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Sample records for magnetic order studied

  1. Moessbauer spectroscopic studies of magnetically ordered biological materials

    International Nuclear Information System (INIS)

    Dickson, D.P.E.

    1987-01-01

    This paper discusses recent work showing the application of Moessbauer spectroscopy to the study of the properties of the magnetically ordered materials which occur in a variety of biological systems. These materials display a diversity of behaviour which provides good examples of the various possibilities which can arise with iron-containing particles of different compositions and sizes. (orig.)

  2. Neutron scattering studies on magnetic excitations in complex ordered manganites

    Energy Technology Data Exchange (ETDEWEB)

    Senff, D

    2007-09-15

    This thesis deals with magnetic excitations in three different Manganese oxides, single-layered LaSrMnO{sub 4}, charge- and orbital-ordered La{sub 1/2}Sr{sub 3/2}MnO{sub 4}, and multiferroic TbMnO{sub 3}, which are studied by means of inelastic neutron scattering. The properties of the first system, LaSrMnO{sub 4}, are governed by the complex interplay of orbital, spin, and lattice degrees of freedom typical for the physics of manganites. The magnetic low-temperature behavior is quite unusual, and the comprehensive analysis of the spin-wave spectrum of LaSrMnO{sub 4} suggests a heterogenous ground state with ferromagnetic orbital polarons embedded in an antiferromagnetic background. The doped system La{sub 1/2}Sr{sub 3/2}MnO{sub 4} exhibits a stable charge- and orbital-ordered state, which today is discussed very controversially, as it is of great relevance for the colossal increase of electric conductivity at the metal-insulator transition in perovskite manganites. Analyzing the spin-wave dispersion of the ordered state, we find an excellent agreement with classical predictions by Goodenough and reject a recent alternative proposal. The different strength of the ferromagnetic and antiferromagnetic exchange in the CE-type ordering leads to the conclusion that the magnetic state has to be considered as a weak AFM coupling of stable FM elements. This thesis is further supported by the thermal evolution of the ordered state, revealing anisotropic correlations and the close competition of FM and AFM correlations above the Neel transition, as well as by the doping dependence of the charge- and orbital-ordered state, which is interpreted on the basis of a different response of the magnetic system with respect to additional electrons or holes. In the orthorhombic perovskite TbMnO{sub 3} the electric polarization is closely coupled to the magnetic degrees of freedom via a complex, non-collinear magnetic ordering. Precisely characterizing the different magnon excitations

  3. Neutron scattering studies on magnetic excitations in complex ordered manganites

    International Nuclear Information System (INIS)

    Senff, D.

    2007-09-01

    This thesis deals with magnetic excitations in three different Manganese oxides, single-layered LaSrMnO 4 , charge- and orbital-ordered La 1/2 Sr 3/2 MnO 4 , and multiferroic TbMnO 3 , which are studied by means of inelastic neutron scattering. The properties of the first system, LaSrMnO 4 , are governed by the complex interplay of orbital, spin, and lattice degrees of freedom typical for the physics of manganites. The magnetic low-temperature behavior is quite unusual, and the comprehensive analysis of the spin-wave spectrum of LaSrMnO 4 suggests a heterogenous ground state with ferromagnetic orbital polarons embedded in an antiferromagnetic background. The doped system La 1/2 Sr 3/2 MnO 4 exhibits a stable charge- and orbital-ordered state, which today is discussed very controversially, as it is of great relevance for the colossal increase of electric conductivity at the metal-insulator transition in perovskite manganites. Analyzing the spin-wave dispersion of the ordered state, we find an excellent agreement with classical predictions by Goodenough and reject a recent alternative proposal. The different strength of the ferromagnetic and antiferromagnetic exchange in the CE-type ordering leads to the conclusion that the magnetic state has to be considered as a weak AFM coupling of stable FM elements. This thesis is further supported by the thermal evolution of the ordered state, revealing anisotropic correlations and the close competition of FM and AFM correlations above the Neel transition, as well as by the doping dependence of the charge- and orbital-ordered state, which is interpreted on the basis of a different response of the magnetic system with respect to additional electrons or holes. In the orthorhombic perovskite TbMnO 3 the electric polarization is closely coupled to the magnetic degrees of freedom via a complex, non-collinear magnetic ordering. Precisely characterizing the different magnon excitations allows to identify all relevant modes of the

  4. Neutron Diffraction Studies of Nuclear Magnetic Ordering in Copper

    DEFF Research Database (Denmark)

    Jyrkkiö, T.A.; Huiku, M.T.; Siemensmeyer, K.

    1989-01-01

    for measurements in the ordered state; both our calculations and the experiments yield 1 nW beam heating. Polarized neutron experiments show that the scattered intensities from the strong fcc reflections are severely reduced by extinction. This makes the sample not very suitable for further studies with polarized...... to depend strongly on the external magnetic field between zero and the critical fieldB c=0.25 mT, indicating the existence of at least two antiferromagnetic phases. The results are compared to previous measurements of the magnetic susceptibility. Theoretical calculations do not provide a full explanation...

  5. Highly ordered FEPT and FePd magnetic nano-structures: Correlated structural and magnetic studies

    International Nuclear Information System (INIS)

    Lukaszew, Rosa Alejandra; Cebollada, Alfonso; Clavero, Cesar; Garcia-Martin, Jose Miguel

    2006-01-01

    The micro-structure of epitaxial FePt and FePd films grown on MgO (0 0 1) substrates is correlated to their magnetic behavior. The FePd films exhibit high chemical ordering and perpendicular magnetic anisotropy. On the other hand FePt films exhibit low chemical ordering, with nano-grains oriented in two orthogonal directions, forcing the magnetization to remain in the plane of the films

  6. Study of the effect of short ranged ordering on the magnetism in FeCr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jena, Ambika Prasad, E-mail: apjena@bose.res.in [Department of Condensed Matter and Materials Science, S N Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata 700098 (India); Sanyal, Biplab, E-mail: biplab.sanyal@physics.uu.se [Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); Mookerjee, Abhijit, E-mail: abhijit.mookerjee61@gmail.com [Department of Condensed Matter and Materials Science, S N Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata 700098 (India)

    2014-01-15

    For the study of magnetism in systems where the local environment plays an important role, we propose a marriage between the Monte Carlo simulation and Zunger's special quasi-random structures. We apply this technique on disordered FeCr alloys and show that our estimates of the transition temperature is in good agreement with earlier experiments. - Highlights: • The magnetism in FeCr is sensitively depended on the ordering of the atoms : disordered or with short ranged ordering. • This work uses the SQS technique suggested by Zunger has been used to generate various degrees of short range ordering in FeCr. • The electronic structure and pair energies have been obatined from first principles ASR and Lichtenstein methods. • The effect of chemical ordering on magnetic ordering is studied in detail. • Only those situations where the chemical ordering is complete have been studied.

  7. Study of the effect of short ranged ordering on the magnetism in FeCr alloys

    International Nuclear Information System (INIS)

    Jena, Ambika Prasad; Sanyal, Biplab; Mookerjee, Abhijit

    2014-01-01

    For the study of magnetism in systems where the local environment plays an important role, we propose a marriage between the Monte Carlo simulation and Zunger's special quasi-random structures. We apply this technique on disordered FeCr alloys and show that our estimates of the transition temperature is in good agreement with earlier experiments. - Highlights: • The magnetism in FeCr is sensitively depended on the ordering of the atoms : disordered or with short ranged ordering. • This work uses the SQS technique suggested by Zunger has been used to generate various degrees of short range ordering in FeCr. • The electronic structure and pair energies have been obatined from first principles ASR and Lichtenstein methods. • The effect of chemical ordering on magnetic ordering is studied in detail. • Only those situations where the chemical ordering is complete have been studied

  8. High-order coupled cluster method study of frustrated and unfrustrated quantum magnets in external magnetic fields

    International Nuclear Information System (INIS)

    Farnell, D J J; Zinke, R; Richter, J; Schulenburg, J

    2009-01-01

    We apply the coupled cluster method (CCM) in order to study the ground-state properties of the (unfrustrated) square-lattice and (frustrated) triangular-lattice spin-half Heisenberg antiferromagnets in the presence of external magnetic fields. Approximate methods are difficult to apply to the triangular-lattice antiferromagnet because of frustration, and so, for example, the quantum Monte Carlo (QMC) method suffers from the 'sign problem'. Results for this model in the presence of magnetic field are rarer than those for the square-lattice system. Here we determine and solve the basic CCM equations by using the localized approximation scheme commonly referred to as the 'LSUBm' approximation scheme and we carry out high-order calculations by using intensive computational methods. We calculate the ground-state energy, the uniform susceptibility, the total (lattice) magnetization and the local (sublattice) magnetizations as a function of the magnetic field strength. Our results for the lattice magnetization of the square-lattice case compare well to the results from QMC approaches for all values of the applied external magnetic field. We find a value for the magnetic susceptibility of χ = 0.070 for the square-lattice antiferromagnet, which is also in agreement with the results from other approximate methods (e.g., χ = 0.0669 obtained via the QMC approach). Our estimate for the range of the extent of the (M/M s =) 1/3 magnetization plateau for the triangular-lattice antiferromagnet is 1.37 SWT = 0.0794. Higher-order calculations are thus suggested for both SWT and CCM LSUBm calculations in order to determine the value of χ for the triangular lattice conclusively.

  9. 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.)

  10. Magnetism, structure and chemical order in small CoPd clusters: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Mokkath, Junais Habeeb, E-mail: Junais.Mokkath@kaust.edu.sa

    2014-01-15

    The structural, electronic and magnetic properties of small Co{sub m}Pd{sub n}(N=m+n=8,m=0−N) nanoalloy clusters are studied in the framework of a generalized-gradient approximation to density-functional theory. The optimized cluster structures have a clear tendency to maximize the number of nearest-neighbor CoCo pairs. The magnetic order is found to be ferromagnetic-like (FM) for all the ground-state structures. Antiferromagnetic-like spin arrangements were found in some low-lying isomers. The average magnetic moment per atom μ{sup ¯}{sub N} increases approximately linearly with Co content. A remarkable enhancement of the local Co moments is observed as a result of Pd doping. This is a consequence of the increase in the number of Co d holes, due to CoPd charge transfer, combined with the reduced local coordination. The influence of spin–orbit interactions on the cluster properties is also discussed. - Highlights: • This work analyses the structural and magnetic properties of CoPd nanoclusters. • The magnetic order is found to be ferromagnetic-like for all the ground-state structures. • The average magnetic moment per atom increases approximately linearly with Co content. • The influence of spin–orbit interactions on the cluster properties is discussed.

  11. Study of the effect of magnetic ordering on order–disorder transitions in binary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jena, Ambika Prasad [Department of Condensed Matter and Materials Science, S.N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata 700098 (India); Sanyal, Biplab [Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); Mookerjee, Abhijit, E-mail: abhijit@bose.res.in [Department of Condensed Matter and Materials Science, S.N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata 700098 (India)

    2014-06-01

    We set up a mean-field approximation in a random Ising model characterized by two order parameters: the local sublattice magnetization and a mean-field occupation variable which act as an order parameter for the order–disorder transition. In the effective model Hamiltonian the two order-parameters are coupled. We solve the coupled equations arising from this to describe the total phase diagram. The exchange energies for FeCo alloys have then been accurately obtained from first-principles based on the technique of orbital peeling and a Monte Carlo analysis using a coupled Metropolis-Kawasaki updating has been carried out. Our results reasonably successfully agree with earlier experimental data. - Highlights: • In this paper we study the effect of magnetic ordering on order–disorder transitions in binary alloys. • It describes a system with two order parameters, magnetic and chemical ordering, which are coupled. • We set up a mean-field theory for initial understanding and then carry out Monte Carlo simulations. • One parameter follows Kawasaki-dynamics and the other Metropolis. • It is an interesting system for study and we apply it to FeCo with exchanges calculated from first principles techniques.

  12. Non-conventional ordering studied by magnetic resonance in Fe-doped manganites

    International Nuclear Information System (INIS)

    Gutierrez, J.; Siruguri, V.; Barandiaran, J.M.; Pena, A.; Lezama, L.; Rojo, T.

    2006-01-01

    Coexistence of ferromagnetic (FM) and paramagnetic (PM) phases in La 0.7 Pb 0.3 (Mn 1-x Fe x )O 3 (0.1=< x=<0.3) manganites is studied by the electron spin resonance (ESR) technique. Doping with Fe gives rise to a progressive decrease both in the low-temperature magnetic moment and magnetic order temperature values. Obtained spectra show narrow resonance signals above Curie temperature that transform to asymmetric Dyson-like signals as temperature decreases. The evolution of line width with temperature shows minima that correlate directly with the obtained paramagnetic Curie temperatures. Analysis of spectra above and below magnetic order temperatures reveals features of complex PM to FM transitions and coexistence of both type of phases in a wide range of temperatures

  13. An experimental study of the magnetic ordering in Pd-based Fe and Mn alloys

    International Nuclear Information System (INIS)

    Verbeek, B.H.

    1979-01-01

    This thesis presents the results of an investigation on the magnetic ordering phenomena in some Pd based alloys with small concentrations of magnetic impurities. It has been the object to explore the ordering mechanisms in these alloys which lead to various types of magnetism at low temperature. The experimental techniques used are described. (Auth.)

  14. Bandstructure study of magnetic and orbital order in BaCoO3

    International Nuclear Information System (INIS)

    Pardo, V.; Blaha, P.; Iglesias, M.; Baldomir, D.; Schwarz, K.; Pereiro, M.; Botana, J.; Arias, J.E.

    2005-01-01

    Ab initio calculations were performed in the quasi-one-dimensional BaCoO 3 using the FP-APW+lo method as implemented in the WIEN2k package utilizing the LDA+U approach. Several magnetic configurations were studied, exploring different intra- and inter-chain couplings. The most stable configuration is the ferromagnetic low-spin state. The electronic structure of the Co 4+ ion (t 2g 5 ) has an orbital degree of freedom. When an 'alternating-orbital' ordering is allowed along the Co chains, the energy of the system is drastically reduced, whereas the magnetic order is a secondary effect. This orbital ordered state reproduces the experimentally found semiconducting behaviour, which is analysed studying the bandstructure of the material

  15. The magnetic order of GdMn₂Ge₂ studied by neutron diffraction and x-ray resonant magnetic scattering.

    Science.gov (United States)

    Granovsky, S A; Kreyssig, A; Doerr, M; Ritter, C; Dudzik, E; Feyerherm, R; Canfield, P C; Loewenhaupt, M

    2010-06-09

    The magnetic structure of GdMn₂Ge₂ (tetragonal I4/mmm) has been studied by hot neutron powder diffraction and x-ray resonant magnetic scattering techniques. These measurements, along with the results of bulk experiments, confirm the collinear ferrimagnetic structure with moment direction parallel to the c-axis below T(C) = 96 K and the collinear antiferromagnetic phase in the temperature region T(C) < T < T(N) = 365 K. In the antiferromagnetic phase, x-ray resonant magnetic scattering has been detected at Mn K and Gd L₂ absorption edges. The Gd contribution is a result of an induced Gd 5d electron polarization caused by the antiferromagnetic order of Mn-moments.

  16. Neutron diffraction studies of magnetic ordering in Ni-doped LaCoO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Rajeevan, N.E. [Department of Physics, Z.G. College, Calicut 673014, Kerala (India); Kumar, Vinod; Kumar, Rajesh [Department of Physics, National Institute of Technology, Hamirpur 177005, Himachal Pradesh (India); Kumar, Ravi [Beant College of Engineering and Technology, Gurudaspur 143521, Punjab (India); Kaushik, S.D. [UGC-DAE CSR Mumbai Centre, R-5 Shed, BARC, Mumbai 400085, Maharashtra (India)

    2015-11-01

    Research in rare earth cobaltite has recently been intensified due to its fascinating magnetic properties. LaCoO{sub 3}, an important cobaltite, exhibits two prominent susceptibility features at ~90 K and 500 K in low field measurement. The magnetic behavior below 100 K is predominantly antiferromagnetic (AFM), but absence of pure AFM ordering and emergence of ferromagnetic coupling on further decreasing temperature made situation more intricate. The present work of studying the effect of Ni substitution at Co site in polycrystalline LaCo{sub 1−x}Ni{sub x}O{sub 3} (0≤x≤0.3) is motivated by the interesting changes in magnetic and electronic properties. For lucid understanding, temperature dependent neutron diffraction (ND) study was carried out. ND patterns fitted with rhombohedral structure in perovskite form with R-3c space group, elucidated information on phase purity. Further temperature dependent cell parameter, Co–O bond-length and Co–O–Co bond angle were calculated for the series of Ni doped LaCoO{sub 3}. The results are explained in terms of decrease in the crystal field energy which led to the transition of cobalt from low Spin (LS) state to intermediate spin state (IS). - Highlights: • Temperature dependent neutron diffraction (ND) on Ni doped LaCoO{sub 3} are studied. • Microscopic parameters (cell, bond length, bond angle etc.) are determined by ND. • Increase in Co–O bond length and decrease in Co–O–Co bond angle on Ni substitution. • Ionic radii of Co{sup +3} in IS state (0.56 Å) is larger than in LS state (0.54 Å). • Lattice expansion induced increase in Co–O length stabilizes Co{sup +3} in magnetic state.

  17. Magnetism, structure and chemical order in small CoPd clusters: A first-principles study

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-01-01

    The structural, electronic and magnetic properties of small ComPdn (N=m+n=8,m=0-N) nanoalloy clusters are studied in the framework of a generalized-gradient approximation to density-functional theory. The optimized cluster structures have a clear tendency to maximize the number of nearest-neighbor CoCo pairs. The magnetic order is found to be ferromagnetic-like (FM) for all the ground-state structures. Antiferromagnetic-like spin arrangements were found in some low-lying isomers. The average magnetic moment per atom μ̄N increases approximately linearly with Co content. A remarkable enhancement of the local Co moments is observed as a result of Pd doping. This is a consequence of the increase in the number of Co d holes, due to CoPd charge transfer, combined with the reduced local coordination. The influence of spin-orbit interactions on the cluster properties is also discussed. © 2013 Elsevier B.V.

  18. Neutron diffraction studies of magnetic ordering in superconducting ErNi2B2C and TmNi2B2C in an applied magnetic field

    DEFF Research Database (Denmark)

    Toft, Katrine Nørgaard

    The field-induced magnetic structures of ErNi2B2C and TmNi2B2C in are especially interesting because the field suppresses the superconducting order parameter and therefore the magnetic properties can be studied while varying the strength ofsuperconductivity. ErNi2B2C: For magnetic fields along all.......483,0,0). The appearance of the QN phase wasinitially believed to be caused by the suppression of superconductivity. This suppression should make it favorable to create a magnetic order with a Q-vector determined by the maximum in the magnetic susceptibility at the Fermi surface nesting vector QN.The phase diagram...... three symmetry directions, the observed magnetic structures have a period corresponding to the Fermi surface nesting structure. The phase diagrams present all the observed magnetic structures.Two results remain unresolved: 1. When applying the magnetic field along [010], the minority domain (QNB = (0,Q...

  19. Neutron diffraction study of the magnetic long-range order in Tb

    DEFF Research Database (Denmark)

    Dietrich, O.W.; Als-Nielsen, Jens Aage

    1967-01-01

    Like other heavy rare-earth metals, Tb exhibits a magnetic phase with a spiral structure. This appears within the temperature region from 216 to 226deg K between the ferromagnetic phase and the paramagnetic phase. The transition between ferromagnetic and spiral structure is of first order and imp...... at 216deg K to 20.7deg at 226deg K. The temperature variation of the transverse magnetostriction has also been measured and was found to vary approximately in proportion to the square of the magnetic long-range order....

  20. Phase separation and magnetic ordering studied by high resolution neutron diffraction

    International Nuclear Information System (INIS)

    Caspi, E.N.; Melamud, M.; Pinto, H.; Shaked, H.; Chmaissem, O.; Jorgensen, J.D.; Short, S.

    1999-01-01

    Complete text of publication follows. In a previous work on the (U 1-x Nd x )Co 2 Ge 2 system, two magnetic transitions were observed in the temperature dependencies of the magnetic susceptibility and in the intensity of the magnetic reflections in neutron diffraction [1]. Because of insufficient resolution, it was not clear whether this is due to clustering or phase separation. In both cases the U-rich regions are expected to order magnetically at higher temperature than the U-poor ones, resulting in two magnetic transitions. In order to resolve this question a temperature dependent TOF neutron diffraction of the x = 0.25 compound has been performed on the SEPD at Argonne's IPNS [2]. The temperature dependent diffractograms were refined by the Rietveld method. It was found that the compound separates into two phases: x = 0.4 (55 wt%) and x = 0.1 (45 wt%). The temperature dependence of the magnetic moment was obtained for each phase, with the transition temperatures: T N (x=0.4) = 130 K, and T N (x=0.1) = 165 K. (author) [1] E. Caspi et al., Phys. Rev. B, 57 (198) 449.; [2] J.D. Jorgensen et al., J. Appl. Cryst. 22 (1989) 321

  1. Nuclear magnetic ordering in silver

    International Nuclear Information System (INIS)

    Lefmann, K.

    1995-12-01

    Nuclear antiferromagnetic ordering has been observed by neutron diffraction in a single crystal of 109 Ag. The critical temperature is found to 700 pK, and the critical field is 100 μT. From the paramagnetic phase a second order phase transition leads into a type-I 1-k structure with long range order. The experiments have taken place at the Hahn-Meitner Institut in Berlin in collaboration with the low Temperature Laboratory in Helsinki, the Niels Bohr Institute in Copenhagen, and Risoe National Laboratory, Roskilde. The present report is a Ph.D. thesis which has been successfully defended at the Niels Bohr Institute. Besides the results of the nuclear ordering experiments the thesis contains a description of the theoretical background for nuclear magnetism and a review of earlier nuclear ordering experiments as well as theoretical work. The principles for studying polarized nuclei with use of polarized and unpolarized neutrons are presented, as well as the results of such experiments. (au) 11 tabs., 59 ills., 143 refs

  2. Nuclear magnetic ordering in silver

    Energy Technology Data Exchange (ETDEWEB)

    Lefmann, K

    1995-12-01

    Nuclear antiferromagnetic ordering has been observed by neutron diffraction in a single crystal of {sup 109}Ag. The critical temperature is found to 700 pK, and the critical field is 100 {mu}T. From the paramagnetic phase a second order phase transition leads into a type-I 1-k structure with long range order. The experiments have taken place at the Hahn-Meitner Institut in Berlin in collaboration with the low Temperature Laboratory in Helsinki, the Niels Bohr Institute in Copenhagen, and Risoe National Laboratory, Roskilde. The present report is a Ph.D. thesis which has been successfully defended at the Niels Bohr Institute. Besides the results of the nuclear ordering experiments the thesis contains a description of the theoretical background for nuclear magnetism and a review of earlier nuclear ordering experiments as well as theoretical work. The principles for studying polarized nuclei with use of polarized and unpolarized neutrons are presented, as well as the results of such experiments. (au) 11 tabs., 59 ills., 143 refs.

  3. Theoretical study of the magnetic order in α-CoV2O6

    Science.gov (United States)

    Saúl, A.; Vodenicarevic, D.; Radtke, G.

    2013-01-01

    The electronic structure and magnetic properties of α-CoV2O6 are investigated using density functional theory calculations including spin-orbit coupling and orbital polarization effects. These calculations reveal a strong magnetocrystalline anisotropy with a magnetization easy axis close to the c axis. The evaluation of magnetic couplings on the basis of broken-symmetry formalism suggests the occurrence of an antiferromagnetic ground-state order where ferromagnetic chains running along b are coupled antiferromagnetically to their nearest neighbors along a and c. Monte Carlo simulations are finally employed to explore the origins of the 1/3 plateau observed in the magnetization curves of this compound and to propose a structure for the corresponding state.

  4. Magnetic Excitations and Magnetic Ordering in Praseodymium

    DEFF Research Database (Denmark)

    Houmann, Jens Christian Gylden; Chapellier, M.; Mackintosh, A. R.

    1975-01-01

    The dispersion relations for magnetic excitons propagating on the hexagonal sites of double-hcp Pr provide clear evidence for a pronounced anisotropy in the exchange. The energy of the excitations decreases rapidly as the temperature is lowered, but becomes almost constant below about 7 K......, in agreement with a random-phase-approximation calculation. No evidence of magnetic ordering has been observed above 0.4 K, although the exchange is close to the critical value necessary for an antiferromagnetic state....

  5. 57Fe Moessbauer effect studies of magnetic ordering in Lasub(1-x) Srsub(x)CoO3

    International Nuclear Information System (INIS)

    Bhide, V.G.; Rajoria, D.S.

    1975-01-01

    A detailed investigation of the Lasub(1-x)Srsub(x)CoO 3 system was performed for the entire range of Sr concentrations using X-ray diffraction for structural studies, DTA for phase transition analysis, Moessbauer and magnetic susceptibility studies for magnetic properties, and electrical resistivity and Seebeck coefficient studies for electron transport properties. Among other interesting results, samples with x > 0.125 were found to show ferromagnetic ordering. (A.K.)

  6. Muon spin rotation studies of magnetic order and strong magnetic correlations in magnetic and superconducting systems based on the high Tc copper oxide structures

    International Nuclear Information System (INIS)

    Rudnick, J.J.; Filipkowski, M.E.; Tan, Z.; Chamberland, B.; Niedermayer, C.; Weidinger, A.; Golnik, A.; Simon, R.; Rauer, M.; Recknagel, E.; Gluckler, H.; Baines, C.

    1990-01-01

    In this paper the authors review results of a series of muon spin rotation (μSR) studies extending down to milli Kelvin temperatures in order to explore the existence of magnetic correlations below T C in the La 2-x Sr x CuO 4 system. Evidence is presented for the existence of local magnetic fields thought to originate from Cu electronic moments in both superconducting La 2-x Sr x CuO 4 and in superconducting oxygen deficient YBa 2 Cu 3 O 6.6 . μSR results are also presented for oxygen deficient and superconducting GdBa 2 Cu 3 O 6+x samples. Some discussion of the relevance of these results to recent proposals for pairing mechanisms is presented

  7. Magnetic Order and Crystal Field Excitations in Er2Ru2O7: A Neutron Scattering Study

    International Nuclear Information System (INIS)

    Ehlers, Georg; Gardner, Jason

    2009-01-01

    The magnetic pyrochlore Er 2 Ru 2 O 7 has been studied with neutron scattering and susceptibility measurements down to a base temperature of 270 mK. For the low temperature phase in which the Er sublattice orders, new magnetic Bragg peaks are reported which can be indexed with integer (hkl) for a face centered cubic cell. Inelastic measurements reveal a wealth of crystal field levels of the Er ion and a copious amount of magnetic scattering below 15 meV. The three lowest groups of crystal field levels are at 6.7, 9.1 and 18.5 meV.

  8. Comparative study of magnetic ordering in bulk and nanoparticles of Sm0.65Ca0.35MnO3: Magnetization and electron magnetic resonance measurements

    International Nuclear Information System (INIS)

    Goveas, Lora Rita; Anuradha, K. N.; Bhagyashree, K. S.; Bhat, S. V.

    2015-01-01

    To explore the effect of size reduction to nanoscale on the hole doped Sm 0.65 Ca 0.35 MnO 3 compound, dc magnetic measurements and electron magnetic resonance (EMR) were done on bulk and nanoparticle samples in the temperature range 10 ≤ T ≤ 300 K. Magnetization measurement showed that the bulk sample undergoes a charge ordering transition at 240 K and shows a mixed magnetic phase at low temperature. However, the nanosample underwent a ferromagnetic transition at 75 K, and the charge ordered state was destabilized on size reduction down to nanoscale. The low-temperature ferromagnetic component is found to be enhanced in nanoparticles as compared to their bulk counterpart. Interestingly around room temperature, bulk particles show higher magnetization where as at low temperature nanoparticles show higher magnetization. Ferromagnetism in the bulk is due to super exchange where as ferromagnetism in nanoparticles is due to uncompensated spins of the surface layer. Temperature variation of EMR parameters correlates well with the results of magnetic measurements. The magnetic behaviour of the nanoparticles is understood in terms of the core shell scenario

  9. Comparative study of magnetic ordering in bulk and nanoparticles of Sm0.65Ca0.35MnO3: Magnetization and electron magnetic resonance measurements

    Science.gov (United States)

    Goveas, Lora Rita; Anuradha, K. N.; Bhagyashree, K. S.; Bhat, S. V.

    2015-05-01

    To explore the effect of size reduction to nanoscale on the hole doped Sm0.65Ca0.35MnO3 compound, dc magnetic measurements and electron magnetic resonance (EMR) were done on bulk and nanoparticle samples in the temperature range 10 ≤ T ≤ 300 K. Magnetization measurement showed that the bulk sample undergoes a charge ordering transition at 240 K and shows a mixed magnetic phase at low temperature. However, the nanosample underwent a ferromagnetic transition at 75 K, and the charge ordered state was destabilized on size reduction down to nanoscale. The low-temperature ferromagnetic component is found to be enhanced in nanoparticles as compared to their bulk counterpart. Interestingly around room temperature, bulk particles show higher magnetization where as at low temperature nanoparticles show higher magnetization. Ferromagnetism in the bulk is due to super exchange where as ferromagnetism in nanoparticles is due to uncompensated spins of the surface layer. Temperature variation of EMR parameters correlates well with the results of magnetic measurements. The magnetic behaviour of the nanoparticles is understood in terms of the core shell scenario.

  10. Structural studies of charge disproportionation and magnetic order in CaFeO3

    International Nuclear Information System (INIS)

    Woodward, P.M.; Cox, D.E.; Moshopoulou, E.; Sleight, A.W.; Morimoto, S.

    2000-01-01

    The crystal and magnetic structures of CaFeO 3 have been determined at 300 and 15 K using synchrotron x-ray and neutron powder-diffraction techniques. At 300 K, CaFeO 3 adopts the GdFeO 3 structure, space group Pbnm with unit-cell dimensions a=5.326 30(4), b=5.352 70(4), and c=7.539 86(6) A. This structure is distorted from the ideal perovskite structure by tilting of the FeO 6 octahedra about [110] and [001]. The average Fe-O distance is 1.922(2) A, and the Fe-O-Fe angles are 158.4(2) deg. and 158.1(1) deg. . At 15 K the crystal structure belongs to space group P2 1 /n with a=5.311 82(3), b=5.347 75(4), c=7.520 58(5) A and β=90.065(1) deg. , and contains two distinct Fe sites. The average Fe-O bond length is 1.872(6) A about the one iron site, and 1.974(6) A about the second site, with bond valence sums of 4.58 and 3.48, respectively. This provides quantitative evidence for charge disproportionation, 2Fe 4+ →Fe 3+ +Fe 5+ , at low temperature. The temperature evolution of the lattice parameters indicates a second- (or higher-) order phase transition from the orthorhombic charge-delocalized state to the monoclinic charge-disproportionated state, beginning just below room temperature. The magnetic structure at 15 K is incommensurate, having a modulation vector [δ,0,δ] with δ ∼0.322, corresponding to one of the directions in the pseudocubic cell. A reasonable fit to the magnetic intensities is obtained with the recently proposed screw spiral structure [S. Kawasaki et al., J. Phys. Soc. Jpn. 67, 1529 (1998)], with Fe moments of 3.5 and 2.5μ B , respectively. However, a comparable fit is given by a sinusoidal amplitude-modulated model in which the Fe moments are directed along [010], which leaves open the possibility that the true magnetic structure may be intermediate between the spiral and sinusoidal models (a fan structure)

  11. In-situ magnetization/heating electron holography to study the magnetic ordering in arrays of nickel metallic nanowires

    Directory of Open Access Journals (Sweden)

    Eduardo Ortega

    2018-05-01

    Full Text Available Magnetic nanostructures of different size, shape, and composition possess a great potential to improve current technologies like data storage and electromagnetic sensing. In thin ferromagnetic nanowires, their magnetization behavior is dominated by the competition between magnetocrystalline anisotropy (related to the crystalline structure and shape anisotropy. In this way electron diffraction methods like precession electron diffraction (PED can be used to link the magnetic behavior observed by Electron Holography (EH with its crystallinity. Using off-axis electron holography under Lorentz conditions, we can experimentally determine the magnetization distribution over neighboring nanostructures and their diamagnetic matrix. In the case of a single row of nickel nanowires within the alumina template, the thin TEM samples showed a dominant antiferromagnetic arrangement demonstrating long-range magnetostatic interactions playing a major role.

  12. Structural and magnetic order of ThMn12-type rare earth-iron-aluminium intermetallics studied by neutron diffraction

    International Nuclear Information System (INIS)

    Schaefer, W.; Halevy, I.; Gal, J.

    2000-01-01

    neutron powder diffraction data of ThMn 12 -type compounds RFe 4 Al 8 , RFe 5 Al 7 , and RFe 6 Al 6 (R = heavy rare earth) are compared to work out the structural variations and the different magnetic properties of these ternary intermetallics as a function of increasing iron concentrations. The variations of unit cell metric, of atomic coordinations and of interatomic distances are discussed. A magnetic phase diagram is presented showing the increase of the magnetic ordering temperatures from 120 K to 340 K and the change of the magnetic order from two separate magnetic phase transitions of rare earth and iron sublattices to one common ferrimagnetic transition of both sublattices, when changing the ratio of Fe/Al atoms from 4/8 to 6/6, respectively. Long range order is hampered by frozen spins. Magnetically ordered rare earth and iron moments are given. (orig.)

  13. The magnetic order of GdMn{sub 2}Ge{sub 2} studied by neutron diffraction and x-ray resonant magnetic scattering

    Energy Technology Data Exchange (ETDEWEB)

    Granovsky, S A [M V Lomonosov Moscow State University, 119991 GSP-1 Moscow (Russian Federation); Kreyssig, A; Canfield, P C [Ames Laboratory USDOE, Iowa State University, Ames, IA 50011 (United States); Doerr, M; Loewenhaupt, M [TU Dresden, Institut fuer Festkoerperphysik, D-01062, Dresden (Germany); Ritter, C [Institut Laue-Langevin, F-38042 Grenoble Cedex 9 (France); Dudzik, E; Feyerherm, R, E-mail: ser@plms.r [Helmholtz-Zentrum Berlin fuer Materialien und Energie GmbH, BESSY, D-12489, Berlin (Germany)

    2010-06-09

    The magnetic structure of GdMn{sub 2}Ge{sub 2} (tetragonal I4/mmm) has been studied by hot neutron powder diffraction and x-ray resonant magnetic scattering techniques. These measurements, along with the results of bulk experiments, confirm the collinear ferrimagnetic structure with moment direction parallel to the c-axis below T{sub C} = 96 K and the collinear antiferromagnetic phase in the temperature region T{sub C} < T < T{sub N} = 365 K. In the antiferromagnetic phase, x-ray resonant magnetic scattering has been detected at Mn K and Gd L{sub 2} absorption edges. The Gd contribution is a result of an induced Gd 5d electron polarization caused by the antiferromagnetic order of Mn-moments.

  14. {mu}SR studies of the interplay of magnetic spin stripe order with superconductivity in transition metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Klauss, Hans-Henning, E-mail: h.klauss@physik.tu-dresden.de [Institute for Solid State Physics, TU Dresden, D-01069 Dresden (Germany)

    2012-11-01

    In this work we review muon spin relaxation experiments on the layered La{sub 2-x}Sr{sub x}NiO{sub 4} nickelate as well as La{sub 2-x}Ba{sub x}CuO{sub 4} and La{sub 2-x}Sr{sub x}CuO{sub 4} cuprate systems to examine spin stripe order. In particular, the interplay of stripe order with superconductivity in Nd and Eu doped La{sub 2-x}Sr{sub x}CuO{sub 4} cuprates is discussed. Detailed studies of the electronic phase diagrams as well as the magnetic and superconducting order parameters for different rare-earth and Sr doping levels in La{sub 2-x-y}RE{sub y}Sr{sub x}CuO{sub 4} revealed the strong correlation of static spin stripe order with the structural distortion in the low temperature tetragonal (LTT) phase and the competition with the superconducting ground state. High magnetic field studies demonstrate the nearly degenerate ground state energy of the different electronic phases. Slow transverse fluctuations of the charge stripes are found in nickelates and cuprates at low temperatures.

  15. Development of magnetic order in superconducting systems

    International Nuclear Information System (INIS)

    Moncton, D.E.; Shirane, G.; Thomlinson, W.

    1979-08-01

    Two different classes of rare-earth (RE) ternary superconductors (RERh 4 B 4 and REMo 6 S 8 , X=S, Se) have provided the first instances in which chemically ordered sublattices of magnetic ions exist in superconductors. Neutron scattering studies show that simple, conventional antiferromagnetism coexists with superconductivity in a number of systems, while destruction of superconductivity occurs with the onset of ferromagnetism. The magnetic structural details are summarized for the coexistent antiferromagnets, and review measurements on the superconducting → ferromagnetic transition in ErRh 4 B 4

  16. Neutron diffraction study of the pressure-induced magnetic ordering in the spin gap system TlCuCl3

    International Nuclear Information System (INIS)

    Oosawa, Akira; Osakabe, Toyotaka; Kakurai, Kazuhisa; Tanaka, Hidekazu

    2003-01-01

    Neutron elastic scattering measurements have been performed under a hydrostatic pressure in order to investigate the spin structure of the pressure-induced magnetic ordering in the spin gap system TlCuCl 3 . Below the ordering temperature T N = 16.9 K for the hydrostatic pressure P = 1.48 GPa, magnetic Bragg reflections were observed at reciprocal lattice points Q = (h, 0, l) with integer h and odd l, which are equivalent to those points with the lowest magnetic excitation energy at ambient pressure. This indicates that the spin gap close due to the applied pressure. The spin structure of the pressure-induced magnetic ordered state for P = 1.48 GPa was determined. (author)

  17. Magnetic short range order and the exchange coupling in magnets

    International Nuclear Information System (INIS)

    Antropov, V.P.

    2006-01-01

    We discuss our recent results of time-dependent density functional simulations of magnetic properties of Fe and Ni at finite temperatures. These results indicated that a strong magnetic short range order is responsible for the magnetic properties of elementary Ni and any itinerant magnet in general. We demonstrated that one can use the value of the magnetic short range order parameter to produce new quantitative classification of magnets. We also discuss the nature of the exchange coupling and its connection with the short range order. The spin-wave like propagating and diffusive excitations in paramagnetic localized systems with small short range order have been predicted while in the itinerant systems the short range order is more complicated. The possible smallness of the quantum factor in the itinerant magnets with short range order is discussed

  18. Magnetic nanoparticles: synthesis, ordering and properties

    International Nuclear Information System (INIS)

    Vazquez, M.; Luna, C.; Morales, M.P.; Sanz, R.; Serna, C.J.; Mijangos, C.

    2004-01-01

    Polyol methods to synthesize nanoparticles and their arrays are firstly described. Magnetic nanoparticles self-assemble under particular conditions into spherical superstructures, like CoNi nanoparticles, or planar structures with hexagonal ordering, like FePt nanoparticles. Particles and their arrays are structurally analysed by techniques like TEM, X-ray, etc. Magnetic characterization is firstly performed by VSM magnetomer as a function of the nanoparticles size paying particular attention to the transition from multidomain to single-domain structures. Later on, magnetic exchange coupling effects are discussed including the temperature dependence of magnetic parameters as coercive and exchange bias fields, as well as the influence of field or zero-field cooling processes. Finally, magnetic polymers consisting of magnetic nanoparticles embedded into PVC polymeric matrix are prepared and magnetically analysed

  19. Magnetic order and crystal structure study of YNi{sub 4}Si-type NdNi{sub 4}Si

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Jinlei [Research Center for Solid State Physics and Materials, School of Mathematics and Physics, Suzhou University of Science and Technology, Suzhou 215009 (China); Isnard, O. [Université Grenoble Alpes, Inst NEEL, BP166, Grenoble F-38042 (France); CNRS, Institut NEEL, 25 rue des martyrs, Grenoble F-38042 (France); Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation); Ivanova, T.I. [Physics Department, Moscow State University, Moscow 119992 (Russian Federation); Koshkid' ko, Yu.S. [International Laboratory of High Magnetic Fields and Low Temperatures, Wrocław (Poland); VSB-Technical University of Ostrava, Ostrava-Poruba 70833 (Czech Republic); Bogdanov, A.E.; Nikitin, S.A. [Physics Department, Moscow State University, Moscow 119992 (Russian Federation); Suski, W. [International Laboratory of High Magnetic Fields and Low Temperatures, Wrocław (Poland); Polish Academy of Sciences, Trzebiatowski Institute of Low Temperatures and Structure Research, P.O. Box 1410, 50-950 Wrocław 2 (Poland)

    2015-02-15

    Magnetic measurements and neutron powder diffraction investigation of the magnetic structure of the orthorhombic YNi{sub 4}Si-type (space group Cmmm) NdNi{sub 4}Si compound are presented. The magnetocaloric effect of NdNi{sub 4}Si is calculated in terms of the isothermal magnetic entropy change and it reaches the maximum value of –3.3 J/kg K for a field change of 50 kOe near T{sub C}=12 K. Below ∼12 K, NdNi{sub 4}Si exhibits a commensurate b-axis collinear ferromagnetic ordering with the Cmm′m magnetic space group in a zero magnetic field. At 1.5 K, the neodymium atoms have the magnetic moment of 2.37(5) μ{sub B}. The orthorhombic crystal structure and its thermal evolution are discussed in comparison with the CaCu{sub 5}-type compound. - Graphical abstract: The NdNi{sub 4}Si supplement the series of the orthorhombic derivative of the CaCu{sub 5}-type, namely the YNi{sub 4}Si-type, RNi{sub 4}Si compounds (R=Y, La, Ce, Sm, Gd–Ho). Below ∼12 K in a zero applied magnetic field, NdNi{sub 4}Si exhibits a commensurate b-axis collinear ferromagnetic ordering with the Cmm′m magnetic space group. Compared to the CaCu{sub 5}-type NdNi{sub 4}Si compound, the YNi{sub 4}Si-type counterpart has the relatively high ferromagnetic ordering temperature (9.2 K vs. 12 K), the small magnetocaloric effect (–7.3 J/kg K vs. –3.3 J/kg K for ∆H=50 kOe), and the large magnetic anisotropy at low temperatures. In contrast with CaCu{sub 5}-type NdNi{sub 4}Si, YNi{sub 4}Si-type NdNi{sub 4}Si shows distinct hysteresis loop at 2 K.We suggest that orthorhombic distortion may be used as a prospective route for optimization of permanent magnetic properties in the family of CaCu{sub 5}-type rare earth materials. - Highlights: • Below ∼12 K the YNi{sub 4}Si-type NdNi{sub 4}Si shows a ferromagnetic ordering. • MCE of NdNi{sub 4}Si reaches value of –3.3 J/kg K in 0–50 kOe near Curie point. • NdNi{sub 4}Si exhibits b-axis ferromagnetic order with the Cmm′m magnetic space

  20. Magnetic short range order in Gd

    International Nuclear Information System (INIS)

    Child, H.R.

    1976-01-01

    Quasielastic neutron scattering has been used to investigate magnetic short range order in Gd for 80 0 K 0 K. Short range order exists throughout this range from well below T/sub C/ = 291 0 K to well above it and can be reasonably well described by an anisotropic Orstein-Zernike form for chi

  1. Magnetic ordering in TmGa

    DEFF Research Database (Denmark)

    Cadogan, J.M.; Stewart, G.A.; Muños Pérez, S.

    2014-01-01

    We have determined the magnetic structure of the intermetallic compound TmGa by high-resolution neutron powder diffraction and 169Tm Mössbauer spectroscopy. This compound crystallizes in the orthorhombic (Cmcm) CrB-type structure and its magnetic structure is characterized by magnetic order...... of the Tm sublattice along the a-axis. The initial magnetic ordering occurs at 15(1) K and yields an incommensurate antiferromagnetic structure described by the propagation vector k1 = [0 0.275(2) 0]. At 12 K the dominant ferromagnetic ordering of the Tm sublattice along the a-axis develops in what appears...... to be a first-order transition. At 3 K the magnetic structure of TmGa is predominantly ferromagnetic but a weakened incommensurate component remains. The ferromagnetic Tm moment reaches 6.7(2) μB at 3 K and the amplitude of the remaining incommensurate component is 2.7(4) μB. The 169Tm hyperfine magnetic field...

  2. Nuclear signals in magnetically ordered media

    International Nuclear Information System (INIS)

    Ignatchenko, V.A.; Tsifrinovich, V.I.

    1993-01-01

    The book contains a review of theoretical and experimental investigations in the field of nuclear magnetism in magnetically ordered media. The semiclassical theory of nuclear spins motion is developed that takes into consideration three main features of magnetically ordered media: Suhl-Nakamura interaction, quadrupole interaction and microscopic inhomogeneity of nuclear frequencies. The detailed classification of nuclear spin echo signals is given for standard conditions of experiments, when the Suhl-Nakamura interaction is small in comparison with the NMR line width. The extremal states of the electron - nuclear magnetic system are described in detail: the coexistence of NMR and FMR, nuclear ferromagnetism and NMR at fast remagnetization of a ferromagnet. 157 refs., 20 figs

  3. Magnetic short-range order in Gd

    International Nuclear Information System (INIS)

    Child, H.R.

    1978-01-01

    The magnetic short-range order in a ferromagnetic, isotopically enriched 160 Gd metal single crystal has been investigated by quasielastic scattering of 81-meV neutrons. Since Gd behaves as an S-state ion in the metal, little anisotropy is expected in its magnetic behavior. However, the data show that there is anisotropic short-range order present over a large temperature interval both above and below T/sub C/. The data have been analyzed in terms of an Ornstein-Zernike Lorentzian form with anisotropic correlation ranges. These correlation ranges as deduced from the observed data behave normally above T/sub C/ but seem to remain constant over a fairly large interval below T/sub C/ before becoming unobservable at lower temperatures. These observations suggest that the magnetic ordering in Gd may be a more complicated phenomenon than first believed

  4. A comprehensive study of piezomagnetic response in CrPS4 monolayer: mechanical, electronic properties and magnetic ordering under strains

    Science.gov (United States)

    Joe, Minwoong; Lee, Hosik; Menderes Alyörük, M.; Lee, Jinhwan; Youb Kim, Sung; Lee, Changgu; Lee, Jun Hee

    2017-10-01

    We performed first-principles calculations to investigate the magnetic, mechanical and electronic properties of the tetrachalcogenide CrPS4. Although bulk CrPS4 has been shown to exhibit a low-dimensional antiferromagnetic (AFM) ground state where ferromagnetic (FM) Cr-chains are coupled antiferromagnetically, our calculations indicated that the monolayer can be transformed to an FM material by applying a uniaxial tensile strain of  ⩾4% along the FM Cr-chain direction. The AFM-to-FM transition is explained to be driven by an increase of the exchange interaction induced by a decrease in the distance between the FM Cr-chains. A huge nonlinear piezomagnetism was predicted at the strain-induced magnetic phase boundary. Our study provides insight about rational design of single-layer magnetic materials for a wide range of spintronic devices and energy applications.

  5. Magnetic ordering in arrays of one-dimensional nanoparticle chains

    International Nuclear Information System (INIS)

    Serantes, D; Baldomir, D; Pereiro, M; Hernando, B; Prida, V M; Sanchez Llamazares, J L; Zhukov, A; Ilyn, M; Gonzalez, J

    2009-01-01

    The magnetic order in parallel-aligned one-dimensional (1D) chains of magnetic nanoparticles is studied using a Monte Carlo technique. If the easy anisotropy axes are collinear along the chains a macroscopic mean-field approach indicates antiferromagnetic (AFM) order even when no interparticle interactions are taken into account, which evidences that a mean-field treatment is inadequate for the study of the magnetic order in these highly anisotropic systems. From the direct microscopic analysis of the evolution of the magnetic moments, we observe spontaneous intra-chain ferromagnetic (FM)-type and inter-chain AFM-type ordering at low temperatures (although not completely regular) for the easy-axes collinear case, whereas a random distribution of the anisotropy axes leads to a sort of intra-chain AFM arrangement with no inter-chain regular order. When the magnetic anisotropy is neglected a perfectly regular intra-chain FM-like order is attained. Therefore it is shown that the magnetic anisotropy, and particularly the spatial distribution of the easy axes, is a key parameter governing the magnetic ordering type of 1D-nanoparticle chains.

  6. Local order and magnetism of amorphous and disordered solids

    International Nuclear Information System (INIS)

    Friedt, J.M.

    1985-01-01

    Some topics related with the magnetic properties and local order in amorphous and disordered solids studied by Moessbauer spectroscopy, EXAFS, static and dynamical susceptibilities are presented. (L.C.) [pt

  7. Nuclear magnetic ordering in PrNi5

    International Nuclear Information System (INIS)

    Kubota, M.

    1980-11-01

    The specific heat of the hyperfine enhanced nuclear magnetic system PrNi 5 has been measured from 0.2 mK to 100 mK and in magnetic fields up to 6 T. The system was found to order at (0.40+-0.02) mK. From the study of the measured thermodynamic quantities in various magnetic fields, we obtain various information, the order at T=0 K is ferromagnetic, the hyperfine enhancement factor 1+K=(12.2+-0.5), the enhanced nuclear magnetic moment is (0.027+-0.004)μsub(B) and a nuclear exchange parameter μsub(j)Ksup(N)sub(ij)/ksub(B)=(0.20+-0.04) mK. The nature of the interactions which cause the ordering is discussed, together with the magnetic properties of the system deduced from the analysis. (orig.)

  8. Magnetic ordering of GdMn2

    International Nuclear Information System (INIS)

    Ouladdiaf, B.; Ritter, C.; Ballou, R.; Deportes, J.

    1999-01-01

    Complete text of publication follows. GdMn 2 crystallizes in the C15 cubic Laves phase structure. Within this structure Mn atoms lie at the vertices of regular tetrahedra stacked in the diamond arrangement connected by sharing vertices, leading to a strong geometric frustration. An antiferromagnetic magnetic order sets in below T N ∼ 105 K. It gives rise to a large magnetovolume effect (ΔV/V ∼ 1%). Thermal expansion data show two anomalies at 105 K and 35 K. The second anomaly was often interpreted as the ferromagnetic ordering of Gd sublattice. Moessbauer data indicate however, that Gd sublattice orders at T N ∼ 105 K as the Mn moments. Elastic neutron scattering measurements were performed using short wavelength neutron beam (λ = 0.5 A) on D9 at ILL. No magnetic contribution to the nuclear peaks was found excluding thereby any K = [0 0 0] component. However antiferromagnetic peaks indexed by a propagation vector [2/3 2/3 0] were observed leading to a non collinear magnetic arrangement of both Mn and Gd sublattices. The results are discussed by invoking the geometric frustration associated with the Mn atomic packing and the singlet state of the Gd ions. (author)

  9. Neutron scattering studies of the coexistence of long-range magnetic order and superconductivity in Dy12Mo6S8 and Tb12Mo6S8

    International Nuclear Information System (INIS)

    Thomlinson, W.; Shirane, G.; Moncton, D.E.; Ishikawa, M.; Fischer, O.

