developed and tested several highly diluted tinctures and here we describe the biological activity of M1, M2, and M8 both in vitro in immune cells from mice and human, and in vivo in mice. Cytotoxicity, cytokines released and NF-κB activation were determined after in vitro treatment. Cell viability, oxidative response, lipid peroxidation, bone marrow and lymph node cells immunophenotyping were accessed after mice in vivo treatment. Results None of the highly diluted tinctures tested were cytotoxic to macrophages or K562. Lipopolysaccharide (LPS-stimulated macrophages treated with all highly diluted tinctures decreased tumour necrosis factor alpha (TNF-α release and M1, and M8 decreased IFN-γ production. M1 has decreased NF-κB activity on TNF-α stimulated reporter cell line. In vivo treatment lead to a decrease in reactive oxygen species (ROS, nitric oxide (NO production was increased by M1, and M8, and lipid peroxidation was induced by M1, and M2. All compounds enhanced the innate immunity, but M1 also augmented acquired immunity and M2 diminished B lymphocytes, responsible to acquired immunity. Conclusions Based on the results presented here, these highly diluted tinctures were shown to modulate immune responses. Even though further investigation is needed there is an indication that these highly diluted tinctures could be used as therapeutic interventions in disorders where the immune system is compromised.

  2. Anisotropic magnetic phase diagram of Kondo-Lattice compound Ce3Pd20Ge6 with quadrupolar ordering

    International Nuclear Information System (INIS)

    Kitagawa, Jiro; Takeda, Naoya; Ishikawa, Masayasu; Yoshida, Toshiya; Ishiguro, Akiko; Kimura, Noriaki; Komatsubara, Takemi

    1999-01-01

    We have measured the specific heat and the electrical resistivity of Ce 3 Pd 20 Ge 6 in magnetic fields up to 4T applied along three principal directions. The compound shows the large negative magnetoresistance in the quadrupolar phase. The coefficient of the electronic specific heat and T 2 -coefficient of the electrical resistivity are considerably reduced at 4T. The magnetic phase diagram constructed from these measurements suggests the existence of a highly anisotropic interaction between the electric quadrupolar moments and the magnetic dipolar moments. (author)

  3. Absence of magnetic long-range order in Y2CrSbO7 : Bond-disorder-induced magnetic frustration in a ferromagnetic pyrochlore

    Science.gov (United States)

    Shen, L.; Greaves, C.; Riyat, R.; Hansen, T. C.; Blackburn, E.

    2017-09-01

    The consequences of random nonmagnetic-ion dilution for the pyrochlore family Y2(M 1 -xN x)2O7 (M = magnetic ion, N = nonmagnetic ion) have been investigated. As a first step, we experimentally examine the magnetic properties of Y2CrSbO7 (x =0.5 ), in which the magnetic sites (Cr3 +) are percolative. Although the effective Cr-Cr spin exchange is ferromagnetic, as evidenced by a positive Curie-Weiss temperature, ΘCW ≃19.5 K , our high-resolution neutron powder diffraction measurements detect no sign of magnetic long-range order down to 2 K. In order to understand our observations, we construct a lattice model to numerically study the bond disorder introduced by the ionic size mismatch between M and N , which reveals that the bond disorder percolates at xb ≃0.23 , explaining the absence of magnetic long-range order. This model could be applied to a series of frustrated magnets with a pyrochlore sublattice, for example, the spinel compound Zn (Cr1 -xGax )2O4 , wherein a Néel to spin glass phase transition occurs between x =0.2 and 0.25 [Lee et al., Phys. Rev. B 77, 014405 (2008), 10.1103/PhysRevB.77.014405]. Our study stresses the non-negligible role of bond disorder on magnetic frustration, even in ferromagnets.

  4. A rotary permanent magnet magnetic refrigerator based on AMR cycle

    International Nuclear Information System (INIS)

    Aprea, C.; Cardillo, G.; Greco, A.; Maiorino, A.; Masselli, C.