    1978-10-01

    Both Dy 1 2 Mo 6 S 8 and Tb 1 2 Mo 6 S 8 are superconducting below T/sub c/ = 2.05 K. Neutron scattering studies show that these compounds in zero applied magnetic field develop long-range antiferromagnetic order (greater than 300 A) at T/sub M/ = 0.4 K and T/sub M/ = 1.0 K, respectively, which does not destroy the superconducting state. Magnetization measurements at temperatures below T/sub M/ suggest the development of ferromagnetic order as the applied magnetic field increases. In the case of Tb 1 2 Mo 6 S 8 the neutron data show long-range ferromagnetic order developing for H greater than or equal to H/sub c2/ = 1.9 kOe where H/sub c2/ is the upper critical field for superconductivity. However, for Dy 1 2 Mo 6 S 8 long-range ferromagnetic order begins to develop at H = 200 Oe, a field much less than H/sub c2/ = 1.2 kOe. As the ferromagnetic intensity increases, the antiferromagnetic intensity decreases. Between H = 200 Oe and H = 1.2 kOe both ferromagnetic and antiferromagnetic order occur with the sample in the superconducting state

  10. Neutron diffraction studies of magnetic ordering in superconducting ErNi{sub 2}B{sub 2}C and TmNi{sub 2}B{sub 2}C in an applied magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Toft, K.N

    2004-01-01

    The field-induced magnetic structures of ErNi{sub 2}B{sub 2}C and TmNi{sub 2}B{sub 2}C in are especially interesting because the field suppresses the superconducting order parameter and therefore the magnetic properties can be studied while varying the strength of superconductivity. ErNi{sub 2}B{sub 2}C: For magnetic fields along all three symmetry directions, the observed magnetic structures have a period corresponding to the Fermi surface nesting structure. The phase diagrams present all the observed magnetic structures. Two results remain unresolved: 1. When applying the magnetic field along [010], the minority domain (Q{sub N}{sup B} = (0,Q,0) with moments perpendicular to the field) shows no signs of hysteresis. I expected it to be a meta-stable state, which would be gradually suppressed by a magnetic field, and when decreasing the field it would not reappear until some small field of approximately 0.1 T. 2. When the field is applied along [110], the magnetic structure rotates a small angle of 0.5 degrees away from the symmetry direction. TmNi{sub 2}B{sub 2}C: A magnetic field applied in the [100] direction suppresses the zero field magnetic structure Q{sub F} = (0.094,0.094,0) (T{sub N} = 1.6 K), in favor of the Fermi surface nesting structure Q{sub N} = (0.483,0,0). The appearance of the Q{sub N} phase was initially believed to be caused by the suppression of superconductivity. This suppression should make it favorable to create a magnetic order with a Q-vector determined by the maximum in the magnetic susceptibility at the Fermi surface nesting vector Q{sub N}. The phase diagram for the magnetic structures is presented, however several properties of the Q{sub N} magnetic structure cannot be explained within any known models. Quadrupolar ordering is suggested as a possible candidate for explaining these features of the Q{sub N} structure. (au)

  11. Comparative study of magnetic ordering in bulk and nanoparticles of Sm{sub 0.65}Ca{sub 0.35}MnO{sub 3}: Magnetization and electron magnetic resonance measurements

    Energy Technology Data Exchange (ETDEWEB)

    Goveas, Lora Rita, E-mail: loragoveas@gmail.com [Department of Physics, Dr. Ambedkar Institute of Technology, Bangalore 560056 (India); St. Joseph' s College of Arts and Science, Bangalore 560027 (India); Anuradha, K. N. [Department of Physics, Dr. Ambedkar Institute of Technology, Bangalore 560056 (India); Bhagyashree, K. S.; Bhat, S. V. [Department of Physics, Indian Institute of Science, Bangalore 560012 (India)

    2015-05-07

    To explore the effect of size reduction to nanoscale on the hole doped Sm{sub 0.65}Ca{sub 0.35}MnO{sub 3} compound, dc magnetic measurements and electron magnetic resonance (EMR) were done on bulk and nanoparticle samples in the temperature range 10 ≤ T ≤ 300 K. Magnetization measurement showed that the bulk sample undergoes a charge ordering transition at 240 K and shows a mixed magnetic phase at low temperature. However, the nanosample underwent a ferromagnetic transition at 75 K, and the charge ordered state was destabilized on size reduction down to nanoscale. The low-temperature ferromagnetic component is found to be enhanced in nanoparticles as compared to their bulk counterpart. Interestingly around room temperature, bulk particles show higher magnetization where as at low temperature nanoparticles show higher magnetization. Ferromagnetism in the bulk is due to super exchange where as ferromagnetism in nanoparticles is due to uncompensated spins of the surface layer. Temperature variation of EMR parameters correlates well with the results of magnetic measurements. The magnetic behaviour of the nanoparticles is understood in terms of the core shell scenario.

  12. Magnetic order of Nd5Pb3 single crystals

    Science.gov (United States)

    Yan, J.-Q.; Ochi, M.; Cao, H. B.; Saparov, B.; Cheng, J.-G.; Uwatoko, Y.; Arita, R.; Sales, B. C.; Mandrus, D. G.

    2018-04-01

    We report millimeter-sized Nd5Pb3 single crystals grown out of a Nd-Co flux. We experimentally study the magnetic order of Nd5Pb3 single crystals by measuring the anisotropic magnetic properties, electrical resistivity under high pressure up to 8 GPa, specific heat, and neutron single crystal diffraction. Two successive magnetic orders are observed at T N1  =  44 K and T N2  =  8 K. The magnetic cells can be described with a propagation vector k=(0.5, 0, 0) . Cooling below T N1, Nd1 and Nd3 order forming ferromagnetic stripes along the b-axis, and the ferromagnetic stripes are coupled antiferromagnetically along the a-axis for the k=(0.5, 0, 0) magnetic domain. Cooling below T N2, Nd2 orders antiferromagnetically to nearby Nd3 ions. All ordered moments align along the crystallographic c-axis. The magnetic order at T N1 is accompanied by a quick drop of electrical resistivity upon cooling and a lambda-type anomaly in the temperature dependence of specific heat. At T N2, no anomaly was observed in electrical resistivity but there is a weak feature in specific heat. The resistivity measurements under hydrostatic pressures up to 8 GPa suggest a possible phase transition around 6 GPa. Our first-principles band structure calculations show that Nd5Pb3 has the same electronic structure as does Y5Si3 which has been reported to be a one-dimensional electride with anionic electrons that do not belong to any atom. Our study suggests that R 5Pb3 (R  =  rare earth) can be a materials playground for the study of magnetic electrides. This deserves further study after experimental confirmation of the presence of anionic electrons.

  13. Study of multi-layer active magnetic regenerators using magnetocaloric materials with first and second order phase transition

    DEFF Research Database (Denmark)

    Lei, Tian; Engelbrecht, Kurt; Nielsen, Kaspar Kirstein

    2016-01-01

    Magnetocaloric materials (MCM) with a first order phase transition (FOPT) usually exhibit a large, although sharp, isothermal entropy change near their Curie temperature, compared to materials with a second order phase transition (SOPT). Experimental results of applying FOPT materials in recent...

  14. Study of the hyperfine magnetic field acting on Ce probes substituting for the rare earth and the magnetic ordering in intermetallic compounds RAg (R=rare earth) by first principles calculations

    International Nuclear Information System (INIS)

    Pereira, Luciano Fabricio Dias

    2006-01-01

    In this work the magnetic hyperfine field acting on Ce atoms substituting the rare-earths in R Ag compounds (R = Gd e Nd) was studied by means of first-principles electronic structure calculations. The employed method was the Augmented Plane Waves plus local orbitals (APW+lo), embodied in the WIEN2k program, within the framework of the Density Functional Theory (DFT) and with the Generalized Gradient Approximation (GGA) for the exchange and correlation potential. The super-cell approach was utilized in order to simulate for the Ce atoms acting as impurities in the R Ag matrix. In order to improve for correlation effects within the 4f shells, a Hubbard term was added to the DFT Hamiltonian, within a procedure called GGA+U. It was found that the magnetic hyperfine field (MHF) generated by the Ce 4f electron is the main component of the total MHF and that the Ce 4f ground state level is probably a combination of the m l = -2 and m l = -1 sub-levels. In addition, the ground-state magnetic structure was determined for Ho Ag and Nd Ag by observing the behavior of the total energy as a function of the lattice volume for several possible magnetic ordering in these compounds, namely, ferromagnetic, and the (0,0,π), (π,π,0) and ((π,π,π) types of anti-ferromagnetic ordering of rare-earth atoms. It was found that the ground-state magnetic structure is anti-ferromagnetic of type (π,π,0) for both, the Ho Ag and Nd Ag compounds. The energy difference of the ferromagnetic and antiferromagnetic ordering is very small in the case of the Nd Ag compound. (author)

  15. Neutron diffraction study of the pressure-induced magnetic ordering in the spin gap system TlCuCl{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Oosawa, Akira; Osakabe, Toyotaka; Kakurai, Kazuhisa [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Fujisawa, Masashi [Tokyo Inst. of Technology, Dept. of Physics, Tokyo (Japan); Tanaka, Hidekazu [Tokyo Inst. of Technolgy, Research Center for Low Temperature Physics, Tokyo (Japan)

    2003-05-01

    Neutron elastic scattering measurements have been performed under a hydrostatic pressure in order to investigate the spin structure of the pressure-induced magnetic ordering in the spin gap system TlCuCl{sub 3}. Below the ordering temperature T{sub N} = 16.9 K for the hydrostatic pressure P = 1.48 GPa, magnetic Bragg reflections were observed at reciprocal lattice points Q = (h, 0, l) with integer h and odd l, which are equivalent to those points with the lowest magnetic excitation energy at ambient pressure. This indicates that the spin gap close due to the applied pressure. The spin structure of the pressure-induced magnetic ordered state for P = 1.48 GPa was determined. (author)

  16. Neutron diffraction study of the pressure-induced magnetic ordering in the spin gap system TlCuCl sub 3

    CERN Document Server

    Oosawa, A; Kakurai, K; Fujisawa, M; Tanaka, H

    2003-01-01

    Neutron elastic scattering measurements have been performed under a hydrostatic pressure in order to investigate the spin structure of the pressure-induced magnetic ordering in the spin gap system TlCuCl sub 3. Below the ordering temperature T sub N = 16.9 K for the hydrostatic pressure P = 1.48 GPa, magnetic Bragg reflections were observed at reciprocal lattice points Q = (h, 0, l) with integer h and odd l, which are equivalent to those points with the lowest magnetic excitation energy at ambient pressure. This indicates that the spin gap close due to the applied pressure. The spin structure of the pressure-induced magnetic ordered state for P = 1.48 GPa was determined. (author)

  17. Sodium ordering and the control of magnetism in sodium cobaltate

    International Nuclear Information System (INIS)

    Morris, D.J.P.; Roger, M.; Tennant, D.A.; Goff, J.P.; Gutmann, M.J.; Hoffmann, J.-U.; Prabhakaran, D.; Shannon, N.; Lake, B.; Deen, P.P.

    2007-01-01

    The long-range three-dimensional ordering of Na + ions was studied in a sample of composition Na 0.75 CoO 2 using single-crystal neutron diffraction. Large-scale numerical simulations reveal the ordering principle for this system, the formation of multi-vacancy charged droplets then order long range, and the structure factors from these defect clusters are in good agreement with the observed neutron diffraction intensities. The electrostatic potential is found to be the dominant factor in determining the sodium ordering and its associated distortion field. The superstructures induce a periodic potential in the CoO 2 , giving potential wells that are larger than the single-particle hopping frequency and so able to localize holes. The results readily explain many of the observed electrical and magnetic properties, including the three dimensionality of the magnetic excitations

  18. Ferro electricity from magnetic order by neutron measurement

    International Nuclear Information System (INIS)

    Kenzelmann, M.

    2009-01-01

    Magnetic insulators with competing exchange interactions can give rise to strong fluctuations and qualitatively new ground states. The proximity of such systems to quantum critical points can lead to strong cross-coupling between magnetic long-range order and the nuclear lattice. Case in point is a new class of multiferroic materials in which the magnetic and ferroelectric order parameters are directly coupled, and a magnetic field can suppress or switch the electric polarization [1]. Our neutron measurements reveal that ferro electricity is induced by magnetic order and emerges only if the magnetic structure creates a polar axis [2-5]. Our measurements provide evidence that commensurate magnetic order can produce ferro electricity with large electric polarization [6]. The spin dynamics and the field-temperature phase diagram of the ordered phases provide evidence that competing ground states are essential for ferro electricity. (author)

  19. On magnetic ordering in silicon made amorphous by ion implantation

    International Nuclear Information System (INIS)

    Khokhlov, A.F.; Mashin, A.N.; Polyakov, S.M.

    1978-01-01

    Temperature dependences of the EPR intensity for silicon irradiated with the neon and argon ions at (2-4)x10 17 cm -2 doses have been studied. Paramagnetic defects with 2.0055 g-factor were recorded. Intensity jump associated with the transformation of the irradiated layer part to ferromagnetic state is observed at approximately 140 K. Paramagnetic centre distributions at temperatures above and lower the magnetic ordering temperature have heen investigated. It has been found, that ferromagnetic ordering is observed in a layer with the defect concentrations (3-7)x10 20 cm -3 , located at a depth > 100 A. Magnetic-ordered layer thickness is proportional to the incident ion energy

  20. Crossover phenomena in the critical range near magnetic ordering transition

    Science.gov (United States)

    Köbler, U.

    2018-05-01

    Among the most important issues of Renormalization Group (RG) theory are crossover events and relevant (or non-relevant) interactions. These terms are unknown to atomistic theories but they will be decisive for future field theories of magnetism. In this experimental study the importance of these terms for the critical dynamics above and below magnetic ordering transition is demonstrated on account of new analyses of published data. When crossover events are overlooked and critical data are fitted by a single power function of temperature over a temperature range including a crossover event, imprecise critical exponents result. The rather unsystematic and floating critical exponents reported in literature seem largely to be due to this problem. It is shown that for appropriate data analyses critical exponents are obtained that are to a good approximation rational numbers. In fact, rational critical exponents can be expected when spin dynamics is controlled by the bosons of the continuous magnetic medium (Goldstone bosons). The bosons are essentially magnetic dipole radiation generated by the precessing spins. As a result of the here performed data analyses, critical exponents for the magnetic order parameter of β = 1/2, 1/3, 1/4 and 1/6 are obtained. For the critical paramagnetic susceptibility the exponents are γ = 1 and γ = 4/3.

  1. 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.)

  2. Influence of magnetic anisotropy on the superferromagnetic ordering in nanocomposites

    DEFF Research Database (Denmark)

    Mørup, Steen; Christiansen, Gunnar Dan

    1993-01-01

    Magnetic interaction between ultrafine particles may result in superferromagnetism, i.e., ordering of the magnetic moments of particles which would be superparamagnetic if they were noninteracting. In this article we discuss the influence of the magnetic anisotropy on the temperature dependence o...

  3. Magnetic susceptibility of multiferroics and chemical ordering

    Czech Academy of Sciences Publication Activity Database

    Maryško, Miroslav; Laguta, Valentyn; Raevski, I. P.; Kuzian, R. O.; Olekhnovich, N.M.; Pushkarev, A.V.; Radyush, Yu.V.; Raevskaya, S. I.; Titov, V.V.; Kubrin, S.P.

    2017-01-01

    Roč. 7, č. 5 (2017), s. 1-6, č. článku 056409. ISSN 2158-3226 R&D Projects: GA ČR GA13-11473S Institutional support: RVO:68378271 Keywords : multiferroic * spin glass * antiferromagnetic * ferroelectrics Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 1.568, year: 2016

  4. Magnetic order in graphite: Experimental evidence, intrinsic and extrinsic difficulties

    International Nuclear Information System (INIS)

    Esquinazi, P.; Barzola-Quiquia, J.; Spemann, D.; Rothermel, M.; Ohldag, H.; Garcia, N.; Setzer, A.; Butz, T.

    2010-01-01

    We discuss recently obtained data using different experimental methods including magnetoresistance measurements that indicate the existence of metal-free high-temperature magnetic order in graphite. Intrinsic as well as extrinsic difficulties to trigger magnetic order by irradiation of graphite are discussed in view of recently published theoretical work.

  5. Magnetic order in PrBa2Cu3O6+x

    DEFF Research Database (Denmark)

    Longmore, A.; Nutley, M.P.; Boothroyd, A.T.

    1994-01-01

    We have studied the magnetic ordering of the Cu and Pr ions in PrBa2Cu3O6+x by neutron diffraction on single crystals with different oxygen contents. Two types of Cu ordering were observed, qualitatively similar to the anti-ferromagnetic phases reported in some studies of YBa2Cu3O6+x. A third...... magnetic structure was observed below 15K, which we believe corresponds to the magnetic ordering of the Pr sub-lattice....

  6. Hybrid superconducting-magnetic memory device using competing order parameters.

    Science.gov (United States)

    Baek, Burm; Rippard, William H; Benz, Samuel P; Russek, Stephen E; Dresselhaus, Paul D

    2014-05-28

    In a hybrid superconducting-magnetic device, two order parameters compete, with one type of order suppressing the other. Recent interest in ultra-low-power, high-density cryogenic memories has spurred new efforts to simultaneously exploit superconducting and magnetic properties so as to create novel switching elements having these two competing orders. Here we describe a reconfigurable two-layer magnetic spin valve integrated within a Josephson junction. Our measurements separate the suppression in the superconducting coupling due to the exchange field in the magnetic layers, which causes depairing of the supercurrent, from the suppression due to the stray magnetic field. The exchange field suppression of the superconducting order parameter is a tunable and switchable behaviour that is also scalable to nanometer device dimensions. These devices demonstrate non-volatile, size-independent switching of Josephson coupling, in magnitude as well as phase, and they may enable practical nanoscale superconducting memory devices.

  7. Absence of a long-range ordered magnetic ground state in Pr3Rh4Sn13 studied through specific heat and inelastic neutron scattering

    Science.gov (United States)

    Nair, Harikrishnan S.; Ogunbunmi, Michael O.; Ghosh, S. K.; Adroja, D. T.; Koza, M. M.; Guidi, T.; Strydom, A. M.

    2018-04-01

    Signatures of absence of a long-range ordered magnetic ground state down to 0.36 K are observed in magnetic susceptibility, specific heat, thermal/electrical transport and inelastic neutron scattering data of the quasi-skutterudite compound Pr3Rh4Sn13 which crystallizes in the Yb3Rh4Sn13-type structure with a cage-like network of Sn atoms. In this structure, Pr3+ occupies a lattice site with D 2d point symmetry having a ninefold degeneracy corresponding to J  =  4. The magnetic susceptibility of Pr3Rh4Sn13 shows only a weak temperature dependence below 10 K otherwise remaining paramagnetic-like in the range, 10 K-300 K. From the inelastic neutron scattering intensity of Pr3Rh4Sn13 recorded at different temperatures, we identify excitations at 4.5(7) K, 5.42(6) K, 10.77(5) K, 27.27(5) K, 192.28(4) K and 308.33(3) K through a careful peak analysis. However, no signatures of long-range magnetic order are observed in the neutron data down to 1.5 K, which is also confirmed by the specific heat data down to 0.36 K. A broad Schottky-like peak is recovered for the magnetic part of the specific heat, C 4f, which suggests the role of crystal electric fields of Pr3+ . A crystalline electric field model consisting of 7 levels was applied to C 4f which leads to the estimation of energy levels at 4.48(2) K, 6.94(4) K, 11.23(8) K, 27.01(5) K, 193.12(6) K and 367.30(2) K. The CEF energy levels estimated from the heat capacity analysis are in close agreement with the excitation energies seen in the neutron data. The Sommerfeld coefficient estimated from the analysis of magnetic specific heat is γ = 761(6) mJ K-2 mol-Pr which suggests the formation of heavy itinerant quasi-particles in Pr3Rh4Sn13. Combining inelastic neutron scattering results, analysis of the specific heat data down to 0.36 K, magnetic susceptibility and, electrical and thermal transport, we establish the absence of long-range ordered magnetic ground state in Pr3Rh4Sn13.

  8. Size effect on magnetic ordering in Ce3Al11

    International Nuclear Information System (INIS)

    Wang, C.R.; Chen, Y.Y.; Neeleshwar, S.; Ou, M.N.; Ho, J.C.

    2003-01-01

    To study the size dependence of magnetic ordering, magnetic measurements have been made between 1.8 and 300 K on Ce 3 Al 11 particles having an average particle size of 1400 A. The nanoparticles were single phase as confirmed by X-ray diffraction. At low temperatures a ferromagnetic transition occurs at T C =6.2 K, which is the same as that for the bulk material. On the other hand, the antiferromagnetic transition at T N =3.2 K for the bulk material is not visible down to 1.8 K. Meanwhile, the slightly smaller Curie constant of nanoparticles as compared to that of the bulk indicates a certain degree of demagnetization of Ce ions when the particle size is sufficiently reduced

  9. Higher order magnetic modulation structures in rare earth metal, alloys and compounds under extreme conditions

    International Nuclear Information System (INIS)

    Kawano, S.

    2003-01-01

    Magnetic materials consisting of rare earth ions form modulation structures such as a helical or sinusoidal structure caused by the oscillating magnetic interaction between rare earth ions due to RKKY magnetic interaction. These modulation structures, in some cases, develop further to higher order modulation structures by additional modulations caused by higher order crystalline electric field, magnetic interactions such as spin-lattice interaction, external magnetic field and pressure. The higher order modulation structures are observed in a spin-slip structure or a helifan structure in Ho, and a tilt helix structure in a TbEr alloy. Paramagnetic ions originated from frustration generate many magnetic phases under applied external magnetic field. KUR neutron diffraction groups have performed the development and adjustment of high-pressure instruments and external magnetic fields for neutron diffraction spectrometers. The studies of 'neutron diffraction under extreme conditions' by the seven groups are described in this report. (Y. Kazumata)

  10. Neutron Scattering studies of magnetic molecular magnets

    International Nuclear Information System (INIS)

    Chaboussant, G.

    2009-01-01

    This work deals with inelastic neutron scattering studies of magnetic molecular magnets and focuses on their magnetic properties at low temperature and low energies. Several molecular magnets (Mn 12 , V 15 , Ni 12 , Mn 4 , etc.) are reviewed. Inelastic neutron scattering is shown to be a perfectly suited spectroscopy tool to -a) probe magnetic energy levels in such systems and -b) provide key information to understand the quantum tunnel effect of the magnetization in molecular spin clusters. (author)

  11. Phase domain structures in cylindrical magnets under conditions of a first-order magnetic phase transition

    International Nuclear Information System (INIS)

    Dzhezherya, Yu.I.; Klymuk, O.S.

    2011-01-01

    The magnetic and resonance properties of cylindrical magnets at first-order phase transition from paramagnetic to ferromagnetic state were theoretically studied. It has been shown that in the external magnetic field directed perpendicularly to the rotation axis, formation of a specific domain structure of paramagnetic and ferromagnetic layers can be energetically favorable. The parameters of cylindrical phase domains as well as their dependences on temperature, magnetic field and material characteristics have been calculated. Peculiarities of the magnetic resonance spectra appearing as a result of the phase domain formation have been considered. Dependence of the resonance field of the system of ferromagnetic domains on magnetization and temperature has been obtained. - Highlights: → Parameters of the equilibrium system of cylindrical phase domains are calculated. → The range of fields for PM and FM phases coexistence is found. → FMR field of the disk domains is found to be lower than that of the PMR field.→ The resonance field increases with the decrease of temperature lower than T || .

  12. Neutron scattering studies on frustrated magnets

    International Nuclear Information System (INIS)

    Arima, Taka-hisa

    2013-01-01

    A lot of frustrated magnetic systems exhibit a nontrivial magnetic order, such as long-wavelength modulation, noncollinear, or noncoplanar order. The nontrivial order may pave the way for the novel magnetic function of matter. Neutron studies are necessary to determine the magnetic structures in the frustrated magnetic systems. In particular, spin-polarized neutron scattering is a useful technique for the investigation of the novel physical properties relevant to the nontrivial spin arrangement. Here some neutron studies on a multiferroic perovskite manganese oxide system are demonstrated as a typical case. The frustrated magnetic systems may also a playground of novel types of local magnetic excitations, which behave like particles in contrast to the magnetic waves. It is becoming a good challenge to study such particle-type magnetic excitations relevant to the magnetic frustration. (author)

  13. μSR Study of the Unusual Magnetic Ordering in the Frustrated Antiferromagnet Zn(CrxGa1-x)2O4

    International Nuclear Information System (INIS)

    Kikuchi, H.; Fukushima, H.; Higemoto, W.; Nishiyama, K.

    2001-01-01

    μSR spectra on the spin frustrating spinel antiferromagnet Zn(Cr x Ga 1-x ) 2 O 4 (x=0.9,1.0) have been measured. For x=1.0 compound, both the relaxation rate and the initial asymmetry showed distinct anomalies at the Neel temperature. The magnetic susceptibility for the x=0.9 compound was known to have a faint peak at around 12 K, whose origin was not clear so far. Our μSR study revealed that this temperature is the onset temperature of development of the magnetic correlation accompanied by appreciable spin fluctuations.

  14. Fifth-order aberrations in magnetic quadrupole-octupole systems

    International Nuclear Information System (INIS)

    Ling, K.M.

    1990-01-01

    Explicit integral expressions are given for the fifth-order geometrical aberration coefficients in rectilinear magnetic quadrupole-octupole systems used for the transport of nonrelativistic charged particle beams. The numerical values of the fifth-order geometrical aberration coefficients for a rare earth cobalt (REC) quadrupole doublet are given as an example. 26 refs., 5 figs., 4 tabs

  15. Design and Parametric Study of the Magnetic Sensor for Position Detection in Linear Motor Based on Nonlinear Parametric model order reduction.

    Science.gov (United States)

    Paul, Sarbajit; Chang, Junghwan

    2017-07-01

    This paper presents a design approach for a magnetic sensor module to detect mover position using the proper orthogonal decomposition-dynamic mode decomposition (POD-DMD)-based nonlinear parametric model order reduction (PMOR). The parameterization of the sensor module is achieved by using the multipolar moment matching method. Several geometric variables of the sensor module are considered while developing the parametric study. The operation of the sensor module is based on the principle of the airgap flux density distribution detection by the Hall Effect IC. Therefore, the design objective is to achieve a peak flux density (PFD) greater than 0.1 T and total harmonic distortion (THD) less than 3%. To fulfill the constraint conditions, the specifications for the sensor module is achieved by using POD-DMD based reduced model. The POD-DMD based reduced model provides a platform to analyze the high number of design models very fast, with less computational burden. Finally, with the final specifications, the experimental prototype is designed and tested. Two different modes, 90° and 120° modes respectively are used to obtain the position information of the linear motor mover. The position information thus obtained are compared with that of the linear scale data, used as a reference signal. The position information obtained using the 120° mode has a standard deviation of 0.10 mm from the reference linear scale signal, whereas the 90° mode position signal shows a deviation of 0.23 mm from the reference. The deviation in the output arises due to the mechanical tolerances introduced into the specification during the manufacturing process. This provides a scope for coupling the reliability based design optimization in the design process as a future extension.

  16. Electrically tuned magnetic order and magnetoresistance in a topological insulator.

    Science.gov (United States)

    Zhang, Zuocheng; Feng, Xiao; Guo, Minghua; Li, Kang; Zhang, Jinsong; Ou, Yunbo; Feng, Yang; Wang, Lili; Chen, Xi; He, Ke; Ma, Xucun; Xue, Qikun; Wang, Yayu

    2014-09-15

    The interplay between topological protection and broken time reversal symmetry in topological insulators may lead to highly unconventional magnetoresistance behaviour that can find unique applications in magnetic sensing and data storage. However, the magnetoresistance of topological insulators with spontaneously broken time reversal symmetry is still poorly understood. In this work, we investigate the transport properties of a ferromagnetic topological insulator thin film fabricated into a field effect transistor device. We observe a complex evolution of gate-tuned magnetoresistance, which is positive when the Fermi level lies close to the Dirac point but becomes negative at higher energies. This trend is opposite to that expected from the Berry phase picture, but is intimately correlated with the gate-tuned magnetic order. The underlying physics is the competition between the topology-induced weak antilocalization and magnetism-induced negative magnetoresistance. The simultaneous electrical control of magnetic order and magnetoresistance facilitates future topological insulator based spintronic devices.

  17. 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

  18. Concurrent transition of ferroelectric and magnetic ordering near room temperature.

    Science.gov (United States)

    Ko, Kyung-Tae; Jung, Min Hwa; He, Qing; Lee, Jin Hong; Woo, Chang Su; Chu, Kanghyun; Seidel, Jan; Jeon, Byung-Gu; Oh, Yoon Seok; Kim, Kee Hoon; Liang, Wen-I; Chen, Hsiang-Jung; Chu, Ying-Hao; Jeong, Yoon Hee; Ramesh, Ramamoorthy; Park, Jae-Hoon; Yang, Chan-Ho

    2011-11-29

    Strong spin-lattice coupling in condensed matter gives rise to intriguing physical phenomena such as colossal magnetoresistance and giant magnetoelectric effects. The phenomenological hallmark of such a strong spin-lattice coupling is the manifestation of a large anomaly in the crystal structure at the magnetic transition temperature. Here we report that the magnetic Néel temperature of the multiferroic compound BiFeO(3) is suppressed to around room temperature by heteroepitaxial misfit strain. Remarkably, the ferroelectric state undergoes a first-order transition to another ferroelectric state simultaneously with the magnetic transition temperature. Our findings provide a unique example of a concurrent magnetic and ferroelectric transition at the same temperature among proper ferroelectrics, taking a step toward room temperature magnetoelectric applications.

  19. Magnetic ordering and spin-reorientation transitions in TbCo3B2

    International Nuclear Information System (INIS)

    Dubman, Moshe; Caspi, El'ad N.; Ettedgui, Hanania; Keller, Lukas; Melamud, Mordechai; Shaked, Hagai

    2005-01-01

    The magnetic structure of the compound TbCo 3 B 2 has been studied in the temperature range 1.5 K≤T≤300 K by means of neutron powder diffraction, magnetization, magnetic ac susceptibility, and heat capacity measurements. The compound is of hexagonal symmetry and is paramagnetic at 300 K, undergoes a magnetic Co-Co ordering transition at ∼170 K, and a second magnetic Tb-Tb ordering transition at ∼30 K. The latter induces a spin-reorientation transition, in which the magnetic axis rotates from the c axis toward the basal plane. Below this transition a symmetry decrease (γ magnetostriction) sets in, leading to an orthorhombic distortion of the crystal lattice. The crystal and magnetic structures and interactions and their evolution with temperature are discussed using a microscopic physical model

  20. Optimization of permanent-magnet undulator magnets ordering using simulated annealing algorithm

    International Nuclear Information System (INIS)

    Chen Nian; He Duohui; Li Ge; Jia Qika; Zhang Pengfei; Xu Hongliang; Cai Genwang

    2005-01-01

    Pure permanent-magnet undulator consists of many magnets. The unavoidable remanence divergence of these magnets causes the undulator magnetic field error, which will affect the functional mode of the storage ring and the quality of the spontaneous emission spectrum. Optimizing permanent-magnet undulator magnets ordering using simulated annealing algorithm before installing undulator magnets, the first field integral can be reduced to 10 -6 T·m, the second integral to 10 -6 T·m 2 and the peak field error to less than 10 -4 . The optimized results are independent of the initial solution. This paper gives the optimizing process in detail and puts forward a method to quickly calculate the peak field error and field integral according to the magnet remanence. (authors)

  1. Study of axial magnetic effect

    Energy Technology Data Exchange (ETDEWEB)

    Braguta, Victor [IHEP, Protvino, Moscow region, 142284 Russia ITEP, B. Cheremushkinskaya street 25, Moscow, 117218 (Russian Federation); School of Biomedicine, Far Eastern Federal University, Ajax 10 Building 25, Russian island, Vladivostok, 690922 (Russian Federation); Chernodub, M. N. [CNRS, Laboratoire de Mathématiques et Physique Théorique, Université François-Rabelais Tours, Fédération Denis Poisson, Parc de Grandmont, 37200 Tours, France Department of Physics and Astronomy, University of Gent, Krijgslaan 281, S9, B-9000 Gent (Belgium); School of Biomedicine, Far Eastern Federal University, Ajax 10 Building 25, Russian island, Vladivostok, 690922 (Russian Federation); Goy, V. A. [School of Natural Sciences, Far Eastern Federal University, Sukhanova street 8, Vladivostok, 690950 (Russian Federation); Landsteiner, K. [Instituto de Física Teórica UAM/CSIC, C/ Nicolás Cabrera 13-15, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Molochkov, A. V. [School of Biomedicine, Far Eastern Federal University, Ajax 10 Building 25, Russian island, Vladivostok, 690922 (Russian Federation); Ulybyshev, M. [ITEP, B. Cheremushkinskaya street 25, Moscow, 117218 Russia Institute for Theoretical Problems of Microphysics, Moscow State University, Moscow, 119899 (Russian Federation)

    2016-01-22

    The Axial Magnetic Effect manifests itself as an equilibrium energy flow of massless fermions induced by the axial (chiral) magnetic field. Here we study the Axial Magnetic Effect in the quenched SU(2) lattice gauge theory with massless overlap fermions at finite temperature. We numerically observe that in the low-temperature hadron phase the effect is absent due to the quark confinement. In the high-temperature deconfinement phase the energy flow is an increasing function of the temperature which reaches the predicted asymptotic T{sup 2} behavior at high temperatures. We find, however, that energy flow is about one order of magnitude lower compared to a theoretical prediction.

  2. Probing α -RuCl3 Beyond Magnetic Order: Effects of Temperature and Magnetic Field

    Science.gov (United States)

    Winter, Stephen M.; Riedl, Kira; Kaib, David; Coldea, Radu; Valentí, Roser

    2018-02-01

    Recent studies have brought α -RuCl3 to the forefront of experimental searches for materials realizing Kitaev spin-liquid physics. This material exhibits strongly anisotropic exchange interactions afforded by the spin-orbit coupling of the 4 d Ru centers. We investigate the dynamical response at finite temperature and magnetic field for a realistic model of the magnetic interactions in α -RuCl3 . These regimes are thought to host unconventional paramagnetic states that emerge from the suppression of magnetic order. Using exact diagonalization calculations of the quantum model complemented by semiclassical analysis, we find a very rich evolution of the spin dynamics as the applied field suppresses the zigzag order and stabilizes a quantum paramagnetic state that is adiabatically connected to the fully polarized state at high fields. At finite temperature, we observe large redistributions of spectral weight that can be attributed to the anisotropic frustration of the model. These results are compared to recent experiments and provide a road map for further studies of these regimes.

  3. Centimeter-order view for magnetic domain imaging with local magnetization direction by longitudinal Kerr effect

    Directory of Open Access Journals (Sweden)

    Sakae Meguro

    2016-05-01

    Full Text Available An observation system of centimeter-order of view of magnetic domain with local magnetization direction was developed by designing a telecentric optical system of finite design through the extension of microscope technology. The field of view realized in the developed system was 1.40 × 1.05 cm as suppressing defocus and distortion. Detection of the local magnetization direction has become possible by longitudinal Kerr observation from the orthogonal two directions. This system can be applied to the domain observation of rough surface samples and time resolved analysis for soft magnetic materials such as amorphous foil strips and soft magnetic thin films.

  4. Magnetic ordering in PrBa2Cu3-yAlyO6+x

    DEFF Research Database (Denmark)

    Longmore, A.; Boothroyd, A.T.; Chen, C.K.

    1996-01-01

    The magnetic ordering in single crystals of PrBa2CU3O6+x has been investigated by elastic neutron scattering over the full range of temperatures for reduced and oxygenated crystals. The crystals were grown in alumina crucibles and therefore contained dissolved aluminum on the Cu(1) site. Both...... aluminum and oxygen contents were analyzed in detail in order to establish their effects on the magnetic ordering, Our crystals exhibited Pr ordering and the two types of antiferromagnetic Cu ordering frequently reported in related compounds, but our results differ in several respects from previous studies...... axis, we find the moment to be aligned well away from the c axis, in agreement with recent Yb-170(3+) Mossbauer spectroscopy results. Ridges of scattering indicative of 2D magnetic ordering were seen in both oxygenated and reduced crystals, though we believe different magnetic moments are responsible...

  5. Magnetoresistance and magnetic ordering in praseodymium and neodymium hexaborides

    International Nuclear Information System (INIS)

    Anisimov, M. A.; Bogach, A. V.; Glushkov, V. V.; Demishev, S. V.; Samarin, N. A.; Filipov, V. B.; Shitsevalova, N. Yu.; Kuznetsov, A. V.; Sluchanko, N. E.

    2009-01-01

    The magnetoresistance Δρ/ρ of single-crystal samples of praseodymium and neodymium hexaborides (PrB 6 and NdB 6 ) has been measured at temperatures ranging from 2 to 20 K in a magnetic field of up to 80 kOe. The results obtained have revealed a crossover of the regime from a small negative magnetoresistance in the paramagnetic state to a large positive magnetoresistive effect in magnetically ordered phases of the PrB 6 and NdB 6 compounds. An analysis of the dependences Δρ(H)/ρ has made it possible to separate three contributions to the magnetoresistance for the compounds under investigation. In addition to the main negative contribution, which is quadratic in the magnetic field (-Δρ/ρ ∝ H 2 ), a linear positive contribution (Δρ/ρ ∝ H) and a nonlinear ferromagnetic contribution have been found. Upon transition to a magnetically ordered state, the linear positive component in the magnetoresistance of the PrB 6 and NdB 6 compounds becomes dominant, whereas the quadratic contribution to the negative magnetoresistance is completely suppressed in the commensurate magnetic phase of these compounds. The presence of several components in the magnetoresistance has been explained by assuming that, in the antiferromagnetic phases of PrB 6 and NdB 6 , ferromagnetic nanoregions (ferrons) are formed in the 5d band in the vicinity of the rareearth ions. The origin of the quadratic contribution to the negative magnetoresistance is interpreted in terms of the Yosida model, which takes into account scattering of conduction electrons by localized magnetic moments of rare-earth ions. Within the approach used, the local magnetic susceptibility χ loc has been estimated. It has been demonstrated that, in the temperature range T N loc for the compounds under investigation can be described with good accuracy by the Curie-Weiss dependence χ loc ∝ (T - Θ p ) -1 .

  6. Magnetic study of turbidites

    Science.gov (United States)

    Tanty, Cyrielle; Valet, Jean Pierre; Carlut, Julie

    2015-04-01

    Turbidites induce sedimentary reworking and re-deposition caused by tsunami, earthquake, volcanic processes, and other catastrophic events. They result from rapid depositional processes and are thus considered not being pertinent for comparison with pelagic sediments. Turbidites are evidently ruled out from paleomagnetic records dealing with time-series. Consequently, no attention has ever been paid to the magnetization of turbidites which is fully justified if the high level of turbulence governing the depositional processes influences the acquisition of magnetization. In certain conditions like channeled turbidity currents, levees of sediment are generated and then associated with relatively calm although very fast redeposition processes. Such conditions will thus govern the subsequent acquisition of magnetization through mechanical lock-in of the magnetic grains. This situation is actually quite similar to what happens during the experiences of artificial redeposition that are conducted in laboratory. Therefore, combining laboratory experiments and studies of natural turbidites could reveal important information on the processes involved in the acquisition of magnetization, especially if the comparison with the overlying hemipelagic sediments does not show any striking difference. We will present the results of magnetic measurements performed on four different and relatively recent turbidites. We selected different origins associated either with spillover of channeled turbidity currents or with co-seismic faulting. Each event is characterized by a different thickness (ten to few tens of cm), lithology and mean granulometry (few tens of μm to hundreds of μm). We have carried out measurements of magnetic susceptibility, magnetic remanence, anisotropy of magnetic susceptibility (AMS) and we also scrutinize the evolution of various rock magnetic parameters (ARM, IRM, S ratio, magnetic grain sizes, hysteresis parameters…). The magnetic characteristics of the

  7. Ordering due to disorder in frustrated quantum magnetic system

    International Nuclear Information System (INIS)

    Yildirim, T.

    1999-01-01

    The phenomenon of order by disorder in frustrated magnetic systems is reviewed. Disorder (thermal or quantum fluctuations) may sometimes give rise to long range ordering in systems with frustration, where one must often consider the selection among classically degenerate ground states which are not equivalent by any symmetry. The lowest order effects of quantum fluctuations in such frustrated systems usually resolves the continues degeneracy of the ground state manifold into discrete Ising-type degeneracy. A unique ground state selection out of this Ising degenerate manifold then occurs due to higher order effects of quantum fluctuations. For systems such as face-centered cubic and body-centered tetragonal antiferromagnets where the number of Ising parameters to describe the ground state manifold is not macroscopic, we show that quantum fluctuations choose a unique ground state at the first order in 1/S

  8. Microscopic evidence for magnetic ordering in NdCu3Ru4O12 : 63,65Cu nuclear quadrupole resonance study

    Science.gov (United States)

    Yogi, M.; Niki, H.; Hedo, M.; Komesu, S.; Nakama, T.

    2018-05-01

    We have conducted 63,65Cu nuclear quadrupole resonance (NQR) measurements on A-site ordered perovskite compounds LaCu3Ru4O12 and NdCu3Ru4O12 to investigate their ground state and spin fluctuations. While there is only one Cu site in the crystal structure, multiple NQR resonance lines were observed. This is presumed to be due to the presence of slight distortion and lattice defects in the samples. The nuclear spin-lattice relaxation rate divided by temperature, 1 /T1 T , for LaCu3Ru4O12 showed almost constant value indicating the Fermi-liquid state. A remarkable increase in 1 /T1 T due to spin fluctuations was observed in NdCu3Ru4O12 . Furthermore, an evident magnetic phase transition at TM = 0.6 K was revealed from the distinct peak of 1 /T1 T and the broadening of the NQR spectrum.

  9. Elaboration and evolution in temperature of the amorphous alloy Tb65Cu35, study of short and medium range atomic order and low temperature magnetic order related to the elaboration process

    International Nuclear Information System (INIS)

    El Gadi, M.

    1986-12-01

    The thesis presents the study of the amorphous metallic alloy Tb 65 Cu 35 prepared by rapid quenching and sputtering. Differential scanning calorimetry (DSC) measurements establish the annealing procedure needed to obtain a stable amorphous state through structural relaxation. Nearest neighbour distances as determined by neutron diffraction measurements shows a high coordination for Tb atom and a relatively low one for Cu atom. In addition, small-angle neutron scattering (SANS) experiments carried out as a function of temperature show the existence of Tb bubbles with very high magnetization at low-temperature. The region between the bubbles shows composition fluctuations. The SANS measurements also indicate the coexistence of phases with compositions bordering the eutectic value and in the form of domains having sizes of a few thousand Angstroms. An unexpected result in the observation of an hundred fold increase in the intensity of low-angle magnetic scattering when the samples are hand-polished with simple sand paper. This clearly indicates the importance of sample surface state. Finally, this work establishes that samples prepared by two different techniques show identical properties [fr

  10. Magnetic and electrical studies on La{sub 0.4}Sm{sub 0.1}Ca{sub 0.5}MnO{sub 3} charge ordered manganite

    Energy Technology Data Exchange (ETDEWEB)

    Krichene, A., E-mail: akramkri@hotmail.fr [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Solanki, P.S. [Department of Physics, Saurashtra University, Rajkot 360005 (India); Venkateshwarlu, D. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017 (India); Rayaprol, S. [UGC-DAE Consortium for Scientific Research, Mumbai Centre, B.A.R.C. Campus, Mumbai 400085 (India); Ganesan, V. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017 (India); Boujelben, W. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Université de Sfax, B. P. 1171, 3000 Sfax (Tunisia); Kuberkar, D.G. [Department of Physics, Saurashtra University, Rajkot 360005 (India)

    2015-05-01

    We have reported in this work the effect of the partial substitution of lanthanum by samarium on the structural, electrical and magnetic properties of La{sub 0.5}Ca{sub 0.5}MnO{sub 3}. The magnetic study indicated that substitution promotes charge ordering and weakens ferromagnetism. Below T{sub C}=123 K, the compound La{sub 0.4}Sm{sub 0.1}Ca{sub 0.5}MnO{sub 3} is a mixture of ferromagnetic and charge ordered antiferromagnetic domains. Between T{sub C} and T{sub CO}=215 K, the structure is paramagnetic with the presence of antiferromagnetic domains. The fractions of the coexisting magnetic phases are highly dependent on the applied magnetic field value. Resistivity measurements reveal the presence of an insulating-metal transition at T{sub ρ}=123 K. The equality between T{sub C} and T{sub ρ} indicates the presence of a correlation between magnetization and resistivity. For only 1 T applied field, we have reported a colossal value of magnetoresistance reaching 73% around T{sub C}. The origin of this high value is attributed to phase separation phenomenon. - Highlights: • Sm doping enhances charge ordering and weakens ferromagnetism in La{sub 0.5}Ca{sub 0.5}MnO{sub 3.} • Colossal magnetoresistance (73%) is recorded at 123 K for only 1 T applied field. • Phase separation is responsible for the magnetic and the magnetoresistive behavior.

  11. Spin model for nontrivial types of magnetic order in inverse-perovskite antiferromagnets

    Science.gov (United States)

    Mochizuki, Masahito; Kobayashi, Masaya; Okabe, Reoya; Yamamoto, Daisuke

    2018-02-01

    Nontrivial magnetic orders in the inverse-perovskite manganese nitrides are theoretically studied by constructing a classical spin model describing the magnetic anisotropy and frustrated exchange interactions inherent in specific crystal and electronic structures of these materials. With a replica-exchange Monte Carlo technique, a theoretical analysis of this model reproduces the experimentally observed triangular Γ5 g and Γ4 g spin-ordered patterns and the systematic evolution of magnetic orders. Our Rapid Communication solves a 40-year-old problem of nontrivial magnetism for the inverse-perovskite manganese nitrides and provides a firm basis for clarifying the magnetism-driven negative thermal expansion phenomenon discovered in this class of materials.

  12. Incommensurate magnetic ordering of PrPdAl

    Energy Technology Data Exchange (ETDEWEB)

    Keller, L. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Doenni, A. [National Research Inst. for Metals, Tsukuba, Ibaraki (Japan). Tsukuba Lab.; Fauth, F. [Institut Max von Laue - Paul Langevin, 75 - Paris (France)

    1997-09-01

    The intermetallic rare earth compound PrPdAl with ZrNiAl-type structure was investigated by means of powder neutron diffraction. PrPdAl orders below T{sub N} {approx_equal}4.2 K with an incommensurate antiferromagnetic propagation vector k = [1/2,0,{tau}], {tau}=0.398. The best fit was obtained with a sinusoidal modulation of the magnetic moments along the c-axis. (author) 2 figs., 2 refs.

  13. Evidence of the extended orientational order in amorphous alloys obtained from magnetic measurements

    International Nuclear Information System (INIS)

    Chudnovsky, E.M.; Tejada, J.

    1993-01-01

    Magnetic measurements of R-Fe-B (R = rare earth) amorphous alloys show that magnetic anisotropy axes are correlated on the scale ∼ 100 A. The X-ray study of these materials does not reveal any positional correlations beyond the 10 A scale. These observations support theoretical suggestions that the orientational order in amorphous systems can be much more extended than the positional order. (orig.)

  14. First-Order Transitions and the Magnetic Phase Diagram of CeSb

    DEFF Research Database (Denmark)

    Lebech, Bente; Clausen, Kurt Nørgaard; Vogt, O.

    1980-01-01

    might exist in the magnetic phase diagram of CeSb at 16K for a field of approximately 0.3 T. The present study concludes that the transitions from the paramagnetic to the magnetically ordered states are of first order for fields below 0.8 T. Within the experimental accuracy no change has been observed......The high-temperature (14-17K) low-magnetic field (0-0.8 T) region of the phase diagram of the anomalous antiferromagnet CeSb has been reinvestigated by neutron diffraction in an attempt to locate a possible tricritical point. Previous neutron diffraction studies indicated that a tricritical point...

  15. Impurity effects on the magnetic ordering in chromium

    International Nuclear Information System (INIS)

    Fishman, R.S.

    1992-05-01

    It is well-known that impurities profoundly alter the magnetic properties of chromium. While vanadium impurities suppress the Neel temperature T N , manganese impurities enhanced T N substantially. As evidenced by neutron scattering experiments, doping with as little as 0.2% vanadium changes the transition from weakly first order to second order. Young and Sokoloff explained that the first-order transition in pure chromium is caused by a charge-density wave which is the second harmonic of the spin-density wave. By examining the subtle balance between the spin-density and charge- density wave terms in the mean-field free energy, we find that the first-order transition is destroyed when the vanadium concentration exceeds about 0.15%, in agreement with experiments

  16. Dynamic magnetic susceptibility of systems with long-range magnetic order

    International Nuclear Information System (INIS)

    Vannette, Matthew Dano

    2009-01-01

    The utility of the TDR as an instrument in the study of magnetically ordered materials has been expanded beyond the simple demonstration purposes. Results of static applied magnetic field dependent measurements of the dynamic magnetic susceptibility, ?, of various ferromagnetic (FM) and antiferromagnetic (AFM) materials showing a range of transition temperatures (1-800 K) are presented. Data was collected primarily with a tunnel diode resonator (TDR) at different radio-frequencies (∼10-30 MHz). In the vicinity of TC local moment ferromagnets show a very sharp, narrow peak in ? which is suppressed in amplitude and shifted to higher temperatures as the static bias field is increased. Unexpectedly, critical scaling analysis fails for these data. It is seen that these data are frequency dependent, however there is no simple method whereby measurement frequency can be changed in a controllable fashion. In contrast, itinerant ferromagnets show a broad maximum in ? well below TC which is suppressed and shifts to lower temperatures as the dc bias field is increased. The data on itinerant ferromagnets is fitted to a semi-phenomenological model that suggests the sample response is dominated by the uncompensated minority spins in the conduction band. Concluding remarks suggest possible scenarios to achieve frequency resolved data using the TDR as well as other fields in which the apparatus may be exploited.

  17. Experimental and theoretical study of magnetic ordering and local atomic polarization in Ru-substituted Lu.sub.2./sub.Fe.sub.17./sub..

    Czech Academy of Sciences Publication Activity Database

    Tereshina, Evgeniya; Isnard, O.; Smekhova, A.; Andreev, Alexander V.; Rogalev, A.; Khmelevskyi, S.

    2014-01-01

    Roč. 89, č. 9 (2014), "094420-1"-"094420-2" ISSN 1098-0121 R&D Projects: GA ČR GAP204/12/0150 Institutional support: RVO:68378271 Keywords : rare- earth intermetallics * antiferromagnetism * field -induced magnetic phase transition * XMCD * neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  18. The role of order-disorder transitions in the quest for molecular multiferroics: structural and magnetic neutron studies of a mixed valence iron(II)-iron(III) formate framework.

    Science.gov (United States)

    Cañadillas-Delgado, Laura; Fabelo, Oscar; Rodríguez-Velamazán, J Alberto; Lemée-Cailleau, Marie-Hélène; Mason, Sax A; Pardo, Emilio; Lloret, Francesc; Zhao, Jiong-Peng; Bu, Xian-He; Simonet, Virginie; Colin, Claire V; Rodríguez-Carvajal, Juan

    2012-12-05

    Neutron diffraction studies have been carried out to shed light on the unprecedented order-disorder phase transition (ca. 155 K) observed in the mixed-valence iron(II)-iron(III) formate framework compound [NH(2)(CH(3))(2)](n)[Fe(III)Fe(II)(HCOO)(6)](n). The crystal structure at 220 K was first determined from Laue diffraction data, then a second refinement at 175 K and the crystal structure determination in the low temperature phase at 45 K were done with data from the monochromatic high resolution single crystal diffractometer D19. The 45 K nuclear structure reveals that the phase transition is associated with the order-disorder of the dimethylammonium counterion that is weakly anchored in the cavities of the [Fe(III)Fe(II)(HCOO)(6)](n) framework. In the low-temperature phase, a change in space group from P31c to R3c occurs, involving a tripling of the c-axis due to the ordering of the dimethylammonium counterion. The occurrence of this nuclear phase transition is associated with an electric transition, from paraelectric to antiferroelectric. A combination of powder and single crystal neutron diffraction measurements below the magnetic order transition (ca. 37 K) has been used to determine unequivocally the magnetic structure of this Néel N-Type ferrimagnet, proving that the ferrimagnetic behavior is due to a noncompensation of the different Fe(II) and Fe(III) magnetic moments.

  19. Microscopic interplay of superconducting and magnetic order parameters in ferropnictides

    Energy Technology Data Exchange (ETDEWEB)

    Maeter, H.; Goltz, T.; Spehling, J.; Klauss, H.H. [Institut fuer Festkoerperphysik, TU Dresden (Germany); Bendele, M.; Luetkens, H.; Khasanov, R.; Pascua, G.; Shermadini, Z.; Amato, A. [Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, Villigen (Switzerland); Aswartham, S.; Hamann-Borrero, J.E.; Kondrat, A.; Hess, C.; Wolter, A.; Wurmehl, S.; Behr, G.; Buechner, B. [Leibniz-Institut fuer Festkoerper- und Werkstoffforschung Dresden (Germany); Wiesenmayer, E.; Johrendt, D. [Department Chemie, Ludwig-Maximilians-Universitaet Muenchen (Germany); Potts, H.; Banusch, B. [Swiss Nanoscience Institute, Universitaet Basel (Switzerland)

    2012-07-01

    We present results of {mu}SR experiments of Ba{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} that show a large coupling of the superconducting and magnetic order parameters. This is unexpected in light of the phase separation in Ba{sub 1-x}K{sub x}Fe{sub 2}As{sub 2}. However, in a {mu}SR study of Ba{sub 1-x}K{sub x}Fe{sub 2}As{sub 2} we unambiguously showed microscopic coexistence, even though there are many reports of phase separation in this system. In FeSe{sub 1-x} the interplay of phase separation and microscopic coexistence is also evident, here pressure can induce a change from microscopic coexistence to a combination of both. In light of the {mu}SR results it seems likely that phase separation and microscopic coexistence depend on the microscopic properties much more than on disorder.

  20. Magnetic properties of Gd5(Si1.5Ge2.5) near the temperature and magnetic field induced first order phase transition

    International Nuclear Information System (INIS)

    Levin, E.M.; Gschneidner, K.A.; Pecharsky, V.K.

    2001-01-01

    The temperature (from 5 to 300 K) and DC magnetic field (from 0 to 90 kOe) dependencies of the DC magnetization and magnetic susceptibility, and the temperature (from 5 to 350 K) dependency of the AC magnetic susceptibility of Gd 5 (Si 1.5 Ge 2.5 ) have been studied. The temperature and/or magnetic field induced magnetic phase transition in Gd 5 (Si 1.5 Ge 2.5 ) is a first order ferromagnet-paramagnet transition. The temperature of the magnetic transition in low AC magnetic field is 206 and 217 K for cooling and heating, respectively. The DC magnetic field increases the transition temperature by ∼0.36 K/kOe indicating that the paramagnetic phase can be reversibly transformed into the ferromagnetic phase. When the magnetic field is removed, the ferromagnetic phase transforms into the paramagnetic phase showing a large remanence-free hysteresis. The magnetic phase diagram based on the isothermal magnetic field dependence of the DC magnetization at various temperatures for Gd 5 (Si 1.5 Ge 2.5 ) is proposed. The magnetic field dependence of the magnetization in the vicinity of the first order phase transition shows evidence for the formation of a magnetically heterogeneous system in the volume of Gd 5 (Si 1.5 Ge 2.5 ) specimen where the magnetically ordered (ferromagnetic) and disordered (paramagnetic) phases co-exist

  1. Magnetic anisotropy and order parameter in nanostructured CoPt particles

    Science.gov (United States)

    Komogortsev, S. V.; Iskhakov, R. S.; Zimin, A. A.; Filatov, E. Yu.; Korenev, S. V.; Shubin, Yu. V.; Chizhik, N. A.; Yurkin, G. Yu.; Eremin, E. V.

    2013-10-01

    The correlation of magnetic anisotropy energy with order parameter in the crystallites of CoPt nanostructured particles prepared by thermal decomposition and further annealing has been studied by investigation of the approach magnetization to saturation curves and x-ray powder diffraction pattern profiles. It is shown that magnetic anisotropy energy value in partially ordered CoPt crystallite could be described as an intermediate case between two extremes, corresponding to either single or several c-domains of L10 phase in crystallite.

  2. Spin dynamics and magnetic ordering in mixed valence systems

    International Nuclear Information System (INIS)

    Shapiro, S.M.; Moller, H.B.; Axe, J.D.; Birgeneau, R.J.; Bucher, E.

    1977-01-01

    Neutron scattering measurements are reported on the mixed valence compounds Ce/sub 1-x/Th/sub x/ and TmSe. The Chi''(Q,ω) as derived from the inelastic spectra of Ce 0 . 74 Th 0 . 26 shows a peak in the γ phase near 20.0 meV and shifts abruptly to greater than 70.0 meV at the transition to the α phase. The temperature independence of the susceptibility within the γ phase cannot be simply reconciled with the temperature dependence of the valence within the γ phase. TmSe is shown to order in a type I antiferromagnetic structure below T/sub N/ approx. 3.2 K. The magnetic phase diagram is understood as a successive domain reorientation and a metamagnetic phase transition for T 3+ orders in a type II structure but never achieves long range order

  3. A pulse spectrometer for NMR measurements on magnetically ordered materials

    International Nuclear Information System (INIS)

    Englich, J.; Pikner, B.; Sedlak, B.

    1975-01-01

    A simple design of a pulse nuclear magnetic resonance spectrometer is described. The spectrometer permits spin echo measurements on magnetically ordered substances. It operates in the frequency range 10 to 130 MHz, but this basic range can be extended by a replacement of the compact radiofrequency unit. The transmitter gives radiofrequency pulses with an amplitude of up to 1 kV on the coil with the investigated sample. The pulse programmer makes possible relaxation measurements in a time interval of 10 -5 to 10 -1 s. Attention was devoted to obtaining a maximum signal-to-noise ratio in the whole frequency range. Sensitivity of the spectrometer is demonstrated by spin echo measurement on pure iron powder. (author)

  4. Order of magnetic transition and large magnetocaloric effect in Er3Co

    International Nuclear Information System (INIS)

    Jun, Shen; Jian-Feng, Wu; Jin-Liang, Zhao; Feng-Xia, Hu; Ji-Rong, Sun; Bao-Gen, Shen

    2010-01-01

    We have studied the magnetic and magnetocaloric properties of the Er 3 Co compound, which undergoes ferromagnetic ordering below the Curie temperature T C = 13 K. It is found by fitting the isothermal magnetization curves that the Landau model is appropriate to describe the Er 3 Co compound. The giant magnetocaloric effect (MCE) without hysteresis loss around T C is found to result from the second-order ferromagnetic-to-paramagnetic transition. The maximal value of magnetic entropy change is 24.5 J/kg·K with a refrigerant capacity (RC) value of 476 J/kg for a field change of 0–5 T. Large reversible MEC and RC indicate the potentiality of Er 3 Co as a candidate magnetic refrigerant at low temperatures. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  5. TmCd quadrupolar ordering and magnetic interactions

    International Nuclear Information System (INIS)

    Aleonard, R.; Morin, P.

    1979-01-01

    The paramagnetic compound TmCd crystallizes with the CsCl-type structure. Its Jahn-Teller behavior was first observed by Luethi and coworkers. We analyze here various physical properties with a pure-harmonic-elasticity model. The structural transition between cubic and tetragonal phases is now fully described (first-order character and temperature of occurrence) as well as the magnetic susceptibility, magnetization process, specific-heat, elastic-constant, and strain data. The relevant Hamiltonian takes into account the second-order magnetoelastic coupling and the quadrupolar exchange in addition to the cubic crystal field and the Heisenberg bilinear interactions. TmCd appears to be closely related to isomorphous TmZn and completes the illustration of the competition between bilinear and quadrupolar interactions occurring in some rare-earth intermetallics. In these two compounds, the quadrupolar exchange is many times stronger than the magnetoelastic coupling and the quadrupolar ordering then drives the structural transition. This situation is opposite to that occurring in (actual) Jahn-Teller compounds

  6. Medium-range order of magnetic amorphous alloys containing rare earth metals

    International Nuclear Information System (INIS)

    Boucher, B.

    1989-01-01

    The influence of nuclear order and surface layers on the magnetic order and the existence of two characteristic lengths (ξ=2π/k∼10 3 A or 10 A) have been established. The principal conclusions of theorists: concerning the abscence of infinite ferromagnetic clusters and the correlated spin glass or ferromagnet with wandering axis models are verified. The published results seem to indicate the existence of a critical temperature. The role of 3d ions in the magnetic ordering has not been extensively studied; it seems that the presence of 3d ions leads smaller correlation lengths. The Lorentzian scattering term correspond not only to spin waves but also to a static order. The origin of the L 3/2 scattering term observed in severals cases is discussed. It would be very useful to carry out measurements at lower q values so as to obtain more detailed informations concerning the nuclear or magnetic medium range order

  7. Second order semiclassics with self-generated magnetic fields

    DEFF Research Database (Denmark)

    Erdös, Laszlo; Fournais, Søren; Solovej, Jan Philip

    2012-01-01

    $ effectively determines the strength of the field. We consider the weak field regime with $\\beta h^{2}\\ge {const}>0$, where $h$ is the semiclassical parameter. For smooth potentials we prove that the semiclassical asymptotics of the total energy is given by the non-magnetic Weyl term to leading order...... with an error bound that is smaller by a factor $h^{1+\\e}$, i.e. the subleading term vanishes. However, for potentials with a Coulomb singularity the subleading term does not vanish due to the non-semiclassical effect of the singularity. Combined with a multiscale technique, this refined estimate is used...

  8. Spin Dynamics and Magnetic Ordering in Mixed Valence Systems

    DEFF Research Database (Denmark)

    Shapiro, S. M.; Bjerrum Møller, Hans; Axe, J. D.

    1978-01-01

    . 0 meV at the transition to the alpha phase. The temperature independence of the susceptibility within the gamma phase cannot be simply reconciled with the temperature dependence of the valence within the gamma phase. TmSe is shown to order in a type I antiferromagnetic structure below T//N similar 3....... 2 K. The magnetic phase diagram is understood as a successive domain reorientation and a metamagnetic phase transition for T less than 3 K with increasing field. The mixed valence nature manifests itself in a reduced moment and a markedly altered crystal field. Another sample of TmSe with a lattice...

  9. Spin-lattice dynamics simulation of external field effect on magnetic order of ferromagnetic iron

    Directory of Open Access Journals (Sweden)

    C. P. Chui

    2014-03-01

    Full Text Available Modeling of field-induced magnetization in ferromagnetic materials has been an active topic in the last dozen years, yet a dynamic treatment of distance-dependent exchange integral has been lacking. In view of that, we employ spin-lattice dynamics (SLD simulations to study the external field effect on magnetic order of ferromagnetic iron. Our results show that an external field can increase the inflection point of the temperature. Also the model provides a better description of the effect of spin correlation in response to an external field than the mean-field theory. An external field has a more prominent effect on the long range magnetic order than on the short range counterpart. Furthermore, an external field allows the magnon dispersion curves and the uniform precession modes to exhibit magnetic order variation from their temperature dependence.

  10. Orbital studies of lunar magnetism

    Science.gov (United States)

    Mcleod, M. G.; Coleman, P. J., Jr.

    1982-01-01

    Limitations of present lunar magnetic maps are considered. Optimal processing of satellite derived magnetic anomaly data is also considered. Studies of coastal and core geomagnetism are discussed. Lunar remanent and induced lunar magnetization are included.

  11. Study of magnetization switching in coupled magnetic nanostructured systems

    Science.gov (United States)

    Radu, Cosmin

    A study of magnetization dynamics experiments in nanostructured materials using the rf susceptibility tunnel diode oscillator (TDO) method is presented along with a extensive theoretical analysis. An original, computer controlled experimental setup that measures the change in susceptibility with the variation in external magnetic field and sample temperature was constructed. The TDO-based experiment design and construction is explained in detail, showing all the elements of originality. This experimental technique has proven reliable for characterizing samples with uncoupled magnetic structure and various magnetic anisotropies like: CrO2, FeCo/IrMn and Co/SiO2 thin films. The TDO was subsequently used to explore the magnetization switching in coupled magnetic systems, like synthetic antiferromagnet (SAF) structures. Magnetoresistive random access memory (MRAM) is an important example of devices where the use of SAF structure is essential. To support the understanding of the SAF magnetic behavior, its configuration and application are reviewed and more details are provided in an appendix. Current problems in increasing the scalability and decreasing the error rate of MRAM devices are closely connected to the switching properties of the SAF structures. Several theoretical studies that were devoted to the understanding of the concepts of SAF critical curve are reviewed. As one can notice, there was no experimental determination of SAF critical curve, due to the difficulties in characterizing a magnetic coupled structure. Depending of the coupling strength between the two ferromagnetic layers, on the SAF critical curve one distinguishes several new features, inexistent in the case of uncoupled systems. Knowing the configuration of the SAF critical curve is of great importance in order to control its switching characteristics. For the first time a method of experimentally recording the critical curve for SAF is proposed in this work. In order to overcome technological

  12. 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)

  13. Electric–magnetic duality of lattice systems with topological order

    Energy Technology Data Exchange (ETDEWEB)

    Buerschaper, Oliver [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario, N2L 2Y5 (Canada); Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, D-85748 Garching (Germany); Christandl, Matthias [Institute for Theoretical Physics, ETH Zurich, 8093 Zurich (Switzerland); Kong, Liang, E-mail: kong.fan.liang@gmail.com [Institute for Advanced Study (Science Hall), Tsinghua University, Beijing 100084 (China); Department of Mathematics and Statistics University of New Hampshire, Durham, NH 03824 (United States); Aguado, Miguel [Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, D-85748 Garching (Germany)

    2013-11-11

    We investigate the duality structure of quantum lattice systems with topological order, a collective order also appearing in fractional quantum Hall systems. We define electromagnetic (EM) duality for all of Kitaev's quantum double models based on discrete gauge theories with Abelian and non-Abelian groups, and identify its natural habitat as a new class of topological models based on Hopf algebras. We interpret these as extended string-net models, whereupon Levin and Wen's string-nets, which describe all intrinsic topological orders on the lattice with parity and time-reversal invariance, arise as magnetic and electric projections of the extended models. We conjecture that all string-net models can be extended in an analogous way, using more general algebraic and tensor-categorical structures, such that EM duality continues to hold. We also identify this EM duality with an invertible domain wall. Physical applications include topology measurements in the form of pairs of dual tensor networks.

  14. Coupling of demixing and magnetic ordering phase transitions probed by turbidimetric measurements in a binary mixture doped with magnetic nanoparticles

    International Nuclear Information System (INIS)

    Hernandez-Diaz, Lorenzo; Hernandez-Reta, Juan Carlos; Encinas, Armando; Nahmad-Molinari, Yuri

    2010-01-01

    We present a novel study on the effect of a magnetic field applied on a binary mixture doped with magnetic nanoparticles close to its demixing transition. Turbidity measurements in the Faraday configuration show that the effect of applying an external field produces changes in the critical opalescence of the mixture that allow us to track an aggregation produced by critical Casimir forces and a reversible aggregation due to the formation of chain-like flocks in response to the external magnetic field. The observation of a crossover of the aggregation curves through optical signals is interpreted as the evolution from low to high power dispersion nuclei due to an increase in the radius of the condensation seed brought about by Casimir or magnetic interactions. Finally, evidence of an enhanced magnetocaloric effect due to the coupling between mixing and ordering phase transitions is presented which opens up a nonsolid state approach of designing refrigerating cycles and devices.

  15. Coupling of demixing and magnetic ordering phase transitions probed by turbidimetric measurements in a binary mixture doped with magnetic nanoparticles

    Science.gov (United States)

    Hernández-Díaz, Lorenzo; Hernández-Reta, Juan Carlos; Encinas, Armando; Nahmad-Molinari, Yuri

    2010-05-01

    We present a novel study on the effect of a magnetic field applied on a binary mixture doped with magnetic nanoparticles close to its demixing transition. Turbidity measurements in the Faraday configuration show that the effect of applying an external field produces changes in the critical opalescence of the mixture that allow us to track an aggregation produced by critical Casimir forces and a reversible aggregation due to the formation of chain-like flocks in response to the external magnetic field. The observation of a crossover of the aggregation curves through optical signals is interpreted as the evolution from low to high power dispersion nuclei due to an increase in the radius of the condensation seed brought about by Casimir or magnetic interactions. Finally, evidence of an enhanced magnetocaloric effect due to the coupling between mixing and ordering phase transitions is presented which opens up a nonsolid state approach of designing refrigerating cycles and devices.

  16. Coupling of demixing and magnetic ordering phase transitions probed by turbidimetric measurements in a binary mixture doped with magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Diaz, Lorenzo; Hernandez-Reta, Juan Carlos; Encinas, Armando; Nahmad-Molinari, Yuri, E-mail: yuri@ifisica.uaslp.m [Instituto de Fisica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi (Mexico)

    2010-05-19

    We present a novel study on the effect of a magnetic field applied on a binary mixture doped with magnetic nanoparticles close to its demixing transition. Turbidity measurements in the Faraday configuration show that the effect of applying an external field produces changes in the critical opalescence of the mixture that allow us to track an aggregation produced by critical Casimir forces and a reversible aggregation due to the formation of chain-like flocks in response to the external magnetic field. The observation of a crossover of the aggregation curves through optical signals is interpreted as the evolution from low to high power dispersion nuclei due to an increase in the radius of the condensation seed brought about by Casimir or magnetic interactions. Finally, evidence of an enhanced magnetocaloric effect due to the coupling between mixing and ordering phase transitions is presented which opens up a nonsolid state approach of designing refrigerating cycles and devices.

  17. Mechanism of nuclear cross-relaxation in magnetically ordered media

    Energy Technology Data Exchange (ETDEWEB)

    Buishvili, L L; Volzhan, E B; Giorgadze, N P [AN Gruzinskoj SSR, Tbilisi. Inst. Fiziki

    1975-09-01

    A mechanism of two-step nuclear relaxation in magnetic ordered dielectrics is proposed. The case is considered where the energy conservation in the cross relaxation (CR) process is ensured by the lattice itself without spin-spin interactions. Expressions have been obtained describing the temperature dependence of the CR rate. For a nonuniform broadened NMR line it has been shown that the spin-lattice relaxation time for a spin packet taken out from the equilibrium may be determined by the CR time owing to the mechanism suggested. When the quantization axes for electron and nuclear spins coincide, the spin-lattice relaxation is due to the three-magnon mechanism. The cross-relaxation stage has been shown to play a significant role in the range of low temperatures (T<10 deg K) and to become negligible with a temperature increase.

  18. Magnetic ordering of four particle exchange model in BCC 3He

    International Nuclear Information System (INIS)

    Ishikawa, Koji; Okada, Isamu

    1978-01-01

    The low temperature magnetic ordering of BCC 3 He within the mean field approximation was studied. A model including four particle exchange interactions was considered. Two types of cyclic quadrupole exchange process, planar and folded, were taken into account. Assuming four sublattices, it was considered to minimize the spin energy with respect to the classical spin vector and to find out four ordered states at the absolute zero point. They are antiferromagnetic (AF), weak ferromagnetic (WF) and two kinds of simple cubic antiferromagnetic states (SCAF). The condition for the existence of each ordered state is given, and the free energies of the ordered states are calculated in the mean field approximation. The transition between AF or SCAF and the paramagnetic states is of the first order. The phase diagram is drawn in the parameter space. The phase diagram was obtained numerically at Hetherington and Willard's value and at its neighbouring values. The difference between the present result and HW's is that of magnetic field direction in the perpendicular simple cubic antiferromagnetic states. The second order transition disappears, and the WF state changes gradually into AF state. With respect to the first order transition, the transition temperature increases with magnetic field. In this case, a critical magnetic field exists. (Kato, T

  19. Ordering and thermal excitations in dipolar coupled single domain magnet arrays (Presentation Recording)

    Science.gov (United States)

    Östman, Erik; Arnalds, Unnar; Kapaklis, Vassilios; Hjörvarsson, Björgvin

    2015-09-01

    For a small island of a magnetic material the magnetic state of the island is mainly determined by the exchange interaction and the shape anisotropy. Two or more islands placed in close proximity will interact through dipolar interactions. The state of a large system will thus be dictated by interactions at both these length scales. Enabling internal thermal fluctuations, e.g. by the choice of material, of the individual islands allows for the study of thermal ordering in extended nano-patterned magnetic arrays [1,2]. As a result nano-magnetic arrays represent an ideal playground for the study of physical model systems. Here we present three different studies all having used magneto-optical imaging techniques to observe, in real space, the order of the systems. The first study is done on a square lattice of circular islands. The remanent magnetic state of each island is a magnetic vortex structure and we can study the temperature dependence of the vortex nucleation and annihilation fields [3]. The second are long chains of dipolar coupled elongated islands where the magnetization direction in each island only can point in one of two possible directions. This creates a system which in many ways mimics the Ising model [4] and we can relate the correlation length to the temperature. The third one is a spin ice system where elongated islands are placed in a square lattice. Thermal excitations in such systems resemble magnetic monopoles [2] and we can investigate their properties as a function of temperature and lattice parameters. [1] V. Kapaklis et al., New J. Phys. 14, 035009 (2012) [2] V. Kapaklis et al., Nature Nanotech 9, 514(2014) [3] E. Östman et al.,New J. Phys. 16, 053002 (2014) [4] E. Östman et al.,Thermal ordering in mesoscopic Ising chains, In manuscript.

  20. Neutron-scattering studies of magnetic superconductors

    International Nuclear Information System (INIS)

    Sinha, S.K.; Crabtree, G.W.; Hinks, D.G.; Mook, H.A.; Pringle, O.A.

    1982-01-01

    Results obtained in the last few years obtained by neutron diffraction on the nature of the magnetic ordering in magnetic superconductors are reviewed. Emphasis is given to studies of the complex intermediate phase in ferromagnetic superconductors where both superconductivity and ferromagnetism appear to coexist

  1. The bonding character and magnetic properties of Fe3Al: Comparison between disordered and ordered alloy

    International Nuclear Information System (INIS)

    Fan Runhua; Qi Liang; Sun Kangning; Min Guanghui; Gong Hongyu

    2006-01-01

    Fe 3 Al with D0 3 -ordered structure is one of the few structural intermetallics that can be disordered using non-equilibrium processing techniques. The bonding and magnetic character of the stoichiometric Fe 3 Al, with D0 3 -ordered or disordered structure, have been studied using the empirical electron theory of solid and molecular (EET). It was found that the magnetic property is basically dictated by the chemical bonding. There is a change of the character of the interatomic bonds from 3d(Fe)-3p(Al) for the D0 3 -ordered Fe 3 Al to 4sp(Fe)-3p(Al) for the disordered Fe 3 Al. For the latter, while the Fe 3d electrons participating in bonding is reduced, the mean magnetic moment is increased

  2. Shape induced magnetic vortex state in hexagonal ordered cofe nanodot arrays using ultrathin alumina shadow mask

    Science.gov (United States)

    Sellarajan, B.; Saravanan, P.; Ghosh, S. K.; Nagaraja, H. S.; Barshilia, Harish C.; Chowdhury, P.

    2018-04-01

    The magnetization reversal process of hexagonal ordered CoFe nanodot arrays was investigated as a function of nanodot thickness (td) varying from 10 to 30 nm with fixed diameter. For this purpose, ordered CoFe nanodots with a diameter of 80 ± 4 nm were grown by sputtering using ultra-thin alumina mask. The vortex annihilation and the dynamic spin configuration in the ordered CoFe nanodots were analyzed by means of magnetic hysteresis loops in complement with the micromagnetic simulation studies. A highly pinched hysteresis loop observed at 20 nm thickness suggests the occurrence of vortex state in these nanodots. With increase in dot thickness from 10 to 30 nm, the estimated coercivity values tend to increase from 80 to 175 Oe, indicating irreversible change in the nucleation/annihilation field of vortex state. The measured magnetic properties were then corroborated with the change in the shape of the nanodots from disk to hemisphere through micromagnetic simulation.

  3. Evolution of magnetic order in mechanically alloyed Al-1 at%Fe

    International Nuclear Information System (INIS)

    Sebastian, Varkey; Lakshmi, N.; Venugopalan, K.

    2007-01-01

    The evolution of ferromagnetic order in high-energy ball-milled Al-1 at% Fe before the onset of a considerable Fe-Al solid solution phase has been investigated using 57 Fe Moessbauer and bulk magnetization studies. The unmilled sample does not exhibit bulk magnetic properties and an onset of bulk magnetization is observed only after 30 min of milling, when the grain size becomes comparable to the ferromagnetic exchange length. The Curie temperatures of all the samples are less than that of pure iron. The reduction in grain size is accompanied by an increase in coercivity and reduced remanence and a decrease in T C . The effective magnetic moment per iron atom decreases with the development of a non-magnetic, Al-rich Fe-Al solution on longer milling. The clustering of Fe at grain boundaries is responsible for the observed bulk magnetic ordering. The systematic variation of the magnetic properties has been qualitatively correlated with the evolution of microstructure, reduction in grain size and enhanced inter-granular exchange coupling

  4. Noncollinear magnetic ordering in a frustrated magnet: Metallic regime and the role of frustration

    Science.gov (United States)

    Shahzad, Munir; Sengupta, Pinaki

    2017-12-01

    We explore the magnetic phases in a Kondo lattice model on the geometrically frustrated Shastry-Sutherland lattice at metallic electron densities, searching for noncollinear and noncoplanar spin textures. Motivated by experimental observations in many rare-earth-based frustrated metallic magnets, we treat the local moments as classical spins and set the coupling between the itinerant electrons and local moments as the largest energy scale in the problem. Our results show that a noncollinear flux state is stabilized over an extended range of Hamiltonian parameters. These spin states can be quenched efficiently by external fields like temperature and magnetic field as well as by varying the degree of frustration in the electronic itinerancy and exchange coupling between local moments. Interestingly, unlike insulating electron densities that we discussed in paper I of this sequence, a Dzyaloshinskii-Moriya interaction between the local moments is not essential for the emergence of their noncollinear ordering.

  5. Magnetic susceptibility as a method of investigation of short-range order in strongly nonstoichiometric carbides

    International Nuclear Information System (INIS)

    Nazarova, S.Z.; Gusev, A.I.

    2001-01-01

    Magnetic susceptibility in disordered and ordered carbides of transition metals (M = Ti, Zr, Hf, Nb, Ta) was studied, the results are generalized. It was ascertained that the change in carbide susceptibility induced by deviation from stoichiometry stems from specific features of electronic spectra of the compounds. The use of magnetic susceptibility for determining structural disorder-order transitions is discussed. It is shown that change in the contribution made by orbital paramagnetism, resulting from short-range order formation, is the reason of decrease in susceptibility of nonstoichiometric carbides during the ordering. Experimentally obtained data on susceptibility permitted evaluating short- and far-range order parameters in NbC y , TaC y , TiC y and HfC y carbides [ru

  6. Interplay of charge, orbital and magnetic order in Pr1-xCaxMnO3

    International Nuclear Information System (INIS)

    Zimmermann V, M.; Hill, J.P.; Gibbs, D.; Blume, M.; Casa, D.; Keimer, B.; Murakami, Y.; Tomioka, Y.; Tokura, Y.

    1999-01-01

    The authors report resonant x-ray scattering studies of charge and orbital order in Pr 1-x Ca x MnO 3 with x = 0.4 and 0.5. Below the ordering temperature, T O = 245 K, the charge and orbital order intensities follow the same temperature dependence, including an increase at the antiferromagnetic ordering temperature, T N . High resolution measurements reveal, however, that long range orbital order is never achieved. Rather, an orbital domain state is formed. Above T O , the charge order fluctuations are more highly correlated than the orbital fluctuations. Similar phenomenology is observed in a magnetic field. They conclude that the charge order drives the orbital order at the transition

  7. Magnetic order, magnetic correlations, and spin dynamics in the pyrochlore antiferromagnet Er2Ti2O7

    Science.gov (United States)

    Dalmas de Réotier, P.; Yaouanc, A.; Chapuis, Y.; Curnoe, S. H.; Grenier, B.; Ressouche, E.; Marin, C.; Lago, J.; Baines, C.; Giblin, S. R.

    2012-09-01

    Er2Ti2O7 is believed to be a realization of an XY antiferromagnet on a frustrated lattice of corner-sharing regular tetrahedra. It is presented as an example of the order-by-disorder mechanism in which fluctuations lift the degeneracy of the ground state, leading to an ordered state. Here we report detailed measurements of the low-temperature magnetic properties of Er2Ti2O7, which displays a second-order phase transition at TN≃1.2 K with coexisting short- and long-range orders. Magnetic susceptibility studies show that there is no spin-glass-like irreversible effect. Heat capacity measurements reveal that the paramagnetic critical exponent is typical of a 3-dimensional XY magnet while the low-temperature specific heat sets an upper limit on the possible spin-gap value and provides an estimate for the spin-wave velocity. Muon spin relaxation measurements show the presence of spin dynamics in the nanosecond time scale down to 21 mK. This time range is intermediate between the shorter time characterizing the spin dynamics in Tb2Sn2O7, which also displays long- and short-range magnetic order, and the time scale typical of conventional magnets. Hence the ground state is characterized by exotic spin dynamics. We determine the parameters of a symmetry-dictated Hamiltonian restricted to the spins in a tetrahedron, by fitting the paramagnetic diffuse neutron scattering intensity for two reciprocal lattice planes. These data are recorded in a temperature region where the assumption that the correlations are limited to nearest neighbors is fair.

  8. Specific heat and magnetic susceptibility vs long range order in V3Ga

    International Nuclear Information System (INIS)

    Junod, A.; Fluekiger, R.; Treyvaud, A.; Muller, J.

    1976-01-01

    A new technique of studying the magnetic susceptibility together with the specific heat and the superconducting transition of typical A15-type compounds in different ordering states enables us to consistently isolate the spin paramagnetism. Satisfactory results are obtained for V 3 Ga and these are compared with data on V 3 Au and Nb 3 (Au-Pt). (author)

  9. Study of the hyperfine magnetic field acting on Ce probes substituting for the rare earth and the magnetic ordering in intermetallic compounds RAg (R=rare earth) by first principles calculations; Estudo do campo hiperfino magnetico na sonda de Ce colocada nos compostos intermetalicos do tipo RAg (R=terra rara) e do ordenamento magnetico desses compostos usando calculos de primeiros principios

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Luciano Fabricio Dias

    2006-07-01

    In this work the magnetic hyperfine field acting on Ce atoms substituting the rare-earths in R Ag compounds (R = Gd e Nd) was studied by means of first-principles electronic structure calculations. The employed method was the Augmented Plane Waves plus local orbitals (APW+lo), embodied in the WIEN2k program, within the framework of the Density Functional Theory (DFT) and with the Generalized Gradient Approximation (GGA) for the exchange and correlation potential. The super-cell approach was utilized in order to simulate for the Ce atoms acting as impurities in the R Ag matrix. In order to improve for correlation effects within the 4f shells, a Hubbard term was added to the DFT Hamiltonian, within a procedure called GGA+U. It was found that the magnetic hyperfine field (MHF) generated by the Ce 4f electron is the main component of the total MHF and that the Ce 4f ground state level is probably a combination of the m{sub l} = -2 and m{sub l} = -1 sub-levels. In addition, the ground-state magnetic structure was determined for Ho Ag and Nd Ag by observing the behavior of the total energy as a function of the lattice volume for several possible magnetic ordering in these compounds, namely, ferromagnetic, and the (0,0,{pi}), ({pi},{pi},0) and (({pi},{pi},{pi}) types of anti-ferromagnetic ordering of rare-earth atoms. It was found that the ground-state magnetic structure is anti-ferromagnetic of type ({pi},{pi},0) for both, the Ho Ag and Nd Ag compounds. The energy difference of the ferromagnetic and antiferromagnetic ordering is very small in the case of the Nd Ag compound. (author)

  10. On magnetic ordering in heavily sodium substituted hole doped lanthanum manganites

    Energy Technology Data Exchange (ETDEWEB)

    Sethulakshmi, N. [Department of Physics, Cochin University of Science and Technology, Cochin 682022, Kerala (India); Unnimaya, A.N. [Centre for Materials for Electronic Technology (CMET), Thrissur 680581, Kerala (India); Al-Omari, I.A.; Al-Harthi, Salim [Department of Physics, Sultan Qaboos University, PC 123 Muscat (Oman); Sagar, S. [Government College for Women, Thiruvananthapuram 695014, Kerala (India); Thomas, Senoy [Materials Science and Technology Division, National Institute for Interdisciplinary Science and Technology, Thiruvananthapuram 695019, Kerala (India); Srinivasan, G. [Department of Physics, Oakland University, Rochester (United States); Anantharaman, M.R., E-mail: mraiyer@yahoo.com [Department of Physics, Cochin University of Science and Technology, Cochin 682022, Kerala (India)

    2015-10-01

    Mixed valence manganite system with monovalent sodium substituted lanthanum manganites form the basis of the present work. Lanthanum manganites belonging to the series La{sub 1−x}Na{sub x}MnO{sub 3} with x=0.5–0.9 were synthesized using modified citrate gel method. Variation of lattice parameters and unit cell volume with Na concentration were analyzed and the magnetization measurements indicated ferromagnetic ordering in all samples at room temperature. Low temperature magnetization behavior indicated that all samples exhibit antiferromagnetism along with ferromagnetism and it has also been observed that antiferromagnetic ordering dominates ferromagnetic ordering as concentration is increased. Evidence for such a magnetic inhomogeneity in these samples has been confirmed from the variation in Mn{sup 3+}/Mn{sup 4+} ion ratio from X-ray Photoelectron Spectroscopy and from the absorption peak studies using Ferromagnetic Resonance Spectroscopy. - Highlights: • Higher substitution of more than 50 percent of monovalent ion, sodium for La sites in lanthanum manganites scarce in literature. • Structural studies using XRD and further structure refinement by Rietveld refinement confirmed orthorhombic pbnm spacegroup. • Ferromagnetic behavior at room temperature with saturation magnetization decreasing with increase in sodium concentration. • M vs T measurements using FC ZFC proved coexisting FM/AFM behavior arising from exchange interactions between different valence states of Mn ions. • Disparity in ratio of Mn valence ions indicated presence of vacancies providing the role of vacancies and oxygen stoichiometry in deciding magnetic inhomogeneity.

  11. Distinguishing magnetic particle size of iron oxide nanoparticles with first-order reversal curves

    Energy Technology Data Exchange (ETDEWEB)

    Kumari, Monika; Hirt, Ann M., E-mail: ann.hirt@erdw.ethz.ch [Department of Earth Sciences, Institute of Geophysics, ETH-Zurich, Sonneggstrasse 5, CH-8092 Zurich (Switzerland); Widdrat, Marc; Faivre, Damien [Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Science Park Golm, D-14424 Potsdam (Germany); Tompa, Éva; Pósfai, Mihály [Department of Earth and Environmental Sciences, University of Pannonia, Egyetem u. 10, H-8200 Veszprém (Hungary); Uebe, Rene; Schüler, Dirk [Department Biologie I, LMU Munich, Großhaderner Str. 2, D-82152 Martinsried (Germany)

    2014-09-28

    Magnetic nanoparticles encompass a wide range of scientific study and technological applications. The success of using the nanoparticles in various applications demands control over size, dispersibility, and magnetics. Hence, the nanoparticles are often characterized by transmission electron microscopy (TEM), X-ray diffraction, and magnetic hysteresis loops. TEM analysis requires a thin layer of dispersed particles on the grid, which may often lead to particle aggregation thus making size analysis difficult. Magnetic hysteresis loops on the other hand provide information on the bulk property of the material without discriminating size, composition, and interaction effects. First order reversal curves (FORCs), described as an assembly of partial hysteresis loops originating from the major loop are efficient in identifying the domain size, composition, and interaction in a magnetic system. This study presents FORC diagrams on a variety of well-characterized biogenic and synthetic magnetite nanoparticles. It also introduces deconvoluted reversible and irreversible components from FORC as an important method for obtaining a semi-quantitative measure of the effective magnetic particle size. This is particularly important in a system with aggregation and interaction among the particles that often leads to either the differences between physical size and effective magnetic size. We also emphasize the extraction of secondary components by masking dominant coercivity fraction on FORC diagram to explore more detailed characterization of nanoparticle systems.

  12. Distinguishing magnetic particle size of iron oxide nanoparticles with first-order reversal curves

    International Nuclear Information System (INIS)

    Kumari, Monika; Hirt, Ann M.; Widdrat, Marc; Faivre, Damien; Tompa, Éva; Pósfai, Mihály; Uebe, Rene; Schüler, Dirk

    2014-01-01

    Magnetic nanoparticles encompass a wide range of scientific study and technological applications. The success of using the nanoparticles in various applications demands control over size, dispersibility, and magnetics. Hence, the nanoparticles are often characterized by transmission electron microscopy (TEM), X-ray diffraction, and magnetic hysteresis loops. TEM analysis requires a thin layer of dispersed particles on the grid, which may often lead to particle aggregation thus making size analysis difficult. Magnetic hysteresis loops on the other hand provide information on the bulk property of the material without discriminating size, composition, and interaction effects. First order reversal curves (FORCs), described as an assembly of partial hysteresis loops originating from the major loop are efficient in identifying the domain size, composition, and interaction in a magnetic system. This study presents FORC diagrams on a variety of well-characterized biogenic and synthetic magnetite nanoparticles. It also introduces deconvoluted reversible and irreversible components from FORC as an important method for obtaining a semi-quantitative measure of the effective magnetic particle size. This is particularly important in a system with aggregation and interaction among the particles that often leads to either the differences between physical size and effective magnetic size. We also emphasize the extraction of secondary components by masking dominant coercivity fraction on FORC diagram to explore more detailed characterization of nanoparticle systems.

  13. Magnetic order of Au nanoparticle with clean surface

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Ryuju; Ishikawa, Soichiro; Sato, Hiroyuki; Sato, Tetsuya, E-mail: satoh@appi.keio.ac.jp

    2015-11-01

    Au nanoparticles, which are kept in vacuum after the preparation by gas evaporation method, show ferromagnetism even in 1.7 nm in diameter. The intrinsic magnetism is examined by detecting the disappearance of spontaneous magnetization in Au bulk prepared by heating the nanoparticles without exposure to the air. The temperature dependence of spontaneous magnetization is not monotonic and the increase in magnetization is observed after Au nanoparticles are exposed to the air. The magnetic behavior can be interpreted by the ferrimagnetic-like core–shell structure with shell thickness of 0.16±0.01 nm and magnetic moment of (1.5±0.1)×10{sup −2} μ{sub B}/Au atom, respectively. - Highlights: • Au nanoparticles with clean surface were prepared by the gas evaporation method. • The spontaneous magnetization was observed in Au nanoparticles. • Temperature dependent spontaneous magnetization of smaller Au particles was not monotonic. • The magnetic behavior was interpreted by the ferrimagnetic-like core–shell model. • The shell thickness and the magnetic moment per Au atom were estimated.

  14. Annealing influence on the atomic ordering and magnetic moment in a Ni-Mn-Ga alloy

    International Nuclear Information System (INIS)

    Gutierrez, J.; Lazpita, P.; Barandiaran, J.M.; Fdez-Gubieda, M.L.; Chaboy, J.; Kawamura, N.

    2007-01-01

    We have studied an alloy of composition Ni 51 Mn 28 Ga 21 prepared by rapid quenching in the form of a ribbon, with transformation temperature T M =337 K below the magnetic-order temperature, T C =344 K. Annealing of the samples was performed at 600 K for different times. From magnetic characterization a clear increase of the saturation magnetization accompanied with an increase of T C (up to 20 K) and T M (about 10 K) has been observed. XMCD measurements of both as-quenched and annealed samples have revealed great changes for the Mn and also the existence of a strong Ni signal. These results point out a possible non-negligible role of Ni, through the polarization of the conduction band, into driving the interplay between annealing and the magnetic properties in these materials

  15. Explicit higher order symplectic integrator for s-dependent magnetic field

    International Nuclear Information System (INIS)

    Wu, Y.; Forest, E.; Robin, D.S.

    2001-01-01

    We derive second and higher order explicit symplectic integrators for the charged particle motion in an s-dependent magnetic field with the paraxial approximation. The Hamiltonian of such a system takes the form of H (summation) k (p k - a k (rvec q), s) 2 + V((rvec q), s). This work solves a long-standing problem for modeling s-dependent magnetic elements. Important applications of this work include the studies of the charged particle dynamics in a storage ring with strong field wigglers, arbitrarily polarized insertion devices,and super-conducting magnets with strong fringe fields. Consequently, this work will have a significant impact on the optimal use of the above magnetic devices in the light source rings as well as in next generation linear collider damping rings

  16. 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

  17. 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.

  18. Study of a 900 bending magnet for H- beams

    International Nuclear Information System (INIS)

    Sherman, J.D.; Allison, P.W.

    1979-01-01

    Three different magnetic pole face configurations with field indices not equal to 0 have been studied to minimize second-order magnetic focusing aberrations. One pole face with a substantial second-order magnetic field inhomogeneity reduces the measured aberration coefficient to zero. A calculation using first- and second-order ion optics provides a qualitative explanation for the aberration variations seen in these magnets. The pepper pot emittance measurement technique was used

  19. Impact of local order and stoichiometry on the ultrafast magnetization dynamics of Heusler compounds

    International Nuclear Information System (INIS)

    Steil, Daniel; Schmitt, Oliver; Fetzer, Roman; Aeschlimann, Martin; Cinchetti, Mirko; Kubota, Takahide; Naganuma, Hiroshi; Oogane, Mikihiko; Ando, Yasuo; Rodan, Steven; Blum, Christian G F; Wurmehl, Sabine; Balke, Benjamin

    2015-01-01

    Nowadays, a wealth of information on ultrafast magnetization dynamics of thin ferromagnetic films exists in the literature. Information is, however, scarce on bulk single crystals, which may be especially important for the case of multi-sublattice systems. In Heusler compounds, representing prominent examples for such multi-sublattice systems, off-stoichiometry and degree of order can significantly change the magnetic properties of thin films, while bulk single crystals may be generally produced with a much more well-defined stoichiometry and a higher degree of ordering. A careful characterization of the local structure of thin films versus bulk single crystals combined with ultrafast demagnetization studies can, thus, help to understand the impact of stoichiometry and order on ultrafast spin dynamics.Here, we present a comparative study of the structural ordering and magnetization dynamics for thin films and bulk single crystals of the family of Heusler alloys with composition Co 2 Fe 1 − x Mn x Si. The local ordering is studied by 59 Co nuclear magnetic resonance (NMR) spectroscopy, while the time-resolved magneto-optical Kerr effect gives access to the ultrafast magnetization dynamics. In the NMR studies we find significant differences between bulk single crystals and thin films, both regarding local ordering and stoichiometry. The ultrafast magnetization dynamics, on the other hand, turns out to be mostly unaffected by the observed structural differences, especially on the time scale of some hundreds of femtoseconds. These results confirm hole-mediated spin-flip processes as the main mechanism for ultrafast demagnetization and the robustness of this demagnetization channel against defect states in the minority band gap as well as against the energetic position of the band gap with respect to the Fermi energy. The very small differences observed in the magnetization dynamics on the picosecond time-scale, on the other hand, can be explained by considering the

  20. Spin-phonon induced magnetic order in magnetized Spin Ice systems

    International Nuclear Information System (INIS)

    Albarracín, F A Gómez; Cabra, D C; Rosales, H D; Rossini, G L

    2014-01-01

    We study the behavior of spin ice pyrochlore systems above the well known [111] 1/3 plateau, under slight deviations of the direction of the external field. We model the relevant degrees of freedom by Ising spins on the kagome lattice. We propose the inclusion of lattice deformations, which imply phononic degrees of freedom in the adiabatic limit. We use analytical calculations to estimate how these new degrees of freedom affect the short and long range spin interactions in the presence of an external magnetic field. We then obtain the magnetization curves, explore the phases and the ground states of this system in the presence of magnetic field by Monte Carlo simulations. We discuss comparisons with experimental results

  1. Charge order suppression, emergence of ferromagnetism and absence of exchange bias effect in Bi0.25Ca0.75MnO3 nanoparticles: Electron paramagnetic resonance and magnetization studies

    Science.gov (United States)

    Singh, Geetanjali; Bhat, S. V.

    2012-06-01

    We report the results of magnetization and electron paramagnetic resonance (EPR) studies on nanoparticles (average diameter ˜ 30 nm) of Bi0.25Ca0.75MnO3 (BCMO) and compare them with the results on bulk BCMO. The nanoparticles were prepared using the nonaqueous sol-gel technique and characterized by XRD and TEM analysis. Magnetization measurements were carried out with a commercial physical property measurement system (PPMS). While the bulk BCMO exhibits a charge ordering transition at ˜230 K and an antiferromagnetic (AFM) transition at ˜130 K, in the nanoparticles, the CO phase is seen to have disappeared and a transition to a ferromagnetic (FM) state is observed at Tc ˜ 120 K. However, interestingly, the exchange bias effect observed in other nanomanganite ferromagnets is absent in BCMO nanoparticles. EPR measurements were carried out in the X-band between 8 and 300 K. Lineshape fitting to a Lorentzian with two terms (accounting for both the clockwise and anticlockwise rotations of the microwave field) was employed to obtain the relevant EPR parameters as functions of temperature. The results confirm the occurrence of ferromagnetism in the nanoparticles of BCMO.

  2. Observations of imposed ordered structures in a dusty plasma at high magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Edward, E-mail: etjr@auburn.edu; Lynch, Brian; Konopka, Uwe [Physics Department, Auburn University, Auburn, Alabama 36849 (United States); Merlino, Robert L. [Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242 (United States); Rosenberg, Marlene [Department of Electrical and Computer Engineering, University of California–San Diego, La Jolla, California 92093 (United States)

    2015-03-15

    Dusty plasmas have been studied in argon, rf glow discharge plasmas at magnetic fields up to 2 T, where the electrons and ions are strongly magnetized. In this experiment, plasmas are generated between two parallel plate electrodes where the lower, powered electrode is solid and the upper, electrically floating electrode supports a semi-transparent, titanium mesh. We report on the formation of an ordered dusty plasma, where the dust particles form a spatial structure that is aligned to the mesh. We discuss possible mechanisms that may lead to the formation of the “dust grid” and point out potential implications and applications of these observations.

  3. Longitudinal Spin Excitations and Magnetic Anisotropy in Antiferromagnetically Ordered BaFe_{2}As_{2}

    Directory of Open Access Journals (Sweden)

    Chong Wang

    2013-12-01

    Full Text Available We report on a spin-polarized inelastic neutron-scattering study of spin waves in the antiferromagnetically ordered state of BaFe_{2}As_{2}. Three distinct excitation components are identified, with spins fluctuating along the c axis, perpendicular to the ordering direction in the ab plane and parallel to the ordering direction. While the first two “transverse” components can be described by a linear spin-wave theory with magnetic anisotropy and interlayer coupling, the third “longitudinal” component is generically incompatible with the local-moment picture. It points toward a contribution of itinerant electrons to the magnetism that is already in the parent compound of this family of Fe-based superconductors.

  4. Order-disorder transitions in adsorbed systems on magnetic surfaces

    International Nuclear Information System (INIS)

    Aguilera-Granja, F.; Moran-Lopez, J.L.; Instituto Politecnico Nacional, Mexico City. Centro de Investigacion y de Estudios Avanzados); Falicov, L.M.

    1984-01-01

    It is investigated the effect of adsorbed atoms on the magnetic properties of ferromagnets. The Ising model is employed considering nearest neigbours with antiferromagnetic coupling between atoms. (M.W.O.) [pt

  5. Magnetic-Field-Enhanced Incommensurate Magnetic Order in the Underdoped High-Temperature Superconductor YBa2Cu3O6.45

    DEFF Research Database (Denmark)

    Haug, D.; Hinkov, V.; Suchaneck, A.

    2009-01-01

    We present a neutron-scattering study of the static and dynamic spin correlations in the underdoped high-temperature superconductor YBa2Cu3O6.45 in magnetic fields up to 15 T. The field strongly enhances static incommensurate magnetic order at low temperatures and induces a spectral-weight shift...

  6. Magnetic quasi-long-range ordering in nematic systems due to competition between higher-order couplings

    Science.gov (United States)

    Žukovič, Milan; Kalagov, Georgii

    2018-05-01

    Critical properties of the two-dimensional X Y model involving solely nematic-like terms of the second and third orders are investigated by spin-wave analysis and Monte Carlo simulation. It is found that, even though neither of the nematic-like terms alone can induce magnetic ordering, their coexistence and competition leads to an extended phase of the magnetic quasi-long-range-order phase, wedged between the two nematic-like phases induced by the respective couplings. Thus, except for the multicritical point, at which all the phases meet, for any finite value of the coupling parameters ratio there are two phase transition: one from the paramagnetic phase to one of the two nematic-like phases followed by another one at lower temperatures to the magnetic phase. The finite-size scaling analysis indicates that the phase transitions between the magnetic and nematic-like phases belong to the Ising and three-state Potts universality classes. Inside the competition-induced algebraic magnetic phase, the spin-pair correlation function is found to decay even much more slowly than in the standard X Y model with purely magnetic interactions. Such a magnetic phase is characterized by an extremely low vortex-antivortex pair density attaining a minimum close to the point at which the two couplings are of about equal strength.

  7. Magnetic study of iron sorbitol

    Energy Technology Data Exchange (ETDEWEB)

    Lazaro, F.J. E-mail: osoro@posta.unizar.es; Larrea, A.; Abadia, A.R.; Romero, M.S

    2002-09-01

    A magnetic study of iron sorbitol, an iron-containing drug to treat the iron deficiency anemia is presented. Transmission electron microscopy reveals that the system contains nanometric particles with an average diameter of 3 nm whose composition is close to two-line ferrihydrite. The characterisation by magnetisation and AC susceptibility measurements indicates superparamagnetic behaviour with progressive magnetic blocking starting at 8 K. The quantitative analysis of the magnetic results indicates that the system consists of an assembly of very small magnetic moments, presumably originated by spin uncompensation of the antiferromagnetic nanoparticles, with Arrhenius type magnetic dynamics.