    2016-01-01

    Magnetic refrigeration is an emerging, environment-friendly technology based on a magnetic solid that acts as a refrigerant by magneto-caloric effect (MCE). The reference cycle for magnetic refrigeration is AMR (Active Magnetic Regenerative refrigeration). In order to demonstrate the potential of magnetic refrigeration to provide useful cooling in the near room temperature range, a novel Rotary Permanent Magnet Magnetic Refrigerator (RPMMR) is described in this paper. Gadolinium has been selected as magnetic refrigerant and demineralized water has been employed as regenerating fluid. The total mass of gadolinium (1.20 kg), shaped as packed bed spheres, is housed in 8 regenerators. A magnetic system, based on a double U configuration of permanent magnets, provides a magnetic flux density of 1.25 T with an air gap of 43 mm. A rotary vane pump forces the regenerating fluid through the regenerators. The operational principle of the magnetic refrigerator and initial experimental results are reported and analyzed.

  5. Study of the magnetic phase transitions and magnetocaloric effect in Dy{sub 2}Cu{sub 2}In compound

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yikun, E-mail: ykzhang10@hotmail.com [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai, 200072 (China); Shanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University, Shanghai, 200072 (China); School of Materials Science and Engineering, Shanghai University, 200072 (China); Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Straße 10, D-48149, Münster (Germany); Xu, Xiao; Yang, Yang; Hou, Long; Ren, Zhongming [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai, 200072 (China); Shanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University, Shanghai, 200072 (China); School of Materials Science and Engineering, Shanghai University, 200072 (China); Li, Xi, E-mail: lx_net@sina.com [State Key Laboratory of Advanced Special Steels, Shanghai University, Shanghai, 200072 (China); Shanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University, Shanghai, 200072 (China); School of Materials Science and Engineering, Shanghai University, 200072 (China); Wilde, Gerhard [Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Straße 10, D-48149, Münster (Germany)

    2016-05-15

    The magnetic properties and magnetocaloric effect (MCE) in Dy{sub 2}Cu{sub 2}In compound have been investigated. Dy{sub 2}Cu{sub 2}In undergoes two magnetic phase transitions, a paramagnetic to ferromagnetic (FM) at T{sub C} ∼ 49.5 K followed by a spin reorientation (SR) at T{sub SR} ∼ 19.5 K. For a magnetic field change of 0–7 T, the maximum values of the magnetic entropy change (−ΔS{sub M}{sup max}) are estimated to be 16.5 around T{sub C} and 6.7 J/kg K around T{sub SR} with a large relative cooling power (RCP) value of 617 J/kg. The modified Arrott plots and universal curves of the rescaled ΔS{sub M} confirmed that the magnetic phase transitions in Dy{sub 2}Cu{sub 2}In compound belongs the second order phase transitions. The present results may provide some clues to search for new magnetocaloric materials belonging to RE{sub 2}T{sub 2}X system. - Highlights: • Magnetic properties and magnetocaloric effect in Dy{sub 2}Cu{sub 2}In was studied. • The Dy{sub 2}Cu{sub 2}In undergoes 2 s order magnetic phase transitions. • A large reversible MCE was observed in Dy{sub 2}Cu{sub 2}In. • The origin of MCE and its potential application in Dy{sub 2}Cu{sub 2}In were discussed.

  6. Nature of the magnetic ground state in the mixed valence compound CeRuSn: a single-crystal study

    International Nuclear Information System (INIS)