  8. Loss of long-range magnetic order in a nanoparticle assembly due to random anisotropy

    International Nuclear Information System (INIS)

    Binns, C; Howes, P B; Baker, S H; Marchetto, H; Potenza, A; Steadman, P; Dhesi, S S; Roy, M; Everard, M J; Rushforth, A

    2008-01-01

    We have used soft x-ray photoemission electron microscopy (XPEEM) combined with x-ray magnetic circular dichroism (XMCD) and DC SQUID (superconducting quantum interference device) magnetometry to probe the magnetic ground state in Fe thin films produced by depositing size-selected gas-phase Fe nanoparticles with a diameter of 1.7 nm (∼200 atoms) onto Si substrates. The depositions were carried out in ultrahigh vacuum conditions and thicknesses of the deposited film in the range 5-50 nm were studied. The magnetometry data are consistent with the film forming a correlated super-spin glass with a magnetic correlation length ∼5 nm. The XPEEM magnetic maps from the cluster-assembled films were compared to those for a conventional thin Fe film with a thickness of 20 nm produced by a molecular beam epitaxy (MBE) source. Whereas a normal magnetic domain structure is observed in the conventional MBE thin film, no domain structure could be observed in any of the nanoparticle films down to the resolution limit of the XMCD based XPEEM (100 nm) confirming the ground state indicated by the magnetometry measurements. This observation is consistent with the theoretical prediction that an arbitrarily weak random anisotropy field will destroy long-range magnetic order

  9. Tenth-Order Lepton Anomalous Magnetic Moment--Sixth-Order Vertices Containing Vacuum-Polarization Subdiagrams

    International Nuclear Information System (INIS)

    Aoyama, Tatsumi; Hayakawa, Masashi; Kinoshita, Toichiro; Nio, Makiko

    2011-01-01

    This paper reports the values of contributions to the electron g-2 from 300 Feynman diagrams of the gauge-invariant Set III(a) and 450 Feynman diagrams of the gauge-invariant Set III(b). The evaluation is carried out in two versions. Version A is to start from the sixth-order magnetic anomaly M 6 obtained in the previous work. The mass-independent contributions of Set III(a) and Set III(b) are 2.1275(2) and 3.3271(6) in units of (α/π) 5 , respectively. Version B is based on the recently developed automatic code generation scheme. This method yields 2.1271(3) and 3.3271(8) in units of (α/π) 5 , respectively. They are in excellent agreement with the results of the first method within the uncertainties of numerical integration. Combining these results as statistically independent we obtain the best values, 2.1273(2), and 3.3271(5) times (α/π) 5 , for the mass-independent contributions of the Set III(a) and Set III(b), respectively. We have also evaluated mass-dependent contributions of diagrams containing muon and/or tau-particle loop. Including them the total contribution of Set III(a) is 2.1349(2) and that of Set III(b) is 3.3299(5) in units of (α/π) 5 . The total contributions to the muon g-2 of various leptonic vacuum-polarization loops of Set III(a) and Set III(b) are 112.418(32) and 15.407(5) in units of (α/π) 5 , respectively.

  10. Competing superconducting and magnetic order parameters and field-induced magnetism in electron doped Ba(Fe1-xCox)2As2

    DEFF Research Database (Denmark)

    Larsen, Jacob; Uranga, B. Mencia; Stieber, G.

    2015-01-01

    We have studied the magnetic and superconducting properties of Ba(Fe1-xCox)2As2 as a function of temperature and external magnetic field using neutron scattering and muon spin rotation. Below the superconducting transition temperature the magnetic and superconducting order parameters coexist...... and compete. A magnetic field can significantly enhance the magnetic scattering in the superconducting state, roughly doubling the Bragg intensity at 13.5 T. We perform a microscopic modelling of the data by use of a five-band Hamiltonian relevant to iron pnictides. In the superconducting state, vortices can...... slow down and freeze spin fluctuations locally. When such regions couple they result in a long-range ordered antiferromagnetic phase producing the enhanced magnetic elastic scattering in agreement with experiments....

  11. Absence of magnetic ordering and field-induced phase diagram in the gadolinium aluminum garnet

    Science.gov (United States)

    Florea, O.; Lhotel, E.; Jacobsen, H.; Knee, C. S.; Deen, P. P.

    2017-12-01

    The robustness of spin liquids with respect to small perturbations, and the way magnetic frustration can be lifted by slight changes in the balance between competing magnetic interactions, remains a rich and open issue. We address this question through the study of the gadolinium aluminum garnet Gd3Al5O12 , a related compound to the extensively studied Gd3Ga5O12 . We report on its magnetic properties at very low temperatures. We show that despite a freezing at about 300 mK, no magnetic transition is observed, suggesting the presence of a spin-liquid state down to the lowest temperatures, similarly to Gd3Ga5O12 , in spite of a larger ratio between exchange and dipolar interactions. Finally, the phase diagram as a function of field and temperature is strongly reminiscent of the one reported in Gd3Ga5O12 . This study reveals the robust nature of the spin-liquid phase for Gd ions on the garnet lattice, in stark contrast to Gd ions on the pyrochlore lattice for which a slight perturbation drives the compound into a range of magnetically ordered states.

  12. Magnetic Ordering in Sr3YCo4O10+x.

    Science.gov (United States)

    Kishida, Takayoshi; Kapetanakis, Myron D; Yan, Jiaqiang; Sales, Brian C; Pantelides, Sokrates T; Pennycook, Stephen J; Chisholm, Matthew F

    2016-01-28

    Transition-metal oxides often exhibit complex magnetic behavior due to the strong interplay between atomic-structure, electronic and magnetic degrees of freedom. Cobaltates, especially, exhibit complex behavior because of cobalt's ability to adopt various valence and spin state configurations. The case of the oxygen-deficient perovskite Sr3YCo4O10+x (SYCO) has attracted considerable attention because of persisting uncertainties about its structure and the origin of the observed room temperature ferromagnetism. Here we report a combined investigation of SYCO using aberration-corrected scanning transmission electron microscopy and density functional theory calculations. Guided by theoretical results on Co-O distances projected on different planes, the atomic-scale images of several different orientations, especially of the fully oxygenated planes, allow the unambiguous extraction of the underlying structure. The calculated magnetic properties of the new structure are in excellent agreement with the experimental data.

  13. 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.

  14. Magnetic dipolar ordering and hysteresis of geometrically defined nanoparticle clusters

    DEFF Research Database (Denmark)

    Kure, Mathias; Beleggia, Marco; Frandsen, Cathrine

    2017-01-01

    Magnetic nanoparticle clusters have several biomedical and engineering applications, and revealing the basic interplay between particle configuration and magnetic properties is important for tuning the clusters for specific uses. Here, we consider the nanoparticles as macrospins and use computer...... of the polyhedra, the central moment relaxes along one of the principal axes and induces partial alignment of the surrounding moments. The resulting net moment is up to nearly four times that of the single moment added. Furthermore, we model quasi-static hysteresis loops for structures with and without a central...

  15. Magnetooptics and electronic structure of the magnetic ordering europium chalcogenides

    International Nuclear Information System (INIS)

    Schoenes, J.

    1975-01-01

    The absorption coefficient and the interband Faraday rotation of EuS, EuSe and EuTe thin films have been measured as function of the photon energy (1-6 eV), the temperature (2.7-300 K) and the applied magnetic field (0-11.5 kOe). In addition a magnetic field modulation technique has been developed, with a resolution of 2 x 10 -4 deg. This allows the measurement of the Faraday rotation in fields of only 100 Oe, which is important for metamagnetic samples with low critical fields. (orig./HPoe) [de

  16. Multi-Objective Optimization for Pure Permanent-Magnet Undulator Magnets Ordering Using Modified Simulated Annealing

    CERN Document Server

    Chen Nian; Li, Ge

    2004-01-01

    Undulator field errors influence the electron beam trajectories and lower the radiation quality. Angular deflection of electron beam is determined by first field integral, orbital displacement of electron beam is determined by second field integral and radiation quality can be evaluated by rms field error or phase error. Appropriate ordering of magnets can greatly reduce the errors. We apply a modified simulated annealing algorithm to this multi-objective optimization problem, taking first field integral, second field integral and rms field error as objective functions. Undulator with small field errors can be designed by this method within a reasonable calculation time even for the case of hundreds of magnets (first field integral reduced to 10-6T·m, second integral to 10-6T·m2 and rms field error to 0.01%). Thus, the field correction after assembling of undulator will be greatly simplified. This paper gives the optimizing process in detail and puts forward a new method to quickly calculate the rms field e...

  17. Spin Solid versus Magnetic Charge Ordered State in Artificial Honeycomb Lattice of Connected Elements

    Science.gov (United States)

    Glavic, Artur; Summers, Brock; Dahal, Ashutosh; Kline, Joseph; Van Herck, Walter; Sukhov, Alexander; Ernst, Arthur

    2018-01-01

    Abstract The nature of magnetic correlation at low temperature in two‐dimensional artificial magnetic honeycomb lattice is a strongly debated issue. While theoretical researches suggest that the system will develop a novel zero entropy spin solid state as T → 0 K, a confirmation to this effect in artificial honeycomb lattice of connected elements is lacking. This study reports on the investigation of magnetic correlation in newly designed artificial permalloy honeycomb lattice of ultrasmall elements, with a typical length of ≈12 nm, using neutron scattering measurements and temperature‐dependent micromagnetic simulations. Numerical modeling of the polarized neutron reflectometry data elucidates the temperature‐dependent evolution of spin correlation in this system. As temperature reduces to ≈7 K, the system tends to develop novel spin solid state, manifested by the alternating distribution of magnetic vortex loops of opposite chiralities. Experimental results are complemented by temperature‐dependent micromagnetic simulations that confirm the dominance of spin solid state over local magnetic charge ordered state in the artificial honeycomb lattice with connected elements. These results enable a direct investigation of novel spin solid correlation in the connected honeycomb geometry of 2D artificial structure. PMID:29721429

  18. 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

  19. A symmetric, triply interlaced 3-D anionic MOF that exhibits both magnetic order and SMM behaviour.

    Science.gov (United States)

    Campo, J; Falvello, L R; Forcén-Vázquez, E; Sáenz de Pipaón, C; Palacio, F; Tomás, M

    2016-11-14

    A newly prepared 3-D polymer of cobalt citrate cubanes bridged by high-spin Co(ii) centres displays both single-molecule magnet (SMM) behaviour and magnetic ordering. Triple interpenetration of the 3-D diamondoid polymers yields a crystalline solid with channels that host cations and free water molecules, with the SMM behaviour of the Co 4 O 4 cores preserved. The octahedrally coordinated Co(ii) bridges are implicated in the onset of magnetic order at an experimentally accessible temperature.

  20. Magnetic phase transitions with incommensurate structures in systems with coupled order parameters

    International Nuclear Information System (INIS)

    Izyumov, Yu.A.; Laptev, V.M.; Petrov, S.B.

    1984-01-01

    Modulated magnetic phases are investigated for the case when symmetry does not allow linear by gradients Lifshits invariants and magnetic momenta are converted by two irreducible representations. Possible phase diagrams with participation of incommensurable phases are plotted on the base of Ginsburg-Landau functional for 2 bound parameters of the order. The role of the highest harmonics in spatial distribution of the order parameters is clarified on the example of magnetic phase transitions in Er

  1. Magnetically-guided assembly of microfluidic fibers for ordered construction of diverse netlike modules

    Science.gov (United States)

    Li, Xingfu; Shi, Qing; Wang, Huaping; Sun, Tao; Huang, Qiang; Fukuda, Toshio

    2017-12-01

    In this paper, a magnetically-guided assembly method is proposed to methodically construct diverse modules with a microfiber-based network for promoting nutrient circulation and waste excretion of cell culture. The microfiber is smoothly spun from the microfluidic device via precise control of the volumetric flow rate, and superparamagnetic nanoparticles within the alginate solution of the microfluidic fiber enable its magnetic response. The magnetized device is used to effectively capture the microfiber using its powerful magnetic flux density and high magnetic field gradient. Subsequently, the dot-matrix magnetic flux density is used to distribute the microfibers in an orderly fashion that depends on the array structure of the magnetized device. Furthermore, the magnetic microfluidic fibers are spatially organized into desired locations and are cross-aligned to form highly interconnected netlike modules in a liquid environment. Therefore, the experimental results herein demonstrate the structural controllability and stability of various modules and establish the effectiveness of the proposed method.

  2. Dipolar magnetism in ordered and disordered low-dimensional nanoparticle assemblies

    DEFF Research Database (Denmark)

    Varón, M.; Beleggia, M; Kasama, T

    2013-01-01

    order at ambient temperature in assemblies of closely-spaced nanoparticles with magnetic moments of ≥ 100 μ(B). Here we use electron holography with sub-particle resolution to reveal the correlation between particle arrangement and magnetic order in self-assembled 1D and quasi-2D arrangements of 15 nm...... cobalt nanoparticles. In the initial states, we observe dipolar ferromagnetism, antiferromagnetism and local flux closure, depending on the particle arrangement. Surprisingly, after magnetic saturation, measurements and numerical simulations show that overall ferromagnetic order exists in the present...... nanoparticle assemblies even when their arrangement is completely disordered. Such direct quantification of the correlation between topological and magnetic order is essential for the technological exploitation of magnetic quasi-2D nanoparticle assemblies....

  3. 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.

  4. Lattice dynamics, elasticity and magnetic abnormality in ordered crystalline alloys Fe3Pt at high pressures

    Science.gov (United States)

    Cheng, Tai-min; Yu, Guo-Liang; Su, Yong; Ge, Chong-Yuan; Zhang, Xin-Xin; Zhu, Lin; Li, Lin

    2018-05-01

    The ordered crystalline Invar alloy Fe3Pt is in a special magnetic critical state, under which the lattice dynamic stability of the system is extremely sensitive to external pressures. We studied the pressure dependence of enthalpy and magnetism of Fe3Pt in different crystalline alloys by using the first-principles projector augmented-wave method based on the density functional theory. Results show that the P4/mbm structure is the ground state structure and is more stable relative to other structures at pressures below 18.54 GPa. The total magnetic moments of L12, I4/mmm and DO22 structures decrease rapidly with pressure and oscillate near the ferromagnetic collapse critical pressure. At the pressure of 43 GPa, the ferrimagnetic property in DO22 structure becomes apparently strengthened and its volume increases rapidly. The lattice dynamics calculation for L12 structures at high pressures shows that the spontaneous magnetization of the system in ferromagnetic states induces the softening of the transverse acoustic phonon TA1 (M), and there exists a strong spontaneous volume magnetostriction at pressures below 26.95 GPa. Especially, the lattice dynamics stability is sensitive to pressure, in the pressure range between the ferromagnetic collapse critical pressure (41.9 GPa) and the magnetism completely disappearing pressure (57.25 GPa), and near the pressure of phase transition from L12 to P4/mbm structure (27.27 GPa). Moreover, the instability of magnetic structure leads to a prominent elastic modulus oscillation, and the spin polarizability of electrons near the Fermi level is very sensitive to pressures in that the pressure range. The pressure induces the stability of the phonon spectra of the system at pressures above 57.25 GPa.

  5. Influence of the interplay between helicoidal magnetic ordering and ...

    Indian Academy of Sciences (India)

    ordering and superconductivity on the differential conductance in ... carbide compounds are motivated by the possibility of a detailed investigation of the anisotropy of .... The last equation corresponds to the usual BCS self-consistent ... the actual electron–phonon interaction λ and its effective value, we can expand quanti-.

  6. 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.

  7. Magnetic ordering in the monoclinic structure of Nd5Si1.45Ge2.55 and Pr5Si1.5Ge2.5 studied by means of neutron powder diffraction

    International Nuclear Information System (INIS)

    Magen, C; Ritter, C; Morellon, L; Algarabel, P A; Ibarra, M R

    2004-01-01

    The compounds Nd 5 Si 1.45 Ge 2.55 and Pr 5 Si 1.5 Ge 2.5 have been investigated by means of magnetization measurements and neutron powder diffraction techniques. These alloys present a room-temperature monoclinic Gd 5 Si 2 Ge 2 -type crystallographic structure and, on cooling, both systems order ferromagnetically, at T C = 56 and 32 K, respectively, from a high-temperature paramagnetic to a low-temperature complex canted ferromagnetic state. The monoclinic crystallographic structure remains unchanged upon cooling down to 4 K, demonstrating the existence of a monoclinic ferromagnetic phase, and the possibility of a full decoupling of magnetic and crystallographic degrees of freedom in the 5:4 lanthanide intermetallic compounds

  8. Ab initio investigation on the magnetic ordering in Gd doped ZnO

    KAUST Repository

    Bantounas, Ioannis; Goumri-Said, Souraya; Benali Kanoun, Mohammed; Manchon, Aurelien; Roqan, Iman S.; Schwingenschlö gl, Udo

    2011-01-01

    The current study investigates the magnetic properties of the Gdx Zn1−xO, with x=0.0625 and 0.0185, dopedsemiconductor using the full potential (linearized) augmented plane wave plus local orbital method. We show that in contrast to the findings of Shi et al. [J. Appl. Phys. 106, 023910 (2009)], the implementation of the Hubbard U parameter to the Gd f states favors an antiferromagnetic phase in both wurtzite GdO and Gdx Zn1−xO. Spin polarized calculations on Gdx Zn1−xO indicate that, even if a ferromagnetic ground state were favored, the magnetic influence of Gd in a perfect ZnO wurtzite lattice is highly localized and limited to the first three nearest neighboring O atoms. Increasing the supercell size and thus diluting the concentration of Gd within the ZnO matrix does not show any changes in the net magnetic moment between these three O atoms nor in the remaining lattice sites, indicating that sizing effects do not influence the range of matrix polarization. We conclude that the localized Gd induced polarization can not account for long range magnetic ordering in a defect-free ZnO wurtzite lattice.

  9. Ab initio investigation on the magnetic ordering in Gd doped ZnO

    KAUST Repository

    Bantounas, Ioannis

    2011-04-22

    The current study investigates the magnetic properties of the Gdx Zn1−xO, with x=0.0625 and 0.0185, dopedsemiconductor using the full potential (linearized) augmented plane wave plus local orbital method. We show that in contrast to the findings of Shi et al. [J. Appl. Phys. 106, 023910 (2009)], the implementation of the Hubbard U parameter to the Gd f states favors an antiferromagnetic phase in both wurtzite GdO and Gdx Zn1−xO. Spin polarized calculations on Gdx Zn1−xO indicate that, even if a ferromagnetic ground state were favored, the magnetic influence of Gd in a perfect ZnO wurtzite lattice is highly localized and limited to the first three nearest neighboring O atoms. Increasing the supercell size and thus diluting the concentration of Gd within the ZnO matrix does not show any changes in the net magnetic moment between these three O atoms nor in the remaining lattice sites, indicating that sizing effects do not influence the range of matrix polarization. We conclude that the localized Gd induced polarization can not account for long range magnetic ordering in a defect-free ZnO wurtzite lattice.

  10. Comparative Study of Magnetic Ordering and Electrical Transport in Bulk and Nano-Grained Nd{sub 0.67}Sr{sub 0.33}MnO{sub 3} Manganites

    Energy Technology Data Exchange (ETDEWEB)

    Arun, B. [Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum (India); Academy of Scientific and Innovative Research (AcSIR), CSIR, Trivandrum (India); Suneesh, M.V. [Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum (India); Vasundhara, M., E-mail: vasu.mutta@gmail.com [Materials Science and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology, Trivandrum (India)

    2016-11-15

    We have prepared bulk and nano-sized Nd{sub 0.67}Sr{sub 0.33}MnO{sub 3} manganites by solid state and low-temperature mild solgel methods respectively. Both the compounds crystallized into an orthorhombic structure with Pbnm space group confirmed from Rietveld refinement of X-ray powder diffraction patterns. Nano-grained compound shows an average particle size of 22 nm with broad grain size distribution revealed from the Transmission electron micrographs. It appeared that the long range ferromagnetic order becomes unstable upon the reduction of the samples dimension down to nano meter scale. DC magnetization and AC susceptibility results showed frustration of spins in nano-grained compound and thereby it could lead to a cluster glass-like behaviour. Temperature dependence of electrical resistivity under different magnetic fields shows the broad maxima at higher temperatures and a low temperature upturn in both the compounds, however, the latter is more prominent in the nano grained compound. Combination of Kondo effect with electron and phonon interactions govern the low temperature resistivity and a small polaron hopping mechanism dominates at high temperatures for both the compounds. The magnetoresistance is understood by the effect of spin polarized tunneling through the grain boundary. The experimental results revealed that the reduction in particle size influences severely on the magnetic, electrical and magneto transport properties. - Highlights: • Long range ferromagnetic ordered state become unstable in case of nano compound. • It shows broad magnetic transition and cluster glass nature. • Kondo effect with electron-phonon interactions dominate the resistivity at low temperature.

  11. Monte Carlo simulations of magnetic order in Fe-doped manganites

    International Nuclear Information System (INIS)

    Alonso, J.; Gutierrez, J.; Barandiaran, J.M.; Bermejo, F.J.; Brey, L.

    2008-01-01

    The effect of Fe doping on the magnetic properties of La 0.7 Pb 0.3 Mn 1-x Fe x O 3 (x=0, 0.05, 0.1, 0.15 and 0.2) manganites is studied by the Monte Carlo simulation technique. As a first approximation, by means of a simple Heisenberg Hamiltonian, experimental normalized magnetizations at low temperatures have been reproduced for concentrations of Fe (x<0.2), but the calculated order temperatures show a large deviation from the measured ones. This shortcoming can be corrected by using a one electron effective hopping semi-classical Hamiltonian, with a simplified expression for the kinetic energy of the free electrons, which also avoids time-consuming diagonalizations

  12. The dependence of magnetic ordering temperature in amorphous semiconductors on paramagnetic centre concentration

    International Nuclear Information System (INIS)

    Khokhlov, A.F.; Mashin, A.I.; Satanin, A.M.

    1981-01-01

    In silicon amorphized by ion implantation (a-Si) the dependence of magnetic ordering temperature (theta) on localized spin concentration (Nsub(s)) is studied by EPR method. Nsub(s) changes by varying the Ne + ion dose from 6x10 14 to 2x10 17 cm -2 and sample annealing. From the comparison of the data obtained with literature ones conclusions are made about the existence of two critical values of Nsub(s) in a-Si (approximately 10 19 and approximately 2x10 20 cm -3 ), when a transition occurs from paramagnetism to antiferromagnetism (at T < theta) and from antiferromagnetism to ferromagnetism, respectively. (author)

  13. Quadrupolar order, hidden octupolar order and tiny magnetic moment in URu2Si2

    International Nuclear Information System (INIS)

    Tsuruta, Atsushi; Matsuura, Tamifusa; Kuroda, Yoshihiro

    2000-01-01

    Possible orders in URu 2 Si 2 are investigated using a two-channel degenerate Anderson model. The ground state of uranium ions is the non-Kramers quadrupolar doublet Γ 5 with (5f) 2 , and its relevant excited state is the Kramers dipolar doublet Γ 7 with (5f) 1 . These states mix with each other via conduction electrons. At low temperatures, the system forms renormalized bands with both quadrupole and dipole degrees of freedom due to the quadrupolar Kondo effect which slightly mixes quadrupolar Γ 5 , a primary state of uranium ions, with dipolar Γ 7 . At a certain low temperature, conduction electrons in the renormalized bands undergo quadrupolar ordering with a large quadrupolar moment. At a further lower temperature, octupolar ordering occurs, accompanied by a tiny dipolar moment which is attributed to the property of the renormalized bands with primarily the Γ 5 -character slightly mixed with the Γ 7 -character. These phenomena are well described by the 1/N-expansion method with pseudo-fermions for the non-Kramers doublet Γ 5 and slave bosons for the Kramers doublet Γ 7 . (author)

  14. Magnetic field induced third order susceptibility of third order harmonic generation in a ZnMgSe strained quantum well

    Energy Technology Data Exchange (ETDEWEB)

    Mark, J. Abraham Hudson, E-mail: a.john.peter@gmail.com; Peter, A. John, E-mail: a.john.peter@gmail.com [Dept. of Physics, SSM Institute of Engineering and Technology, Dindigul-624002 (India)

    2014-04-24

    Third order susceptibility of third order harmonic generation is investigated in a Zn{sub 0.1}Mg{sub 0.9}Se/Zn{sub 0.8}Mg{sub 0.2}Se/Zn{sub 0.1}Mg{sub 0.9}Se quantum well in the presence of magnetic field strength. The confinement potential is considered as the addition of energy offsets of the conduction band (or valence band) and the strain-induced potential in our calculations. The material dependent effective mass is followed throughout the computation because it has a high influence on the electron energy levels in low dimensional semiconductor systems.

  15. Synthesis of magnetic ordered mesoporous carbon (Fe-OMC) adsorbent and its evaluation for fuel desulfurization

    Energy Technology Data Exchange (ETDEWEB)

    Farzin Nejad, N., E-mail: Farzinnejadn@ripi.ir [Petroleum Refining Technology Development Division, Research Institute of Petroleum Industry, Tehran 14857-33111 (Iran, Islamic Republic of); Shams, E.; Amini, M.K. [Department of Chemistry, University of Isfahan, Isfahan 81746-73441 (Iran, Islamic Republic of)

    2015-09-15

    In this work, magnetic ordered mesoporous carbon adsorbent was synthesized using soft templating method to adsorb sulfur from model oil (dibenzothiophene in n-hexane). Through this research, pluronic F-127, resorcinol-formaldehyde and hydrated iron nitrate were respectively used as soft template, carbon source and iron source. The adsorbent was characterized by X-ray diffraction, nitrogen adsorption–desorption isotherm and transmission electron microscopy. Nitrogen adsorption–desorption measurement revealed the high surface area (810 m{sup 2} g{sup −1}), maxima pore size of 3.3 nm and large pore volume (1.01 cm{sup 3} g{sup −1}) of the synthesized sample. The adsorbent showed a maximum adsorption capacity of 111 mg dibenzothiophene g{sup −1} of adsorbent. Sorption process was described by the pseudo-second-order rate equation and could be better fitted by the Freundlich model, showing the heterogeneous feature of the adsorption process. In addition, the adsorption capacity of regenerated adsorbent was 78.6% of the initial level, after five regeneration cycles. - Highlights: • Adsorptive desulfurization of model oil with magnetic ordered mesoporous carbon adsorbent, Fe-OMC, was studied. • Maximum adsorption capacity (q{sub max}) of Fe-OMC for DBT was found to be 111.1 mg g{sup −1}. • Freundlich isotherm best represents the equilibrium adsorption data. • Rate of DBT adsorption process onto Fe-OMC is controlled by at least two steps.

  16. Synthesis of magnetic ordered mesoporous carbon (Fe-OMC) adsorbent and its evaluation for fuel desulfurization

    International Nuclear Information System (INIS)

    Farzin Nejad, N.; Shams, E.; Amini, M.K.

    2015-01-01

    In this work, magnetic ordered mesoporous carbon adsorbent was synthesized using soft templating method to adsorb sulfur from model oil (dibenzothiophene in n-hexane). Through this research, pluronic F-127, resorcinol-formaldehyde and hydrated iron nitrate were respectively used as soft template, carbon source and iron source. The adsorbent was characterized by X-ray diffraction, nitrogen adsorption–desorption isotherm and transmission electron microscopy. Nitrogen adsorption–desorption measurement revealed the high surface area (810 m 2 g −1 ), maxima pore size of 3.3 nm and large pore volume (1.01 cm 3 g −1 ) of the synthesized sample. The adsorbent showed a maximum adsorption capacity of 111 mg dibenzothiophene g −1 of adsorbent. Sorption process was described by the pseudo-second-order rate equation and could be better fitted by the Freundlich model, showing the heterogeneous feature of the adsorption process. In addition, the adsorption capacity of regenerated adsorbent was 78.6% of the initial level, after five regeneration cycles. - Highlights: • Adsorptive desulfurization of model oil with magnetic ordered mesoporous carbon adsorbent, Fe-OMC, was studied. • Maximum adsorption capacity (q max ) of Fe-OMC for DBT was found to be 111.1 mg g −1 . • Freundlich isotherm best represents the equilibrium adsorption data. • Rate of DBT adsorption process onto Fe-OMC is controlled by at least two steps

  17. Anomalous magnetic ordering in DyxPr1-x alloys

    DEFF Research Database (Denmark)

    Clegg, P.S.; Cowley, R.A.; Goff, J.P.

    2000-01-01

    Epitaxial thin-films of DyxPr1-x alloys have been studied using neutron diffraction and magnetization measurements. The crystal structure changes from HCP to Sm type to DHCP as x decreases; each crystal phase has different magnetic behaviour. Surprisingly, long-range order is suppressed in the DH...... allays, a possible explanation is outlined. (C) 2000 Elsevier Science B.V. All rights reserved....

  18. Medical devices; neurological devices; classification of the transcranial magnetic stimulator for headache. Final order.

    Science.gov (United States)

    2014-07-08

    The Food and Drug Administration (FDA) is classifying the transcranial magnetic stimulator for headache into class II (special controls). The special controls that will apply to the device are identified in this order, and will be part of the codified language for the transcranial magnetic stimulator for headache classification. The Agency is classifying the device into class II (special controls) in order to provide a reasonable assurance of safety and effectiveness of the device.

  19. Excange interactions and induced Eu3+ magnetic order in RMnO3 investigated using resonant X-ray diffraction

    International Nuclear Information System (INIS)

    Skaugen, Arvid

    2015-03-01

    The so-called multiferroics, materials that concomitantly exhibit more than one ferroic order, have in recent years attracted much attention owing to their possible applications in high density data storage, high sensitivity ac magnetic field sensors and novel spintronic devices. In particular, multiferroics with strong magnetoelectric coupling are more attractive. Among such multiferroics, an interesting special class is the orthorhombic manganites with perovskite structure. In these compounds, frustration serves to destabilize ordinary ferromagnetic or antiferromagnetic ordering, giving rise to rich phase diagrams due to several competing magnetic interactions. Interactions between strong rare earth magnetic moments and weaker transition metal moments add another level of complexity, as well as interest. The current dissertation presents results obtained investigating the magnetic structure responsible for ferroelectricity in a few selected multiferroic compounds, using x-ray resonant magnetic scattering (XRMS). In particular, single crystals of Eu 1-x Y x MnO 3 have been studied at low temperatures and in high magnetic fields. This series of compounds is similar in structure to the heavily studied RMnO 3 (R=Tb,Gd,Dy), only without rare earth magnetism. The novel technique of full polarization analysis has been used to determine the complicated cycloidal Mn magnetic ordering, and additional components due to the Dzyaloshinskii-Moriya interactions have been identified. In the compound Eu 0.8 Y 0.2 MnO 3 , two coexisting multiferroic phases were observed, and a magnetoelectric coupling between the two was established. Moreover, magnetic order of the formally non-magnetic rare earth ion Eu 3+ was observed in the same compound. It has been concluded to result from a Van Vleck type excitation of the J = 0 ground state due to the symmetry-breaking internal exchange field from the Mn magnetic moments. In addition, this dissertation reports on high field investigations

  20. Ginsburg-Landau theory of two antagonistic order parameters: magnetism and superconductivity

    International Nuclear Information System (INIS)

    Suhl, H.

    1978-01-01

    An attempt is made to construct a Ginsburg-Landau theory of so-called magnetic superconductors. Two order parameters, the magnetization field and the gap function, are introduced in such a way as to inhibit each others growth. It is found that the non-local character of the superconducting order parameter must be taken into account in any evaluation of effects of the critical magnetic fluctuations. Some predictions are made within the limits of Ornstein-Zoernicke-like fluctuation theory and some comparison is made with available data. (Auth.)

  1. Error studies of Halbach Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Brooks, S. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2017-03-02

    These error studies were done on the Halbach magnets for the CBETA “First Girder” as described in note [CBETA001]. The CBETA magnets have since changed slightly to the lattice in [CBETA009]. However, this is not a large enough change to significantly affect the results here. The QF and BD arc FFAG magnets are considered. For each assumed set of error distributions and each ideal magnet, 100 random magnets with errors are generated. These are then run through an automated version of the iron wire multipole cancellation algorithm. The maximum wire diameter allowed is 0.063” as in the proof-of-principle magnets. Initially, 32 wires (2 per Halbach wedge) are tried, then if this does not achieve 1e-­4 level accuracy in the simulation, 48 and then 64 wires. By “1e-4 accuracy”, it is meant the FOM defined by √(Σn≥sextupole an 2+bn 2) is less than 1 unit, where the multipoles are taken at the maximum nominal beam radius, R=23mm for these magnets. The algorithm initially uses 20 convergence interations. If 64 wires does not achieve 1e-­4 accuracy, this is increased to 50 iterations to check for slow converging cases. There are also classifications for magnets that do not achieve 1e-4 but do achieve 1e-3 (FOM ≤ 10 units). This is technically within the spec discussed in the Jan 30, 2017 review; however, there will be errors in practical shimming not dealt with in the simulation, so it is preferable to do much better than the spec in the simulation.

  2. Magnetism, Superconductivity, and Spontaneous Orbital Order in Iron-Based Superconductors: Which Comes First and Why?

    Directory of Open Access Journals (Sweden)

    Andrey V. Chubukov

    2016-12-01

    Full Text Available Magnetism and nematic order are the two nonsuperconducting orders observed in iron-based superconductors. To elucidate the interplay between them and ultimately unveil the pairing mechanism, several models have been investigated. In models with quenched orbital degrees of freedom, magnetic fluctuations promote stripe magnetism, which induces orbital order. In models with quenched spin degrees of freedom, charge fluctuations promote spontaneous orbital order, which induces stripe magnetism. Here, we develop an unbiased approach, in which we treat magnetic and orbital fluctuations on equal footing. Key to our approach is the inclusion of the orbital character of the low-energy electronic states into renormalization group (RG analysis. We analyze the RG flow of the couplings and argue that the same magnetic fluctuations, which are known to promote s^{+-} superconductivity, also promote an attraction in the orbital channel, even if the bare orbital interaction is repulsive. We next analyze the RG flow of the susceptibilities and show that, if all Fermi pockets are small, the system first develops a spontaneous orbital order, then s^{+-} superconductivity, and magnetic order does not develop down to T=0. We argue that this scenario applies to FeSe. In systems with larger pockets, such as BaFe_{2}As_{2} and LaFeAsO, we find that the leading instability is either towards a spin-density wave or superconductivity. We argue that in this situation nematic order is caused by composite spin fluctuations and is vestigial to stripe magnetism. Our results provide a unifying description of different iron-based materials.

  3. A second-order approximation of particle motion in the fringing field of a dipole magnet

    International Nuclear Information System (INIS)

    Tarantin, N.I.

    1980-01-01

    The radial and axial motion of charged particles in the fringing field of an arbitrary dipole magnet has been considered with accuracy to the second-order of small quantities. The dipole magnet has an inhomogeneous field and oblique entrance and exit boundaries in the form of second-order curves. The region of the fringing field has a variable extension. A new definition of the effective boundary of the real fringing field has a variable extension. A new definition of the effective boundary of the real fringing field of the dipole magnet is used. A better understanding of the influence of the fringing magnetic field on the motion of charged particles in the pole gap of the dipole magnet has been obtained. In particular, it is shown that it is important to take into account, in the second approximation, some terms related formally to the next approximations. The results are presented in a form convenient for practical calculations. (orig.)

  4. An order-by-disorder process in the cyclic phase of spin-2 condensate with a weak magnetic field

    International Nuclear Information System (INIS)

    Zheng, Gong-Ping; Xu, Lei-Kuan; Qin, Shuai-Feng; Jian, Wen-Tian; Liang, J.-Q.

    2013-01-01

    We present in this paper a model study on the “order-by-disorder” process in the cyclic phase of spin-2 condensate, which forms a family of incommensurable, spiral degenerate ground states. On the basis of the ordering mechanism of entropic splitting, it is demonstrated that the energy corrections resulting from quantum fluctuations of disorder lift the accidental degeneracy of the cyclic configurations and thus lead to an eventual spiral order called the cyclic order. The order-by-disorder phenomenon is then realized even if the magnetic field exists. Finally, we show that our theoretic observations can be verified experimentally by direct detection of the cyclic order in the 87 Rb condensate of a spin-2 manifold with a weak magnetic field. -- Highlights: •A model for the order-by-disorder process in the cyclic phase of spin-2 condensate is presented. •The second-order quantum fluctuations of the mean-field states are studied. •The energy corrections lift the accidental degeneracy of the cyclic configurations. •The order-by-disorder phenomenon is realized even if a magnetic field exists. •The theoretic observations can be verified experimentally for 87 Rb condensate

  5. Evidence for coexisting magnetic order in frustrated three-dimensional honeycomb iridates Li2IrO3

    Science.gov (United States)

    Breznay, Nicholas; Ruiz, Alejandro; Frano, Alex; Analytis, James

    The search for unconventional magnetism has found a fertile hunting ground in 5d iridium oxide (iridate) materials. The competition between coulomb, spin-orbit, and crystal field energy scales in honeycomb iridates leads to a quantum magnetic system with localized spin-1/2 moments communicating through spin-anisotropic Kitaev exchange interactions. Although early and ongoing work has focused on layered two-dimensional honeycomb compounds such as Na2IrO3 and a 4d analog, RuCl3, recently discovered polytypes of Li2IrO3 take on three-dimensional honeycomb structures. Bulk thermodynamic studies, as well as recent resonant x-ray diffraction and absorption spectroscopy experiments, have uncovered a rich phase diagram for these three-dimensional honeycomb iridates. Low temperature incommensurate and commensurate magnetic orders can be stabilized by tuning the applied magnetic field, displaying a delicate coexistence that signals highly frustrated magnetism.

  6. Initial measurements of two- and three-dimensional ordering, waves, and plasma filamentation in the Magnetized Dusty Plasma Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Edward, E-mail: etjr@auburn.edu; Konopka, Uwe [Physics Department, Auburn University, Auburn, Alabama 36849 (United States); Merlino, Robert L. [Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242 (United States); Rosenberg, Marlene [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States)

    2016-05-15

    The Magnetized Dusty Plasma Experiment at Auburn University has been operational for over one year. In that time, a number of experiments have been performed at magnetic fields up to B = 2.5 T to explore the interaction between magnetized plasmas and charged, micron-sized dust particles. This paper reports on the initial results from studies of: (a) the formation of imposed, ordered structures, (b) the properties of dust wave waves in a rotating frame, and (c) the generation of plasma filaments.

  7. A study on stability of rotating magnets

    International Nuclear Information System (INIS)

    Higuchi, N.; Kaiho, K.; Ishii, I.

    1996-01-01

    Superconducting power generators are being developed in Japan, as a part of a R and D program on energy technology, the New Sunshine Project. In this development, national laboratories are taking a role of fundamental studies to contribute to the R and D being carried out mainly by the manufacturers involved in a research association, Super-GM. Stabilities of magnets in a high gravitational field up to 2,000 G are discussed, based upon the experimental results of forced quench tests in a set of rotating magnets, in order to establish the stability design criterion of field windings of superconducting generators. Relations of propagation velocities, recovery currents, minimum quench energy and heat transfer characteristics are studied, a good agreement between the experimental results and a theory confirmed the improvement of magnet stability in a high gravitational field because of the enhanced heat transfer characteristics

  8. Magnetism and rotation effect on surface waves in fibre-reinforced anisotropic general viscoelastic media of higher order

    Energy Technology Data Exchange (ETDEWEB)

    Abo-Dahab, S. M. [Taif University, Taif (Saudi Arabia); Abd-Alla, A. M. [SVU, Qena (Egypt); Khan, Aftab [Sohag University, Sohag (Egypt)

    2015-08-15

    The aim of this paper is to study the propagation of surface waves in a rotating fibre-reinforced viscoelastic media of higher order under the influence of magnetic field. The general surface wave speeds derived to study the effects of rotation and magnetic field on surface waves. Particular cases for Stoneley, Love and Rayleigh waves are also discussed and dispersion relation for the waves has been deduced. The results obtained in this investigation are more general in the sense that some earlier published results are obtained from our result as special cases. For order zero our results are well agreement to fibre-reinforced materials. Also by neglecting the reinforced elastic parameters, the results reduce to well known isotropic medium. It is observed that in a rotating medium the surface waves are dispersive. Also magnetic effects play a significant roll. It is observed that Love wave remain unaffected in a rotating medium but remain under the influence of magnetic field. Rayleigh waves are affected by rotation and magnetic field whereas Stoneley waves are independent of Maxwell stresses. It is also observed that, surface waves cannot propagate in a fast rotating medium or in the presence of magnetic field of high intensity. Numerical results for particular materials are given and illustrated graphically. The results indicate that the effect of rotation and magnetic field are very pronounced.

  9. Magnetism and rotation effect on surface waves in fibre-reinforced anisotropic general viscoelastic media of higher order

    International Nuclear Information System (INIS)

    Abo-Dahab, S. M.; Abd-Alla, A. M.; Khan, Aftab

    2015-01-01

    The aim of this paper is to study the propagation of surface waves in a rotating fibre-reinforced viscoelastic media of higher order under the influence of magnetic field. The general surface wave speeds derived to study the effects of rotation and magnetic field on surface waves. Particular cases for Stoneley, Love and Rayleigh waves are also discussed and dispersion relation for the waves has been deduced. The results obtained in this investigation are more general in the sense that some earlier published results are obtained from our result as special cases. For order zero our results are well agreement to fibre-reinforced materials. Also by neglecting the reinforced elastic parameters, the results reduce to well known isotropic medium. It is observed that in a rotating medium the surface waves are dispersive. Also magnetic effects play a significant roll. It is observed that Love wave remain unaffected in a rotating medium but remain under the influence of magnetic field. Rayleigh waves are affected by rotation and magnetic field whereas Stoneley waves are independent of Maxwell stresses. It is also observed that, surface waves cannot propagate in a fast rotating medium or in the presence of magnetic field of high intensity. Numerical results for particular materials are given and illustrated graphically. The results indicate that the effect of rotation and magnetic field are very pronounced.

  10. Magnetic ordering at low temperatures in some random superconducting and insulating compounds

    International Nuclear Information System (INIS)

    Hueser, D.

    1985-01-01

    This thesis presents the results of some investigations on the magnetic ordering phenomena in some random superconducting and insulating materials. The results are described of an investigation of the coexistence of superconductivity and random magnetic freezing in (Th,Nd)Ru 2 . On the basis of various measurements as function of temperature and external magnetic field the author found that spin glass-like freezing can occur far below the superconductivity and even that a sample may re-enter the superconducting state below a freezing temperature. Associated with the isothermal remanent magnetization of a random magnetic material he observed strong anomalies in the critical field versus temperature curves. Also a magnetic field memory effect has been found. (Auth.)

  11. Shear- and magnetic-field-induced ordering in magnetic nanoparticle dispersion from small-angle neutron scattering

    International Nuclear Information System (INIS)

    Krishnamurthy, V.V.; Bhandar, A.S.; Piao, M.; Zoto, I.; Lane, A.M.; Nikles, D.E.; Wiest, J.M.; Mankey, G.J.; Porcar, L.; Glinka, C.J.

    2003-01-01

    Small-angle neutron scattering experiments have been performed to investigate orientational ordering of a dispersion of rod-shaped ferromagnetic nanoparticles under the influence of shear flow and static magnetic field. In this experiment, the flow and flow gradient directions are perpendicular to the direction of the applied magnetic field. The scattering intensity is isotropic in zero-shear-rate or zero-applied-field conditions, indicating that the particles are randomly oriented. Anisotropic scattering is observed both in a shear flow and in a static magnetic field, showing that both flow and field induce orientational order in the dispersion. The anisotropy increases with the increase of field and with the increase of shear rate. Three states of order have been observed with the application of both shear flow and magnetic field. At low shear rates, the particles are aligned in the field direction. When increasing shear rate is applied, the particles revert to random orientations at a characteristic shear rate that depends on the strength of the applied magnetic field. Above the characteristic shear rate, the particles align along the flow direction. The experimental results agree qualitatively with the predictions of a mean field model

  12. The bonding character and magnetic properties of Fe{sub 3}Al: Comparison between disordered and ordered alloy

    Energy Technology Data Exchange (ETDEWEB)

    Fan Runhua [MOE Key Laboratory for Liquid Structure and Heredity of Materials, Shandong University, Jinan 250061 (China)]. E-mail: fan@sdu.edu.cn; Qi Liang [MOE Key Laboratory for Liquid Structure and Heredity of Materials, Shandong University, Jinan 250061 (China); Sun Kangning [MOE Key Laboratory for Liquid Structure and Heredity of Materials, Shandong University, Jinan 250061 (China); Min Guanghui [MOE Key Laboratory for Liquid Structure and Heredity of Materials, Shandong University, Jinan 250061 (China); Gong Hongyu [MOE Key Laboratory for Liquid Structure and Heredity of Materials, Shandong University, Jinan 250061 (China)

    2006-12-25

    Fe{sub 3}Al with D0{sub 3}-ordered structure is one of the few structural intermetallics that can be disordered using non-equilibrium processing techniques. The bonding and magnetic character of the stoichiometric Fe{sub 3}Al, with D0{sub 3}-ordered or disordered structure, have been studied using the empirical electron theory of solid and molecular (EET). It was found that the magnetic property is basically dictated by the chemical bonding. There is a change of the character of the interatomic bonds from 3d(Fe)-3p(Al) for the D0{sub 3}-ordered Fe{sub 3}Al to 4sp(Fe)-3p(Al) for the disordered Fe{sub 3}Al. For the latter, while the Fe 3d electrons participating in bonding is reduced, the mean magnetic moment is increased.

  13. Magnetic, structural and electrical properties of ordered and disordered Co50Fe50 films

    International Nuclear Information System (INIS)

    Chen, Y.T.; Jen, S.U.; Yao, Y.D.; Wu, J.M.; Hwang, G.H.; Tsai, T.L.; Chang, Y.C.; Sun, A.C.

    2006-01-01

    Co 50 Fe 50 films with thickness varying from 100 to 500 A were deposited on a glass substrate by sputtering process, respectively. Two kinds of CoFe films were studied: one was the as-deposited film, and the other the annealed film. The annealing procedure was to keep the films at 400 deg. C for 5 h in a vacuum of 5x10 -6 mbar. From the X-ray study, we find that the as-deposited film prefers the CoFe(1 1 0) orientation. Moreover, the body-centered cubic (bcc) CoFe(1 1 0) line is split into two peaks: one corresponding to the ordered body-centered tetragonal (bct) phase, and the other, the disordered bcc phase. After annealing, the peak intensity of the ordered bct phase becomes much stronger, while that of the disordered bcc phase disappears. The annealing has also caused the ordered CoFe(2 0 0) line to appear. When the amount of the ordered bct phase in Co 50 Fe 50 is increased, the saturation magnetization (M s ) and coercivity (H c ) become larger, but the electrical resistivity (ρ) decreases. From the temperature coefficient of resistance (TCR) measurement, we learn that the bct grains in the CoFe film start to grow at temperature 82 deg. C

  14. Analytical determination of 5th-order transfer matrices of magnetic quadrupole fringing fields

    International Nuclear Information System (INIS)

    Hartmann, B.; Irnich, H.; Wollnik, H.

    1993-01-01

    The fringing-field effects on particle trajectories in magnetic quadrupoles are described to 5th order by fringing-field integrals. It is shown that this method improves the description of fringing-field effects noticeably over the so far known use of third-order fringing-field integrals. (Author)

  15. Creation of second order magnetic barrier inside chaos created by NTMs in the ASDEX UG

    Science.gov (United States)

    Ali, Halima; Punjabi, Alkesh

    2012-10-01

    Understanding and stabilization of neoclassical tearing modes (NTM) in tokamaks is an important problem. For low temperature plasmas, tearing modes are believed to be mainly driven by current density gradient. For collisionless plasmas, even when plasma is stable to classical tearing modes, helical reduction in bootstrap current in O-point of an island can destabilize NTMs when an initial island is seeded by other global MHD instabilities or when microturbulence triggers the transition from a linear to nonlinear instability. The onset of NTMs leads to the most serious beta limit in ASDEX UG tokamak [O. Gubner et al 2005 NF 39 1321]. The important NTMs in the ASDDEX UG are (m,n)=(3,2)+(4,3)+(1,1). Realistic parameterization of these NTMs and the safety factor in ASDEX UG are given in [O. Dumbrajs et al 2005 POP 12 1107004]. We use a symplectic map in magnetic coordinates for the ASDEX UG to integrate field lines in presence of the NTMs. We add a second order control term [H. Ali and A. Punjabi 2007 PPCF 49 1565] to this ASDEX UG field line Hamiltonian to create an invariant magnetic surface inside the chaos generated by the NTMs. The relative strength, robustness, and resilience of this barrier are studied to ascertain the most desirable noble barrier in the ASDEX UG with NTMs. We present preliminary results of this work, and discuss its implications with regard to magnetic transport barriers for increasing strength of magnetic perturbations. This work is supported by the grants DE-FG02-01ER54624 and DE-FG02-04ER54793.

  16. Magnetic study of iron-containing carbon nanotubes: Feasibility for magnetic hyperthermia

    Energy Technology Data Exchange (ETDEWEB)

    Krupskaya, Y. [Leibniz-Institute for Solid State and Materials Research IFW Dresden, 01171 Dresden (Germany)], E-mail: y.krupskaya@ifw-dresden.de; Mahn, C.; Parameswaran, A. [Leibniz-Institute for Solid State and Materials Research IFW Dresden, 01171 Dresden (Germany); Taylor, A.; Kraemer, K. [Department of Urology, Dresden University of Technology, 01307 Dresden (Germany); Hampel, S.; Leonhardt, A.; Ritschel, M.; Buechner, B.; Klingeler, R. [Leibniz-Institute for Solid State and Materials Research IFW Dresden, 01171 Dresden (Germany)

    2009-12-15

    We present a detailed magnetic study of iron containing carbon nanotubes (Fe-CNT), which highlights their potential for contactless magnetic heating in hyperthermia cancer treatment. Magnetic field dependent AC inductive heating experiments on Fe-CNT dispersions show a substantial temperature increase of Fe-CNT dispersions in applied AC magnetic fields. DC and AC magnetization studies have been done in order to elucidate the heating mechanism. We observe a different magnetic response of Fe-CNT powder compared to Fe-CNT dispersed in aqueous solution, e.g., ferromagnetic Fe-CNT in powder do not show any hysteresis when being dispersed in liquid. Our data indicate the motion of Fe-CNT in liquid in applied magnetic fields.

  17. Partial magnetic order in the itinerant-electron magnet MnSi

    Indian Academy of Sciences (India)

    Neutron scattering techniques have been used to investigate the magnetic structure at and above c, i.e. triple-axis spectrometry and small angle neutron scattering. Surprisingly, sizeable quasi-static moments were found to survive to pressures considerably above c. They are, however, organized in a highly unusual way ...

  18. Study on magnetic property and fracture behavior of magnetic materials

    International Nuclear Information System (INIS)

    Miya, Kenzo; Demachi, Kazuyuki; Aoto, Kazumi; Nagae, Yuji

    2002-04-01

    Establishment of evaluation methods of material degradation before crack initiation is needed very much to enhance the reliability of structural components. We remark magnetic methods in this report. Our objectives are to reveal the relation between degradation and magnetic property and to develop evaluation methods of material degradation, especially plastic deformation and stress corrosion cracking (SCC). In the former part of this report, evaluation methods for plastic deformation are discussed. At first, the study that shows the relation between the magnetic flux leakage and plastic deformation is reviewed. We developed the inverse analysis method of magnetization to specify the degradation distribution. Moreover, we propose inverse analysis of magnetic susceptibility for quantitative evaluation. In the latter part, the topic is SCC. We measured the magnetic flux leakage from the sample induced a SCC crack (Inconel 600). Inconel 600 is a paramagnetic material at room temperature but the sample shows ferromagnetic and the magnetic flux leakage was changed near the SCC crack. The possibility of detection of a SCC crack is shown by the inverse analysis result from the magnetic flux leakage. Finally, it is recognized by observation of the micro magnetic distributions by using a magnetic force microscope that the magnetization has relation with chromium depletion near grain boundaries and it is weak near the SCC crack. From these results, the magnetic method is very effective for evaluation of degradation. (author)

  19. Effect of Jahn-Teller distortion on the short range magnetic order in copper ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Abdellatif, M.H., E-mail: Mohamed.abdellatif@iit.it [Nanostrctures Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Innocenti, Claudia [INSTM—Department of Chemistry, University of Florence, via della Lastruccia 3, I-50019 Sesto Fiorentino, FI (Italy); Liakos, Ioannis [Nanostrctures Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Scarpellini, Alice; Marras, Sergio [Nanochemistry Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy); Salerno, Marco [Nanostrctures Department, Istituto Italiano di Tecnologia, via Morego 30, I-16163 Genova (Italy)

    2017-02-15

    Copper ferrite of spinel crystal structure was synthesized in the form of nano-particles using citrate-gel auto-combustion method. The sample morphology and composition were identified using scanning electron microscopy, X-ray diffraction, and X-ray spectroscopy. The latter technique reveals an inverse spinel structure with Jahn-Teller tetragonal distortion. The static magnetization was measured using vibrating sample magnetometer. Magnetic force microscopy was used in combination with the magnetization data to demonstrate the finite size effect of the magnetic spins and their casting behavior due to the introduction of copper ions in the tetrahedral magnetic sub-lattices, which results in tetragonal distorting the spinel structure of the copper ferrite. The magnetic properties of materials are a result of the collective behavior of the magnetic spins, and magnetic force microscopy can probe the collective behavior of the magnetic spins in copper ferrite, yet providing a sufficient resolution to map the effects below the micrometer size scale, such as the magnetic spin canting. A theoretical study was done to clarify the finite size effect of Jahn-Teller distortion on the magnetic properties of the material. When the particles are in the nano-scale, below the single domain size, their magnetic properties are very sensitive to their size change. - Highlights: • The spin canting due to Jahn-Teller distortion in Copper ferrite can be detected using magnetic force microscope. • The contrast in the magnetic AFM image can be analyzed to give information not only about the surface spins but also about the canting of the core spins inside the aggregated cluster of magnetic nanoparticle.

  20. Bond-order potential for magnetic body-centered-cubic iron and its transferability

    Science.gov (United States)

    Lin, Yi-Shen; Mrovec, M.; Vitek, V.

    2016-06-01

    We derived and thoroughly tested a bond-order potential (BOP) for body-centered-cubic (bcc) magnetic iron that can be employed in atomistic calculations of a broad variety of crystal defects that control structural, mechanical, and thermodynamic properties of this technologically important metal. The constructed BOP reflects correctly the mixed nearly free electron and covalent bonding arising from the partially filled d band as well as the ferromagnetism that is actually responsible for the stability of the bcc structure of iron at low temperatures. The covalent part of the cohesive energy is determined within the tight-binding bond model with the Green's function of the Schrödinger equation determined using the method of continued fractions terminated at a sufficient level of the moments of the density of states. This makes the BOP an O (N ) method usable for very large numbers of particles. Only d d bonds are included explicitly, but the effect of s electrons on the covalent energy is included via their screening of the corresponding d d bonds. The magnetic part of the cohesive energy is included using the Stoner model of itinerant magnetism. The repulsive part of the cohesive energy is represented, as in any tight-binding scheme, by an empirical formula. Its functional form is physically justified by studies of the repulsion in face-centered-cubic (fcc) solid argon under very high pressure where the repulsion originates from overlapping s and p closed-shell electrons just as it does from closed-shell s electrons in transition metals squeezed into the ion core under the influence of the large covalent d bonding. Testing of the transferability of the developed BOP to environments significantly different from those of the ideal bcc lattice was carried out by studying crystal structures and magnetic states alternative to the ferromagnetic bcc lattice, vacancies, divacancies, self-interstitial atoms (SIAs), paths continuously transforming the bcc structure to

  1. Magnetism and atomic short-range order in Ni-Rh alloys

    Science.gov (United States)

    Carnegie, D. W., Jr.; Claus, H.

    1984-07-01

    Low-field ac susceptibility measurements of Ni-Rh samples of various concentrations are presented. Giant effects of the metallurgical state on the magnetic ordering temperature are associated with changes in the degree of atomic short-range order. By careful control of this degree of short-range order, it is possible to demonstrate the existence of a spin-glass state in Ni-Rh alloys.

  2. Revealing the correlation between real-space structure and chiral magnetic order at the atomic scale

    Science.gov (United States)

    Hauptmann, Nadine; Dupé, Melanie; Hung, Tzu-Chao; Lemmens, Alexander K.; Wegner, Daniel; Dupé, Bertrand; Khajetoorians, Alexander A.

    2018-03-01

    We image simultaneously the geometric, the electronic, and the magnetic structures of a buckled iron bilayer film that exhibits chiral magnetic order. We achieve this by combining spin-polarized scanning tunneling microscopy and magnetic exchange force microscopy (SPEX) to independently characterize the geometric as well as the electronic and magnetic structures of nonflat surfaces. This new SPEX imaging technique reveals the geometric height corrugation of the reconstruction lines resulting from strong strain relaxation in the bilayer, enabling the decomposition of the real-space from the electronic structure at the atomic level and the correlation with the resultant spin-spiral ground state. By additionally utilizing adatom manipulation, we reveal the chiral magnetic ground state of portions of the unit cell that were not previously imaged with spin-polarized scanning tunneling microscopy alone. Using density functional theory, we investigate the structural and electronic properties of the reconstructed bilayer and identify the favorable stoichiometry regime in agreement with our experimental result.

  3. Magnetic ordering and specific heat analysis of TmPtSn

    Czech Academy of Sciences Publication Activity Database

    Vejpravová, J.; Svoboda, P.; Šebek, Josef; Janeček, M.; Komatsubara, T.

    2003-01-01

    Roč. 328, - (2003), s. 142-144 ISSN 0921-4526 R&D Projects: GA ČR GA106/02/0943 Grant - others:GA UK(CZ) 165/01; VACUUM PRAHA(CZ) 2002 Keywords : rare-earth intermetallic compounds * magnetic ordering * specific heat Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.908, year: 2003

  4. Non-equilibrium magnetic colloidal dispersions at liquid-air interfaces: dynamic patterns, magnetic order and self-assembled swimmers

    International Nuclear Information System (INIS)

    Snezhko, Alexey

    2011-01-01

    Colloidal dispersions of interacting particles subjected to an external periodic forcing often develop nontrivial self-assembled patterns and complex collective behavior. A fundamental issue is how collective ordering in such non-equilibrium systems arises from the dynamics of discrete interacting components. In addition, from a practical viewpoint, by working in regimes far from equilibrium new self-organized structures which are generally not available through equilibrium thermodynamics can be created. In this review spontaneous self-assembly phenomena in magnetic colloidal dispersions suspended at liquid-air interfaces and driven out of equilibrium by an alternating magnetic field are presented. Experiments reveal a new type of nontrivially ordered self-assembled structures emerging in such systems in a certain range of excitation parameters. These dynamic structures emerge as a result of the competition between magnetic and hydrodynamic forces and have complex unconventional magnetic ordering. Nontrivial self-induced hydrodynamic fields accompany each out-of-equilibrium pattern. Spontaneous symmetry breaking of the self-induced surface flows leading to a formation of self-propelled microstructures has been discovered. Some features of the self-localized structures can be understood in the framework of the amplitude equation (Ginzburg-Landau type equation) for parametric waves coupled to the conservation law equation describing the evolution of the magnetic particle density and the Navier-Stokes equation for hydrodynamic flows. To understand the fundamental microscopic mechanisms governing self-assembly processes in magnetic colloidal dispersions at liquid-air interfaces a first-principle model for a non-equilibrium self-assembly is presented. The latter model allows us to capture in detail the entire process of out-of-equilibrium self-assembly in the system and reproduces most of the observed phenomenology. (topical review)

  5. Soft-edged magnet models for higher-order beam-optics map codes

    International Nuclear Information System (INIS)

    Walstrom, P.L.

    2004-01-01

    Continuously varying surface and volume source-density distributions are used to model magnetic fields inside of cylindrical volumes. From these distributions, a package of subroutines computes on-axis generalized gradients and their derivatives at arbitrary points on the magnet axis for input to the numerical map-generating subroutines of the Lie-algebraic map code Marylie. In the present version of the package, the magnet menu includes: (1) cylindrical current-sheet or radially thick current distributions with either open boundaries or with a surrounding cylindrical boundary with normal field lines (which models high-permeability iron), (2) Halbach-type permanent multipole magnets, either as sheet magnets or as radially thick magnets, (3) modeling of arbitrary fields inside a cylinder by use of a fictitious current sheet. The subroutines provide on-axis gradients and their z derivatives to essentially arbitrary order, although in the present third- and fifth-order Marylie only the zeroth through sixth derivatives are needed. The formalism is especially useful in beam-optics applications, such as magnetic lenses, where realistic treatment of fringe-field effects is needed

  6. Spin ordered phase transitions in neutron matter under the presence of a strong magnetic field

    International Nuclear Information System (INIS)

    Isayev, A.A.; Yang, J.

    2011-01-01

    In dense neutron matter under the presence of a strong magnetic field, considered in the model with the Skyrme effective interaction, there are possible two types of spin ordered states. In one of them the majority of neutron spins are aligned opposite to magnetic field (thermodynamically preferable state), and in other one the majority of spins are aligned along the field (metastable state). The equation of state, incompressibility modulus and velocity of sound are determined in each case with the aim to find the peculiarities allowing to distinguish between two spin ordered phases.

  7. A model for metastable magnetism in the hidden-order phase of URu2Si2

    Science.gov (United States)

    Boyer, Lance; Yakovenko, Victor M.

    2018-01-01

    We propose an explanation for the experiment by Schemm et al. (2015) where the polar Kerr effect (PKE), indicating time-reversal symmetry (TRS) breaking, was observed in the hidden-order (HO) phase of URu2Si2. The PKE signal on warmup was seen only if a training magnetic field was present on cool-down. Using a Ginzburg-Landau model for a complex order parameter, we show that the system can have a metastable ferromagnetic state producing the PKE, even if the HO ground state respects TRS. We predict that a strong reversed magnetic field should reset the PKE to zero.

  8. Mixed convection peristaltic flow of third order nanofluid with an induced magnetic field.

    Science.gov (United States)

    Noreen, Saima

    2013-01-01

    This research is concerned with the peristaltic flow of third order nanofluid in an asymmetric channel. The governing equations of third order nanofluid are modelled in wave frame of reference. Effect of induced magnetic field is considered. Long wavelength and low Reynolds number situation is tackled. Numerical solutions of the governing problem are computed and analyzed. The effects of Brownian motion and thermophoretic diffusion of nano particles are particularly emphasized. Physical quantities such as velocity, pressure rise, temperature, induced magnetic field and concentration distributions are discussed.

  9. Mixed convection peristaltic flow of third order nanofluid with an induced magnetic field.

    Directory of Open Access Journals (Sweden)

    Saima Noreen

    Full Text Available This research is concerned with the peristaltic flow of third order nanofluid in an asymmetric channel. The governing equations of third order nanofluid are modelled in wave frame of reference. Effect of induced magnetic field is considered. Long wavelength and low Reynolds number situation is tackled. Numerical solutions of the governing problem are computed and analyzed. The effects of Brownian motion and thermophoretic diffusion of nano particles are particularly emphasized. Physical quantities such as velocity, pressure rise, temperature, induced magnetic field and concentration distributions are discussed.

  10. The magnetic ordering in high magnetoresistance Mn-doped ZnO thin films

    KAUST Repository

    Venkatesh, S.

    2016-03-24

    We studied the nature of magnetic ordering in Mn-doped ZnO thin films that exhibited ferromagnetism at 300 K and superparamagnetism at 5 K. We directly inter-related the magnetisation and magnetoresistance by invoking the polaronpercolation theory and variable range of hopping conduction below the metal-to-insulator transition. By obtaining a qualitative agreement between these two models, we attribute the ferromagnetism to the s-d exchange-induced spin splitting that was indicated by large positive magnetoresistance (∼40 %). Low temperature superparamagnetism was attributed to the localization of carriers and non-interacting polaron clusters. This analysis can assist in understanding the presence or absence of ferromagnetism in doped/un-doped ZnO.

  11. The magnetic ordering in high magnetoresistance Mn-doped ZnO thin films

    Energy Technology Data Exchange (ETDEWEB)

    Venkatesh, S.; Baras, A.; Roqan, I. S., E-mail: Iman.roqan@kaust.edu.sa [Physical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia); Lee, J.-S. [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

    2016-03-15

    We studied the nature of magnetic ordering in Mn-doped ZnO thin films that exhibited ferromagnetism at 300 K and superparamagnetism at 5 K. We directly inter-related the magnetisation and magnetoresistance by invoking the polaron percolation theory and variable range of hopping conduction below the metal-to-insulator transition. By obtaining a qualitative agreement between these two models, we attribute the ferromagnetism to the s-d exchange-induced spin splitting that was indicated by large positive magnetoresistance (∼40 %). Low temperature superparamagnetism was attributed to the localization of carriers and non-interacting polaron clusters. This analysis can assist in understanding the presence or absence of ferromagnetism in doped/un-doped ZnO.

  12. Excitonic magnet in external field: Complex order parameter and spin currents

    Science.gov (United States)

    Geffroy, D.; Hariki, A.; Kuneš, J.

    2018-04-01

    We investigate spin-triplet exciton condensation in the two-orbital Hubbard model close to half-filling by means of dynamical mean-field theory. Employing an impurity solver that handles complex off-diagonal hybridization functions, we study the behavior of excitonic condensate in stoichiometric and doped systems subject to external magnetic field. We find a general tendency of the triplet order parameter to lie perpendicular with the applied field and identify exceptions from this rule. For solutions exhibiting k -odd spin textures, we discuss the Bloch theorem, which, in the absence of spin-orbit coupling, forbids the appearance of spontaneous net spin current. We demonstrate that the Bloch theorem is not obeyed by the dynamical mean-field theory.

  13. Recent development in magnetic neutron scattering studies

    International Nuclear Information System (INIS)

    Endoh, Yasuo

    1993-01-01

    Neutron scattering results contain many new concepts in modern magnetism. We review here the most recent neutron magnetic scattering studies from so called '214' copper oxide lamellar materials, because a number of important developments in magnetism are condensed in this novel subject. We show that neutron scattering has played crucial role in our understanding of modern magnetism. (author)

  14. Superconductivity and magnetic fluctuations developing in the vicinity of strong first-order magnetic transition in CrAs

    International Nuclear Information System (INIS)

    Kotegawa, H; Matsushima, K; Nakahara, S; Tou, H; Kaneyoshi, J; Nishiwaki, T; Matsuoka, E; Sugawara, H; Harima, H

    2017-01-01

    We report single crystal preparation, resistivity, and nuclear quadrupole resonance (NQR) measurements for new pressure-induced superconductor CrAs. In the first part, we present the difference between crystals made by different thermal sequences and methods, and show the sample dependence of superconductivity in CrAs. In the latter part, we show NQR data focusing the microscopic electronic state at the phase boundary between the helimagnetic and the paramagnetic phases. They suggest strongly that a quantum critical point is absent on the pressure-temperature phase diagram of CrAs, because of the strong first-order character of the magnetic transition; however, the spin fluctuations are observed in the paramagnetic phase. The close relationship between the spin fluctuations and superconductivity can be seen even in the vicinity of the first-order magnetic transition in CrAs. (paper)

  15. Pressure-induced instability of magnetic order in Kondo-lattice system. Neutron diffraction study of the pseudo-binary alloy system Ce(Ru sub 0 sub . sub 9 sub 0 Rh sub 0 sub . sub 1 sub 0) sub 2 (Si sub 1 sub - sub y Ge sub y) sub 2

    CERN Document Server

    Watanabe, K; Kanadani, C; Taniguchi, T; Kawarazaki, S; Uwatoko, Y; Kadowaki, H

    2003-01-01

    Neutron diffraction experiments have been carried out to study the nature of the magnetic order of the pseudo-binary alloy system Ce(Ru sub 0 sub . sub 9 sub 0 Rh sub 0 sub . sub 1 sub 0) sub 2 (Si sub 1 sub - sub y Ge sub y) sub 2. Response of the ordered atomic magnetic moment, mu, the transition temperature, T sub N , and the magnitude of the magnetic modulation vector, q, to the chemical pressure and also to the applied hydrostatic pressure, P, were examined at low temperatures. When y changes, all of mu, T sub N and q show a sudden alteration of the manner of the y-dependence at around y - 0.08. The P-dependence of q shows quite different features for different y's of 0.0, 0.2 and 0.25. On the basis of these observations the possibility of a pressure-induced alternation of the magnetic regime of the order is discussed. (author)

  16. Atom-vacancy ordering and magnetic susceptibility of nonstoichiometric hafnium carbide

    International Nuclear Information System (INIS)

    Gusev, A.I.; Zyryanova, A.N.

    1999-01-01

    Experimental results on magnetic susceptibility of nonstoichiometric hafnium carbide HfC y (0.6 0.71 , HfC 0.78 and HfC 0.83 in the range of 870-930 K the anomalies are revealed which are associated with superstructure short-range ordering in a non-metallics sublattice. It is shown that a short-range order in HfC 0.71 and HfC 0.78 carbides corresponds to Hf 3 C 2 ordered phase, and in HfC 0.83 carbide - to Hf 6 C 5 ordered phase. HfC 0.78 carbide is found to possesses zero magnetic susceptibility in temperature range 910-980 K [ru

  17. Evidence for a New Magnetoelectric Effect of Current-Induced Magnetization in a Toroidal Magnetic Ordered State of UNi$_4$B

    OpenAIRE

    Saito, Hiraku; Uenishi, Kenta; Miura, Naoyuki; Tabata, Chihiro; Hidaka, Hiroyuki; Yanagisawa, Tatsuya; Amitsuka, Hiroshi

    2018-01-01

    Magnetization measurements under direct electric currents were performed for toroidal magnetic ordered state of UNi$_4$B to test a recent theoretical prediction of current-induced magnetization in a metallic system lacking local inversion symmetry.We found that each of the electric currents parallel to [$2\\bar{1}\\bar{1}0$] and [$0001$] in the hexagonal 4-index notation induces uniform magnetization in the direction of [$01\\bar{1}0$].The observed behavior of the induced magnetization is essent...

  18. ESR of Gd3+ in magnetically ordered Eu2CuO4

    International Nuclear Information System (INIS)

    Rettori, C.; Oseroff, S.B.; Rao, D.; Valdivia, J.A.; Barberis, G.E.; Martins, G.B.; Sarrao, J.; Fisk, Z.; Tovar, M.

    1996-01-01

    Electron spin resonance (ESR) experiments of Gd 3+ in the antiferromagnetic (AF) ordered phase (T N ) of Eu 2 CuO 4 can be interpreted in terms of four magnetically nonequivalent rare-earth sites with local internal fields H i =±310(30) Oe along the [100] and [010] directions. The internal field is well described by a dipolar magnetic field of a noncollinear AF array of 0.35(4) μ B per Cu moment aligned along the [100] and [010] directions. This is consistent with recent results of magnetic-field-dependent neutron-diffraction experiments. From the ESR and magnetic susceptibility data, the crystal field parameters for Gd 3+ and Eu 3+ in Eu 2 CuO 4 are determined. The exchange parameters between the rare earths are also estimated. copyright 1996 The American Physical Society

  19. Magnetic and magnetocaloric properties in La{sub 0.7}Ca{sub 0.3−x}Na{sub x}MnO{sub 3} exhibiting first-order and second-order magnetic phase transitions

    Energy Technology Data Exchange (ETDEWEB)

    Ho, T.A. [Department of Materials Science and Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Dang, N.T. [Institute of Research and Development, Duy Tan University, Da Nang (Viet Nam); Phan, The-Long [Department of Physics and Oxide Research Center, Hankuk University of Foreign Studies, Yongin 449-791 (Korea, Republic of); Yang, D.S. [Physics Division, School of Science Education, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Lee, B.W. [Department of Physics and Oxide Research Center, Hankuk University of Foreign Studies, Yongin 449-791 (Korea, Republic of); Yu, S.C., E-mail: scyu@chungbuk.ac.kr [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of)

    2016-08-15

    Polycrystalline orthorhombic samples La{sub 0.7}Ca{sub 0.3−x}Na{sub x}MnO{sub 3} (x = 0–0.09) were prepared by solid-state reaction. The study of magnetic properties revealed that the ferromagnetic-paramagnetic (FM-PM) transition temperature (T{sub C}) increases from 255 to about 271 K with increasing Na-doping content (x) from 0 to 0.09, respectively. Around the T{sub C}, we have found the samples showing a large magnetocaloric (MC) effect with maximum values of magnetic entropy change (|ΔS{sub max}|) of 7–8 J kg{sup −1} K{sup −1} and relative cooling power RCP = 232–236 J/kg for the samples x = 0.03–0.09 in a magnetic-field interval ΔH = 40 kOe. Detailed analyses of isothermal magnetization data M(T, H) based on Banerjee's criteria indicated a first-to-second-order magnetic-phase transformation taking place at a threshold Na-doping concentration x{sub c} ≈ 0.06. This could also be observed clearly from the feature of entropy universal curves. An assessment of the magnetic-ordering exponent N = dLn|ΔS{sub m}|/dLnH demonstrates an existence of short-range magnetic order in the samples. We believe that the changes of the magnetic properties and MC effect in La{sub 0.7}Ca{sub 0.3−x}Na{sub x}MnO{sub 3} caused by Na doping are related to the changes in the structural parameters and Mn{sup 4+}/Mn{sup 3+} ratio, which are confirmed by the geometrical and electronic analyses based on X-ray diffraction and X-ray absorption fine structure. - Highlights: • Geometrical and electronic structures of La{sub 0.7}Ca{sub 0.3−x}Na{sub x}MnO{sub 3}. • Threshold of first-to-second-order phase transformation in La{sub 0.7}Ca{sub 0.3−x}Na{sub x}MnO{sub 3}. • Large magneto-caloric effect with |ΔS{sub max}| ≈ 7–8 J kg{sup −1} K{sup −1}, and RCP = 232–236 J/kg. • Universal curve of magnetic-entropy change.

  20. A search for strong, ordered magnetic fields in Herbig Ae/Be stars

    Science.gov (United States)

    Wade, G. A.; Bagnulo, S.; Drouin, D.; Landstreet, J. D.; Monin, D.

    2007-04-01

    The origin of magnetic fields in intermediate- and high-mass stars is fundamentally a mystery. Clues towards solving this basic astrophysical problem can likely be found at the pre-main-sequence (PMS) evolutionary stage. With this work, we perform the largest and most sensitive search for magnetic fields in PMS Herbig Ae/Be (HAeBe) stars. We seek to determine whether strong, ordered magnetic fields, similar to those of main-sequence Ap/Bp stars, can be detected in these objects, and if so, to determine the intensities, geometrical characteristics, and statistical incidence of such fields. 68 observations of 50 HAeBe stars have been obtained in circularly polarized light using the FORS1 spectropolarimeter at the ESO VLT. An analysis of both Balmer and metallic lines reveals the possible presence of weak longitudinal magnetic fields in photospheric lines of two HAeBe stars, HD 101412 and BF Ori. Results for two additional stars, CPD-53 295 and HD 36112, are suggestive of the presence of magnetic fields, but no firm conclusions can be drawn based on the available data. The intensity of the longitudinal fields detected in HD 101412 and BF Ori suggest that they correspond to globally ordered magnetic fields with surface intensities of order 1 kG. On the other hand, no magnetic field is detected in 4 other HAeBe stars in our sample in which magnetic fields had previously been confirmed. Monte Carlo simulations of the longitudinal field measurements of the undetected stars allow us to place an upper limit of about 300 G on the general presence of aligned magnetic dipole magnetic fields, and of about 500 G on perpendicular dipole fields. Taking into account the results of our survey and other published results, we find that the observed bulk incidence of magnetic HAeBe stars in our sample is 8-12 per cent, in good agreement with that of magnetic main-sequence stars of similar masses. We also find that the rms longitudinal field intensity of magnetically detected HAe

  1. Electron paramagnetic resonance response and magnetic interactions in ordered solid solutions of lithium nickel oxides

    Energy Technology Data Exchange (ETDEWEB)

    Azzoni, C.B. [Istituto Nazionale di Fisica della Materia, Dipartimento di Fisica ' Alessandro Volta' , Universita di Pavia, Pavia (Italy); Paleari, A. [Istituto Nazionale di Fisica della Materia, Dipartimento di Fisica, Universita di Milano, Milan (Italy); Massarotti, V.; Capsoni, D. [Dipartimento di Chimica-Fisica, Universita di Pavia, Pavia (Italy)

    1996-09-23

    EPR data of ordered solid solutions of lithium nickel oxides are reported as a function of the lithium content. The features of the signal and the EPR centre density are analysed by a model of dynamical trapping of holes in [(Ni{sup 2+}-O-Ni{sup 2+})-h{sup +}] complexes. The possible origin of the interactions responsible for the magnetic ordering and some features of the transport properties are also discussed. (author)

  2. Octacyanoniobate(IV)-based molecular magnets revealing 3D long-range order

    Energy Technology Data Exchange (ETDEWEB)

    Pelka, R; Balanda, M [Institute of Physics PAN, Radzikowskiego 152, 31-342, Krakow (Poland); Pinkowicz, D; Drath, O; Nitek, W; Sieklucka, B [Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland); Rams, M; Majcher, A, E-mail: robert.pelka@ifj.edu.pl [Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland)

    2011-07-06

    Isostructural series of chemical formula {l_brace}[M{sup II}(pirazol){sub 4}]{sub 2}[Nb{sup IV}(CN){sub 8}]{center_dot} 4H{sub 2}O{r_brace}{sub n} (M{sup II} = Mn (1), Fe (2), Co (3), Ni (4)) has been obtained by the self-assembly technique. Its unique crystallographic structure consists in the formation of a 3D extended network of magnetic centers braced by geometrically identical cyanido bridges. Magnetic measurements reveal the transitions to the 3D order at temperatures 23.7, 8.3, 5.9, 13.4 K for 1, 2, 3, and 4, respectively. The character of order is demonstrated to be ferrimagnetic for 1 and 2 and ferromagnetic for 3 and 4. The mean-field approach is used to determine the corresponding exchange coupling constants. The observed interactions are discussed within the magnetic orbital model.

  3. Octacyanoniobate(IV)-based molecular magnets revealing 3D long-range order

    International Nuclear Information System (INIS)

    Pelka, R; Balanda, M; Pinkowicz, D; Drath, O; Nitek, W; Sieklucka, B; Rams, M; Majcher, A

    2011-01-01

    Isostructural series of chemical formula {[M II (pirazol) 4 ] 2 [Nb IV (CN) 8 ]· 4H 2 O} n (M II = Mn (1), Fe (2), Co (3), Ni (4)) has been obtained by the self-assembly technique. Its unique crystallographic structure consists in the formation of a 3D extended network of magnetic centers braced by geometrically identical cyanido bridges. Magnetic measurements reveal the transitions to the 3D order at temperatures 23.7, 8.3, 5.9, 13.4 K for 1, 2, 3, and 4, respectively. The character of order is demonstrated to be ferrimagnetic for 1 and 2 and ferromagnetic for 3 and 4. The mean-field approach is used to determine the corresponding exchange coupling constants. The observed interactions are discussed within the magnetic orbital model.

  4. Octacyanoniobate(IV)-based molecular magnets revealing 3D long-range order

    Science.gov (United States)

    Pełka, R.; Pinkowicz, D.; Drath, O.; Bałanda, M.; Rams, M.; Majcher, A.; Nitek, W.; Sieklucka, B.

    2011-07-01

    Isostructural series of chemical formula {[MII(pirazol)4]2[NbIV(CN)8]· 4H2O}n (MII = Mn (1), Fe (2), Co (3), Ni (4)) has been obtained by the self-assembly technique. Its unique crystallographic structure consists in the formation of a 3D extended network of magnetic centers braced by geometrically identical cyanido bridges. Magnetic measurements reveal the transitions to the 3D order at temperatures 23.7, 8.3, 5.9, 13.4 K for 1, 2, 3, and 4, respectively. The character of order is demonstrated to be ferrimagnetic for 1 and 2 and ferromagnetic for 3 and 4. The mean-field approach is used to determine the corresponding exchange coupling constants. The observed interactions are discussed within the magnetic orbital model.

  5. Creation of Spin-Triplet Cooper Pairs in the Absence of Magnetic Ordering

    Science.gov (United States)

    Breunig, Daniel; Burset, Pablo; Trauzettel, Björn

    2018-01-01

    In superconducting spintronics, it is essential to generate spin-triplet Cooper pairs on demand. Up to now, proposals to do so concentrate on hybrid structures in which a superconductor (SC) is combined with a magnetically ordered material (or an external magnetic field). We, instead, identify a novel way to create and isolate spin-triplet Cooper pairs in the absence of any magnetic ordering. This achievement is only possible because we drive a system with strong spin-orbit interaction—the Dirac surface states of a strong topological insulator (TI)-out of equilibrium. In particular, we consider a bipolar TI-SC-TI junction, where the electrochemical potentials in the outer leads differ in their overall sign. As a result, we find that nonlocal singlet pairing across the junction is completely suppressed for any excitation energy. Hence, this junction acts as a perfect spin-triplet filter across the SC, generating equal-spin Cooper pairs via crossed Andreev reflection.

  6. Electronic structure and magnetic ordering of the unconventional antiferromagnet Yb3Pt4

    KAUST Repository

    Schwingenschlögl, Udo

    2009-12-01

    Applying density functional theory within the generalized gradient approximation, we investigate the electronic and magnetic properties of the intermetallic rare-earth system Yb3Pt4. This material recently has been put forward as host for quantum criticality, while details of the magnetic ordering could not be established (Bennett N. C.et al., J. Magn. & Magn. Mater., 321 (2009) 2021). In this context, we investigate the effect of spin-orbit coupling and compare various spin patterns from the energetic point of view, which enables us to determine the electronic ground state of Yb3Pt4. The assumption of an elementary superexchange mechanism yields a magnetic-coupling constant in good agreement with the experimental ordering temperature. Copyright © 2009 EPLA.

  7. Electronic structure and magnetic ordering of the unconventional antiferromagnet Yb3Pt4

    KAUST Repository

    Schwingenschlö gl, Udo; Gó mez, Javier Alexandra M; Grau-Crespo, Ricardo

    2009-01-01

    Applying density functional theory within the generalized gradient approximation, we investigate the electronic and magnetic properties of the intermetallic rare-earth system Yb3Pt4. This material recently has been put forward as host for quantum criticality, while details of the magnetic ordering could not be established (Bennett N. C.et al., J. Magn. & Magn. Mater., 321 (2009) 2021). In this context, we investigate the effect of spin-orbit coupling and compare various spin patterns from the energetic point of view, which enables us to determine the electronic ground state of Yb3Pt4. The assumption of an elementary superexchange mechanism yields a magnetic-coupling constant in good agreement with the experimental ordering temperature. Copyright © 2009 EPLA.

  8. Spin-glass-like ordering of the magnetic moments of interacting nanosized maghemite particles

    DEFF Research Database (Denmark)

    Mørup, Steen; Bødker, Franz; Hendriksen, Peter Vang

    1995-01-01

    Samples of interacting nanosized maghemite particles have been studied by Mössbauer spectroscopy and magnetization measurements. The apparent blocking temperatures obtained from Mössbauer spectroscopy and zero-field-cooled magnetization curves are nearly identical, but the values obtained from...

  9. Neutron scattering studies of modulated magnetic structures

    Energy Technology Data Exchange (ETDEWEB)

    Aagaard Soerensen, Steen

    1999-08-01

    This report describes investigations of the magnetic systems DyFe{sub 4}Al{sub 8} and MnSi by neutron scattering and in the former case also by X-ray magnetic resonant scattering. The report is divided into three parts: An introduction to the technique of neutron scattering with special emphasis on the relation between the scattering cross section and the correlations between the scattering entities of the sample. The theoretical framework of neutron scattering experiments using polarized beam technique is outlined. The second part describes neutron and X-ray scattering investigation of the magnetic structures of DyFe{sub 4}Al{sub 8}. The Fe sublattice of the compound order at 180 K in a cycloidal structure in the basal plane of the bct crystal structure. At 25 K the ordering of the Dy sublattice shows up. By the element specific technique of X-ray resonant magnetic scattering, the basal plane cycloidal structure was also found for the Dy sublattice. The work also includes neutron scattering studies of DyFe{sub 4}Al{sub 8} in magnetic fields up to 5 T applied along a <110> direction. The modulated structure at the Dy sublattice is quenched by a field lower than 1 T, whereas modulation is present at the Fe sublattice even when the 5 T field is applied. In the third part of the report, results from three small angle neutron experiments on MnSi are presented. At ambient pressure, a MnSi is known to form a helical spin density wave at temperature below 29 K. The application of 4.5 kbar pressure intended as hydrostatic decreased the Neel temperature to 25 K and changed the orientation of the modulation vector. To understand this reorientation within the current theoretical framework, anisotropic deformation of the sample crystal must be present. The development of magnetic critical scattering with an isotropic distribution of intensity has been studied at a level of detail higher than that of work found in the literature. Finally the potential of a novel polarization

  10. HTS Insert Magnet Design Study

    CERN Document Server

    Devaux, M; Fleiter, J; Fazilleau, P; Lécrevisse, T; Pes, C; Rey, J-M; Rifflet, J-M; Sorbi, M; Stenvall, A; Tixador, P; Volpini, G

    2011-01-01

    Future accelerator magnets will need to reach higher field in the range of 20 T. This field level is very difficult to reach using only Low Temperature Superconductor materials whereas High Temperature Superconductors (HTS) provide interesting opportunities. High current densities and stress levels are needed to design such magnets. YBCO superconductor indeed carries large current densities under high magnetic field and provides good mechanical properties especially when produced using the IBAD approach. The HFM EUCARD program studies the design and the realization of an HTS insert of 6 T inside a Nb$_{3}$Sn dipole of 13T at 4.2 K. In the2HTS insert, engineering current densities higher than 250 MA/m under 19 T are required to fulfill the specifications. The stress level is also very severe. YBCO IBAD tapes theoretically meet these challenges from presented measurements. The insert protection is also a critical because HTS materials show low quench propagation velocities and the coupling with the Nb$_{3}$Sn m...

  11. Neutron diffraction study of multipole order in light rare-earth ...

    Indian Academy of Sciences (India)

    discussed in connection with recent non-resonant X-ray results by Tanaka et ... experiments, to study the competition between magnetic and QP order ..... [15] J Rossat-Mignod, Magnetic structures, in Neutron scattering edited by D L Price and.

  12. Magnetic order, hysteresis, and phase coexistence in magnetoelectric LiCoPO4

    DEFF Research Database (Denmark)

    Fogh, Ellen; Toft-Petersen, Rasmus; Ressouche, Eric

    2017-01-01

    The magnetic phase diagram of magnetoelectric LiCoPO4 is established using neutron diffraction and magnetometry in fields up to 25.9 T applied along the crystallographic b axis. For fields greater than 11.9 T, the magnetic unit cell triples in size with propagation vector Q = (0, 1...... ≈ to (0, 1/2,0) appear for increasing fields in the hysteresis region below the transition field. Traces of this behavior are also observed in the magnetization. A simple model based on a mean-field approach is proposed to explain these additional ordering vectors. In the field interval 20.5-21.0 T....../3,0). A magnetized elliptic cycloid is formed with spins in the (b, c) plane and the major axis oriented along b. Such a structure allows for the magnetoelectric effect with an electric polarization along c induced by magnetic fields applied along b. Intriguingly, additional ordering vectors Q ≈ to (0, 1/4,0) and Q...

  13. Magnetic ordering and frustration in hexagonal UNi{sub 4}B

    Energy Technology Data Exchange (ETDEWEB)

    Mentink, S A.M. [Rijksuniversiteit Leiden (Netherlands). Kamerlingh Onnes Lab.; Drost, A [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Nieuwenhuys, G J [Rijksuniversiteit Leiden (Netherlands). Kamerlingh Onnes Lab.; Frikkee, E [Netherlands Energy Research Foundation (ECN), Petten (Netherlands); Menovsky, A A [Rijksuniversiteit Leiden (Netherlands). Kamerlingh Onnes Lab.

    1994-05-01

    We have determined unusual magnetic ordering of the hexagonal intermetallic uranium compound UNi{sub 4}B via neutron diffraction. In the easy basal plane the U-moments have triangular symmetry with antiferromagnetic interactions. Along the hard c axis ferromagnetic coupling occurs. Below T{sub N} = 20 K only two out of every three U-moments of 1.2 {mu}{sub B} order in vortex-like arrangements around the third paramagnetic spin. This novel magnetic structure is related to the occurrence of a crystallographic superstructure. Previously observed anomalies in bulk properties below T{sub N} are attributed to unconventional spin-wave excitations associated with this type of ordering. (orig.).

  14. Effect of Dzyaloshinskii-Moriya on Magnetic orders of J_1-J_2 Antiferromagnetic Heisenberg model

    Directory of Open Access Journals (Sweden)

    Fariba Masoudi

    2017-11-01

    Full Text Available Motivated by recent experiments that detects Dzyaloshinskii-Moriya (DM interaction in , we study the effects of DM interaction on magnetic orders of J1-J2 antiferromagnetic Heisenberg model. First, we find the classical phase diagram of the model using Luttinger-Tisza approximation. In this approximation, the classical phase diagram has two phases. For , the model has canted Neel and DM interaction cants the spins of one on the subluttices. The ground state of model is classically degenerate for , including infinit numbers of vorticity vectors that are able to minimize the model. This phase is important because of the probability of the existence of quantum spin liquid in this region. To investigate the effect of quantum fluctuation on the stability of the classical phase diagram, linear spin wave theory of  Holstein-Primakoff is used. The results show that in the classical degeneracy regime, the quantum fluctuations for  cause spiral order in this region. The ground state of model remains disorder for, and this region is a good place for finding quantum spin liquid

  15. Quasi-discrete particle motion in an externally imposed, ordered structure in a dusty plasma at high magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, Edward, E-mail: etjr@auburn.edu; Konopka, Uwe; Lynch, Brian; Adams, Stephen; LeBlanc, Spencer [Physics Department, Auburn University, Auburn, Alabama 36849 (United States); Merlino, Robert L. [Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242 (United States); Rosenberg, Marlene [Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California 92093 (United States)

    2015-11-15

    Dusty plasmas have been studied in argon, radio frequency (rf) glow discharge plasmas at magnetic fields up to 2.5 T where the electrons and ions are strongly magnetized. Plasmas are generated between two parallel plate electrodes where the lower, powered electrode is solid and the upper electrode supports a dual mesh consisting of #24 brass and #30 aluminum wire cloth. In this experiment, we study the formation of imposed ordered structures and particle dynamics as a function of magnetic field. Through observations of trapped particles and the quasi-discrete (i.e., “hopping”) motion of particles between the trapping locations, it is possible to make a preliminary estimate of the potential structure that confines the particles to a grid structure in the plasma. This information is used to gain insight into the formation of the imposed grid pattern of the dust particles in the plasma.

  16. Higher-order hadronic and heavy-lepton contributions to the anomalous magnetic moment

    International Nuclear Information System (INIS)

    Kurz, Alexander; Liu, Tao; Steinhauser, Matthias

    2014-07-01

    We report about recent results obtained for the muon anomalous magnetic moment. Three-loop kernel functions have been computed to obtain the next-to-next-to-leading-order hadronic vacuum polarization contributions. The numerical result, a μ had,NNLO = 1.24 ± 0.01 x 10 -10 , is of the same order of magnitude as the current uncertainty from the hadronic contributions. For heavy-lepton corrections, analytical results are obtained at four-loop order and compared with the known results.

  17. 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.

  18. Emergence of magnetic order in ultra-thin pyrochlore iridate films

    Science.gov (United States)

    Cheema, Suraj; Serrao, Claudy; Mundy, Julia; Patankar, Shreyas; Birgeneau, Robert; Orenstein, Joseph; Salahuddin, Sayeef; Ramesh, Ramamoorthy

    We report on thickness-dependent magnetotransport in (111) - oriented Pb2Ir2O7-x (Pb227) epitaxial thin films. For thicknesses greater than 4 nm, the magnetoresistance (MR) of metallic Pb227 is positive, linear and non-saturated up to 14 T. Meanwhile at 4 nm, the conduction turns nonmetallic and the MR becomes negative and asymmetric upon field-cooling; such traits are reminiscent of all-in-all-out (AIAO) magnetic order in the insulating pyrochlore iridates. Hysteretic low-field MR dips and trained-untrained resistivity bifurcations suggest the presence of magnetic conducting domain walls within the chiral AIAO spin structure. Beyond just AIAO order, angular-dependent MR indicates a magnetic phase space hosting 2-in-2-out (2I2O) spin ice order. Such anomalous magnetotransport calls for re-evaluation of the pyrochlore iridate phase diagram, as epitaxially strained Pb227 exhibits traits reminiscent of both the insulating magnetic and metallic spin-liquid members. Furthermore, these results open avenues for realizing topological phase predictions in (111) - oriented pyrochlore slabs of kagome-triangular iridate heterostructures. This work is supported by the Office of Basic Energy Sciences of the US Department of Energy under Contract No. DE-AC02-05CH11231.

  19. Synthesis and characterization of chemically ordered FePt magnetic nano-particles

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasa Rao, K. [Centre for Materials for Electronics Technology (C-MET), IDA phase-III, Cherlapally, Hyderabad 500 051 (India); Balaji, T., E-mail: theerthambalaji@yahoo.co [Centre for Materials for Electronics Technology (C-MET), IDA phase-III, Cherlapally, Hyderabad 500 051 (India); Lingappa, Y. [Department of Chemistry, Sri Venkateswara University, Tirupati 517 502 (India); Reddy, M.R.P.; Kumar, Arbind; Prakash, T.L. [Centre for Materials for Electronics Technology (C-MET), IDA phase-III, Cherlapally, Hyderabad 500 051 (India)

    2010-08-15

    Monodispersed FePt alloy magnetic nano-particles are prepared by reduction of platinum acetyl acetonate and iron acetyl acetonate salts together in the presence of oleic acid and oleyl amine stabilizers by polyol process. The particle size of FePt is in the range of 2-3 nm confirmed by transmission electron microscopy (TEM). As-synthesized FePt nano-particles are chemically disordered with face centre cubic (fcc) structure where as after vacuum annealing these particles changed to face centre tetragonal (fct) ordered structure confirmed by the X-ray diffraction technique. Magnetic coercivity of 5.247 KOe was observed for fct structure.

  20. Origin of second-order transverse magnetic anisotropy in Mn12-acetate

    International Nuclear Information System (INIS)

    Cornia, A.; Sessoli, R.; Sorace, L.; Gatteschi, D.; Barra, A. L.; Daiguebonne, C.

    2002-01-01

    The symmetry breaking effects for quantum tunneling of the magnetization in Mn 12 -acetate, a molecular nanomagnet, represent an open problem. We present structural evidence that the disorder of the acetic acid of crystallization induces sizable distortion of the Mn(III) sites, giving rise to six different isomers. Four isomers have symmetry lower than tetragonal and a nonzero second-order transverse magnetic anisotropy, which has been evaluated using a ligand field approach. The result of the calculation leads to an improved simulation of electron paramagnetic resonance spectra and justifies the tunnel splitting distribution derived from the field sweep rate dependence of the hysteresis loops

  1. Possible pitfalls in search of magnetic order in thin films deposited on single crystalline sapphire substrates

    International Nuclear Information System (INIS)

    Salzer, R.; Spemann, D.; Esquinazi, P.; Hoehne, R.; Setzer, A.; Schindler, K.; Schmidt, H.; Butz, T.

    2007-01-01

    We have studied the field and temperature dependence of the magnetic moment of single crystalline sapphire substrates with different surface orientations. All the substrates show a ferromagnetic behavior that partially changes after surface cleaning. The amount of magnetic impurities in the substrates was determined by particle induced X-ray emission. The overall analysis of the data indicates that the magnetic impurities very likely contribute to the measured ferromagnetic behavior but does not rule out completely intrinsic contributions. Our work stresses the necessity to use other than bulk characterization methods for the study of weak ferromagnetic signals of thin films grown on oxide substrates

  2. SMARTer for magnetic structure studies

    Indian Academy of Sciences (India)

    Small angle neutron scattering; magnetic structure; Cu(NiFe); CuCo; ... micromagnetism, magnetic clusters embedded in a solid nonmagnetic matrix, mag- .... project. E G R Putra acknowledges the support from IAEA through the ISNS2008.

  3. Monte Carlo study of the magnetic properties in a bilayer dendrimer structure with non-magnetic layers

    Science.gov (United States)

    Jabar, A.; Masrour, R.

    2017-12-01

    In this paper, we study the Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions and magnetic layer effects on the bilayer transitions of a spin-5/2 Blume-Capel model formed by two magnetic blocs separated by a non-magnetic spacer of finite thickness. The thermalization process of magnetization for systems sizes has been given. We have shown that the magnetic order in the two magnetic blocs depend on the thickness of the magnetic layer. In the total magnetization profiles, the susceptibility peaks correspond to the reduced critical temperature. This critical temperature is displaced towards higher temperatures when increasing the number of magnetic layers. In addition, we have discussed and interpreted the behaviors of the magnetic hysteresis loops.

  4. The study of superconducting order parameter dynamics

    International Nuclear Information System (INIS)

    Goldman, A.M.

    1988-01-01

    Flux quantization experiments have demonstrated the importance of long range phase coherence in the description of the superconducting state, an idea originally proposed as an integral part of the phenomenological theory of the Meissner-Ochsenfeld effect. The most striking experimental demonstration of the phase coherence of the superconducting state is that the maximum dc Josephson current in a thin-film tunneling junction exhibits a Fraunhofer-like dependence on magnetic field

  5. Nonlinear spectroscopic studies of interfacial molecular ordering

    International Nuclear Information System (INIS)

    Superfine, R.

    1991-07-01

    The second order nonlinear optical processes of second harmonic generation and sum frequency generation are powerful new probes of surfaces. They possess unusual surface sensitivity due to the symmetry properties of the nonlinear susceptibility. In particular, infrared-visible sum frequency generation (SFG) can obtain the vibrational spectrum of sub-monolayer coverages of molecules. In this thesis, we explore the unique information that can be obtained from SFG. We take advantage of the sensitivity of SFG to the conformation of alkane chains to study the interaction between adsorbed liquid crystal molecules and surfactant treated surfaces. The sign of the SFG susceptibility depends on the sign of the molecular polarizability and the orientation, up or down, of the molecule. We experimentally determine the sign of the susceptibility and use it to determine the absolute orientation to obtain the sign of the molecular polarizability and show that this quantity contains important information about the dynamics of molecular charge distributions. Finally, we study the vibrational spectra and the molecular orientation at the pure liquid/vapor interface of methanol and water and present the most detailed evidence yet obtained for the structure of the pure water surface. 32 refs., 4 figs., 2 tabs

  6. Characterizing the Magnetic Properties of Natural Samples Using First-Order Reversal Curve Diagrams

    Science.gov (United States)

    Pike, C. R.; Roberts, A. P.; Verosub, K. L.

    2001-12-01

    A FORC diagram is calculated from a class of partial hysteresis curves known as first-order reversal curves or FORCs. The measurement of a FORC begins by saturating a sample in a large positive applied field. The field is then decreased to a specified field and reversed; the FORC consists of the magnetization curve that results when the applied field is increased from this reversal field back to saturation. By repeating this measurement for different reversal fields, one obtains a suite of curves that provide detailed information on the distribution of particle switching fields (coercivities) and interaction fields in the sample. These magnetization data are transformed into a FORC distribution by calculating a second derivative of the magnetization data, and by applying a change in co-ordinates. The FORC distribution is, therefore, an empirically well-defined quantity that can be used to probe subtle variations in hysteresis behavior. We have used FORC diagrams to characterize the main types of hysteresis behavior observed in rock magnetism and environmental magnetism. FORC diagrams can be calculated using room-temperature or low-temperature data and enable identification of superparamagnetic, single domain and multi-domain grains, as well as magnetostatic interactions, even in mixed magnetic mineral assemblages. Routine use of FORC diagrams to examine representative bulk samples from large sample collections can provide important information concerning the magnetic particles that cannot be obtained using standard hysteresis measurements. In addition to using FORC diagrams to identify specific magnetic components in a sample, they can also be used to understand fundamental problems in rock magnetism. Our results suggest that pseudo-single domain grains contain contributions from single domain and multi-domain moments and that the hysteresis behavior observed in the multi-domain grains typically encountered in rock magnetism cannot be solely explained through

  7. Order-disorder criticality, wetting, and morphological phase transitions in the irreversible growth of far-from-equilibrium magnetic films

    International Nuclear Information System (INIS)

    Candia, J.Julian; Albano, E.V.Ezequiel V.

    2003-01-01

    An exhaustive numerical investigation of the growth of magnetic films in confined (d+1)-dimensional stripped geometries (d=1,2) is carried out by means of extensive Monte Carlo simulations. Films in contact with a thermal bath at temperature T, are grown by adding spins having two possible orientations and considering ferromagnetic (nearest-neighbor) interactions. At low temperatures, thin films of thickness L are constituted by a sequence of well-ordered domains of average length l D >>L. These domains have opposite magnetization. So, the films exhibit 'spontaneous magnetization reversal' during the growth process. Such reversal occurs within a short characteristic length l R , such that l D >>l R ∼L. Furthermore, it is found that for d=1 the system is non-critical, while a continuous order-disorder phase transition at finite temperature takes place in the d=2 case. Using standard finite-size scaling procedures, the critical temperature and some relevant critical exponents are determined. Finally, the growth of magnetic films in (2+1) dimensions with competing short-range magnetic fields acting along the confinement walls is studied. Due to the antisymmetric condition considered, an interface between domains with spins having opposite orientation develops along the growing direction. Such an interface undergoes a localization-delocalization transition that is the precursor of a wetting transition in the thermodynamic limit. Furthermore, the growing interface also undergoes morphological transitions in the growth mode. A comparison between the well-studied equilibrium Ising model and the studied irreversible magnetic growth model is performed throughout. Although valuable analogies are encountered, it is found that the non-equilibrium nature of the latter introduces new and rich physical features of interest

  8. Magnetic ordering induced giant optical property change in tetragonal BiFeO3

    Science.gov (United States)

    Tong, Wen-Yi; Ding, Hang-Chen; Gong, Shi Jing; Wan, Xiangang; Duan, Chun-Gang

    2015-12-01

    Magnetic ordering could have significant influence on band structures, spin-dependent transport, and other important properties of materials. Its measurement, especially for the case of antiferromagnetic (AFM) ordering, however, is generally difficult to be achieved. Here we demonstrate the feasibility of magnetic ordering detection using a noncontact and nondestructive optical method. Taking the tetragonal BiFeO3 (BFO) as an example and combining density functional theory calculations with tight-binding models, we find that when BFO changes from C1-type to G-type AFM phase, the top of valance band shifts from the Z point to Γ point, which makes the original direct band gap become indirect. This can be explained by Slater-Koster parameters using the Harrison approach. The impact of magnetic ordering on band dispersion dramatically changes the optical properties. For the linear ones, the energy shift of the optical band gap could be as large as 0.4 eV. As for the nonlinear ones, the change is even larger. The second-harmonic generation coefficient d33 of G-AFM becomes more than 13 times smaller than that of C1-AFM case. Finally, we propose a practical way to distinguish the two AFM phases of BFO using the optical method, which is of great importance in next-generation information storage technologies.

  9. Toward Monte Carlo simulation of general cases of static muon spin relaxation in disordered magnetic materials: long-range magnetic order in alloys

    International Nuclear Information System (INIS)

    Noakes, D.R.

    2001-01-01

    Monte Carlo simulations of zero-field (ZF) muon spin relaxation (μSR) functions generated by long-range-ordered states with disorder are presented, for the completely static limit. Understanding of this is necessary before Monte Carlo simulation of the effect of short-range magnetic ordering on μSR in spin glasses can begin. Alloy disorder, controlled by the magnetic ion concentration parameter f m , and partial ordering of each moment, controlled by the order parameter f o , are considered. Qualitatively different behavior is seen depending on whether the dense moment, perfect-order limit ( f m =1, f o =1) field at the muon site is non-zero, or cancels (as can happen in high-symmetry materials). Around the edges of the two-dimensional ( f m ,f o ) parameter space, four limit cases with qualitatively different behavior are identified: (A) f o →0, the random frozen spin glass for arbitrary magnetic ion concentration; (B) f o →1, nearly perfect magnetic ordering in a alloy of arbitrary magnetic ion concentration; (C) f m →0, magnetic order developing (as f o increases) in a dilute magnetic alloy; (D) f m →1, magnetic order developing (as f o increases) in a dense magnetic material. Case A was discussed in a previous publication. The results for case D answer the question of how the Gaussian Kubo-Toyabe relaxation function for perfect disorder develops into an oscillating function as magnetic order develops in a material. Case C indicates that the effects of magnetic ordering in the dilute moment limit produce only subtle effects in ZF-μSR spectra that would be difficult to unambiguously identify as due to ordering in a real-world experiment. Case B generates complicated multi-frequency behavior

  10. Theoretical investigation into the possibility of multiorbital magnetically ordered states in isotropically superstrained graphene

    Science.gov (United States)

    Craco, L.