    Fikáček, J; Prokleška, J; Prchal, J; Custers, J; Sechovský, V

    2013-01-01

    We report on detailed low-temperature measurements of the magnetization, the specific heat and the electrical resistivity on high-quality CeRuSn single crystals. The compound orders antiferromagnetically at T N = 2.8 K with the Ce 3+ ions locked within the a–c plane of the monoclinic structure. Magnetization shows that below T N CeRuSn undergoes a metamagnetic transition when applying a magnetic field of 1.5 and 0.8 T along the a- and c-axis, respectively. This transition manifests in a tremendous negative jump of ∼25% in the magnetoresistance. The value of the saturated magnetization along the easy magnetization direction (c-axis) and the magnetic entropy above T N derived from specific heat data correspond to the scenario of only one third of the Ce ions in the compound being trivalent and carrying a stable Ce 3+ magnetic moment, whereas the other two thirds of the Ce ions are in a nonmagnetic tetravalent and/or mixed valence state. This is consistent with the low-temperature CeRuSn crystal structure i.e., a superstructure consisting of three unit cells of the CeCoAl type piled up along the c-axis, and in which the Ce 3+ ions are characterized by large distances from the Ru ligands while the Ce–Ru distances of the other Ce ions are much shorter causing a strong 4f-ligand hybridization and hence leading to tetravalent and/or mixed valence Ce ions. (paper)

  7. Magnetic order close to superconductivity in the iron-based layered LaO1-xFxFeAs systems

    Science.gov (United States)

    de La Cruz, Clarina; Huang, Q.; Lynn, J. W.; Li, Jiying; , W. Ratcliff, II; Zarestky, J. L.; Mook, H. A.; Chen, G. F.; Luo, J. L.; Wang, N. L.; Dai, Pengcheng

    2008-06-01

    Following the discovery of long-range antiferromagnetic order in the parent compounds of high-transition-temperature (high-Tc) copper oxides, there have been efforts to understand the role of magnetism in the superconductivity that occurs when mobile `electrons' or `holes' are doped into the antiferromagnetic parent compounds. Superconductivity in the newly discovered rare-earth iron-based oxide systems ROFeAs (R, rare-earth metal) also arises from either electron or hole doping of their non-superconducting parent compounds. The parent material LaOFeAs is metallic but shows anomalies near 150K in both resistivity and d.c. magnetic susceptibility. Although optical conductivity and theoretical calculations suggest that LaOFeAs exhibits a spin-density-wave (SDW) instability that is suppressed by doping with electrons to induce superconductivity, there has been no direct evidence of SDW order. Here we report neutron-scattering experiments that demonstrate that LaOFeAs undergoes an abrupt structural distortion below 155K, changing the symmetry from tetragonal (space group P4/nmm) to monoclinic (space group P112/n) at low temperatures, and then, at ~137K, develops long-range SDW-type antiferromagnetic order with a small moment but simple magnetic structure. Doping the system with fluorine suppresses both the magnetic order and the structural distortion in favour of superconductivity. Therefore, like high-Tc copper oxides, the superconducting regime in these iron-based materials occurs in close proximity to a long-range-ordered antiferromagnetic ground state.

  8. Magnetic and electrical properties of In doped FeCr{sub 2}S{sub 4} compound

    Energy Technology Data Exchange (ETDEWEB)

    Sagredo, V. [Lab. de Magnetismo, Facultad de Ciencias, Universidad de los Andes, Merida, 5101 (Venezuela)], E-mail: sagredo@ula.ve; Davila, Y. [Lab. de Magnetismo, Facultad de Ciencias, Universidad de los Andes, Merida, 5101 (Venezuela); Goya, G.F. [Instituto Universitario de Investigacion en Nanociencia de Aragon, Zaragoza (Spain)

    2008-07-15

    Single crystals of FeIn{sub 1-x}Cr{sub 2x}S{sub 4} compounds have been grown by using the chemical transport method. DC magnetization measurements on single crystals for 0.6{<=}x{<=}1.0 revealed a reentrant behavior below T{sub sg}=120-170 K depending on the Cr concentration sample. The transition temperature T{sub c} increases as the indium concentration increases. The electrical resistivity measurements on polycrystalline materials above the Curie temperature revealed that the conduction behavior could be described as magnetic-polaron transport.

  9. A probabilistic analysis of rapid boron dilution scenarios

    International Nuclear Information System (INIS)

    Kohut, P.; Diamond, D.J.