    2017-10-01

    Using density functional dynamical mean-field theory (DFDMFT) we address the problem of antiferromagnetic spin ordering in isotropically superstrained graphene. It is shown that the interplay between strain-induced one-particle band narrowing and sizable on-site electron-electron interactions naturally stabilizes a magnetic phase with orbital-selective spin-polarized p -band electronic states. While an antiferromagnetic phase with strong local moments arises in the pz orbitals, the px ,y bands reveal a metallic state with quenched sublattice magnetization. We next investigate the possibility of superconductivity to emerge in this selective magnetoelectronic state. Our theory is expected to be an important step to understanding the next generation of flexible electronics made of Mott localized carbon-based materials as well as the ability of superstrained graphene to host coexisting superconductivity and magnetism at low temperatures.

  11. On the determination of the magnetic entropy change in materials with first-order transitions

    International Nuclear Information System (INIS)

    Caron, L.; Ou, Z.Q.; Nguyen, T.T.; Cam Thanh, D.T.; Tegus, O.; Brueck, E.

    2009-01-01

    An accurate method to determine the magnetic entropy change in materials with hysteretic first-order transitions is presented, which is needed to estimate their potential for applications. We have investigated the effect of the maximal entropy change derived from magnetization measurements performed in different measurement processes. The results show that the isothermal entropy change can be derived from the Maxwell relations even for samples with large thermal hysteresis. In the temperature region with hysteresis, overestimating the entropy change can be avoided by measuring the isothermal magnetization of the sample after it is cooled from the paramagnetic state to the measurement temperature. In this way the so-called peak effect is not observed as shown here for a few compounds.

  12. Transitions to improved core electron heat confinement triggered by low order rational magnetic surfaces in the stellarator TJ-II

    International Nuclear Information System (INIS)

    Estrada, T.; Medina, F.; Lopez-Bruna, D.; AscasIbar, E.; BalbIn, R.; Cappa, A.; Castejon, F.; Eguilior, S.; Fernandez, A.; Guasp, J.; Hidalgo, C.; Petrov, S.

    2007-01-01

    Transitions to improved core electron heat confinement are triggered by low order rational magnetic surfaces in TJ-II electron cyclotron heated (ECH) plasmas. Experiments are performed changing the magnetic shear around the rational surface n = 3/m = 2 to study its influence on the transition; ECH power modulation is used to look at transport properties. The improvement in the electron heat confinement shows no obvious dependence on the magnetic shear. Transitions triggered by the rational surface n = 4/m = 2 show, in addition, an increase in the ion temperature synchronized with the increase in the electron temperature. Ion temperature changes had not been previously observed either in TJ-II or in any other helical device. SXR measurements demonstrate that, under certain circumstances, the rational surface positioned inside the plasma core region precedes and provides a trigger for the transition

  13. 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

  14. Breathing mode distortion and magnetic order in rare-earth nickelates RNiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Hampel, Alexander; Ederer, Claude [Materials Theory, ETH Zuerich (Switzerland)

    2016-07-01

    Rare-earth nickelate perovskites display a rich and not yet fully understood phase diagram, where all RNiO{sub 3} compounds with R from Sm to Lu undergo a non-magnetic metal-insulator transition (MIT). This transition is connected to a lattice distortion, which can be described as breathing mode of the oxygen octahedra surrounding the Ni cations. Between 100-250 K the RNiO{sub 3} compounds undergo a magnetic transition to an antiferromagnetic (AFM) state, with a wave-vector k= [(1)/(4) (1)/(4) (1)/(4)] relative to the underlying simple cubic perovskite structure. Here, we use density functional theory and its extensions (DFT+U, DFT+DMFT) together with distortion mode analysis to explore the interplay between lattice distortions, magnetic order, and the strength of the local Coulomb interaction U in rare earth nickelates. Our results show a strong dependency of the breathing mode amplitude on the magnetic order, with a much larger breathing mode obtained for the AFM state compared to the ferromagnetic case. Furthermore, we demonstrate that DFT+U is able to capture the correct trends of the lattice distortions across the nickelate series.

  15. Magnetic order in Pu2M3Si5 (M = Co, Ni)

    International Nuclear Information System (INIS)

    Bauer, E D; Tobash, P H; Mitchell, J N; Kennison, J A; Ronning, F; Scott, B L; Thompson, J D

    2011-01-01

    The physical properties including magnetic susceptibility, specific heat, and electrical resistivity of two new plutonium compounds Pu 2 M 3 Si 5 (M = Co, Ni) are reported. Pu 2 Ni 3 Si 5 crystallizes in the orthorhombic U 2 Co 3 Si 5 structure type, which can be considered a variant of the BaAl 4 tetragonal structure, while Pu 2 Co 3 Si 5 adopts the closely related monoclinic Lu 2 Co 3 Si 5 type. Magnetic order is observed in both compounds, with Pu 2 Ni 3 Si 5 ordering ferromagnetically at T C = 65 K then undergoing a transition into an antiferromagnetic state below T N = 35 K. Two successive magnetic transitions are also observed at T mag1 = 38 K and T mag2 = 5 K in Pu 2 Co 3 Si 5 . Specific heat measurements reveal that these two materials have a moderately enhanced Sommerfeld coefficient γ ∼ 100 mJ/mol Pu K 2 in the magnetic state with comparable RKKY and Kondo energy scales.

  16. Investigation of magnetic and magneto-transport properties of ferromagnetic-charge ordered core-shell nanostructures

    Science.gov (United States)

    Das, Kalipada

    2017-10-01

    In our present study, we address in detail the magnetic and magneto-transport properties of ferromagnetic-charge ordered core-shell nanostructures. In these core-shell nanostructures, well-known half metallic La0.67Sr0.33MnO3 nanoparticles (average particle size, ˜20 nm) are wrapped by the charge ordered antiferromagnetic Pr0.67Ca0.33MnO3 (PCMO) matrix. The intrinsic properties of PCMO markedly modify it into such a core-shell form. The robustness of the PCMO matrix becomes fragile and melts at an external magnetic field (H) of ˜20 kOe. The analysis of magneto-transport data indicates the systematic reduction of the electron-electron and electron-magnon interactions in the presence of an external magnetic field in these nanostructures. The pronounced training effect appears in this phase separated compound, which was analyzed by considering the second order tunneling through the grain boundaries of the nanostructures. Additionally, the analysis of low field magnetoconductance data supports the second order tunneling and shows the close value of the universal limit (˜1.33).

  17. Neutron diffraction studies on ordered and disordered materials

    International Nuclear Information System (INIS)

    Krishna, P.S.R

    2016-01-01

    Knowledge of the symmetry and distribution of atoms in the unit cell and the bonding between atoms is the key point for understanding, designing and manipulating chemical behavior or physical properties of novel materials for technological applications. This could be achieved using diffraction techniques. At the Dhruva national facility, BARC, Mumbai, a Powder diffractometer (PD2) and a High-Q diffractometer (HQD) are in operation for more than 2 decades. PD2 and HQD are equipped with banks of 5 and 10 position sensitive detectors (PSD) respectively, to cover the Q-ranges 9.4 Å -1 and 15 Å -1 respectively. The resolutions (Δd/d) of these instruments are 0.8% (λ = 1.24 Å) and 2.5% (λ = 0.78 Å). We report about the studies of changes in the long range order in crystalline materials as a function of temperature and/or composition as well as short and intermediate range orders studied in amorphous materials on these diffractometers in recent years. PD2 has been extensively used in the structural/phase transition studies of ferroics, multiferroics, nanoferrites along with magnetic structure determinations. On the other hand, HQD has been extensively used to understand the short and intermediate range order in network glasses like chalcogenides, H-bonded alcohols, Telluride glasses etc. We will be discussing the recent structural results obtained on many of these crystalline systems, glasses and molecular fluids on both of these diffractometers. (author)

  18. Magnetic Fields at First Order Phase Transition: A Threat to Electroweak Baryogenesis

    CERN Document Server

    De Simone, Andrea; Quiros, Mariano; Riotto, Antonio

    2011-01-01

    The generation of the observed baryon asymmetry may have taken place during the electroweak phase transition, thus involving physics testable at LHC, a scenario dubbed electroweak baryogenesis. In this paper we point out that the magnetic field which is produced in the bubbles of a first order phase transition endangers the baryon asymmetry produced in the bubble walls. The reason being that the produced magnetic field couples to the sphaleron magnetic moment and lowers the sphaleron energy; this strengthens the sphaleron transitions inside the bubbles and triggers a more effective wash out of the baryon asymmetry. We apply this scenario to the Minimal Supersymmetric extension of the Standard Model (MSSM) where, in the absence of a magnetic field, successful electroweak baryogenesis requires the lightest CP-even Higgs and the right-handed stop masses to be lighter than about 127 GeV and 120 GeV, respectively. We show that even for moderate values of the magnetic field, the Higgs mass required to preserve the ...

  19. Non-Commutative Orders. A Preliminary Study

    International Nuclear Information System (INIS)

    Brzezinski, T.

    2011-01-01

    The first steps towards linearization of partial orders and equivalence relations are described. The definitions of partial orders and equivalence relations (on sets) are formulated in a way that is standard in category theory and that makes the linearization (almost) automatic. The linearization is then achieved by replacing sets by coalgebras and the Cartesian product by the tensor product of vector spaces. As a result, definitions of orders and equivalence relations on coalgebras are proposed. These are illustrated by explicit examples that include relations on coalgebras spanned by grouplike elements (or linearized sets), the diagonal relation, and an order on a three-dimensional non-cocommutative coalgebra. Although relations on coalgebras are defined for vector spaces, all the definitions are formulated in a way that is immediately applicable to other braided monoidal categories. (author)

  20. Fast magnetic energy dissipation in relativistic plasma induced by high order laser modes

    Czech Academy of Sciences Publication Activity Database

    Gu, Yanjun; Yu, Q.; Klimo, Ondřej; Esirkepov, T.Z.; Bulanov, S.V.; Weber, Stefan A.; Korn, Georg

    2016-01-01

    Roč. 4, Jun (2016), 1-5, č. článku e19. ISSN 2095-4719 R&D Projects: GA MŠk EF15_008/0000162 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : high order laser mode * laser–plasma interaction * magnetic annihilation Subject RIV: BL - Plasma and Gas Discharge Physics

  1. Fractional order nonlinear variable speed and current regulation of a permanent magnet synchronous generator wind turbine system

    Directory of Open Access Journals (Sweden)

    Anitha Karthikeyan

    2018-03-01

    Full Text Available In this paper we derived the fractional order model of the Permanent Magnet Synchronous Generator (PMSG from its integer model. The PMSG was employing a shaft sensor for the speed sensing and control. But this sensor would increase the hardware complexity as well as the cost of the system. Hence we have developed a Fractional order Nonlinear adaptive control method for speed and current tracking of the PMSG. The objective of an adaptive controller is to first define a virtual control state and force it to become a stabilizing function in accordance with a corresponding error dynamics. In order to study the Lyapunov exponents of the fractional order controller, we proposed a new method which would remove the complexity of finding the sign of the Lyapunov first derivative. The Fractional order control scheme is implemented in LabVIEW for simulation results. The simulation results indicated that the estimated rotor position and speed correspond to their actual values well. Keywords: Chaos suppression, Fractional order systems, Permanent magnet synchronous generator, Speed and current control, Lyapunov stability

  2. High performance electrical, magnetic, electromagnetic and electrooptical devices enabled by three dimensionally ordered nanodots and nanorods

    Science.gov (United States)

    Goyal, Amit , Kang; Sukill, [Knoxville, TN

    2012-02-21

    Novel articles and methods to fabricate same with self-assembled nanodots and/or nanorods of a single or multicomponent material within another single or multicomponent material for use in electrical, electronic, magnetic, electromagnetic and electrooptical devices is disclosed. Self-assembled nanodots and/or nanorods are ordered arrays wherein ordering occurs due to strain minimization during growth of the materials. A simple method to accomplish this when depositing in-situ films is also disclosed. Device applications of resulting materials are in areas of superconductivity, photovoltaics, ferroelectrics, magnetoresistance, high density storage, solid state lighting, non-volatile memory, photoluminescence, thermoelectrics and in quantum dot lasers.

  3. Application of matriciant method for calculation of the third order aberration coefficients for magnetic field with regard to boundary effects

    International Nuclear Information System (INIS)

    Mordik, S.N.; Ponomarev, A.G.

    2001-01-01

    To study nonlinear dynamics of charged particles in magnetic sector analyzers one applied the matriciant method. When calculating matriciants (transfer matrices) one took account of the boundary-value effects associated with the effect of scattering field, as well as, the higher harmonics of the sector magnetic field up to the third order inclusive. In case of the rectangular distribution of field components along the optical axis one obtained analytical expressions for all aberration coefficients up to the third order exclusive. To simulate the real field with the width of scattering field not equal to zero one applied smooth distribution of components for which calculation of similar aberration coefficients was conducted using the conservative numerical method [ru

  4. High-order Two-Fluid Plasma Solver for Direct Numerical Simulations of Magnetic Flows with Realistic Transport Phenomena

    Science.gov (United States)

    Li, Zhaorui; Livescu, Daniel

    2017-11-01

    The two-fluid plasma equations with full transport terms, including temperature and magnetic field dependent ion and electron viscous stresses and heat fluxes, frictional drag force, and ohmic heating term have been solved by using the sixth-order non-dissipative compact scheme for plasma flows in several different regimes. In order to be able to fully resolve all the dynamically relevant time and length scales while maintaining computational feasibility, the assumptions of infinite speed of light and negligible electron inertia have been made. The accuracy and robustness of this two-fluid plasma solver in handling plasma flows have been tested against a series of canonical problems, such as Alfven-Whistler dispersion relation, electromagnetic plasma shock, magnetic reconnection, etc. For all test cases, grid convergence tests have been conducted to achieve fully resolved results. The roles of heat flux, viscosity, resistivity, Hall and Biermann battery effects, are investigated for the canonical flows studied.

  5. Magnetic stripping studies for SPL

    CERN Document Server

    Posocco, P; CERN. Geneva. BE Department

    2010-01-01

    Magnetic stripping of H- can seriously enhance the beam losses along the SPL machine. These losses depend on the beam energy, on the beam transverse distribution and on the intensity of the magnetic field. For radioprotection issues the losses must be limited to 1 W/m. In this paper we will concentrate on the stripping phenomena inside the quadrupole magnets with the aim of defining the quadrupole range for the design phase of SPL.

  6. Magnetic structures: neutron diffraction studies

    International Nuclear Information System (INIS)

    Bouree-Vigneron, F.

    1990-01-01

    Neutron diffraction is often an unequivocal method for determining magnetic structures. Here we present some typical examples, stressing the sequence through experiments, data analysis, interpretation and modelisation. Two series of compounds are chosen: Tb Ni 2 Ge 2 and RBe 13 (R = Gd, Tb, Dy, Ho, Er). Depending on the nature of the elements, the magnetic structures produced can be commensurate, incommensurate or even show a transition between two such phases as a function of temperature. A model, taking magnetic exchange and anisotropy into account, will be presented in the case of commensurate-incommensurate magnetic transitions in RBe 13

  7. Group theory for magnetic structure determination: Recent developments and quadrupolar ordering analysis

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, W. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, al.Mickiewicza 30, 30-059 Cracow (Poland)]. E-mail: sikora@novell.ftj.agh.edu.pl; Pytlik, L. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, al.Mickiewicza 30, 30-059 Cracow (Poland); Bialas, F. [Nowy Sacz School of Busines-National Louis University, 33-300 Nowy Sacz (Poland); Malinowski, J. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, al.Mickiewicza 30, 30-059 Cracow (Poland)

    2007-09-13

    In this paper, the recent developments in practical applications of symmetry analysis are described. The theoretical basis shortly described in Section 1 has been implemented in several computer applications, one of which is the program 'MODY-win', developed by the authors of the paper. The program calculates the so-called basis vectors of irreducible representations of a given symmetry group, which can be used for calculation of possible ordering modes. Its practical application is demonstrated on some examples, presenting the recent aspects of using the symmetry analysis to description of various types of ordering encountered in solids. The scalar-type ordering (occupation probability) is discussed shortly for occupation of interstitial sites by hydrogen atoms in inter-metallic compounds. The description of vector ordering is demonstrated on the magnetic ordering modes, with special attention focused on the freedom that is left in the structure after imposing all the symmetry constraints. In practice, the final ordering mode usually contains some free parameters that cannot be determined from the symmetry itself. The last application presented in the paper is the description of quadrupolar ordering, recently found in some compounds of 4f (5f) elements. For the latter case, an additional advantage is demonstrated by calculation of possible displacements of neighboring atoms after the establishment of non-zero quadrupolar order parameter on the central atom.

  8. The Effect of Magnetic Field and Initial Stress on Fractional Order Generalized Thermoelastic Half-Space

    Directory of Open Access Journals (Sweden)

    Sunita Deswal

    2013-01-01

    Full Text Available The aim of this paper is to study magneto-thermoelastic interactions in an initially stressed isotropic homogeneous half-space in the context of fractional order theory of generalized thermoelasticity. State space formulation with the Laplace transform technique is used to obtain the general solution, and the resulting formulation is applied to the ramp type increase in thermal load and zero stress. Solutions of the problem in the physical domain are obtained by using a numerical method of the Laplace inverse transform based on the Fourier expansion technique, and the expressions for the displacement, temperature, and stress inside the half-space are obtained. Numerical computations are carried out for a particular material for illustrating the results. Results obtained for the field variables are displayed graphically. Some comparisons have been shown in figures to present the effect of fractional parameter, ramp parameter, magnetic field, and initial stress on the field variables. Some particular cases of special interest have been deduced from the present investigation.

  9. Study of marine magnetic field

    Digital Repository Service at National Institute of Oceanography (India)

    Bhattacharya, G.C.

    magnetized in the direction of the Earth’s magnetic field at that time. As seafloor spreading pulls the new oceanic crust apart, stripes of approximately the same size gets carried away from the ridge on each side. The basaltic oceanic crust formed...

  10. Anti-Invar properties and magnetic order in fcc Fe-Ni-C alloy

    International Nuclear Information System (INIS)

    Nadutov, V.M.; Kosintsev, S.G.; Svystunov, Ye.O.; Garamus, V.M.; Willumeit, R.; Eckerlebe, H.; Ericsson, T.; Annersten, H.

    2011-01-01

    Anti-Invar effect was revealed in the fcc Fe-25.3%Ni-0.73%C (wt%) alloy, which demonstrates high values of thermal expansion coefficient (TEC) (15-21)x10 -6 K -1 accompanied by almost temperature-insensitive behavior in temperature range of 122-525 K. Alloying with carbon considerably expanded the low temperature range of anti-Invar behavior in fcc Fe-Ni-based alloy. The Curie temperature of the alloy T C =195 K was determined on measurements of temperature dependences of magnetic susceptibility and saturation magnetization. The Moessbauer and small-angle neutron scattering (SANS) experiments on the fcc Fe-25.3%Ni-(0.73-0.78)%C alloys with the varying temperatures below and above the Curie point and in external magnetic field of 1.5-5 T were conducted. Low value of the Debye temperature Θ D =180 K was estimated using the temperature dependence of the integral intensity of Moessbauer spectra for specified temperature range. The inequality B eff =(0.7-0.9)B ext was obtained in external field Moessbauer measurement that points to antiferromagnetically coupled Fe atoms, which have a tendency to align their spins perpendicular to B ext . Nano length scale magnetic inhomogeneities nearby and far above T C were revealed, which assumed that it is caused by mixed antiferromagnetically and ferromagnetically coupled Fe atom spins. The anti-Invar behavior of Fe-Ni-C alloy is explained in terms of evolution of magnetic order with changing temperature resulting from thermally varied interspin interaction and decreasing stiffness of interatomic bond. - Highlights: → Anti-Invar effect was revealed in the fcc Fe-25.3%Ni-0.73%C (wt%) alloy. → Carbon expanded the temperature range of anti-Invar behavior in Fe-Ni-based alloy. → Moessbauer data point to mixed interspin interaction and low the Dedye temperature. → The SANS experiments reveal nano length scale magnetic inhomogeneities ≤6 nm. → Anti-Invar behavior of Fe-Ni-C alloy explained by thermally varied magnetic order.

  11. Magnetic ordering in Ho-doped Bi{sub 2}Te{sub 3} topological insulator

    Energy Technology Data Exchange (ETDEWEB)

    Figueroa, A.I.; Van der Laan, G.; Hesjedal, T. [Magnetic Spectroscopy Group, Diamond Light Source, Didcot (United Kingdom); Harrison, S.E. [Department of Physics, Clarendon Laboratory, University of Oxford (United Kingdom); Department of Electrical Engineering, Stanford University, Stanford, CA (United States); Collins-McIntyre, L.J. [Department of Physics, Clarendon Laboratory, University of Oxford (United Kingdom)

    2016-06-15

    We investigate the magnetic properties of Ho-doped Bi{sub 2}Te{sub 3} thin films grown by molecular beam epitaxy. Analysis of the polarized X-ray absorption spectra at the Ho M{sub 5} absorption edge gives an effective 4f magnetic moment which is ∝45% of the Hund's rule ground state value. X-ray magnetic circular dichroism (XMCD) shows no significant anisotropy, which suggests that the reduced spin moment is not due to the crystal field effects, but rather the presence of non-magnetic or antiferromagnetic Ho sites. Extrapolating the temperature dependence of the XMCD measured in total electron yield and fluorescence yield mode in a field of 7 T gives a Curie-Weiss temperature of and vartheta;{sub CW} ∼ -30 K, which suggests antiferromagnetic ordering, in contrast to the paramagnetic behavior observed with SQUID magnetometry. From the anomaly of the XMCD signal at low temperatures, a Neel temperature T{sub N} between 10 K and 25 K is estimated. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Precursor phenomena at the magnetic ordering of the cubic helimagnet FeGe

    Energy Technology Data Exchange (ETDEWEB)

    Baenitz, Michael; Schmidt, Marcus [MPI CPfS, Dresden (Germany); Wilhelm, Heribert [Diamond Light Source Ltd., Chilton (United Kingdom); Roessler, Ulrich K.; Bogdanov, Alexei N.; Leonov, Andrey A. [IFW Dresden (Germany)

    2011-07-01

    We report on detailed magnetic measurements on the cubic helimagnet FeGe in external magnetic fields parallel to the direction and temperatures in the vicinity of the onset of long-range magnetic order at T{sub c}{approx}278 K. Depending on the temperature and field, a helical state (Hmagnets, the A{sub 1} phase could indicate existence of a +{pi} Skyrmion lattice, however, the A{sub 2} phase seems related to helicoids propagating in directions perpendicular to the applied field. We suggest that the observation of this A{sub 2}-phase can be explained by hexagonal arrays of spiral domains consisting essentially of helicoids.

  13. Large magnetoelectric coupling in magnetically short-range ordered Bi₅Ti₃FeO₁₅ film.

    Science.gov (United States)

    Zhao, Hongyang; Kimura, Hideo; Cheng, Zhenxiang; Osada, Minoru; Wang, Jianli; Wang, Xiaolin; Dou, Shixue; Liu, Yan; Yu, Jianding; Matsumoto, Takao; Tohei, Tetsuya; Shibata, Naoya; Ikuhara, Yuichi

    2014-06-11

    Multiferroic materials, which offer the possibility of manipulating the magnetic state by an electric field or vice versa, are of great current interest. However, single-phase materials with such cross-coupling properties at room temperature exist rarely in nature; new design of nano-engineered thin films with a strong magneto-electric coupling is a fundamental challenge. Here we demonstrate a robust room-temperature magneto-electric coupling in a bismuth-layer-structured ferroelectric Bi₅Ti₃FeO₁₅ with high ferroelectric Curie temperature of ~1000 K. Bi₅Ti₃FeO₁₅ thin films grown by pulsed laser deposition are single-phase layered perovskit with nearly (00l)-orientation. Room-temperature multiferroic behavior is demonstrated by a large modulation in magneto-polarization and magneto-dielectric responses. Local structural characterizations by transmission electron microscopy and Mössbauer spectroscopy reveal the existence of Fe-rich nanodomains, which cause a short-range magnetic ordering at ~620 K. In Bi₅Ti₃FeO₁₅ with a stable ferroelectric order, the spin canting of magnetic-ion-based nanodomains via the Dzyaloshinskii-Moriya interaction might yield a robust magneto-electric coupling of ~400 mV/Oe·cm even at room temperature.

  14. Organization dependent collective magnetic properties of secondary nanostructures with differential spatial ordering and magnetic easy axis orientation

    Energy Technology Data Exchange (ETDEWEB)

    Saikia, K. [Department of Physics, Tezpur University (Central University), Tezpur 784028 (India); Sarma, D.D. [Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012 (India); Deb, P., E-mail: pdeb@tezu.ernet.in [Department of Physics, Tezpur University (Central University), Tezpur 784028 (India)

    2016-06-15

    Achieving control on the formation of different organization states of magnetic nanoparticles is crucial to harness their organization dependent physical properties in desired ways. In this study, three organization states of iron oxide nanoparticles (γ-Fe{sub 2}O{sub 3}), defining as (i) assembly (ii) network aggregate and (iii) cluster, have been developed by simply changing the solvent evaporation conditions. All three systems have retained the same phase and polydispersity of primary particles. Magnetic measurements show that the partial alignment of the easy axes of the particles in the network system due to the stacking aggregation morphology can result in significant enhancement of the coercivity and remanence values, while the opposite is obtained for the cluster system due to the random orientation of easy axes. Partial alignment in the aggregate system also results in noticeable non-monotonic field dependence of ZFC peak temperature (T{sub peak}). The lowest value of the blocking temperature (T{sub B}) for the cluster system is related to the lowering of the effective anisotropy due to the strongest demagnetizing effect. FC (Field cooled) memory effect was observed to be decreasing with the increasing strength of dipolar interaction of organization states. Therefore, the stacking aggregation and the cluster formation are two interesting ways of magnetic nanoparticles organization for modulating collective magnetic properties significantly, which can have renewed application potentials from recording devices to biomedicine. - Highlights: • Three organization states of magnetic nanoparticles were developed. • Aggregation enhances the H{sub c} and M{sub r}/M{sub s,} while spherical clustering shows opposite. • Organization morphology hardly effects on FC memory effect. • Developed secondary systems can have renewed application potentials in wide spectrum.

  15. Chaos Suppression in Fractional order Permanent Magnet Synchronous Generator in Wind Turbine Systems

    Science.gov (United States)

    Rajagopal, Karthikeyan; Karthikeyan, Anitha; Duraisamy, Prakash

    2017-06-01

    In this paper we investigate the control of three-dimensional non-autonomous fractional-order uncertain model of a permanent magnet synchronous generator (PMSG) via a adaptive control technique. We derive a dimensionless fractional order model of the PMSM from the integer order presented in the literatures. Various dynamic properties of the fractional order model like eigen values, Lyapunov exponents, bifurcation and bicoherence are investigated. The system chaotic behavior for various orders of fractional calculus are presented. An adaptive controller is derived to suppress the chaotic oscillations of the fractional order model. As the direct Lyapunov stability analysis of the robust controller is difficult for a fractional order first derivative, we have derived a new lemma to analyze the stability of the system. Numerical simulations of the proposed chaos suppression methodology are given to prove the analytical results derived through which we show that for the derived adaptive controller and the parameter update law, the origin of the system for any bounded initial conditions is asymptotically stable.

  16. Experimental validation of Villain's conjecture about magnetic ordering in quasi-1D helimagnets

    Energy Technology Data Exchange (ETDEWEB)

    Cinti, F., E-mail: fabio.cinti@fi.infn.i [CNISM and Department of Physics, University of Florence, 50019 Sesto Fiorentino (Italy); CNR-INFM S3 National Research Center, I-41100 Modena (Italy); Rettori, A. [CNISM and Department of Physics, University of Florence, 50019 Sesto Fiorentino (Italy); CNR-INFM S3 National Research Center, I-41100 Modena (Italy); Pini, M.G. [ISC-CNR, Via Madonna del Piano 10, I-50019 Sesto Fiorentino (Italy); Mariani, M.; Micotti, E. [Department of Physics A. Volta and CNR-INFM, University of Pavia, Via Bassi 6, I-27100 Pavia (Italy); Lascialfari, A. [Department of Physics A. Volta and CNR-INFM, University of Pavia, Via Bassi 6, I-27100 Pavia (Italy); Institute of General Physiology and Biological Chemistry, University of Milano, Via Trentacoste 2, I-20134 Milano (Italy); CNR-INFM S3 National Research Center, I-41100 Modena (Italy); Papinutto, N. [CIMeC, University of Trento, Via delle Regole, 101 38060 Mattarello (Italy); Department of Physics A. Volta and CNR-INFM, University of Pavia, Via Bassi 6, I-27100 Pavia (Italy); Amato, A. [Paul Scherrer Institute, CH-5232 Villingen PSI (Switzerland); Caneschi, A.; Gatteschi, D. [INSTM R.U. Firenze and Department of Chemistry, University of Florence, Via della Lastruccia 3, I-50019 Sesto Fiorentino (Italy); Affronte, M. [CNR-INFM S3 National Research Center, I-41100 Modena (Italy); Department of Physics, University of Modena and Reggio Emilia Via Campi 213/A, I-41100 Modena (Italy)

    2010-05-15

    Low-temperature magnetic susceptibility, zero-field muon spin resonance and specific heat measurements have been performed in the quasi-one-dimensional (1D) molecular helimagnetic compound Gd(hfac){sub 3}NITEt. The specific heat presents two anomalies at T{sub 0}=2.19(2)K and T{sub N}=1.88(2)K, while susceptibility and zero-field muon spin resonance show anomalies only at T{sub N}=1.88(2)K. The results suggest an experimental validation of Villain's conjecture of a two-step magnetic ordering in quasi-1D XY helimagnets: the paramagnetic phase and the helical spin solid phases are separated by a chiral spin liquid, where translational invariance is broken without violation of rotational invariance.

  17. Experimental validation of Villain's conjecture about magnetic ordering in quasi-1D helimagnets

    International Nuclear Information System (INIS)

    Cinti, F.; Rettori, A.; Pini, M.G.; Mariani, M.; Micotti, E.; Lascialfari, A.; Papinutto, N.; Amato, A.; Caneschi, A.; Gatteschi, D.; Affronte, M.

    2010-01-01

    Low-temperature magnetic susceptibility, zero-field muon spin resonance and specific heat measurements have been performed in the quasi-one-dimensional (1D) molecular helimagnetic compound Gd(hfac) 3 NITEt. The specific heat presents two anomalies at T 0 =2.19(2)K and T N =1.88(2)K, while susceptibility and zero-field muon spin resonance show anomalies only at T N =1.88(2)K. The results suggest an experimental validation of Villain's conjecture of a two-step magnetic ordering in quasi-1D XY helimagnets: the paramagnetic phase and the helical spin solid phases are separated by a chiral spin liquid, where translational invariance is broken without violation of rotational invariance.

  18. Magnetic nanoparticles studied by small angle X-ray scattering

    International Nuclear Information System (INIS)

    Oliveira, Cristiano Luis Pinto; Antonel, Soledad; Negri, Martin

    2011-01-01

    because they exhibit magnetic (ferromagnetic) and electrical properties in the same material. Then, the nickel nanoparticles could be used for the development of electroelastic materials. In this case, the electrical conductivity of the material can be strongly dependent on the applied magnetic field, for example the case of nickel metal nanoparticles dispersed in a polymer, resulting in an anisotropic material with combined piezomagnetic and piezoelectric properties. In order to investigate the structural characteristics of cobalt-iron oxides and nickel nanoparticles, powder samples of those magnetic materials were studied by Small-Angle X-Ray Scattering. As will be shown, from the analysis and modeling of the scattering data, structural information could be obtained, enabling a detailed description of the structural properties of the studied samples which could be directly correlated to the magnetic properties. (author)

  19. Magnetic nanoparticles studied by small angle X-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Cristiano Luis Pinto [Universidade de Sao Paulo (IF/USP), SP (Brazil). Inst. de Fisica. Grupo de Fluidos Complexos; Antonel, Soledad; Negri, Martin [Universidad de Buenos Aires (UBA) (Argentina). Facultad de Ciencias Exactas y Naturales. Dept. de Quimica Inorganica, Analitica y Quimica Fisica

    2011-07-01

    nanoparticles are very interesting because they exhibit magnetic (ferromagnetic) and electrical properties in the same material. Then, the nickel nanoparticles could be used for the development of electroelastic materials. In this case, the electrical conductivity of the material can be strongly dependent on the applied magnetic field, for example the case of nickel metal nanoparticles dispersed in a polymer, resulting in an anisotropic material with combined piezomagnetic and piezoelectric properties. In order to investigate the structural characteristics of cobalt-iron oxides and nickel nanoparticles, powder samples of those magnetic materials were studied by Small-Angle X-Ray Scattering. As will be shown, from the analysis and modeling of the scattering data, structural information could be obtained, enabling a detailed description of the structural properties of the studied samples which could be directly correlated to the magnetic properties. (author)

  20. A microspectroscopic study of the electronic homogeneity of ordered ...

    Indian Academy of Sciences (India)

    Unknown

    We investigate the origin of such diversity by performing spatially resolved photoemission spectroscopy on various ... tance (MR) property,1,2 as well as its unusual origin of magnetism.3 Fully ordered Sr2FeMoO6 is a half- ... tronic inhomogeneities. 2. Experimental details. Disordered SFMO was synthesized by mixing high.

  1. Magnetic ordering in tetragonal FeS: Evidence for strong itinerant spin fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, K.D.; Refson, K.; Bone, S.; Qiao, R.; Yang, W.; Liu, Z.; Sposito, G.

    2010-11-01

    Mackinawite is a naturally occurring layer-type FeS mineral important in biogeochemical cycles and, more recently, in the development of microbial fuel cells. Conflicting results have been published as to the magnetic properties of this mineral, with Moessbauer spectroscopy indicating no magnetic ordering down to 4.2 K but density functional theory (DFT) predicting an antiferromagnetic ground state, similar to the Fe-based high-temperature superconductors with which it is isostructural and for which it is known that magnetism is suppressed by strong itinerant spin fluctuations. We investigated this latter possibility for mackinawite using photoemission spectroscopy, near-edge x-ray absorption fine structure spectroscopy, and DFT computations. Our Fe 3{sub s} core-level photoemission spectrum of mackinawite showed a clear exchange-energy splitting (2.9 eV) consistent with a 1 {micro}{sub B} magnetic moment on the Fe ions, while the Fe L-edge x-ray absorption spectrum indicated rather delocalized Fe 3{sub d} electrons in mackinawite similar to those in Fe metal. Our DFT computations demonstrated that the ground state of mackinawite is single-stripe antiferromagnetic, with an Fe magnetic moment (2.7 {micro}{sub B}) that is significantly larger than the experimental estimate and has a strong dependence on the S height and lattice parameters. All of these trends signal the existence of strong itinerant spin fluctuations. If spin fluctuations prove to be mediators of electron pairing, we conjecture that mackinawite may be one of the simplest Fe-based superconductors.

  2. A Highly Ordered Magnetic Field in a Crushed Pulsar Wind Nebula in G327.1-1.1

    Science.gov (United States)

    Ma, Yik Ki; Ng, Chi-Yung; Bucciantini, Niccolò; Gaensler, Bryan M.; Slane, Patrick O.; Temim, Tea

    2015-01-01

    A significant fraction of a pulsar's spin-down luminosity is in the form of a relativistic magnetized particle outflow known as a pulsar wind. Confinement of the wind by the ambient medium creates a synchrotron-emitting bubble called a pulsar wind nebula (PWN). Studies of PWNe is important for understanding the physics of relativistic shocks and particle acceleration. Simulations suggest that a PWN will be crushed by the reverse shock of its surrounding supernova remnant at an age of ~10^4 yr, resulting in a turbulent environment. However, given the short timescale of the interaction stage, only a few such systems are observed.We present radio polarization observations of the PWN in supernova remnant G327.1-1.1, taken with the Australia Telescope Compact Array. Previous works suggest that this system has recently interacted with the supernova reverse shock, providing a rare example for the study of magnetic field in a crushed PWN. We found a highly ordered magnetic field in the PWN, which is unexpected given the presumed turbulent interior of the nebula. This suggests that the magnetic pressure in the PWN could play an important role in the interaction with supernova reverse shock.The Australia Telescope Compact Array is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.YKM and CYN are supported by a ECS grant of the Hong Kong Government under HKU 709713P

  3. In situ investigation of ordering phase transformations in FePt magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Wittig, James E., E-mail: j.wittig@vanderbilt.edu [Interdisciplinary Materials Science, Vanderbilt University, PMB 351683, 2301 Vanderbilt Place, Nashville, TN 37232 (United States); Bentley, James, E-mail: bentleyj48@gmail.com [Materials Science and Technology Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6376 (United States); Allard, Lawrence F., E-mail: allardlfjr@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831-6376 (United States)

    2017-05-15

    In situ high-resolution electron microscopy was used to reveal information at the atomic level for the disordered-to-ordered phase transformation of equiatomic FePt nanoparticles that can exhibit outstanding magnetic properties after transforming from disordered face-centered-cubic into the tetragonal L1{sub 0} ordered structure. High-angle annular dark-field imaging in the scanning transmission electron microscope provided sufficient contrast between the Fe and Pt atoms to readily monitor the ordering of the atoms during in situ heating experiments. However, during continuous high-magnification imaging the electron beam influenced the kinetics of the transformation so annealing had to be performed with the electron beam blanked. At 500 °C where the reaction rate was relatively slow, observation of the transformation mechanisms using this sequential imaging protocol revealed that ordering proceeded from (002) surface facets but was incomplete and multiple-domain particles were formed that contained anti-phase domain boundaries and anti-site defects. At 600 and 700 °C, the limitations of sequential imaging were revealed as a consequence of increased transformation kinetics. Annealing for only 5 min at 700 °C produced complete single-domain L1{sub 0} order; such single-domain particles were more spherical in shape with (002) facets. The in situ experiments also provided information concerning nanoparticle sintering, coalescence, and consolidation. Although there was resistance to complete sintering due to the crystallography of L1{sub 0} order, the driving force from the large surface-area-to-volume ratio resulted in considerable nanoparticle coalescence, which would render such FePt nanoparticles unsuitable for use as magnetic recording media. Comparison of the in situ data acquired using the protocol described above with parallel ex situ annealing experiments showed that identical behavior resulted in all cases. - Highlights: • HAADF STEM imaging reveals the

  4. Neutron scattering study of unstable magnetic long-range order in the random two-dimensional Ising antiferromagnets Rb/sub 2/Cosub(c)Mgsub(1-c)F/sub 4/

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, H; Suzuki, M [Ochanomizu Univ., Tokyo (Japan). Dept. of Physics; Hutchings, M T [UKAEA Atomic Energy Research Establishment, Harwell. Materials Physics Div.

    1979-01-01

    The spin correlation between two-dimensionally (2D) ordered antiferromagnetic layers in the random antiferromagnets Rb/sub 2/Cosub(c)Mgsub(1-c)F/sub 4/ depends strongly on the rate at which the sample is cooled through the Neel point Tsub(N) and decreases markedly with decreasing Co/sup 2 +/ ion concentration c. Preliminary data are presented which indicate that the order below sub(N) is metastable and relaxes to a fully correlated 3D ordered state on a finite, measurable, time-scale.

  5. Magnetic viscosity study in FePt/C granular films

    International Nuclear Information System (INIS)

    Huang, Y.; Butler, W.; Zhang, Y.; Hadjipanayis, G.C.; Weller, D.

    2004-01-01

    The magnetic viscosity of FePt/C granular thin films was studied in the temperature range from 2 to 300 K in order to examine the thermal stability of the nanoparticles. The magnetic viscosity coefficient (S max ) was found to decrease with temperature because of decreased thermal activation. At low temperatures, S max showed an almost linear dependence on temperature. However, S max does not extrapolate to zero but seems to have a finite value at cryogenic temperatures

  6. The influence of molecular order and microstructure on the R2* and the magnetic susceptibility tensor.

    Science.gov (United States)

    Wisnieff, Cynthia; Liu, Tian; Wang, Yi; Spincemaille, Pascal

    2016-06-01

    In this work, we demonstrate that in the presence of ordered sub-voxel structure such as tubular organization, biomaterials with molecular isotropy exhibits only apparent R2* anisotropy, while biomaterials with molecular anisotropy exhibit both apparent R2* and susceptibility anisotropy by means of susceptibility tensor imaging (STI). To this end, R2* and STI from gradient echo magnitude and phase data were examined in phantoms made from carbon fiber and Gadolinium (Gd) solutions with and without intrinsic molecular order and sub-voxel structure as well as in the in vivo brain. Confidence in the tensor reconstructions was evaluated with a wild bootstrap analysis. Carbon fiber showed both apparent anisotropy in R2* and anisotropy in STI, while the Gd filled capillary tubes only showed apparent anisotropy on R2*. Similarly, white matter showed anisotropic R2* and magnetic susceptibility with higher confidence, while the cerebral veins displayed only strong apparent R2* tensor anisotropy. Ordered sub-voxel tissue microstructure leads to apparent R2* anisotropy, which can be found in both white matter tracts and cerebral veins. However, additional molecular anisotropy is required for magnetic susceptibility anisotropy, which can be found in white matter tracts but not in cerebral veins. Copyright © 2016 Elsevier Inc. All rights reserved.

  7. Artificial dispersion via high-order homogenization: magnetoelectric coupling and magnetism from dielectric layers

    Science.gov (United States)

    Liu, Yan; Guenneau, Sébastien; Gralak, Boris

    2013-01-01

    We investigate a high-order homogenization (HOH) algorithm for periodic multi-layered stacks. The mathematical tool of choice is a transfer matrix method. Expressions for effective permeability, permittivity and magnetoelectric coupling are explored by frequency power expansions. On the physical side, this HOH uncovers a magnetoelectric coupling effect (odd-order approximation) and artificial magnetism (even-order approximation) in moderate contrast photonic crystals. Comparing the effective parameters' expressions of a stack with three layers against that of a stack with two layers, we note that the magnetoelectric coupling effect vanishes while the artificial magnetism can still be achieved in a centre-symmetric periodic structure. Furthermore, we numerically check the effective parameters through the dispersion law and transmission property of a stack with two dielectric layers against that of an effective bianisotropic medium: they are in good agreement throughout the low-frequency (acoustic) band until the first stop band, where the analyticity of the logarithm function of the transfer matrix () breaks down. PMID:24101891

  8. A drift-ordered short mean-free path description of a partially ionized magnetized plasma

    International Nuclear Information System (INIS)

    Simakov, Andrei N

    2009-01-01

    Neutral particles that are present at the edge of plasma magnetic confinement devices can play an important role in energy and momentum transport, and their effects should be accounted for. This work uses the drift ordering to derive a closed fluid description for a collisional, magnetized, partially ionized plasma. Charge-exchange, ionization and recombination processes are taken into account. It is assumed that electron distribution function is unaffected by atomic processes, so that electron-ion momentum and energy exchange are described by the usual expressions for a fully ionized plasma, and that neutral-neutral collisions are unimportant. The collisional fluid equations derived herein generalize the drift-ordered description of a fully ionized collisional plasma (Catto P J et al 2004 Phys. Plasmas 11 90), agree with the MHD-ordered description of a partially ionized plasma (Helander P et al 1994 Phys. Plasmas 1 3174) in the large-flow limit and can be used to describe both turbulent and collisional behavior of a partially ionized plasma.

  9. The interplay of long-range magnetic order and single-ion anisotropy in rare earth nickel germanides

    International Nuclear Information System (INIS)

    Islam, Z.

    1999-01-01

    This dissertation is concerned with the interplay of long-range order and anisotropy in the tetragonal RNi 2 Ge 2 (R = rare earth) family of compounds. Microscopic magnetic structures were studied using both neutron and x-ray resonant exchange scattering (XRES) techniques. The magnetic structures of Tb, Dy, Eu and Gd members have been determined using high-quality single-crystal samples. This work has correlated a strong Fermi surface nesting to the magnetic ordering in the RNi 2 Ge 2 compounds. Generalized susceptibility, χ 0 (q), calculations found nesting to be responsible for both incommensurate ordering wave vector in GdNi 2 Ge 2 , and the commensurate structure in EuNi 2 Ge 2 . A continuous transition from incommensurate to commensurate magnetic structures via band filling is predicted. The surprisingly higher T N in EuNi 2 Ge 2 than that in GdNi 2 Ge 2 is also explained. Next, all the metamagnetic phases in TbNi 2 Ge 2 with an applied field along the c axis have been characterized with neutron diffraction measurements. A mixed phase model for the first metamagnetic structure consisting of fully-saturated as well as reduced-moment Tb ions is presented. The moment reduction may be due to moment instability which is possible if the exchange is comparable to the low-lying CEF level splitting and the ground state is a singlet. In such a case, certain Tb sites may experience a local field below the critical value needed to reach saturation

  10. The interplay of long-range magnetic order and single-ion anisotropy in rare earth nickel germanides

    Energy Technology Data Exchange (ETDEWEB)

    Islam, Z.

    1999-05-10

    This dissertation is concerned with the interplay of long-range order and anisotropy in the tetragonal RNi{sub 2}Ge{sub 2} (R = rare earth) family of compounds. Microscopic magnetic structures were studied using both neutron and x-ray resonant exchange scattering (XRES) techniques. The magnetic structures of Tb, Dy, Eu and Gd members have been determined using high-quality single-crystal samples. This work has correlated a strong Fermi surface nesting to the magnetic ordering in the RNi{sub 2}Ge{sub 2} compounds. Generalized susceptibility, {chi}{sub 0}(q), calculations found nesting to be responsible for both incommensurate ordering wave vector in GdNi{sub 2}Ge{sub 2}, and the commensurate structure in EuNi{sub 2}Ge{sub 2}. A continuous transition from incommensurate to commensurate magnetic structures via band filling is predicted. The surprisingly higher T{sub N} in EuNi{sub 2}Ge{sub 2} than that in GdNi{sub 2}Ge{sub 2} is also explained. Next, all the metamagnetic phases in TbNi{sub 2}Ge{sub 2} with an applied field along the c axis have been characterized with neutron diffraction measurements. A mixed phase model for the first metamagnetic structure consisting of fully-saturated as well as reduced-moment Tb ions is presented. The moment reduction may be due to moment instability which is possible if the exchange is comparable to the low-lying CEF level splitting and the ground state is a singlet. In such a case, certain Tb sites may experience a local field below the critical value needed to reach saturation.

  11. Storage of magnetization as singlet order by optimal control designed pulses

    DEFF Research Database (Denmark)

    Laustsen, Christoffer; Bowen, Sean; Vinding, Mads Sloth

    2014-01-01

    The use of hyperpolarization to enhance the sensitivity of MRI has so far been limited by the decay of the polarization through T1 relaxation. Recently, methods have been proposed that extend the lifetime of the hyperpolarization by storing the spin order in slowly relaxing singlet states....... With this aim, optimal control theory was applied to create pulses that for near‐equivalent spins accomplish transfers in and out of the singlet state with maximum efficiency while ensuring robustness toward variations in the nuclear spin system Hamiltonian (chemical shift, J‐couplings, B1 and B magnetic field...

  12. Phonon-induced quadrupolar ordering of the magnetic superconductor TmNi2B2C

    DEFF Research Database (Denmark)

    Andersen, N.H.; Jensen, J.; Jensen, T.B.S.

    2006-01-01

    We present synchrotron x-ray diffraction studies revealing that the lattice of thulium borocarbide is distorted below T(Q)similar or equal to 13.5 K at zero field. T-Q increases and the amplitude of the displacements is drastically enhanced by a factor of 10 at 60 kOe when a magnetic field is app...

  13. Recursion method for the quasiparticle structure of a single vortex with induced magnetic order

    DEFF Research Database (Denmark)

    Udby, L.; Andersen, B.M.; Hedegård, P.

    2006-01-01

    . Furthermore, we study the low-energy quasiparticle structure when magnetic vortices operate as pinning centers for surrounding unidirectional spin density waves (stripes). We calculate the Fourier transformed LDOS and show how the energy dependence of relevant Fourier components can be used to determine...

  14. Magnetic resonance study of maghemite-based magnetic fluid

    International Nuclear Information System (INIS)

    Figueiredo, L.C.; Lacava, B.M.; Skeff Neto, K.; Pelegrini, F.; Morais, P.C.

    2008-01-01

    This study reports on the magnetic resonance (MR) data (X-band experiment) of 10.2 nm average diameter maghemite nanoparticle in the temperature range of 100-230 K. Maghemite nanoparticles were suspended as low-pH ionic magnetic fluid containing 2.3x10 17 particles/cm 3 . The temperature dependence of both resonance linewidth and resonance field of the zero-field-cooled sample as well as the resonance field of the field-cooled sample (angular variation experiment) was analyzed using well-established methodology. Information regarding particle size, particle clusterization and surface magnetic anisotropy were obtained from the analysis of the MR data. The number of magnetic sites per particle from the MR data is in excellent agreement with the number provided by the transmission electron microscopy (TEM) data. The demagnetizing field value obtained from the MR data indicates cluster of particles containing on average 1.42 particles. The MR angular variation data suggest that magnetoelastic effect accounts for the non-linearity observed for the surface component of the magnetic anisotropy

  15. Interplanetary sources of magnetic storms: A statistical study

    DEFF Research Database (Denmark)

    Vennerstrøm, Susanne

    2001-01-01

    Magnetic storms are mainly caused by the occurrence of intense southward magnetic fields in the interplanetary medium. These fields can be formed directly either by ejection of magnetic structures from the Sun or by stream interaction processes during solar wind propagation. In the present study we...... examine 30 years of satellite measurement of the solar wind during magnetic storms, with the aim of estimating the relative importance of these two processes. We use the solar wind proton temperature relative to the temperature expected from the empirical relation to the solar wind speed T......-p/T-exp, together with the speed gradient, and the interplanetary magnetic field azimuth in the ecliptic, in order to distinguish between the two processes statistically. We find that compression due to stream interaction is at least as important as the direct effect of ejection of intense fields, and probably more...

  16. Interplanetary sources to magnetic storms - A statistical study

    DEFF Research Database (Denmark)

    Vennerstrøm, Susanne

    2001-01-01

    Magnetic storms are mainly caused by the occurrence of intense southward magnetic fields in the interplanetary medium. These fields can be formed directly either by ejection of magnetic structures from the Sun or by stream interaction processes during solar wind propagation. In the present study we...... examine 30 years of satellite measurement of the solar wind during magnetic storms, with the aim of estimating the relative importance of these two processes. We use the solar wind proton temperature relative to the temperature expected from the empirical relation to the solar wind speed Tp/Texp, together...... with the speed gradient, and the interplanetary magnetic field azimuth in the ecliptic, in order to distinguish between the two processes statistically. We find that compression due to stream interaction is at least as important as the direct effect of ejection of intense fields, and probably more so. Only...

  17. Dosimetry, instrumentation and exposure chambers for dc magnetic field studies

    International Nuclear Information System (INIS)

    Tenforde, T.S.