    1993-01-01

    A probabilistic and deterministic analysis of a rapid boron dilution scenario related to reactor restart was performed. The event is initiated by a loss of off-site power during the startup dilution process. The automatic restart of the charging pump in such cases may lead to the accumulation of a diluted slug of water in the lower plenum. The restart of the reactor coolant pumps may send the diluted slug through the core, adding sufficient reactivity to overcome the shutdown margin and cause a power excursion. The concern is that the power excursion is sufficient in certain circumstances to cause fuel damage. The estimated core damage frequency based on the scoping analysis is 1.0--3.0E-05/yr for the plants analyzed. These are relatively significant values when compared to desirable goals. The analysis contained assumptions related to plant specific design characteristics which may lead to non-conservative estimates. The most important conservative assumptions were that mixing of the injected diluted water is insignificant and that fuel damage occurs when the slug passes through the core

  10. The Melt-Dilute Treatment Technology Offgas Development Status Report

    International Nuclear Information System (INIS)

    Adams, T. M.

    1999-01-01

    The melt-dilute treatment technology is being developed to facilitate the ultimate disposition of highly enriched Al-Base DOE spent nuclear fuels in a geologic repository such as that proposed for Yucca Mountain. The melt-dilute process is a method of preparing DOE spent nuclear fuel for long term storage

  11. Selection of anion exchangers for detoxification of dilute-acid hydrolysates from spruce.

    Science.gov (United States)

    Horváth, Ilona Sárvári; Sjöde, Anders; Nilvebrant, Nils-Olof; Zagorodni, Andrei; Jönsson, Leif J

    2004-01-01

    Six anion-exchange resins with different properties were compared with respect to detoxification of a dilute-acid hydrolysate of spruce prior to ethanolic fermentation with Saccharomyces cerevisiae. The six resins encompassed strong and weak functional groups as well as styrene-, phenol-, and acrylic-based matrices. In an analytical experimental series, fractions from columns packed with the different resins were analyzed regarding pH, glucose, furfural, hydroxymethylfurfural, phenolic compounds, levulinic acid, acetic acid, formic acid, and sulfate. An initial adsorption of glucose occurred in the strong alkaline environment and led to glucose accumulation at a later stage. Acetic and levulinic acid passed through the column before formic acid, whereas sulfate had the strongest affinity. In a preparative experimental series, one fraction from each of six columns packed with the different resins was collected for assay of the fermentability and analysis of glucose, mannose, and fermentation inhibitors. The fractions collected from strong anion-exchange resins with styrene-based matrices displayed the best fermentability: a sevenfold enhancement of ethanol productivity compared with untreated hydrolysate. Fractions from a strong anion exchanger with acrylic-based matrix and a weak exchanger with phenol-based resin displayed an intermediate improvement in fermentability, a four- to fivefold increase in ethanol productivity. The fractions from two weak exchangers with styrene- and acrylic-based matrices displayed a twofold increase in ethanol productivity. Phenolic compounds were more efficiently removed by resins with styrene- and phenol-based matrices than by resins with acrylic-based matrices.

  12. Magnetism and transport studies in off-stoichiometric metallic perovskite compounds GdPd{sub 3}B{sub x} (x=0.25, 0.50 and 0.75)

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Abhishek, E-mail: abhishek.phy@gmail.co [S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata 700098 (India); Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Mazumdar, Chandan, E-mail: chandan.mazumdar@saha.ac.i [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India); Ranganathan, R. [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064 (India)

    2010-12-15

    We report the magnetic and transport properties of the off-stoichiometric metallic perovskite like compounds GdPd{sub 3}B{sub x} (x=0.25, 0.50 and 0.75). Our results show that doping with boron in the lattice of parent binary-compound GdPd{sub 3} leads to lattice expansion. Which in turn manifests in contrasting magnetic and transport behaviors of the doped compounds in comparison with the undoped GdPd{sub 3}. An attempt has been made to compare and correlate the results of magnetic and transport measurements of GdPd{sub 3}B{sub x} with that of stoichiometric compositions GdPd{sub 3}B{sub x}C{sub 1-x}. The comparative study of GdPd{sub 3}B{sub x} and GdPd{sub 3}B{sub x}C{sub 1-x} confirms that there is a strong correlations between the structural, magnetic and transport properties of these compounds.

  13. Comparison of the Magnetic Anisotropy and Spin Relaxation Phenomenon of Dinuclear Terbium(III) Phthalocyaninato Single-Molecule Magnets Using the Geometric Spin Arrangement.

    Science.gov (United States)

    Morita, Takaumi; Damjanović, Marko; Katoh, Keiichi; Kitagawa, Yasutaka; Yasuda, Nobuhiro; Lan, Yanhua; Wernsdorfer, Wolfgang; Breedlove, Brian K; Enders, Markus; Yamashita, Masahiro

    2018-02-28

    Herein we report the synthesis and characterization of a dinuclear Tb III single-molecule magnet (SMM) with two [TbPc 2 ] 0 units connected via a fused-phthalocyaninato ligand. The stable and robust complex [(obPc)Tb(Fused-Pc)Tb(obPc)] (1) was characterized by using synchrotron radiation measurements and other spectroscopic techniques (ESI-MS, FT-IR, UV). The magnetic couplings between the Tb III ions and the two π radicals present in 1 were explored by means of density functional theory (DFT). Direct and alternating current magnetic susceptibility measurements were conducted on magnetically diluted and nondiluted samples of 1, indicating this compound to be an SMM with improved properties compared to those of the well-known [TbPc 2 ] -/0/+ and the axially symmetric dinuclear Tb III phthalocyaninato triple-decker complex (Tb 2 (obPc) 3 ). Assuming that the probability of quantum tunneling of the magnetization (QTM) occurring in one TbPc 2 unit is P QTM , the probability of QTM simultaneously occurring in 1 is P QTM 2 , meaning that QTM is effectively suppressed. Furthermore, nondiluted samples of 1 underwent slow magnetic relaxation times (τ ≈ 1000 s at 0.1 K), and the blocking temperature (T B ) was determined to be ca. 16 K with an energy barrier for spin reversal (U eff ) of 588 cm -1 (847 K) due to D 4d geometry and weak inter- and intramolecular magnetic interactions as an exchange bias (H bias ), reducing QTM. Four hyperfine steps were observed by micro-SQUID measurement. Furthermore, solution NMR measurements (one-dimensional, two-dimensional, and dynamic) were done on 1, which led to the determination of the high rotation barrier (83 ± 10 kJ/mol) of the obPc ligand. A comparison with previously reported Tb III triple-decker compounds shows that ambient temperature NMR measurements can indicate improvements in the design of coordination environments for SMMs. A large U eff causes strong uniaxial magnetic anisotropy in 1, leading to a χ ax value (1.39

  14. States of atoms and interatomic interactions in complex perovskite-like oxides. Communication XXIII. Magnetic dilution in the La(Sr)NiO3-LaGaO3

    International Nuclear Information System (INIS)

    Chezhina, N.V.; Bodritskaya, Eh.V.; Zhuk, N.A.

    2008-01-01

    Magnetic susceptibility of dilute solid solutions of lanthanum gallates doped with nickel and also with nickel and strontium was studied. Calculations showed that the main contribution into the exchange interactions in gallates doped with nickel is made by dimers formed by low-spin nickel(III) (J -20 cm -1 ), and in gallates doped with strontium and nickel the main contribution is due to dimers formed by high-and low-spin nickel (J 10 cm -1 ). Electrical conductivity measurements showed that the samples under study are electron and ion conductors [ru

  15. Magneto-electrochemical recovery of diluted metals using three-dimensionally structured electrodes

    Science.gov (United States)

    Fernández, Dámaris; Romeral, Luis; Lyons, Michael E. G.