    1979-03-01

    The principal objective of this report is to describe in detail an exposure chamber that was developed at the Lawrence Berkeley Laboratory for automated, noninvasive studies of rodent physiology during exposure to high DC magnetic fields. A second objective is to discuss some of the unique instrumentation problems that must be overcome in order to record bioelectric signals from laboratory animals in the presence of a magnetic field. Finally, a description will be given of the various dosimetry techniques that can be employed for quantitation of magnetic field strength

  18. Linear chains of magnetic ions stacked with variable distance: ferromagnetic ordering with a Curie temperature above 20 K

    Energy Technology Data Exchange (ETDEWEB)

    Friedlaender, Stefan; Poeppl, Andreas [Abteilung Magnetische Resonanz komplexer Quantenfestkoerper, Fakultaet fuer Physik und Geowissenschaften, Universitaet Leipzig (Germany); Liu, Jinxuan [Institute of Artificial Photosynthesis, State Key Laboratory of Fine Chemicals, Dalian University of Technology (China); Addicoat, Matt; Petkov, Petko; Vankova, Nina; Rueger, Robert; Kuc, Agnieszka [Wilhelm-Ostwald-Institut fuer Physikalische und Theoretische Chemie, Leipzig (Germany); Guo, Wei; Zhou, Wencai; Wang, Zhengbang; Weidler, Peter G.; Woell, Christof [Institut fuer Funktionelle Grenzflaechen, Karlsruher Institut fuer Technologie, Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen (Germany); Lukose, Binit [Engineering and Science, Department of Physics and Earth Science, Jacobs University Bremen (Germany); Ziese, Michael [Abteilung Supraleitung und Magnetismus, Fakultaet fuer Physik und Geowissenschaften, Universitaet Leipzig (Germany); Heine, Thomas [Engineering and Science, Department of Physics and Earth Science, Jacobs University Bremen (Germany); Wilhelm-Ostwald-Institut fuer Physikalische und Theoretische Chemie, Leipzig (Germany)

    2016-10-04

    We have studied the magnetic properties of the SURMOF-2 series of metal-organic frameworks (MOFs). Contrary to bulk MOF-2 crystals, where Cu{sup 2+} ions form paddlewheels and are antiferromagnetically coupled, in this case the Cu{sup 2+} ions are connected via carboxylate groups in a zipper-like fashion. This unusual coupling of the spin {sup 1}/{sub 2} ions within the resulting one-dimensional chains is found to stabilize a low-temperature, ferromagnetic (FM) phase. In contrast to other ordered 1D systems, no strong magnetic fields are needed to induce the ferromagnetism. The magnetic coupling constants describing the interaction between the individual metal ions have been determined in SQUID experiments. They are fully consistent with the results of ab initio DFT electronic structure calculations. The theoretical results allow the unusual magnetic behavior of this exotic, yet easy-to-fabricate, material to be described in a detailed fashion. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. 50 MeV, Li"3"+ - ion irradiation effect on magnetic ordering of Y"3"+ - substituted yttrium iron garnet

    International Nuclear Information System (INIS)

    Sharma, P. U.; Zankat, K. B.; Dolia, S. N.; Modi, K. B.

    2016-01-01

    This communication presents the effect of non-magnetic Y"3"+ ions substitution for magnetic Fe"3"+ ions and 50 MeV, Li"3"+ ion irradiation (fluence: 5 × 10"1"3 ions/cm"2) on magnetic ordering and Neel temperature of Y_3_+_xFe_5_-_xO_1_2 (x = 0.0, 0.2, 0.4 and 0.6) garnet system, studied by means of X-ray powder diffractometry and thermal variation of low field (0.5 Oe) ac susceptibility measurements. The un-irradiated compositions exhibit normal ferrimagnetic behavior with decrease in transition temperature (T_N) on increasing Y"3"+-concentration (x). The irradiated counterparts are characterized by tailing effect indicative of non-uniform effect of irradiation and lower value of T_N. The results have been discussed based on the weakening of magnetic exchange interactions and cumulative effect of redistribution of cations and fractional creation of localized paramagnetic centers resulting from swift heavy ion irradiation. The Neel temperatures and exchange integrals have been calculated theoretically.

  20. Transition from order to chaos, and density limit, in magnetized plasmas.

    Science.gov (United States)

    Carati, A; Zuin, M; Maiocchi, A; Marino, M; Martines, E; Galgani, L

    2012-09-01

    It is known that a plasma in a magnetic field, conceived microscopically as a system of point charges, can exist in a magnetized state, and thus remain confined, inasmuch as it is in an ordered state of motion, with the charged particles performing gyrational motions transverse to the field. Here, we give an estimate of a threshold, beyond which transverse motions become chaotic, the electrons being unable to perform even one gyration, so that a breakdown should occur, with complete loss of confinement. The estimate is obtained by the methods of perturbation theory, taking as perturbing force acting on each electron that due to the so-called microfield, i.e., the electric field produced by all the other charges. We first obtain a general relation for the threshold, which involves the fluctuations of the microfield. Then, taking for such fluctuations, the formula given by Iglesias, Lebowitz, and MacGowan for the model of a one component plasma with neutralizing background, we obtain a definite formula for the threshold, which corresponds to a density limit increasing as the square of the imposed magnetic field. Such a theoretical density limit is found to fit pretty well the empirical data for collapses of fusion machines.

  1. Interplay between magnetic order at Mn and Tm sites alongside the structural distortion in multiferroic films of o -TmMn O3

    Science.gov (United States)

    Windsor, Y. W.; Ramakrishnan, M.; Rettig, L.; Alberca, A.; Bothschafter, E. M.; Staub, U.; Shimamoto, K.; Hu, Y.; Lippert, T.; Schneider, C. W.

    2015-06-01

    We employ resonant soft x-ray diffraction to individually study the magnetic ordering of the Mn and the Tm sublattices in single-crystalline films of orthorhombic (o -) TmMn O3 . The same magnetic ordering wave vector of (0 q 0 ) with q ≈0.46 is found for both ionic species, suggesting that the familiar antiferromagnetic order of the Mn ions induces a magnetic order on the Tm unpaired 4 f electrons. Indeed, intensity variations of magnetic reflections with temperature corroborate this scenario. Calculated magnetic fields at the Tm sites are used as a model magnetic structure for the Tm, which correctly predicts intensity variations at the Tm resonance upon azimuthal rotation of the sample. The model allows ruling out a b c -cycloid modulation of the Mn ions as the cause for the incommensurate ordering, as found in TbMn O3 . The structural distortion, which occurs in the ferroelectric phase below TC, was followed through nonresonant diffraction of structural reflections forbidden by the high-temperature crystal symmetry. The (0 q 0 ) magnetic reflection appears at the Mn resonance well above TC, indicating that this reflection is sensitive also to the intermediate sinusoidal magnetic phase. The model presented suggests that the Tm 4 f electrons are polarized well above the ferroelectric transition and are possibly not affected by the transition at TC. The successful description of the induced order observed at the Tm resonance is a promising example for future element-selective studies in which "spectator" ions may allow access to previously unobtainable information about other constituent ions.

  2. MFM study of magnetic interaction between recording and soft magnetic layers

    International Nuclear Information System (INIS)

    Honda, Yukio; Tanahashi, Kiwamu; Hirayama, Yoshiyuki; Kikukawa, Atsushi; Futamoto, Masaaki

    2001-01-01

    Magnetic force microscopy was used to study the magnetic interaction between the recording and the soft magnetic layers in double-layer perpendicular media by observing the magnetization structure from the soft magnetic layer side. There was a strong magnetic interaction between the recording and the soft magnetic layers. Introducing a thin nonmagnetic intermediate layer between the two layers greatly reduced the magnetic interaction and drastically reduced the medium noise

  3. Structural order and magnetism of rare-earth metallic amorphous alloys

    International Nuclear Information System (INIS)

    Maurer, M.

    1984-01-01

    Local symmetry (as evaluated from the electric field gradient tensor) and radial distribution functions (obtained by EXAFS measurement) are determined in a series of amorphous rare-earth base alloys. Local order is found to increase with the extent of heteroatomic interactions. Various magnetic phases (including ferromagnetic, spin-glass, reentrant spin-glass) occur for europium alloys with simple metals (Mg, Zn, Cd, Al, Au, ...). This variety reflects the sensitivity of exchange interactions to the presence of non-s conduction electrons. Asperomagnetic structures are established for the Dy alloys. The crystalline electric field interactions at the Dy 3+ ions are interpreted with the help of local symmetry data. Quadratic axial and non-axial crystal field terms are sufficient and necessary in order to account for the hyperfine and bulk experimental results [fr

  4. Four-flavour leading-order hadronic contribution to the muon anomalous magnetic moment

    Energy Technology Data Exchange (ETDEWEB)

    Burger, Florian [Humboldt-Universität zu Berlin, Institut für Physik,Newtonstr. 15, D-12489 Berlin (Germany); Feng, Xu [High Energy Accelerator Research Organization (KEK),Tsukuba 305-0801 (Japan); Hotzel, Grit [Humboldt-Universität zu Berlin, Institut für Physik,Newtonstr. 15, D-12489 Berlin (Germany); Jansen, Karl [NIC, DESY,Platanenallee 6, D-15738 Zeuthen (Germany); Department of Physics, University of Cyprus,P.O.Box 20537, 1678 Nicosia (Cyprus); Petschlies, Marcus [The Cyprus Institute,P.O.Box 27456, 1645 Nicosia (Cyprus); Renner, Dru B. [Jefferson Lab,12000 Jefferson Avenue, Newport News, VA 23606 (United States); Collaboration: The ETM Collaboration

    2014-02-24

    We present a four-flavour lattice calculation of the leading-order hadronic vacuum polarisation contribution to the anomalous magnetic moment of the muon, a{sub μ}{sup hvp}, arising from quark-connected Feynman graphs. It is based on ensembles featuring N{sub f}=2+1+1 dynamical twisted mass fermions generated by the European Twisted Mass Collaboration (ETMC). Several light quark masses are used in order to yield a controlled extrapolation to the physical pion mass. We employ three lattice spacings to examine lattice artefacts and several different volumes to check for finite-size effects. Incorporating the complete first two generations of quarks allows for a direct comparison with phenomenological determinations of a{sub μ}{sup hvp}. Our final result including an estimate of the systematic uncertainty a{sub μ}{sup hvp}=6.74(21)(18)⋅10{sup −8} shows a good overall agreement with these computations.

  5. Four-flavour leading-order hadronic contribution to the muon anomalous magnetic moment

    International Nuclear Information System (INIS)

    Burger, Florian; Feng, Xu; Hotzel, Grit; Jansen, Karl; Petschlies, Marcus; Renner, Dru B.

    2014-01-01

    We present a four-flavour lattice calculation of the leading-order hadronic vacuum polarisation contribution to the anomalous magnetic moment of the muon, a μ hvp , arising from quark-connected Feynman graphs. It is based on ensembles featuring N f =2+1+1 dynamical twisted mass fermions generated by the European Twisted Mass Collaboration (ETMC). Several light quark masses are used in order to yield a controlled extrapolation to the physical pion mass. We employ three lattice spacings to examine lattice artefacts and several different volumes to check for finite-size effects. Incorporating the complete first two generations of quarks allows for a direct comparison with phenomenological determinations of a μ hvp . Our final result including an estimate of the systematic uncertainty a μ hvp =6.74(21)(18)⋅10 −8 shows a good overall agreement with these computations

  6. Relationship between Magnetic Anisotropy below Pseudogap Temperature and Short-Range Antiferromagnetic Order in High-Temperature Cuprate Superconductor

    Science.gov (United States)

    Morinari, Takao

    2018-06-01

    The central issue in high-temperature cuprate superconductors is the pseudogap state appearing below the pseudogap temperature T*, which is well above the superconducting transition temperature. In this study, we theoretically investigate the rapid increase of the magnetic anisotropy below the pseudogap temperature detected by the recent torque-magnetometry measurements on YBa2Cu3Oy [Y. Sato et al., 10.1038/nphys4205" xlink:type="simple">Nat. Phys. 13, 1074 (2017)]. Applying the spin Green's function formalism including the Dzyaloshinskii-Moriya interaction arising from the buckling of the CuO2 plane, we obtain results that are in good agreement with the experiment and find a scaling relationship. Our analysis suggests that the characteristic temperature associated with the magnetic anisotropy, which coincides with T*, is not a phase transition temperature but a crossover temperature associated with the short-range antiferromagnetic order.

  7. The influence of band Jahn-Teller effect and magnetic order on the magneto-resistance in manganite systems

    Energy Technology Data Exchange (ETDEWEB)

    Rout, G.C., E-mail: gcr@iopb.res.i [Condensed Matter Physics Group, Department of Applied Physics and Ballistics, F.M. University, Balasore, Orissa 756019 (India); Parhi, Nilima [Department of Physics, M.P.C. (Autonomous) College, Baripada, Orissa 757001 (India); Behera, S.N. [Institute of Material Science, Bhubaneswar 751004 (India)

    2009-08-01

    A model calculation is presented in order to study the magneto-resistivity through the interplay between magnetic and structural transitions for the manganite systems. The model consists of an orbitally doubly degenerate conduction band and a periodic array of local moments of the t{sub 2g} electrons. The band electrons interact with the local t{sub 2g} electrons via the s-f hybridization. The phonons interact with the band electrons through static and dynamic band Jahn-Teller (J-T) interaction. The model Hamiltonian including the above terms is solved for the single particle Green's functions and the imaginary part of the self-energy gives the electron relaxation time. Thus the magneto-resistivity (MR) is calculated from the Drude formula. The MR effect is explained near the magnetic and structural transition temperatures.

  8. Magnetic properties and microstructure of low ordering temperature L10 FePt thin films

    International Nuclear Information System (INIS)

    Sun, A.C.; Kuo, P.C.; Chen, S.C.; Chou, C.Y.; Huang, H.L.; Hsu, J.H.

    2004-01-01

    Polycrystalline Fe 52 Pt 48 alloy thin films were prepared by dc magnetron sputtering on preheated natural-oxidized silicon wafer substrates. The film thickness was varied from 10 to 100 nm. The as-deposited film was encapsulated in a quartz tube and postannealed in vacuum at various temperatures for 1 h, then furnace cooled. It is found that the ordering temperature from as-deposited soft magnetic fcc FePt phase to hard magnetic fct L1 0 FePt phase could be reduced to about 350 deg. C by preheating substrate and furnace cooling treatment. The magnetic properties measurements indicated that the in-plane coercivity of the films was increased rapidly as annealing temperature is increased from 300 to 400 deg. C, but it decreased when the annealing temperature is higher than 400 deg. C. X-ray diffraction analysis shown that the as-deposited FePt thin film was a disorder fcc FePt phase. The magnetic measurement indicated that the transformation of disorder fcc FePt to fct L1 0 FePt phase was started at about 350 deg. C, which is consistent with the analysis of x-ray diffraction patterns. From scanning electron microscopy observation and selected area energy disperse spectrum analysis, the distributions of Fe and Pt elements in the films became nonuniform when the annealing temperature was higher than 500 deg. C due to the formation of the Fe 3 Pt phase. After annealing at 400 deg. C, the in plane coercivity of Fe 52 Pt 48 thin film with film thickness of 100 nm is 10 kOe, M s is 580 emu/cm3, and grain size is about 12 nm

  9. Chemical short range order and magnetic correction in liquid manganese–gallium zero alloy

    Energy Technology Data Exchange (ETDEWEB)

    Grosdidier, B. [Laboratoire de Chimie Physique – Approche Multi-Echelle des Milieux Complexes, Institut Jean Bariol, Université de Lorraine, Institut de Chimie, Physique et Matériaux, 1 Bd Arago, 57078 Metz Cedex 3 (France); Ben Abdellah, A. [Laboratoire de Chimie Physique – Approche Multi-Echelle des Milieux Complexes, Institut Jean Bariol, Université de Lorraine, Institut de Chimie, Physique et Matériaux, 1 Bd Arago, 57078 Metz Cedex 3 (France); Innovation and Management of Industrial Systems, Abdelmalek Essaadi University, College of Sciences and Techniques of Tangier , P.O. Box 416, Postal code 90000, Tangier (Morocco); Université Internationale de Rabat, Parc Technopolis Rabat-Shore, 11100 Sala El Jadida (Morocco); Osman, S.M., E-mail: osm@squ.edu.om [Physics Department, College of Science, Sultan Qaboos University, P.O. Box 36, Postal Code 123, Al-Khod, Muscat (Oman); Ataati, J. [Innovation and Management of Industrial Systems, Abdelmalek Essaadi University, College of Sciences and Techniques of Tangier, P.O. Box 416, Postal code 90000, Tangier (Morocco); Gasser, J.G. [Laboratoire de Chimie Physique – Approche Multi-Echelle des Milieux Complexes, Institut Jean Bariol, Université de Lorraine, Institut de Chimie, Physique et Matériaux, 1 Bd Arago, 57078 Metz Cedex 3 (France)

    2015-12-15

    The Mn{sub 66}Ga{sub 34} alloy at this particular composition is known to be zero alloy in which the linear combination of the two neutron scattering lengths weighted by the atomic compositions vanish. Thus for this specific concentration, the effect of the partial structure factors S{sub NN} and S{sub NC} is cancelled by a weighted term, which value is zero. Then the measured total structure factor S(q) gives directly the concentration–concentration structure factor S{sub CC}(q). We present here the first experimental results of neutron diffraction on the Mn{sub 66}Ga{sub 34} “null matrix alloy” at 1050 °C. The main peak of the experimental S{sub CC}(q) gives a strong evidence of a hetero-atomic chemical order in this coordinated alloy. This order also appears in real space radial distribution function which is calculated by the Fourier transform of the structure factor. The degree of hetero-coordination is discussed together with other manganese-polyvalent alloys. However manganese also shows abnormal magnetic scattering in the alloy structure factor which must be corrected. This correction gives an experimental information on the mean effective spin of manganese in this liquid alloy. We present the first critical theoretical calculations of the magnetic correction factor in Mn–Ga zero-alloy based on our accurate experimental measurements of S{sub CC}(q).

  10. Fractional Order PID Control of Rotor Suspension by Active Magnetic Bearings

    Directory of Open Access Journals (Sweden)

    Parinya Anantachaisilp

    2017-01-01

    Full Text Available One of the key issues in control design for Active Magnetic Bearing (AMB systems is the tradeoff between the simplicity of the controller structure and the performance of the closed-loop system. To achieve this tradeoff, this paper proposes the design of a fractional order Proportional-Integral-Derivative (FOPID controller. The FOPID controller consists of only two additional parameters in comparison with a conventional PID controller. The feasibility of FOPID for AMB systems is investigated for rotor suspension in both the radial and axial directions. Tuning methods are developed based on the evolutionary algorithms for searching the optimal values of the controller parameters. The resulting FOPID controllers are then tested and compared with a conventional PID controller, as well as with some advanced controllers such as Linear Quadratic Gausian (LQG and H ∞ controllers. The comparison is made in terms of various stability and robustness specifications, as well as the dimensions of the controllers as implemented. Lastly, to validate the proposed method, experimental testing is carried out on a single-stage centrifugal compressor test rig equipped with magnetic bearings. The results show that, with a proper selection of gains and fractional orders, the performance of the resulting FOPID is similar to those of the advanced controllers.

  11. Complex Magnetic Systems Studied with Neutron Scattering

    DEFF Research Database (Denmark)

    Jacobsen, Henrik

    by experimental nonidealities, and must therefore be real. It was therefore concluded that the dynamic stripes are not the Goldstone modes associated with the broken symmetry of the static stripes. In other words, the dynamic and static signals originate in two dierent phases of the sample. This has wide......, resting on loops of 10 spins. This hidden order is quite unusual, as only groups of spins order, while individual spins remain correlated only over short distances. The hidden order has been shown to also be present in GAG, although the magnitude of the order parameter is smaller here. The magnetic...

  12. Nature of the magnetic order in the charge-ordered cuprate La1.48Nd0.4Sr0.12CuO4

    DEFF Research Database (Denmark)

    Christensen, Niels Bech; Rønnow, H.M.; Mesot, J.

    2007-01-01

    Using polarized neutron scattering we establish that the magnetic order in La1.48Nd0.4Sr0.12CuO4 is either (i) one dimensionally modulated and collinear, consistent with the stripe model or (ii) two dimensionally modulated with a novel noncollinear structure. The measurements rule out a number...... of alternative models characterized by 2D electronic order or 1D helical spin order. The low-energy spin excitations are found to be primarily transversely polarized relative to the stripe ordered state, consistent with conventional spin waves....

  13. Room temperature magnetic ordering, enhanced magnetization and exchange bias of GdMnO_3 nanoparticles in (GdMnO_3)_0_._7_0(CoFe_2O_4)_0_._3_0

    International Nuclear Information System (INIS)

    Mitra, A.; Mahapatra, A.S.; Mallick, A.; Chakrabarti, P.K.

    2017-01-01

    Nanoparticles of GdMnO_3 (GMO) are prepared by sol-gel method. To enhance the magnetic property and also to obtain the magnetic ordering at room temperature (RT), nanoparticles of GMO are incorporated in the matrix of CoFe_2O_4 (CFO). Desired crystallographic phases of CFO, GMO and GMO-CFO are confirmed by analyzing X-ray diffractrograms (XRD) using Rietveld method. The average size of nanoparticles and their distribution, crystallographic phase, nanocrystallinity etc. are studied by high-resolution transmission electron microscope (HRTEM). Magnetic hysteresis loops (M-H) of GMO-CFO under zero field cooled (ZFC) and field cooled (FC) conditions are observed at different temperatures down to 5 K. Magnetization vs. temperature (M-T) under ZFC and FC conditions are also recorded. Interestingly, exchange bias (EB) is found at low temperature which suggests the encapsulation of the ferromagnetic (FM) nanoparticles of GMO by the ferrimagnetic nanoparticles of CFO below ~100 K. Enhanced magnetization, EB effect and RT magnetic ordering of GMO-CFO would be interesting for both theoretical and experimental investigations. - Highlights: • Nanoparticles of GdMnO_3 are incorporated in the matrix of CoFe_2O_4. • RT magnetic ordering of GMO nanoparticles in GMO-CFO is observed. • Magnetic property of GMO-CFO is highly enhanced compared to GMO. • Exchange bias is found in GMO-CFO at low temperature.

  14. Studies in perpendicular magnetic recording

    Science.gov (United States)

    Valcu, Bogdan F.

    This dissertation uses both micromagnetic simulation and analytical methods to analyze several aspects of a perpendicular recording system. To increase the head field amplitude, the recording layer is grown on top of a soft magnetic layer (keeper). There is concern about the ability of the keeper to conduct the magnetic flux from the head at high data rates. We compute numerically the magnetization motion of the soft underlayer during the reversal process. Generation of non-linear spin waves characterizes the magnetization dynamics in the keeper, the spins are oscillating with a frequency higher than that of the reversal current. However, the recording field applied to the data layer follows the time dependence of the input wave form. The written transition shape is determined by the competition between the head field gradient and the demagnetizing field gradient. An analytical slope model that takes into consideration the angular orientation of the applied field is used to estimate the transition parameter; agreement is shown with the micromagnetic results. On the playback side, the reciprocity principle is applied to calculate the read out signal from a single magnetic transition in the perpendicular medium. The pulse shape is close to an error-function, going through zero when the sensor is above the transition center and decaying from the peak to an asymptotic value when the transition center is far away. Analytical closed forms for both the slope in the origin and the asymptotic value show the dependence on the recording geometry parameters. The Signal-to-Noise Ratio is calculated assuming that the noise is dominated by the medium jitter. To keep the SNR at a readable level while increasing the areal density, the average magnetic grain diameter must decrease; consequently grain size fluctuations will affect the thermal decay. We performed Transmission Electron Microscopy measurements and observed differences in the grain size distribution between various types

  15. Field dependence of magnetic order and excitations in the Kitaev candidate alpha-RuCl3

    Science.gov (United States)

    Banerjee, Arnab; Kelley, Paula; Winn, Barry; Aczel, Adam; Lumsden, Mark; Mandrus, David; Nagler, Stephen

    The search for new quantum states of matter has been one of the forefront endeavors of condensed matter physics. The two-dimensional Kitaev quantum spin liquid (QSL) is of special interest as an exactly solvable spin-liquid model exhibiting exotic fractionalized excitations. Recently, alpha-RuCl3 has been identified as a candidate system for exhibiting some aspects of Kitaev QSL physics. The spins in this material exhibit zig-zag order at low temperatures, and show both low energy spin wave excitation arising from the ordered state as well as a continuum excitation extending to higher energies that has been taken as evidence for QSL relate Majorana fermions. In this talk, we show that the application of an in-plane magnetic field suppresses the zig-zag order possibly resulting in a state devoid of long-range order. Field-dependent inelastic neutron scattering on single-crystal shows a remarkable effect on the excitation spectrum above the critical field. The work is supported by US-DOE, Office of Science, Basic Energy Sciences and User Facilities Divisions, and also the Gordon and Betty Moore Foundation EPiQS Grant GBFM4416.

  16. Neutron diffraction studies of magnetic materials

    International Nuclear Information System (INIS)

    James, W.J.

    1987-01-01

    The ability of neutron diffraction in determining the nature and extent of magnetic ordering is illustrated for the intermetallic compounds, Y/sub 6/(Fe,Mn)/sub 23/ and ErFe/sub 3/. Substitution with other 3d transition metals influences the Fe-Fe exchange forces such as to alter, sometimes considerably, the magnetic properties, e.g., local site magnetic anisotropies in Er)Fe,Ni)/sub 3/ and thermal expansion anomalies in the R/sub 2/)Fe,Co)/sub 14/B compounds. When the 3d atoms are near neighbors in the periodic chart, their nuclear scattering lengths for neutrons are sufficiently different to permit the detection of preferential occupation of the several nonequivalent crystallographic 3d metal sites, i.e., atomic ordering, present in the R/sub 6/M/sub 23/, and R/sub 2/Fe/sub 14/B structures

  17. Study of a magnetically oriented lyotropic mesophase

    International Nuclear Information System (INIS)

    Amaral, L.Q.; Pimentel, C.A.; Tavares, M.R.; Vanin, J.A.

    A study of a magnetically oriented lyomesophase formed by a quaternary system (Na decyl sulfate/water/decanol/ Na sulfate) is reported. Small angle X-ray diffraction measurements have been performed on unoriented samples and samples previously subjected to the action of magnetic fields (H vector). A model of finite planar micelles surrounded by water is proposed [pt

  18. The superexchange interactions and magnetic ordering in low-dimentional ludwigite Ni_5GeB_2O_1_0

    International Nuclear Information System (INIS)

    Sofronova, S.N.; Bezmaternykh, L.N.; Eremin, E.V.; Nazarenko, I.I.; Volkov, N.V.; Kartashev, A.V.; Moshkina, E.M.

    2016-01-01

    The ludwigite Ni_5Ge(BO_5)_2 belongs to a family of oxyborates which have low-dimensional subunits in the form of three-leg ladders unit structure. This material was studied by magnetic and thermodynamic measurements. Ni_5Ge(BO_5)_2 does not show full long-range magnetic order, but one goes into a partial ordering or spin-glass state at 87 K. The superexchange interactions were calculated in the framework of a simple indirect coupling model. Different models of magnetic structure of Ni_5Ge(BO_5)_2 and its unique magnetic behaviour was discussed. - Highlights: • The single crystals of Ni_5Ge(BO_5)_2 with a ludwigite structure were grown. • Magnetic and the specific heat measurements were performed. • The calculation of the exchange interactions shows a competition between interactions. • The magnetic behaviour corresponds to ions moments part freezing or spin-glass state. • We propose two models of magnetic ordering in Ni_5Ge(BO_5)_2.

  19. Ordering and reaccomodation processes for defects in Fe-6.5wt.% Si and its influence on magnetic properties

    International Nuclear Information System (INIS)

    Cano, J.A; Lambri, O.A; Perez-Landazabal, J.I; Recarte, V

    2004-01-01

    Mechanical spectroscopy (MS) and magnetic hysteresis measurements were carried out in order to thoroughly study the effects of the order and reactions of the super dislocations in commercial alloys of Fe-6.5wt.% Si and Fe-3wt% Si with GOSS [110] texture during 1 hour, in a high vacuum, followed by tempering in water. The test pieces that were measured came from cut sheets provided by NKK Corp. The deadening and elastic module measurements were done with an inverted torsion pendulum, inside of which a 10 -5 Pa vacuum was made, expressed as a function of the temperature, and reaching three different final values: 973K, 1050K and 1273K. The magnetic measurements were carried out with an electromagnetic system that traced the hysteresis cycles. The behavior of deadening and the elastic module spectrum in Fe-6.5wt% Si is controlled by the relationship between the maximum temperature reached in the pendulum and the order-disorder transformation temperature. This dependence does not appear in the Fe-3wt% Si with GOSS [110] texture. The quenching defects recovery effects in Fe-3wt% Si are less than for the Fe-6.5wt% Si because of the absence of super dislocations and anti phase borders (APB) (CW)

  20. Magnetic ordering of CoCl2-GIC, a spin ceramic: hierarchical successive transitions and the intermediate glassy phase

    International Nuclear Information System (INIS)

    Suzuki, Masatsugu; Suzuki, Itsuko S; Matsuura, Motohiro

    2007-01-01

    Stage-2 CoCl 2 -graphite intercalation compound (GIC) is a spin ceramic which shows hierarchical successive transitions at T cu (= 8.9 K) and T cl (= 7.0 K) from the paramagnetic phase into an intra-cluster (two-dimensional ferromagnetic) order with inter-cluster disorder and then to an inter-cluster (three-dimensional antiferromagnetic like) order over the whole system. The nature of the inter-cluster disorder was suggested to be of spin glass by nonlinear magnetic response analyses around T cu and by studies on dynamical aspects of ordering between T cu and T cl . Here, we present a further extensive examination of a series of time dependence of zero-field cooled magnetization M ZFC after the ageing protocol below T cu . The time dependence of the relaxation rates S ZFC (t) = (1/H) dM ZFC (t)/dlnt dramatically changes from the curves of simple spin glass ageing effect below T cl to those of two peaks above T cl . The characteristic relaxation behaviour apparently indicates that there coexist two different kinds of glassy correlated region below T cu

  1. Wide aperture multipole magnets of the kinematic separator COMBAS. Correcting pair of multipole magnets M3M4 (M5M6) with compensation for higher order aberrations

    International Nuclear Information System (INIS)

    Artyukh, A.G.; Gridnev, G.F.; Teterev, Yu.G.

    1999-01-01

    The high-resolving large aperture separator COMBAS has been created and commissioned. The magneto-optical structure of the separator is based on the strong focusing principle. The separator consists of eight wide aperture multipole magnets M1-M8. The magnets M1, M2, M7, M8 forming the 1 st order optics together with some higher order optical corrections and M3-M6 being dedicated to higher order corrections of the chromatic and spherical aberrations at the intermediate and exit foci of the separator. The multipole correctors M3-M6 contain the dipolar, sextupole and octupole components in their magnetic field distributions. It was the use of the rectangular dipoles M3-M6 as carriers of sextupole and octupole field components that let achieve high values of the separator angular and momentum acceptances. Measurements of the magnetic field distributions in the median planes of the pairs of magnets M3M6 (M4M5) have been performed. These measurements allowed one to analyze the magnets manufacturing quality. Based on the analysis, shimming of pole pieces of the pair of magnets M3M6 have been done. Pole surface correcting coils for the magnets M4M5 have been foreseen to compensate for small deviations (within a few percents) of the 2 nd and 3 rd order field components from the design values, which are probable due to manufacturing errors in all the magnets M1-M8. The measured magnetic field distributions are supposed to be used for particle trajectory simulations throughout the entire separator

  2. Superconductive energy storage magnet study

    International Nuclear Information System (INIS)

    Rhee, S.W.

    1982-01-01

    Among many methods of energy storages the superconducting energy storage has been considered as the most promising method. Many related technical problems are still unsolved. One of the problems is the magnetizing and demagnetizing loss of superconducting coil. This loss is mainly because of hysteresis of pinning force. In this paper the hysteresis loss is calculated and field dependence of the a.c. losses is explained. The ratio of loss and stored energy is also calculated. (Author)

  3. Magnetic impurity effect on charge and magnetic order in doped La1.5Ca0.5CoO4

    Science.gov (United States)

    Horigane, K.; Hiraka, H.; Tomiyasu, K.; Ohoyama, K.; Louca, D.; Yamada, K.

    2012-02-01

    Neutron scattering experiments were performed on single crystals of magnetic impurity doped cobalt oxides La1.5Ca0.5CoO4 to characterize the charge and spin orders. We newly found contrasting impurity effects. Two types of magnetic peaks are observed at q = (0.5,0,L) with L = half-integer and integer in La1.5Ca0.5CoO4, while magnetic peak at L = half-integer (integer) was only observed in Mn (Fe)-substituted sample. Although Mn and Fe impurities degrade charge and magnetic order, Cr impurity stabilizes the ordering at x = 0.5. Based on the crystal structural analysis of Cr doped sample, we found that the excess oxygen and change of octahedron around Co3+ were realized in Cr doped sample.

  4. Advances in studying order and dynamics in condensed matter by NMR

    International Nuclear Information System (INIS)

    Voda, M.A.

    2006-01-01

    In this thesis, molecular transport in liquid samples is studied in terms of susceptibility induced magnetic field inhomogeneities and spectral distortions for interdiffusion in binary mixtures. Molecular order and dynamics are topics for two different soft solids, natural rubber and polyurethane. The influence of the mixture heterogeneity on the magnetic field homogeneity was investigated in terms of a spatial and time-dependent magnetic susceptibility. The effect of the heterogeneous distribution of magnetic susceptibility in liquid mixtures on the static and rf field homogeneity was simulated together with the corresponding spectral distortions. The problem of low magnetic field homogeneity provided by the Halbach type of magnets is discussed. The design of modified Halbach magnets is studied in order to increase the field homogeneity. The work was focused on two types of Halbach magnets, consisting of 16 and 24 magnet blocks, respectively. Different modifications were applied to these magnet designs, and the field homogeneity was significantly improved. The changes induced in molecular dynamics and order in stretched elastomers was investigated using multispin moments edited by multiple-quantum NMR. The main purpose of this part is to investigate the changes in proton residual dipolar coupling and the sensitivity of multiple quantum coherences of higher order for cross-linked natural rubber under uniaxial deformation. The effect of uniaxial deformation of a natural rubber band was investigated by measurements of second van Vleck moments and fourth moments edited by double-quantum and triple-quantum coherences, respectively. A spin diffusion experiment was employed for the elucidation of the morphology and domain sizes of a series of polyurethane samples. A proton DQ dipolar filer was used to select the magnetization of the rigid phase. The most probable morphology is three-dimensional for the TPU samples with a high content in HS as was established by a

  5. Advances in studying order and dynamics in condensed matter by NMR

    Energy Technology Data Exchange (ETDEWEB)

    Voda, M.A.

    2006-07-13

    In this thesis, molecular transport in liquid samples is studied in terms of susceptibility induced magnetic field inhomogeneities and spectral distortions for interdiffusion in binary mixtures. Molecular order and dynamics are topics for two different soft solids, natural rubber and polyurethane. The influence of the mixture heterogeneity on the magnetic field homogeneity was investigated in terms of a spatial and time-dependent magnetic susceptibility. The effect of the heterogeneous distribution of magnetic susceptibility in liquid mixtures on the static and rf field homogeneity was simulated together with the corresponding spectral distortions. The problem of low magnetic field homogeneity provided by the Halbach type of magnets is discussed. The design of modified Halbach magnets is studied in order to increase the field homogeneity. The work was focused on two types of Halbach magnets, consisting of 16 and 24 magnet blocks, respectively. Different modifications were applied to these magnet designs, and the field homogeneity was significantly improved. The changes induced in molecular dynamics and order in stretched elastomers was investigated using multispin moments edited by multiple-quantum NMR. The main purpose of this part is to investigate the changes in proton residual dipolar coupling and the sensitivity of multiple quantum coherences of higher order for cross-linked natural rubber under uniaxial deformation. The effect of uniaxial deformation of a natural rubber band was investigated by measurements of second van Vleck moments and fourth moments edited by double-quantum and triple-quantum coherences, respectively. A spin diffusion experiment was employed for the elucidation of the morphology and domain sizes of a series of polyurethane samples. A proton DQ dipolar filer was used to select the magnetization of the rigid phase. The most probable morphology is three-dimensional for the TPU samples with a high content in HS as was established by a

  6. Highly polarized light from stable ordered magnetic fields in GRB 120308A.

    Science.gov (United States)

    Mundell, C G; Kopač, D; Arnold, D M; Steele, I A; Gomboc, A; Kobayashi, S; Harrison, R M; Smith, R J; Guidorzi, C; Virgili, F J; Melandri, A; Japelj, J

    2013-12-05

    After the initial burst of γ-rays that defines a γ-ray burst (GRB), expanding ejecta collide with the circumburst medium and begin to decelerate at the onset of the afterglow, during which a forward shock travels outwards and a reverse shock propagates backwards into the oncoming collimated flow, or 'jet'. Light from the reverse shock should be highly polarized if the jet's magnetic field is globally ordered and advected from the central engine, with a position angle that is predicted to remain stable in magnetized baryonic jet models or vary randomly with time if the field is produced locally by plasma or magnetohydrodynamic instabilities. Degrees of linear polarization of P ≈ 10 per cent in the optical band have previously been detected in the early afterglow, but the lack of temporal measurements prevented definitive tests of competing jet models. Hours to days after the γ-ray burst, polarization levels are low (P < 4 per cent), when emission from the shocked ambient medium dominates. Here we report the detection of P =28(+4)(-4) per cent in the immediate afterglow of Swift γ-ray burst GRB 120308A, four minutes after its discovery in the γ-ray band, decreasing to P = 16(+5)(-4) per cent over the subsequent ten minutes. The polarization position angle remains stable, changing by no more than 15 degrees over this time, with a possible trend suggesting gradual rotation and ruling out plasma or magnetohydrodynamic instabilities. Instead, the polarization properties show that GRBs contain magnetized baryonic jets with large-scale uniform fields that can survive long after the initial explosion.

  7. Coupling between magnetic and superconducting order parameters and evidence for the spin excitation gap in the superconducting state of a heavy fermion superconductor UPd2Al3

    International Nuclear Information System (INIS)

    Metoki, Naoto; Haga, Yoshinori; Koike, Yoshihiro; Aso, Naofumi; Onuki, Yoshichika

    1997-01-01

    Neutron scattering experiments have been carried out in order to study the interplay between magnetism and superconductivity in a heavy fermion superconductor, UPd 2 Al 3 . We have observed 1% suppression of the (0 0 0.5) magnetic peak intensity below the superconducting transition temperature T c . This is direct evidence for the coupling of the magnetic order parameter with the superconducting one. Furthermore, we have observed a spin excitation gap associated with superconductivity. The gap energy ΔE g increases continuously from ΔE g =0 to 0.4 meV with decreasing temperature from T c to 0.4 K. This gap energy corresponds to 2k B T c , which is smaller than the superconducting gap expected from the BCS theory (3.5k B T c ). These results are indicative of the strong interplay between magnetism and superconductivity. (author)

  8. Collagene order of articular cartilage by clinical magnetic resonance images and its age dependency

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, P.; Gruender, W. [Inst. of Medical Physics and Biophysics, Univ. of Leipzig (Germany)

    2005-07-01

    The present papers describes a novel method to obtain information on the degree of order of the collagen network of the knee meniscal cartilage by means of a single clinical MRI. Images were obtained from 34 healthy volunteers aged between 6 and 76 years as well as from one patient with clinically-diagnosed arthrosis at the age of 32 and 37 years. A siemens vision (1.5 T) MRT with TR = 750 ms, TE = 50 ms, FoV = 160 mm, and Matrix 512 x 512 was used for this purpose. The MR signal intensities of the cartilage were read out along slices with constant height above the subchondral bone and plotted versus the actual angle to the external magnetic field. The obtained intensity curves were fitted by a model distribution, and the degree of order of the collagen fibers was calculated. For the knee meniscal cartilage, there was an age-dependency of the degree of order and a significant deviation of the volunteer with arthrosis from the normal curve. The results are discussed in view of the arcade model and of a possible use of non-invasive clinical MRT for the detection of early arthrotic changes of cartilage. (orig.)

  9. The interplay of magnetic order and superconductivity in GdxY1-xNi2B2C

    International Nuclear Information System (INIS)

    Drzazga, Z.; Fuchs, G.; Handstein, A.; Nenkov, K.; Mueller, K.-H.

    2003-01-01

    Resistivity, ac susceptibility and magnetization measurements are reported for polycrystalline samples of the Gd x Y 1-x Ni 2 B 2 C series as a function of temperature and magnetic field. The magnetic Gd impurities cause an almost linear decrease of the superconducting transition temperature T c with increasing Gd content in the range of x c have been observed. The effect of the 4f local moments manifests in a complete suppression of superconductivity for x≥0.3 and in antiferromagnetic ordering for x>0.3. In zero applied magnetic field, a distinct concentration region around x∼0.3 has been revealed separating superconductivity and antiferromagneting ordering. A metamagnetic transition has been observed in the compound with x=0.5 at a magnetic field of 0.8 T

  10. Evidence of a New Current-Induced Magnetoelectric Effect in a Toroidal Magnetic Ordered State of UNi4B

    Science.gov (United States)

    Saito, Hiraku; Uenishi, Kenta; Miura, Naoyuki; Tabata, Chihiro; Hidaka, Hiroyuki; Yanagisawa, Tatsuya; Amitsuka, Hiroshi

    2018-03-01

    Magnetization measurements under direct electric current were performed in a toroidal magnetic ordered state of UNi4B to test a recent theoretical prediction of current-induced magnetization in a metallic system lacking local-inversion symmetry. We found that electric current parallel to [2\\bar{1}\\bar{1}0] and [0001] in the hexagonal 4-index notation induces a uniform magnetization along the [01\\bar{1}0] direction. The observed behavior of the induced magnetization is essentially consistent with the theoretical prediction; however, it also shows an inconsistency suggesting that the antiferromagnetic state of UNi4B could not be simply regarded as a uniform toroidal order in the ideal honeycomb layered structure.

  11. Heterogeneous bilayer films NiFe (Fe)-Dy: magnetic circular dichroism and Dy spin ordering

    Energy Technology Data Exchange (ETDEWEB)

    Markov, V.V. E-mail: ise@iph.krasn.ruise@iph.krasnoyarsk.su; Kesler, V.G.; Khudyakov, A.E.; Edelman, I.S.; Bondarenko, G.V

    2001-08-01

    Results of the magnetic circular dichroism (MCD) and Auger electron spectroscopy (AES) investigations in the 3d transition metal-Dy bi-layer films are presented. It is shown that even at room temperature the Dy layer makes a contribution to MCD of the bi-layer film, which corresponds to the MCD value in the single-layer Dy film measured below T{sub C}=85 K. According to the AES data there is no sharp interface between 3d and Dy layers in these films. Some amount of Ni and Fe atoms is dispersed in the Dy layer and some amount of Dy atoms is dispersed in the 3d layer. The comparison of the MCD and AES data allows one to suppose the Dy layer in the bi-layer films to be magnetically ordered at room temperature under the influence of the 3d-layer spin system. The influence spreads to long distances inside Dy layer through the 3d-ions dispersed in it.

  12. Application of diffusion ordered-1H-nuclear magnetic resonance spectroscopy to quantify sucrose in beverages.

    Science.gov (United States)

    Cao, Ruge; Nonaka, Airi; Komura, Fusae; Matsui, Toshiro

    2015-03-15

    This work focuses on a quantitative analysis of sucrose using diffusion ordered-quantitative (1)H-nuclear magnetic resonance spectroscopy (DOSY-qNMR), where an analyte can be isolated from interference based on its characteristic diffusion coefficient (D) in gradient magnetic fields. The D value of sucrose in deuterium oxide at 30°C was 4.9 × 10(-10)m(2)/s at field gradient pulse from 5.0 × 10(-2) to 3.0 × 10(-1)T/m, separated from other carbohydrates (glucose and fructose). Good linearity (r(2)=0.9999) was obtained between sucrose (0.5-20.0 g/L) and the resonance area of target glucopyranosyl-α-C1 proton normalised to that of cellobiose C1 proton (100.0 g/L, as an internal standard) in 1D sliced DOSY spectrum. The DOSY-qNMR method was successfully applied to quantify sucrose in orange juice (36.1 ± 0.5 g/L), pineapple juice (53.5 ± 1.1g/L) and a sports drink (24.7 ± 0.6g/L), in good agreement with the results obtained by an F-kit method. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Asymmetric d-wave superconducting topological insulator in proximity with a magnetic order

    Science.gov (United States)

    Khezerlou, M.; Goudarzi, H.; Asgarifar, S.

    2018-02-01

    In the framework of the Dirac-Bogoliubov-de Gennes formalism, we investigate the transport properties in the surface of a 3-dimensional topological insulator-based hybrid structure, where the ferromagnetic and superconducting orders are simultaneously induced to the surface states via the proximity effect. The superconductor gap is taken to be spin-singlet d-wave symmetry. The asymmetric role of this gap respect to the electron-hole exchange, in one hand, affects the topological insulator superconducting binding excitations and, on the other hand, gives rise to forming distinct Majorana bound states at the ferromagnet/superconductor interface. We propose a topological insulator N/F/FS junction and proceed to clarify the role of d-wave asymmetry pairing in the resulting subgap and overgap tunneling conductance. The perpendicular component of magnetizations in F and FS regions can be at the parallel and antiparallel configurations leading to capture the experimentally important magnetoresistance (MR) of junction. It is found that the zero-bias conductance is strongly sensitive to the magnitude of magnetization in FS region mzfs and orbital rotated angle α of superconductor gap. The negative MR only occurs in zero orbital rotated angle. This result can pave the way to distinguish the unconventional superconducting state in the relating topological insulator hybrid structures.

  14. Heterogeneous bilayer films NiFe (Fe)-Dy: magnetic circular dichroism and Dy spin ordering

    International Nuclear Information System (INIS)

    Markov, V.V.; Kesler, V.G.; Khudyakov, A.E.; Edelman, I.S.; Bondarenko, G.V.

    2001-01-01

    Results of the magnetic circular dichroism (MCD) and Auger electron spectroscopy (AES) investigations in the 3d transition metal-Dy bi-layer films are presented. It is shown that even at room temperature the Dy layer makes a contribution to MCD of the bi-layer film, which corresponds to the MCD value in the single-layer Dy film measured below T C =85 K. According to the AES data there is no sharp interface between 3d and Dy layers in these films. Some amount of Ni and Fe atoms is dispersed in the Dy layer and some amount of Dy atoms is dispersed in the 3d layer. The comparison of the MCD and AES data allows one to suppose the Dy layer in the bi-layer films to be magnetically ordered at room temperature under the influence of the 3d-layer spin system. The influence spreads to long distances inside Dy layer through the 3d-ions dispersed in it

  15. Magnetic phase transitions in Er7Rh3 studied on single crystals

    International Nuclear Information System (INIS)

    Tsutaoka, Takanori; Obata, Keisuke; Cheyvuth, Seng; Koyama, Keiichi

    2014-01-01

    Highlights: • Magnetic and electrical properties of Er 7 Rh 3 were studied on single crystals. • The magnetic phase diagram along the c-axis was constructed. • The field-induced magnetic transitions in Er 7 Rh 3 can be explained by the magnetic structure with two magnetic propagation vectors. • The anomalies of electrical resistivity can also be described by the magnetic structure in Er 7 Rh 3 . - Abstract: Magnetic phase transitions in Er 7 Rh 3 with the Th 7 Fe 3 type hexagonal structure have been studied on single crystals by measuring magnetization, magnetic susceptibility and electrical resistivity. Er 7 Rh 3 possesses antiferromagnetic state below T N = 13 K. In the ordered state, the two successive magnetic transitions at T t1 = 6.2 K and T t2 = 4.5 K were observed. Several field-induced magnetic transitions were also observed along the a- and c-axes below T N ; magnetic field H – temperature T phase diagram along the c-axis was constructed. The field-induced magnetic transitions in Er 7 Rh 3 can be explained by the magnetic structure with two magnetic propagation vectors which were derived by the previous neutron diffraction studies. Electrical resistivity shows humps just below the magnetic transition temperatures, T N and T t1 due to the super-zone gap formation at the Fermi level; these anomalies can also be described by the magnetic structure changes in Er 7 Rh 3

  16. Assessment of higher order structure comparability in therapeutic proteins using nuclear magnetic resonance spectroscopy.

    Science.gov (United States)

    Amezcua, Carlos A; Szabo, Christina M

    2013-06-01

    In this work, we applied nuclear magnetic resonance (NMR) spectroscopy to rapidly assess higher order structure (HOS) comparability in protein samples. Using a variation of the NMR fingerprinting approach described by Panjwani et al. [2010. J Pharm Sci 99(8):3334-3342], three nonglycosylated proteins spanning a molecular weight range of 6.5-67 kDa were analyzed. A simple statistical method termed easy comparability of HOS by NMR (ECHOS-NMR) was developed. In this method, HOS similarity between two samples is measured via the correlation coefficient derived from linear regression analysis of binned NMR spectra. Applications of this method include HOS comparability assessment during new product development, manufacturing process changes, supplier changes, next-generation products, and the development of biosimilars to name just a few. We foresee ECHOS-NMR becoming a routine technique applied to comparability exercises used to complement data from other analytical techniques. Copyright © 2013 Wiley Periodicals, Inc.

  17. Behaviour of the order parameter of the simple magnet in an external field

    Directory of Open Access Journals (Sweden)

    M.P.Kozlovskii

    2005-01-01

    Full Text Available The effect of a homogeneous external field on the three-dimensional uniaxial magnet behaviour near the critical point is investigated within the framework of the nonperturbative collective variables method using the ρ4 model. The research is carried out for the low-temperature region. The analytic explicit expressions for the free energy, average spin moment and susceptibility are obtained for weak and strong fields in comparison with the field value belonging to the pseudocritical line. The calculations are performed on the microscopic level without any adjusting parameters. It is established that the long-wave fluctuations of the order parameter play a crucial role in forming a crossover between the temperature-dependence and field-dependence critical behaviour of the system.

  18. 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.

  19. 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.

  20. Neutron scattering studies of a dilute magnetic semiconductor: Cd1-xMnxTe

    DEFF Research Database (Denmark)

    Steigenberger, Ursula; Lebech, Bente; Galazka, Robert R.

    1986-01-01

    The development of the magnetic ordering in the magnetic semiconductor Cd1-xMnxTe was investigated by elastic neutron scattering. A detailed study of the correlation length and the intensity as a function of temperature, direction in reciprocal space and concentration of the magnetic ions has been...

  1. Influence of low-order rational magnetic surfaces on heat transport in TJ-II heliac ECRH plasmas

    International Nuclear Information System (INIS)

    Castejon, F.; Lopez-Bruna, D.; Estrada, T.; Ascasibar, E.; Zurro, B.; Baciero, A.

    2004-01-01

    We study the effect of low-order rational surfaces on electron heat transport in plasmas confined in the TJ-II stellarator (Alejaldre et al 1990 Fusion Technol. 17 131) and heated by electron cyclotron waves. Enhancement of core electron heat confinement is observed when the rational surface is placed in the vicinity of the power deposition zone, either by performing a magnetic configuration scan or by inducing Ohmic current in a single discharge. The key to improving heat confinement seems to be a locally strong positive radial electric field, which is made possible by a synergistic effect between enhanced electron heat fluxes through radial positions around low-order rationals and pump out mechanisms in the heat deposition zone. (author)

  2. Morphology, microstructure, and magnetic properties of ordered large-pore mesoporous cadmium ferrite thin film spin glasses.