    2015-04-01

    In a typical metal recovery process, where highly purified metals are obtained from a concentrated electrolyte, usually the cathodic electrodes are planar and can be described mainly as bi-dimensional. This leads to a low space-time yield and low normalized space velocity with an impact on production rates. New requirements of low-energy consumption yet intensive production factories impose the need to adequate electrodes in order to comply. Furthermore, a reduction in the number of steps required to achieve a product would be ideal. This suggests that direct electro-precipitation of metals contained in diluted electrolytes would be in principle a desirable technique to implement. However, the less concentrated the solution, the higher the IR drop becomes, making the process more energy-consuming and current efficiency strongly decays. Good potential alternatives arise from three-dimensionally designed electrodes in the form of mesh, porous or fluidized beds, for instance, and several examples are well known in literature. Nevertheless, current efficiency can still be a problem in the more diluted electrolytes. Furthermore, the anodic electrode, where the counter reaction takes place, plays also an important role in determining the current efficiency of the overall process. In this case, the liquid-to-gas phase transition implies that the electrodes get a strong gas shield that increases the IR drop. Whereas shifting from bi-dimensional to three-dimensional electrodes could provide an alternative for achieving better performances, it is still far from the expected targets. Therefore alternative or complementary techniques to improve efficiency are required. It is well known that magnetic fields coupled with electric fields enhance mass transport via de Lorentz and other forces. In this work, the applications and properties of three-dimensional arrays subject to magnetic field interactions are examined and compared with the traditional bi-dimensional electrodes

  16. Dilution Ratios for HB Line Phase I Eductor System

    International Nuclear Information System (INIS)

    Steimke, J.L.

    2002-01-01

    HB Line Phase I product transfer includes an eductor which transfers liquid from Product Hold Tank (PHT) RT-33 or RT-34 to Tank 11.1. The eductor also dilutes the liquid from the PHT with eductant. Dilution must be reliably controlled because of criticality concerns with H Canyon Tanks. The eductor system, which contains a 1 inch Model 264 Schutte and Koerting eductor, was previously modeled [1] in 1998 and dilution ratios were calculated for different flow restrictors, eductant pressures and densities for the eductant and the contents of the PHT. The previous calculation was performed using spreadsheet software no longer supported at SRS. For the previous work dilution ratio was defined as the volume of eductant consumed divided by volume of PHT contents transferred. Since 1998 HB Line Engineering has changed the definition of dilution ratio to the total volume of liquid, eductant consumed plus the volume of PHT liquid transferred, divided by the volume of PHT liquid transferred. The 1998 base case calculation was for a restrictor diameter of 0.334 inches, an eductant supply pressure of 15 psig, full PHT, an eductant specific gravity of 1.385 and a PHT density of 1.015. The base case dilution ratio calculated in 1998 using the current definition was 3.52. After accounting for uncertainty the minimum dilution ratio decreased to 3.23. In 2001 HB Line Engineering requested that the calculation be repeated for a manganous nitrate solution eductant and also a process water eductant. The other conditions were the same as for the 1998 calculation. The objective of this report is to document the calculations and the results

  17. Magnetocaloric effects in MnFeP1-x As x -based compounds

    International Nuclear Information System (INIS)

    Brueck, E.; Ilyn, M.; Tishin, A.M.; Tegus, O.

    2005-01-01

    Here we present the results of an investigation of some magnetic and thermal properties of the compounds MnFeP 0.45 As 0.55 , MnFeP 0.47 As 0.53 , and Mn 1.1 Fe 0.9 P 0.47 As 0.53 which can be regarded as possible magnetic refrigerants for room temperature applications. Magnetization measurements are performed in the temperature range 250-330 K, in magnetic fields up to 5 T. The coexistence of the magnetic and structural first-order phase transitions is revealed in all three samples, suggesting its key role in the large values observed for the magnetocaloric effect. The adiabatic temperature change measured directly was up to 4.0, 3.4, and 4.2 K for a magnetic field change of 1.45 T

  18. Elastic and inelastic neutron scattering studies on 3d and 4f magnetic compounds

    International Nuclear Information System (INIS)

    Erkelens, W.A.C.

    1987-01-01

    First, some theoretical aspects of neutron scattering techniques are given, and the cyrogenic equipment and the neutron spectrometers employed are described. Experiments on a 3-d Ising system are described, performed at very low temperatures and in a magnetic field. Experimental proof has been obtained for the theoretical prediction that the critical behaviour of a d-dimensional Ising system in a transverse magnetic field near T=0 is identical to that of a d+1 dimensional Ising system as a function of temperature in zero field. Experiments are described on a Ni 2+ compound which represents a good example of a 1-d antiferromagnetic Heisenberg (HAF), spin s=1, system. The results give evidence for the so called 'Haldane conjecture', a theory which predicts that the ground state of HAF systems with integer spin is a nonmagnetic many-body singlet. The excited states are separated from the ground state by an energy gap. Contrastingly, half-integer spin systems are predicted to have no such gap. A short introduction is given to phenomena in rare earth, 4f compunds, like the Kondo effect and heavy fermion behaviour. Experimental results on the RE hexaborides are reported, among which CeB 6 , a typical Kondo system with complex magnetic orderings. Furthermore, inelastic neutron scattering experiments on NdB 6 and CeB 6 , performed in order to get insight in the various reaction mechanisms, are presented. Finally a report is given on magnetic correlations and excitations in two nonmagnetically ordered heavy fermion compounds, CeCu 6 and CeRu 2 Si 2 and their interpretation in the light of existing theories. 201 refs.; 61 figs.; 4 tabs

  19. Single-molecule magnets ``without'' intermolecular interactions

    Science.gov (United States)

    Wernsdorfer, W.; Vergnani, L.; Rodriguez-Douton, M. J.; Cornia, A.; Neugebauer, P.; Barra, A. L.; Sorace, L.; Sessoli, R.

    2012-02-01

    Intermolecular magnetic interactions (dipole-dipole and exchange) affect strongly the magnetic relaxation of crystals of single-molecule magnets (SMMs), especially at low temperature, where quantum tunneling of the magnetization (QTM) dominates. This leads to complex many-body problems [l]. Measurements on magnetically diluted samples are desirable to clearly sort out the behaviour of magnetically-isolated SMMs and to reveal, by comparison, the effect of intermolecular interactions. Here, we diluted a Fe4 SMM into a diamagnetic crystal lattice, affording arrays of independent and iso-oriented magnetic units. We found that the resonant tunnel transitions are much sharper, the tunneling efficiency changes significantly, and two-body QTM transitions disappear. These changes have been rationalized on the basis of a dipolar shuffling mechanism and of transverse dipolar fields, whose effect has been analyzed using a multispin model. Our findings directly prove the impact of intermolecular magnetic couplings on the SMM behaviour and disclose the magnetic response of truly-isolated giant spins in a diamagnetic crystalline environment.[4pt] [1] W. Wernsdorfer, at al, PRL 82, 3903 (1999); PRL 89, 197201 (2002); Nature 416, 406 (2002); IS Tupitsyn, PCE Stamp, NV Prokof'ev, PRB 69, 132406 (2004).

  20. High-field magnetization of dilute rare earths in yttrium

    DEFF Research Database (Denmark)

    Touborg, P.; Høg, J.; Cock, G. J.

    1974-01-01

    Magnetization measurements have been performed on single crystals of Y containing small amounts of Tb, Dy, or Er at 4.2 K in fields up to 295 × 105 A/m (370 kOe). Crystal-field and molecular-field parameters obtained from measurements of the initial susceptibility versus temperature give a satisf...... a satisfactory quantitative account of the high-field magnetization. This includes characteristic features due to the crossing and mixing of crystal-field levels....