    Science.gov (United States)

    Reitz, Christian; Suchomski, Christian; Chakravadhanula, Venkata Sai Kiran; Djerdj, Igor; Jagličić, Zvonko; Brezesinski, Torsten

    2013-04-01

    Herein, we report the synthesis, microstructure, and magnetic properties of cadmium ferrite (CdFe2O4) thin films with both an ordered cubic network of 18 nm diameter pores and single-phase spinel grains averaging 13 nm in diameter. These mesoporous materials were produced through facile polymer templating of hydrated nitrate salt precursors. Both the morphology and the microstructure, including cation site occupancy and electronic bonding configuration, were analyzed in detail by electron microscopy, grazing incidence small-angle X-ray scattering, Raman and X-ray photoelectron spectroscopy, and N2-physisorption. The obtained data demonstrate that the network of pores is retained up to annealing temperatures as high as 650 °C--the onset of crystallization is at ϑ = (590 ± 10) °C. Furthermore, they show that the polymer-templated samples exhibit a "partially" inverted spinel structure with inversion parameter λ = 0.40 ± 0.02. This differs from microcrystalline CdFe2O4 which shows virtually no inversion. Magnetic susceptibility studies reveal ferrimagnetic spin coupling below 147 K and further point to the likelihood of glassy behavior at low temperature (T(f) ≈ 60 K). In addition, analysis of room temperature magnetization data indicates the presence of sub-10 nm diameter superparamagnetic clusters in an otherwise paramagnetic environment.

  3. Interaction of magnetic resonators studied by the magnetic field enhancement

    Directory of Open Access Journals (Sweden)

    Yumin Hou

    2013-12-01

    Full Text Available It is the first time that the magnetic field enhancement (MFE is used to study the interaction of magnetic resonators (MRs, which is more sensitive than previous parameters–shift and damping of resonance frequency. To avoid the coherence of lattice and the effect of Bloch wave, the interaction is simulated between two MRs with same primary phase when the distance is changed in the range of several resonance wavelengths, which is also compared with periodic structure. The calculated MFE oscillating and decaying with distance with the period equal to resonance wavelength directly shows the retardation effect. Simulation also shows that the interaction at normal incidence is sensitive to the phase correlation which is related with retardation effect and is ultra-long-distance interaction when the two MRs are strongly localized. When the distance is very short, the amplitude of magnetic resonance is oppressed by the strong interaction and thus the MFE can be much lower than that of single MR. This study provides the design rules of metamaterials for engineering resonant properties of MRs.

  4. Magnetic properties of checkerboard lattice: a Monte Carlo study

    Science.gov (United States)

    Jabar, A.; Masrour, R.; Hamedoun, M.; Benyoussef, A.

    2017-12-01

    The magnetic properties of ferrimagnetic mixed-spin Ising model in the checkerboard lattice are studied using Monte Carlo simulations. The variation of total magnetization and magnetic susceptibility with the crystal field has been established. We have obtained a transition from an order to a disordered phase in some critical value of the physical variables. The reduced transition temperature is obtained for different exchange interactions. The magnetic hysteresis cycles have been established. The multiples hysteresis cycle in checkerboard lattice are obtained. The multiples hysteresis cycle have been established. The ferrimagnetic mixed-spin Ising model in checkerboard lattice is very interesting from the experimental point of view. The mixed spins system have many technological applications such as in domain opto-electronics, memory, nanomedicine and nano-biological systems. The obtained results show that that crystal field induce long-range spin-spin correlations even bellow the reduced transition temperature.

  5. Is There a Magnet-School Effect? A Multisite Study of MSAP-Funded Magnet Schools

    Science.gov (United States)

    Wang, Jia; Schweig, Jonathan D.; Herman, Joan L.

    2017-01-01

    Magnet schools are one of the largest sectors of choice schools in the United States. In this study, we explored the heterogeneity in magnet-school effects on student achievement by examining 24 magnet schools, funded under the Magnet Schools Assistance Program (MSAP), in 5 school districts across 4 states. The magnet effects were synthesized…

  6. Theoretical study of ferromagnetic resonance in exchange - coupled magnetic / nonmagnetic / magnetic multilayer structure

    International Nuclear Information System (INIS)

    Oezdogan, K.; Oezdemir, M.; Yalcin, O.; Aktas, B.

    2002-01-01

    The dispersion relation on ferromagnetic films was calculation by using torque equation of motion with a damping term. The total energy including zeeman, demagnetizing and anisotropy energy terms was used to get ferromagnetic resonance frequency for both uniform and higher order spin wave modes. In antiferromagnetic films, the torque equation of motion for each sub-lattice were written to derive an expression for the dispersion relation. The magnetic trilayer system under investigation consist of two ferromagnetic layers separated by a nonmagnetic layer. The dispersion relation of magnetic/nonmagnetic/magnetic three layers is calculated by using Landau-Lifshitz dynamic equation of motion for the magnetization with interlayer exchange energy. As for the exchange-coupled resonance of ferromagnetic resonance (FMR), the theoretical study has been calculated for both symmetrical and asymmetrical structures. In this systems, the exchange-coupling parameter A 12 between neighboring layers was used to get resonance fields as a function of the angle between the magnetization vectors of each magnetic layers

  7. Conceptual design study of the K-DEMO magnet system

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Keeman, E-mail: kkeeman@nfri.re.kr [National Fusion Research Institute, 169-148 Gwahak-ro, Daejeon 305-806 (Korea, Republic of); Oh, Sangjun; Park, Jong Sung; Lee, Chulhee; Im, Kihak; Kim, Hyung Chan; Lee, Gyung-Su [National Fusion Research Institute, 169-148 Gwahak-ro, Daejeon 305-806 (Korea, Republic of); Neilson, George; Brown, Thomas; Kessel, Charles; Titus, Peter; Zhai, Yuhu [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (United States)

    2015-10-15

    Highlights: • Perform a preliminary conceptual study for a steady-state Korean DEMO reactor. • Present a preliminary design of TF (toroidal field) magnet. • Present a preliminary design of CS (central solenoid) magnet. • Present a preliminary design of PF (toroidal field) magnet. - Abstract: As the ITER is being constructed, there is a growing anticipation for an earlier realization of fusion energy. A major design philosophy for the initiated conceptual design study for a steady-state Korean fusion demonstration reactor (K-DEMO) is engineering feasibility. A two-staged development plan is envisaged. K-DEMO is designed not only to demonstrate a net electricity generation and a self-sustained tritium cycle, but also to be used, in its initial stage, as a component test facility. Then, in its second stage, a major upgrade is carried out by replacing in-vessel components in order to show a net electricity generation on the order of 500 MWe. After a thorough 0-D system analysis, the major radius and minor radius are chosen to be 6.8 m and 2.1 m, respectively. In order to minimize wave deflection, a top-launch high frequency (>200 GHz) electron cyclotron current drive (ECCD) system will be the key system for the current profile control. For matching the high frequency ECCD, a high toroidal field (TF) is required and can be achieved by using high current density Nb{sub 3}Sn superconducting conductor. The peak magnetic field reaches to 16 T with the magnetic field at the plasma center above 7 T. Key features of the K-DEMO magnet system include the use of two TF coil winding packs, each of a different conductor design, to reduce the construction cost and save the space for the magnet structure material.

  8. Conceptual design study of the K-DEMO magnet system

    International Nuclear Information System (INIS)

    Kim, Keeman; Oh, Sangjun; Park, Jong Sung; Lee, Chulhee; Im, Kihak; Kim, Hyung Chan; Lee, Gyung-Su; Neilson, George; Brown, Thomas; Kessel, Charles; Titus, Peter; Zhai, Yuhu

    2015-01-01

    Highlights: • Perform a preliminary conceptual study for a steady-state Korean DEMO reactor. • Present a preliminary design of TF (toroidal field) magnet. • Present a preliminary design of CS (central solenoid) magnet. • Present a preliminary design of PF (toroidal field) magnet. - Abstract: As the ITER is being constructed, there is a growing anticipation for an earlier realization of fusion energy. A major design philosophy for the initiated conceptual design study for a steady-state Korean fusion demonstration reactor (K-DEMO) is engineering feasibility. A two-staged development plan is envisaged. K-DEMO is designed not only to demonstrate a net electricity generation and a self-sustained tritium cycle, but also to be used, in its initial stage, as a component test facility. Then, in its second stage, a major upgrade is carried out by replacing in-vessel components in order to show a net electricity generation on the order of 500 MWe. After a thorough 0-D system analysis, the major radius and minor radius are chosen to be 6.8 m and 2.1 m, respectively. In order to minimize wave deflection, a top-launch high frequency (>200 GHz) electron cyclotron current drive (ECCD) system will be the key system for the current profile control. For matching the high frequency ECCD, a high toroidal field (TF) is required and can be achieved by using high current density Nb_3Sn superconducting conductor. The peak magnetic field reaches to 16 T with the magnetic field at the plasma center above 7 T. Key features of the K-DEMO magnet system include the use of two TF coil winding packs, each of a different conductor design, to reduce the construction cost and save the space for the magnet structure material.

  9. Magnetic and electronic properties of NpCo.sub.2./sub.: Evidence for long-range magnetic order

    Czech Academy of Sciences Publication Activity Database

    Sanchez, J.-P.; Griveau, J.C.; Javorský, P.; Colineau, E.; Eloirdi, R.; Boulet, P.; Rebizant, J.; Wastin, F.; Shick, Alexander; Caciuffo, R.

    2013-01-01

    Roč. 87, č. 13 (2013), "134410-1"-"134410-7" ISSN 1098-0121 Institutional support: RVO:68378271 Keywords : magnetic properties * electronic structure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.664, year: 2013 http://link. aps .org/doi/10.1103/PhysRevB.87.134410

  10. Design Study: ELENA Bending Magnet Prototype

    CERN Document Server

    Schoerling, D

    2013-01-01

    The ELENA bending magnet prototype shall prove that the proposed design meets the requirements set by the ELENA beam dynamics. The following points will be discussed in detail: (i) production process of a magnetic yoke diluted with stainless steel plates, (ii) the stability and repeatability of the field homogeneity of such a yoke over the full working range, (iii) choice of soft magnetic steel, (iv) hysteresis effects, (v) mechanical deformations, (vi) thermal insulation to intercept heat load from baking for activation of NEG coating in the vacuum chamber, (vii) end shim design. In order to verify these points the following measurements will be performed: (i) Hall probe scanning, (ii) integrated field homogeneity measurement (DC), (iii) integrated field homogeneity measurement (AC).

  11. An increase of structural order parameter in Fe endash Co endash V soft magnetic alloy after thermal aging

    International Nuclear Information System (INIS)

    Zhu, Q.; Li, L.; Masteller, M.S.; Del Corso, G.J.

    1996-01-01

    Alloys of Fe 49 Co 49 V 2 (Hiperco Alloy 50) (Hiperco is a registered trademark of CRS Holdings, Inc.), both annealed and thermally aged, were studied using anomalous synchrotron x-ray and neutron powder diffraction. Rietveld and diffraction profile analysis indicated both an increase in the structural order parameter and a small lattice expansion (∼0.0004 A) after aging at 450 degree C for 200 h. In addition, a cubic minority phase (<0.3%) was identified in the open-quote open-quote annealed close-quote close-quote sample, which increased noticeably (0.3%→0.8%) as a result of aging. The presence of antiphase domain boundaries in the alloys was also revealed. These results directly correlate with the observed changes in the magnetization behavior and challenge the notion that a open-quote open-quote fully close-quote close-quote ordered Fe endash Co alloy demonstrates optimum soft magnetic properties. copyright 1996 American Institute of Physics

  12. Synthesis of magnetic ordered mesoporous carbon (Fe-OMC) adsorbent and its evaluation for fuel desulfurization

    Science.gov (United States)

    Farzin Nejad, N.; Shams, E.; Amini, M. K.

    2015-09-01

    In this work, magnetic ordered mesoporous carbon adsorbent was synthesized using soft templating method to adsorb sulfur from model oil (dibenzothiophene in n-hexane). Through this research, pluronic F-127, resorcinol-formaldehyde and hydrated iron nitrate were respectively used as soft template, carbon source and iron source. The adsorbent was characterized by X-ray diffraction, nitrogen adsorption-desorption isotherm and transmission electron microscopy. Nitrogen adsorption-desorption measurement revealed the high surface area (810 m2 g-1), maxima pore size of 3.3 nm and large pore volume (1.01 cm3 g-1) of the synthesized sample. The adsorbent showed a maximum adsorption capacity of 111 mg dibenzothiophene g-1 of adsorbent. Sorption process was described by the pseudo-second-order rate equation and could be better fitted by the Freundlich model, showing the heterogeneous feature of the adsorption process. In addition, the adsorption capacity of regenerated adsorbent was 78.6% of the initial level, after five regeneration cycles.

  13. [Magnet ingestions in children: a French multicenter study].

    Science.gov (United States)

    Talvard, M; Mouttalib, S; Flaum, V; Viala, J; Galinier, P; Olives, J-P; Mas, E

    2015-01-01

    Digestive complications related to the ingestion of magnetic foreign bodies in children are increasing, especially in Asia and North America. In France, several case reports have been reported since 2008. We conducted a retrospective multicentric study to evaluate the frequency of ingestion of magnet foreign bodies and to describe the complicated cases that have occurred in France over the last 5 years. We report 40 cases of which 60% were multiple magnet ingestions. Eighty-eight percent of the children of the group who had swallowed multiple magnets needed interventional management by endoscopy (33%) or surgery (58%). Only two children (12.5%) of the group who swallowed one magnet required removal. This problem is not uncommon in France (2% of the 1132 foreign bodies investigated in the Toulouse center over 5 years), which justifies clear information for healthcare professionals and caregivers in order to avoid potential intestinal complications. We suggest interventional management or very close monitoring in the cases of multiple magnet ingestion. Meanwhile, in the majority of confirmed cases of simple magnet ingestions, we propose home monitoring. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  14. Study on Magnetic Responsibility of Rare Earth Ferrite/Polyacrylamide Magnetic Microsphere

    Institute of Scientific and Technical Information of China (English)

    Zhang Ming; Wang Zhifeng; Zhang Hong; Dai Shaojun; Qiu Guanming; Okamoto Hiroshi

    2005-01-01

    In inverse microemulsion, rare earth ferrite/polyacrylamide magnetic microsphere were prepared and their magnetic responsibility were studied by magnetic balance. Results indicate that the magnetic responsibility of microsphere relates to magnetic moment of rare earth ion, and it can be improved by the addition of dysprosium ion of high magnetic moment. Dysprosium content has an effect on magnetic responsibility of dysprosium ferrite/polyacrylamide magnetic microsphere. The microsphere displays strong magnetic responsibility when the molar ratio of Dy3+/iron is 0.20.

  15. Magnetic-Field-Assisted Assembly of Ordered Multifunctional Ceramic Nanocomposites for Extreme Environments

    Science.gov (United States)

    2016-04-01

    SUBJECT TERMS carbon nanotubes, composite, electromagnetic shielding , extreme environments, magnetism, fibers, woven composite, boron nitride...The samples were sealed in glass vial and exposed to the magnetic field immediately after deposition prior to crystallization of PEG that allowed

  16. Optical and magnetization studies on europium based iron pnictides

    Energy Technology Data Exchange (ETDEWEB)

    Zapf, Sina Maria Ute

    2015-07-01

    The investigations carried out in the framework of this thesis mainly concentrate on europium based iron pnictides. These are a peculiar member of the 122 family as they develop at low temperatures (∝20K) an additional magnetic order of the local rare earth moments. Therefore, europium based iron pnictides provide a unique platform to study the interplay of structural, magnetic and electronic effects in high-temperature superconductors. For this challenging purpose, we have employed SQUID magnetometry and Fourier-transform infrared spectroscopy on EuFe{sub 2}(As{sub 1-x}P{sub x}){sub 2} single crystals. By systematic studies of the in- and out-of-plane magnetic properties of a series of single crystals, we derived the complex magnetic phase diagram of europium based iron pnictides, which contains an A-type antiferromagnetic and a re-entrant spin glass phase. Furthermore, we have investigated the magneto-optical properties of EuFe{sub 2}As{sub 2}, revealing a much more complex magnetic detwinning process than expected. These studies demonstrate a remarkable interdependence between magnetic, electronic and structural effects that might be very important to understand the unconventional superconductivity in these fascinating materials.

  17. Optical and magnetization studies on europium based iron pnictides

    International Nuclear Information System (INIS)

    Zapf, Sina Maria Ute

    2015-01-01

    The investigations carried out in the framework of this thesis mainly concentrate on europium based iron pnictides. These are a peculiar member of the 122 family as they develop at low temperatures (∝20K) an additional magnetic order of the local rare earth moments. Therefore, europium based iron pnictides provide a unique platform to study the interplay of structural, magnetic and electronic effects in high-temperature superconductors. For this challenging purpose, we have employed SQUID magnetometry and Fourier-transform infrared spectroscopy on EuFe 2 (As 1-x P x ) 2 single crystals. By systematic studies of the in- and out-of-plane magnetic properties of a series of single crystals, we derived the complex magnetic phase diagram of europium based iron pnictides, which contains an A-type antiferromagnetic and a re-entrant spin glass phase. Furthermore, we have investigated the magneto-optical properties of EuFe 2 As 2 , revealing a much more complex magnetic detwinning process than expected. These studies demonstrate a remarkable interdependence between magnetic, electronic and structural effects that might be very important to understand the unconventional superconductivity in these fascinating materials.

  18. Patterning nanostructures to study magnetization processes

    International Nuclear Information System (INIS)

    Atkinson, D

    2005-01-01

    Lithography techniques such as electron-beam lithography and focused-ion-beam milling are widely used to fabricate structures with dimensions well below 1 μm. These techniques have been used to produce planar magnetic structures with sub-micrometer dimensions and well controlled geometry. This has allowed the study of basic magnetic behaviour and the development of structures with potential for applications in magnetic recording and magnetic logic devices. The techniques of electron beam lithography and focused-ion-beam milling for the fabrication of magnetic nanostructures are outlined here. These techniques have been used to fabricate ribbon-like planar nanowires to study the behaviour of the individual magnetic domain walls which mediate the reversal process in such elongated structures. These methods allow the production of structures in which the location of domain wall formation and position can be controlled, allowing separation and study of the domain wall nucleation and propagation processes. Domain wall injection and domain wall propagation behaviour are investigated and shown to be stochastic processes

  19. Impact of Cattaneo-Christov heat flux on electroosmotic transport of third-order fluids in a magnetic environment

    Science.gov (United States)

    Misra, J. C.; Mallick, B.; Sinha, A.; Roy Chowdhury, A.

    2018-05-01

    In the case of steady flow of a fluid under the combined influence of external electric and magnetic fields, the fluid moves forward by forming an axial momentum boundary layer. With this end in view a study has been performed here to investigate the problem of entropy generation during electroosmotically modulated flow of a third-order electrically conducting fluid flowing on a microchannel bounded by silicon-made parallel plates under the influence of a magnetic field, by paying due consideration to the steric effect. The associated mechanism of heat transfer has also been duly taken care of, by considering Cattaneo-Christov heat flux. A suitable finite difference scheme has been developed for the numerical procedure. A detailed study of the velocity and temperature distributions has been made by considering their variations with respect to different physical parameters involved in the problem. The results of numerical computation have been displayed graphically. The computational work has been carried out by considering blood as the working fluid, with the motivation of exploring some interesting phenomena in the context of hemodynamical flow in micro-vessels. Among other variables, parametric variations of the important physical variables, viz. i) skin friction and ii) Nusselt number have been investigated. The study confirms that the random motion of the fluid particles can be controlled by a suitable adjustment of the intensity of an externally applied magnetic field in the transverse direction. It is further revealed that the Nusselt number diminishes, as the Prandtl number gradually increases; however, a steady increase in the Nusselt number occurs with increase in thermal relaxation. Entropy generation is also found to be enhanced with increase in Joule heating. The results of the present study have also been validated in a proper manner.

  20. Mechanism of magnetic recovery in the disorder-order transformation of Fe70Al30 mechanically deformed alloys

    International Nuclear Information System (INIS)

    Rodriguez, D. Martin; Apinaniz, E.; Plazaola, F.; Garitaonandia, J.S.; Jimenez, J.A.; Schmool, D.S.; Cuello, G.J.

    2005-01-01

    The degree of order in Fe-Al intermetallic alloys has an important influence on their magnetic properties. Moreover, the deformation of ordered alloys causes a dramatic increase of magnetization. If deformed alloys are heated, their magnetic properties decrease again. The reordering process was monitored by neutron diffraction, Moessbauer spectroscopy, and calorimetric measurements on the Fe 70 Al 30 crushed alloy. This indicates that the reordering process occurs in two stages. In the first (150-200 deg. C) new small B2 phase domains are nucleated due to vacancy migration. A second reordering stage occurs between 300 and 450 deg. C, where dislocation motion induces B2 domain growth and A2 phase elimination. The main mechanism responsible for this decrease of magnetization during the reordering process is the decrease of the disordered A2 phase content in the alloy

  1. Experimental and micromagnetic first-order reversal curves analysis in NdFeB-based bulk 'exchange spring'-type permanent magnets

    Energy Technology Data Exchange (ETDEWEB)

    Chiriac, Horia [National Institute of Research and Development for Technical Physics, 47 Mangeron Boulevard, 700050, Iasi (Romania); Lupu, Nicoleta [National Institute of Research and Development for Technical Physics, 47 Mangeron Boulevard, 700050, Iasi (Romania); Stoleriu, Laurentiu [Al. I. Cuza University, Department of Solid State and Theoretical Physics, Blvd. Carol I, 11, 700506, Iasi (Romania)]. E-mail: lstoler@uaic.ro; Postolache, Petronel [Al. I. Cuza University, Department of Solid State and Theoretical Physics, Blvd. Carol I, 11, 700506, Iasi (Romania); Stancu, Alexandru [Al. I. Cuza University, Department of Solid State and Theoretical Physics, Blvd. Carol I, 11, 700506, Iasi (Romania)

    2007-09-15

    In this paper we present the results of applying the first-order reversal curves (FORC) diagram experimental method to the analysis of the magnetization processes of NdFeB-based permanents magnets. The FORC diagrams for this kind of exchange spring magnets show the existence of two magnetic phases-a soft magnetic phase and a hard magnetic one. Micromagnetic modeling is used for validating the hypotheses regarding the origin of the different features of the experimental FORC diagrams.

  2. Studies of the magnetic configuration of an l=2 stellarator

    International Nuclear Information System (INIS)

    Fedyanin, O.I.

    1975-05-01

    The first part of this report describes a computational study of the effect of first and second order resonances on an l = 2 stellarator, taking as model the PROTO-CLEO experiment. The magnetic surfaces are computed in each case and the break up shown. The second part of the report deals with measurements made with an electron beam on the PROTO-CLEO l = 2 stellarator. The magnetic surfaces are measured by means of a movable probe which intercepts the beams. It is shown that the form of the surfaces, particularly near the separatrix, is sensitive to quite small perturbations of a resonant type. (author)

  3. Magnetic study of the Furnas caldera (Azores

    Directory of Open Access Journals (Sweden)

    J. M. Torta

    1997-06-01

    Full Text Available A local ground magnetic study of the Furnas caldera (S. Miguel Island, Azores has provided new insight into the magnetic structure of this volcano. Analysis of the data comprised removal of the IGRF, reduction to the pole, pseudogravity integration and upward continuation. Also, a spectral method was applied to estimate the depth to the magnetic sources, as well as a 2.5D forward modelling technique. Magnetic properties obtained at the laboratory for some representative sample rocks were considered in the modelling process. The most relevant features are the existence of an important negative anomaly inside the caldera and of an intense positive anomaly to the south of the coast. The former points out a decrease in the magnetization of the caldera filling materials with respect to the surrounding rocks, which could be explained as the result of post-eruption processes such as hydrothermal alteration. This is expected as Furnas has an active hydrothermal system probably related with a magmatic reservoir at high temperature. The positive anomaly suggests the existence of a strongly-magnetized body beneath the south coast.

  4. Nuclear magnetic resonance studies of lipoproteins

    International Nuclear Information System (INIS)

    Hamilton, J.A.; Morrisett, J.D.

    1986-01-01

    Several nuclei in lipoproteins are magnetically active and are thus potential NMR probes of lipoprotein structure. Table I lists the magnetic isotopes preset in the covalent structures of the molecular constituents of lipoproteins: lipids, proteins, and carbohydrates. Every type of nucleus that is part of the endogenous structure of these molecules has at least one magnetic isotope. Each magnetic nucleus represents an intrinsic and completely nonperturbing probe (when at the natural abundance level) of local molecular motion and magnetic environment. The NMR experiment itself is also nonperturbing and nondestructive. Table I also lists for each nucleus its nuclear spin, its natural isotopic abundance, its sensitivity, and its resonance frequency at two commonly employed magnetic in the low field range (21.14 kG or 2.11 Tesla) and the other in the high field range (47.0 kG or 4.70 Tesla). Of the nuclei listed in Table I, /sup 1/H, /sup 13/C, and /sup 31/P have been the primary ones studied in lipoproteins. The general advantages and disadvantages afforded by these and other nuclei as probes of lipoprotein structure are discussed. /sup 13/C NMR spectroscopy, the method which has had the most extensive application (and probably has the greatest future potential) to lipoproteins, is treated in greatest detail, but many of the principles described apply to other nuclei as well

  5. Magnetically frustrated double perovskites: synthesis, structural properties, and magnetic order of Sr{sub 2}BOsO{sub 6} (B = Y, In, Sc)

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Avijit Kumar; Sarapulova, Angelina; Adler, Peter; Kanungo, Sudipta; Mikhailova, Daria; Schnelle, Walter; Hu, Zhiwei; Kuo, Changyang; Yan, Binghai; Felser, Claudia; Tjeng, Liu Hao [Max-Planck-Institut fuer Chemische Physik fester Stoffe,Dresden (Germany); Reehuis, Manfred [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Berlin (Germany); Siruguri, Vasudeva; Rayaprol, Sudhindra [UGC-DAE Consortium for Scientific Research (CSR), Mumbai Centre, Mumbai (India); Soo, Yunlian [Department of Physics, National Tsing Hua University, Hsinchu (China); Jansen, Martin [Max-Planck-Institut fuer Chemische Physik fester Stoffe,Dresden (Germany); Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

    2015-02-15

    Double perovskites Sr{sub 2}BOsO{sub 6} (B = Y, In, and Sc) were prepared from the respective binary metal oxides, and their structural, magnetic, and electronic properties were investigated. At room temperature all these compounds crystallize in the monoclinic space group P2{sub 1}/n. They contain magnetic osmium (Os{sup 5+}, t{sub 2g}{sup 3}) ions and are antiferromagnetic insulators with Neel temperatures T{sub N} = 53 K, 26 K, and 92 K for B = Y, In, and Sc, respectively. Powder neutron diffraction studies on Sr{sub 2}YOsO{sub 6} and Sr{sub 2}InOsO{sub 6} showed that the crystal structures remain unchanged down to 3 K. The Y and In compounds feature a type I antiferromagnetic spin structure with ordered Os moments of 1.91 μ{sub B} and 1.77 μ{sub B}, respectively. The trend in T{sub N} does not simply follow the development of the lattice parameters, which suggests that d{sup 0} compared to d{sup 10} ions on the B site favor a somewhat different balance of exchange interactions in the frustrated Os{sup 5+} fcc-like lattice. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Study on magnetic separation for decontamination of cesium contaminated soil by using superconducting magnet

    Energy Technology Data Exchange (ETDEWEB)

    Igarashi, Susumu, E-mail: igarashi@qb.see.eng.osaka-u.ac.jp; Nomura, Naoki; Mishima, Fumihito; Akiyama, Yoko, E-mail: yoko-ak@see.eng.osaka-u.ac.jp

    2014-09-15

    Highlights: • The method for the soil decontamination by the superconducting magnet is proposed. • Magnetic separation of clay minerals was performed by HGMS. • Soil separation ratio was evaluated by quantitative analysis using XRD. • It is expected that HGMS can be applied to the actual soil decontamination. - Abstract: The accident of Fukushima Daiichi nuclear power plant caused the diffusion of radioactive cesium over the wide area. We examined the possibility of applying magnetic separation method using the superconducting magnet, which can process a large amount of the soil in high speed, to the soil decontamination and volume reduction of the radioactive cesium contaminated soil. Clay minerals are classified as 2:1 and 1:1 types by the difference of their layer structures, and these types of minerals are respectively paramagnetic and diamagnetic including some exception. It is known that most of the radioactive cesium is strongly adsorbed on the clay, especially on 2:1 type clay minerals. It is expected that the method which can separate only 2:1 type clay minerals selectively from the mixture clay minerals can enormously contribute to the volume reduction of the contaminated soil. In this study, the components in the clay before and after separation were evaluated to estimate the magnetic separation efficiency by using X-ray diffraction. From the results, the decontamination efficiency and the volume reduction ratio were estimated in order to examine the appropriate separation conditions for the practical decontamination of the soil.

  7. Selfenergy effect on the magnetic ordering transition in the mono- and bilayer honeycomb Hubbard model

    Energy Technology Data Exchange (ETDEWEB)

    Honerkamp, Carsten [Institute for Theoretical Solid State Physics, RWTH Aachen University (Germany); JARA - Fundamentals of Future Information Technology, Aachen (Germany)

    2017-11-15

    We investigate the impact of electron self-energy corrections on potential antiferromagnetic ordering instabilities in mono- and bilayer graphene, modeled by a Hubbard-type lattice model with onsite interactions among the electrons, using a self-consistent random phase approximation (RPA). In qualitative agreement with earlier studies we find that the electronic interactions cause non-Fermi liquid behavior at low energies. In self-consistent RPA, the transition scales for antiferromagnetic ordering are renormalized significantly by these self-energy effects, both for interaction-driven and temperature-driven cases. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Spin-resolved magnetic studies of focused ion beam etched nano-sized magnetic structures

    International Nuclear Information System (INIS)

    Li Jian; Rau, Carl

    2005-01-01

    Scanning ion microscopy with polarization analysis (SIMPA) is used to study the spin-resolved surface magnetic structure of nano-sized magnetic systems. SIMPA is utilized for in situ topographic and spin-resolved magnetic domain imaging as well as for focused ion beam (FIB) etching of desired structures in magnetic or non-magnetic systems. Ultra-thin Co films are deposited on surfaces of Si(1 0 0) substrates, and ultra-thin, tri-layered, bct Fe(1 0 0)/Mn/bct Fe(1 0 0) wedged magnetic structures are deposited on fcc Pd(1 0 0) substrates. SIMPA experiments clearly show that ion-induced electrons emitted from magnetic surfaces exhibit non-zero electron spin polarization (ESP), whereas electrons emitted from non-magnetic surfaces such as Si and Pd exhibit zero ESP, which can be used to calibrate sputtering rates in situ. We report on new, spin-resolved magnetic microstructures, such as magnetic 'C' states and magnetic vortices, found at surfaces of FIB patterned magnetic elements. It is found that FIB milling has a negligible effect on surface magnetic domain and domain wall structures. It is demonstrated that SIMPA can evolve into an important and efficient tool to study magnetic domain, domain wall and other structures as well as to perform magnetic depth profiling of magnetic nano-systems to be used in ultra-high density magnetic recording and in magnetic sensors

  9. Highly-Ordered Magnetic Nanostructures on Self-Assembled α-Al2O3 and Diblock Copolymer Templates

    International Nuclear Information System (INIS)

    Erb, Denise

    2015-08-01

    This thesis shows the preparation of nanostructured systems with a high degree of morphological uniformity and regularity employing exclusively selfassembly processes, and documents the investigation of these systems by means of atomic force microscopy (AFM), grazing incidence small angle X-ray scattering (GISAXS), and nuclear resonant scattering of synchrotron radiation (NRS). Whenever possible, the X-ray scattering methods are applied in-situ and simultaneously in order to monitor and correlate the evolution of structural and magnetic properties of the nanostructured systems. The following systems are discussed, where highly-ordered magnetic nanostructures are grown on α-Al 2 O 3 substrates with topographical surface patterning and on diblock copolymer templates with chemical surface patterning: - Nanofaceted surfaces of α-Al 2 O 3 - Magnetic nanostructures on nanofaceted α-Al 2 O 3 substrates - Thin films of microphase separated diblock copolymers - Magnetic nanostructures on diblock copolymer thin film templates The fact that the underlying self-assembly processes can be steered by external factors is utilized to optimize the degree of structural order in the nanostructured systems. The highly-ordered systems are well-suited for investigations with X-ray scattering methods, since due to their uniformity the inherently averaged scattered signal of a sample yields meaningful information on the properties of the contained nanostructures: By means of an in-situ GISAXS experiment at temperatures above 1000 C, details on the facet formation on α-Al 2 O 3 surfaces are determined. A novel method, merging in-situ GISAXS and NRS, shows the evolution of magnetic states in a system with correlated structural and magnetic inhomogeneity with lateral resolution. The temperature-dependence of the shape of Fe nanodots growing on diblock copolymer templates is revealed by in-situ GISAXS during sputter deposition of Fe. Combining in-situ GISAXS and NRS, the magnetization

  10. Patterns of order processing : a study of the formalization of the ordering process in order-driven manufacturing companies

    NARCIS (Netherlands)

    Welker, Geertruida Annigje

    2004-01-01

    It is essential for many order-driven manufacturing companies to be able to respond quickly to changing customer demand. In this respect, the ordering process plays a central role, as coordination between demand and production takes places within this process. The ordering process must contribute to

  11. AN ORDERED MAGNETIC FIELD IN THE PROTOPLANETARY DISK OF AB Aur REVEALED BY MID-INFRARED POLARIMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Li, Dan; Pantin, Eric; Telesco, Charles M.; Zhang, Han; Barnes, Peter J.; Mariñas, Naibí [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, FL 32611 (United States); Wright, Christopher M. [School of Physical, Environmental, and Mathematical Sciences, University of New South Wales, Canberra, ACT 2610 (Australia); Packham, Chris, E-mail: d.li@ufl.edu [Physics and Astronomy Department, University of Texas at San Antonio, 1 UTSA Circle, San Antonio, TX 78249 (United States)

    2016-11-20

    Magnetic fields ( B -fields) play a key role in the formation and evolution of protoplanetary disks, but their properties are poorly understood due to the lack of observational constraints. Using CanariCam at the 10.4 m Gran Telescopio Canarias, we have mapped out the mid-infrared polarization of the protoplanetary disk around the Herbig Ae star AB Aur. We detect ∼0.44% polarization at 10.3 μ m from AB Aur's inner disk ( r  < 80 au), rising to ∼1.4% at larger radii. Our simulations imply that the mid-infrared polarization of the inner disk arises from dichroic emission of elongated particles aligned in a disk B -field. The field is well ordered on a spatial scale, commensurate with our resolution (∼50 au), and we infer a poloidal shape tilted from the rotational axis of the disk. The disk of AB Aur is optically thick at 10.3 μ m, so polarimetry at this wavelength is probing the B -field near the disk surface. Our observations therefore confirm that this layer, favored by some theoretical studies for developing magneto-rotational instability and its resultant viscosity, is indeed very likely to be magnetized. At radii beyond ∼80 au, the mid-infrared polarization results primarily from scattering by dust grains with sizes up to ∼1 μ m, a size indicating both grain growth and, probably, turbulent lofting of the particles from the disk mid-plane.

  12. Influence of strain and polycrystalline ordering on magnetic properties of high moment rare earth metals and alloys

    International Nuclear Information System (INIS)

    Scheunert, G; Ward, C; Hendren, W R; Bowman, R M; Lapicki, A A; Hardeman, R; Mooney, M; Gubbins, M

    2014-01-01

    Despite being the most suitable candidates for solenoid pole pieces in state-of-the-art superconductor-based electromagnets, the intrinsic magnetic properties of heavy rare earth metals and their alloys have gained comparatively little attention. With the potential of integration in micro and nanoscale devices, thin films of Gd, Dy, Tb, DyGd and DyTb were plasma-sputtered and investigated for their in-plane magnetic properties, with an emphasis on magnetization versus temperature profiles. Based on crystal structure analysis of the polycrystalline rare earth films, which consist of a low magnetic moment fcc layer at the seed interface topped with a higher moment hcp layer, an experimental protocol is introduced which allows the direct magnetic analysis of the individual layers. In line with the general trend of heavy lanthanides, the saturation magnetization was found to drop with increasing unit cell size. In situ annealed rare earth films exceeded the saturation magnetization of a high-moment Fe 65 Co 35 reference film in the cryogenic temperature regime, proving their potential for pole piece applications; however as-deposited rare earth films were found completely unsuitable. In agreement with theoretical predictions, sufficiently strained crystal phases of Tb and Dy did not exhibit an incommensurate magnetic order, unlike their single-crystal counterparts which have a helical phase. DyGd and DyTb alloys followed the trends of the elemental rare earth metals in terms of crystal structure and magnetic properties. Inter-rare-earth alloys hence present a desirable blend of saturation magnetization and operating temperature. (paper)

  13. Coupling of structure to magnetic and superconducting orders in quasi-one-dimensional K2Cr3As3

    Science.gov (United States)

    Taddei, K. M.; Zheng, Q.; Sefat, A. S.; de la Cruz, C.

    2017-11-01

    Quasi-one-dimensional A2Cr3As3 (with A =K , Cs, Rb) is an intriguing new family of superconductors which exhibit many similar features to the cuprate and iron-based unconventional superconductor families. Yet, in contrast to these systems, no charge or magnetic ordering has been observed which could provide the electronic correlations presumed necessary for an unconventional superconducting pairing mechanism—an absence which defies predictions of first-principles models. We report the results of neutron scattering experiments on polycrystalline K2Cr3As3 (Tc˜7 K ) which probed the low-temperature dynamics near Tc. Neutron diffraction data evidence a subtle response of the nuclear lattice to the onset of superconductivity while inelastic scattering reveals a highly dispersive column of intensity at the commensurate wave vector q =(00 1/2 ) which loses intensity beneath Tc—indicative of short-range magnetic fluctuations. Using linear spin-wave theory, we model the observed scattering and suggest a possible structure to the short-range magnetic order. These observations suggest that K2Cr3As3 is in close proximity to a magnetic instability and that the incipient magnetic order both couples strongly to the lattice and competes with superconductivity, in direct analogy with the iron-based superconductors.

  14. Magnetic microwires a magneto-optical study

    CERN Document Server

    Chizhik, Alexander

    2014-01-01

    PrefaceKerr Effect as Method of Investigation of Magnetization Reversal in Magnetic Wires Cold-Drawn Fe-Rich Amorphous Wire Conventional Co-Rich Amorphous WireInteraction Between Glass-Covered MicrowiresCircular Magnetic Bistability in Co-Rich Amorphous Microwires Effect of High-Frequency Driving Current on Magnetization Reversal in Co-Rich Amorphous MicrowiresRelation Between Surface Magnetization Reversal and Magnetoimpedance Helical Magnetic Structure Magnetization Reversal in Crossed Magnetic Field Visualization of Barkhausen Jump Magnetizatio

  15. Study of aging and ordering processes in titanium carbide

    International Nuclear Information System (INIS)

    Arbuzov, M.P.; Khaenko, B.V.; Kachkovskaya, Eh.T.

    1977-01-01

    Aging and ordering processes in titanium carbide were investigated on monocrystals (fragments of alloys) with the aid of roentgenographic method. The sequence of phase transformations during aging was ascertained,and a monoclinic structure of the carbon atoms ordering is suggested. The microhardness of titanium carbide was studied as a function of the heat treatment of alloys and the main factors (ordering and dislocation structure) which govern the difference in the microhardness of hardened and aged (annealed) specimens were determined

  16. Spontaneous magnetization of thin films of ordered and disordered alloys of transition metals

    International Nuclear Information System (INIS)

    Nguyen Nhat Khanh.

    1989-12-01

    A method of calculation of spontaneous magnetization of thin films of transition metal alloys is described. The method is based on the Hubbard model for d electrons. Use of the Bragg-Williams approximation and two-dimensional canonical transformations has allowed to calculate the magnetization. Results for a Ni 3 Fe thin film are presented. (author). 11 refs, 1 fig

  17. Magnetic behavior study of samarium nitride using density functional theory

    Science.gov (United States)

    Som, Narayan N.; Mankad, Venu H.; Dabhi, Shweta D.; Patel, Anjali; Jha, Prafulla K.

    2018-02-01

    In this work, the state-of-art density functional theory is employed to study the structural, electronic and magnetic properties of samarium nitride (SmN). We have performed calculation for both ferromagnetic and antiferromagnetic states in rock-salt phase. The calculated results of optimized lattice parameter and magnetic moment agree well with the available experimental and theoretical values. From energy band diagram and electronic density of states, we observe a half-metallic behaviour in FM phase of rock salt SmN in while metallicity in AFM I and AFM III phases. We present and discuss our current understanding of the possible half-metallicity together with the magnetic ordering in SmN. The calculated phonon dispersion curves shows dynamical stability of the considered structures. The phonon density of states and Eliashberg functional have also been analysed to understand the superconductivity in SmN.

  18. X-ray scattering studies of non-equilibrium ordering processes

    International Nuclear Information System (INIS)

    Nagler, S.E.

    1992-01-01

    This report summarizes the major results obtained under US DOE Grant Number FG05-90ER45280 from the dates November 1, 1989 through October 31, 1992 inclusive. The principal work includes x-ray scattering studies of phase transition kinetics in binary alloy order-disorder transitions, block co-polymer crystallization, and charge density wave solids under applied electric fields, and studies of magnetic excitations in low dimensional quantum systems

  19. Study on optimization design of superconducting magnet for magnetic force assisted drug delivery system

    International Nuclear Information System (INIS)

    Fukui, S.; Abe, R.; Ogawa, J.; Oka, T.; Yamaguchi, M.; Sato, T.; Imaizumi, H.

    2007-01-01

    Analytical study on the design of the superconducting magnet for the magnetic force assisted drug delivery system is presented in this paper. The necessary magnetic field condition to reside the magnetic drug particle in the blood vessels is determined by analyzing the particle motion in the blood vessel. The design procedure of the superconducting magnet for the M-DDS is presented and some case studies are conducted. The analytical results show that the superconducting magnet to satisfy the magnetic field conduction for the M-DDS is practically feasible

  20. Fabrication and analysis of ordered magnetic cobalt nanoparticles; Herstellung und Untersuchung geordneter magnetischer Kobaltnanoteilchen

    Energy Technology Data Exchange (ETDEWEB)

    Zuern, Klaus P.

    2009-12-17

    In the dissertation on hand monodisperse, wellordered magnetic cobalt and cobalt hydride nanoparticles have been produced and investigated magnetically. The preparation was achieved by diblock-copolymer-micelles filled with cobalt salt, from which nanoparticles of elementary cobalt respectively cobalt hydride were generated in different steps of the procedure. It was evident that the cobalthydride generated by the hydrogen plasma was surprisingly stable. It could even be taken into consideration as a hydrogen storage device for fuel cell. The magnetic properties of the particles has been investigated by x-ray magnetic circular dichroism (XMCD). In addition it was evident, that it was principally impossible to investigate a film layered on a substrate with a SQUID-magnetometer, if this film produces only a small signal as well absolutely as relatively to the magnetically measured total moment of the sample. (orig.)

  1. Change in the order parameter of a superconductor of type I in the presence of magnetic dipoles

    International Nuclear Information System (INIS)

    Lebeau, C.; Pinel, J.

    1977-01-01

    Taking the order parameter to be spatially constant, we show that magnetic dipoles modify the energy with a term proportional to the difference between the local fields in the normal and supercondcuting states. Evaluation of this difference predicts a second-order transition. The transition temperature only depends on the mean value of ferromagnetic magnetisation. Specific heat and susceptibility measurements made on HgFe are compared with this model [fr

  2. Tunable Majorana corner states in a two-dimensional second-order topological superconductor induced by magnetic fields

    Science.gov (United States)

    Zhu, Xiaoyu

    2018-05-01

    A two-dimensional second-order topological superconductor exhibits a finite gap in both bulk and edges, with the nontrivial topology manifesting itself through Majorana zero modes localized at the corners, i.e., Majorana corner states. We investigate a time-reversal-invariant topological superconductor in two dimensions and demonstrate that an in-plane magnetic field could transform it into a second-order topological superconductor. A detailed analysis reveals that the magnetic field gives rise to mass terms which take distinct values among the edges, and Majorana corner states naturally emerge at the intersection of two adjacent edges with opposite masses. With the rotation of the magnetic field, Majorana corner states localized around the boundary may hop from one corner to a neighboring one and eventually make a full circle around the system when the field rotates by 2 π . In the end, we briefly discuss physical realizations of this system.

  3. Magnetic ordering and electrical resistivity in Co0.2Zn0.8Fe2O4 spinel oxide

    International Nuclear Information System (INIS)

    Bhowmik, R.N.; Ranganathan, R.; Ghosh, B.; Kumar, S.; Chattopadhyay, S.

    2008-01-01

    We report the magnetic, Moessbauer spectroscopy and resistivity measurements in order to understand the electronic behaviour of bulk Co 0.2 Zn 0.8 Fe 2 O 4 spinel oxide. The effect of magnetic order on electrical behaviour is observed from the resistivity measurements in the absence and presence of magnetic field. The analysis of Moessbauer spectra suggests the absence of Fe 2+ ions in the system, which implies that complete hopping of charge carriers between localized Fe 3+ /Co 2+ and Fe 2+ /Co 3+ pair of ions in B sublattice is not the favourable mechanism in Co 0.2 Zn 0.8 Fe 2 O 4 . We suggest that electrical behaviour of the present sample may be consistent with a model of fractional charge transfer via Fe B 3+ -O 2- -Co B 2+ superexchange path

  4. First order magnetic transition in single crystal CaFe2As2 detected by 75As NMR

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Seung Ho [Los Alamos National Laboratory; Curro, Nicholas J [UC - DAVIS

    2008-01-01

    We report {sup 75}As Nuclear Magnetic Resonance data in a single crystal of CaFe{sub 2}As{sub 2}. The Knight shift, the electric field gradient, and the spin lattice relaxation rate are strongly temperature dependent in the paramagnetic state, and change discontinuously at the structural transition temperature, T{sub S} = T{sub N} = 167 K. Immediately below, the NMR spectra reveal an internal field at the As site associated with the presence of a commensurate magnetic order. These results indicate that the structural and magnetic transitions in CaFe{sub 2}As{sub 2} are first order and strongly coupled, and that the electron density in the FeAs plane is highly sensitive to the out-of-plane structure.

  5. Size dependence study of the ordering temperature in the Fast Monte Carlo method

    Energy Technology Data Exchange (ETDEWEB)

    Velasquez, E. A., E-mail: eavelas@gmail.com [Universidad de San Buenaventura Seccional Medellin, Grupo de Investigacion en Modelamiento y Simulacion Computacional, Facultad de Ingenierias (Colombia); Mazo-Zuluaga, J., E-mail: johanmazo@gmail.com [Universidad de Antioquia, Grupo de Estado Solido, Grupo de Instrumentacion Cientifica y Microelectronica, Instituto de Fisica-FCEN (Colombia); Mejia-Lopez, J., E-mail: jmejia@puc.cl [Universidad de Antioquia, Instituto de Fisica-FCEN (Colombia)

    2013-02-15

    Based on the framework of the Fast Monte Carlo approach, we study the diameter dependence of the ordering temperature in magnetic nanostructures of cylindrical shape. For the purposes of this study, Fe cylindrical-shaped samples of different sizes (20 nm height, 30-100 nm in diameter) have been chosen, and their magnetic properties have been computed as functions of the scaled temperature. Two main set of results are concluded: (a) the ordering temperature of nanostructures follows a linear scaling relationship as a function of the scaling factor x, for all the studied sizes. This finding rules out a scaling relation T Prime {sub c} = x{sup 3{eta}}T{sub c} (where {eta} is a scaling exponent, and T Prime {sub c} and T{sub c} are the scaled and true ordering temperatures) that has been proposed in the literature, and suggests that temperature should scale linearly with the scaling factor x. (b) For the nanostructures, there are three different order-disorder magnetic transition modes depending on the system's size, in very good agreement with previous experimental reports.

  6. Fundamental study on magnetic separation of aquatic organisms for preservation of marine ecosystem

    International Nuclear Information System (INIS)

    Sakaguchi, F.; Akiyama, Y.; Izumi, Y.; Nishijima, S.

    2009-01-01

    Recently, destruction and disturbance of marine ecosystem have been caused by changes in global environment and transplants of farmed fishes and shellfishes. To solve the problems, water treatment techniques to kill or to remove aquatic organisms are necessary. In this study, application of magnetic separation for removal of the aquatic organisms was examined in order to establish the process with high-speed, compact device and low environmental load. Techniques of magnetic seeding and magnetic separation using superconducting magnet are important for high-speed processing of aquatic organisms. Magnetic seeding is to adhere separating object to the surface of ferromagnetic particles, and magnetic separation is to remove aquatic organisms with magnetic force. First, we confirmed the possibility of magnetic seeding of aquatic organisms, and then interaction between aquatic organisms and ferromagnetic particles was examined. Next, for practical application of magnetic separation system using superconducting magnet for removal of aquatic organisms, particle trajectories were simulated and magnetic separation experiment using superconducting magnet was performed in order to design magnetic separation system to achieve high separation efficiency.

  7. Magnetic ordering of quasi-1 D S=1/2 Heisenberg antiferromagnet Cu benzoate at sub-mK temperatures

    International Nuclear Information System (INIS)

    Karaki, Y.; Masutomi, R.; Kubota, M.; Ishimoto, H.; Asano, T.; Ajiro, Y.

    2003-01-01

    We have measured the AC susceptibility of quasi-1D S=1/2 Heisenberg antiferromagnet Cu benzoate at temperatures down to 0.2 mK. A sharp susceptibility peak is observed at 0.8 mK under an earth field. This fact indicates a 3D ordering of linear chains coupled by a weak magnetic interaction between chains

  8. 2D to 3D crossover of the magnetic properties in ordered arrays of iron oxide nanocrystals

    DEFF Research Database (Denmark)

    Faure, Bertrand; Wetterskog, Erik; Gunnarsson, Klas

    2013-01-01

    The magnetic 2D to 3D crossover behavior of well-ordered arrays of monodomain γ-Fe2O3 spherical nanoparticles with different thicknesses has been investigated by magnetometry and Monte Carlo (MC) simulations. Using the structural information of the arrays obtained from grazing incidence small-ang...

  9. Magnetic resonance studies of solid polymers

    International Nuclear Information System (INIS)

    Lenk, R.

    1969-01-01

    This paper is a review of the application of nuclear magnetic resonance (NMR) to solid polymers. In the first, theoretical part, the elements of the theory of NMR, which are necessary for the study of the properties of solid polymers are discussed: the moments method, nuclear relaxation and the distribution of correlation times. In the second part the experimental results are presented. (author) [fr

  10. Ball solitons in kinetics of the first order magnetic phase transition

    International Nuclear Information System (INIS)

    Nietz, V.V.; Osipov, A.A.

    2007-01-01

    The theory of magnetic ball solitons (BS), arising as a result of the energy fluctuations at the spin-flop transition induced by a magnetic field in antiferromagnets with uniaxial anisotropy, is presented. Such solitons are possible in a wide range of amplitudes and energies, including the negative energy relative to an initial condition. When such an antiferromagnet is in a metastable condition, ball solitons are born with the greatest probability if the energy of solitons is close to zero. Evolution of these solitons, at which they develop into macroscopic domains of a new magnetic phase, is analyzed, thus carrying out full phase reorganization

  11. The order parameter equations of superfluid Fermi-liquid with spin-triplet pairing near Tc in magnetic field

    International Nuclear Information System (INIS)

    Tarasov, A.N.

    1995-01-01

    The article is devoted to description of equilibrium properties of superfluid phases of 3 He in magnetic field at temperatures near the normal-superfluid point T c . The Landau Fermi-liquid (F-L) approach generalized to superfluid Fermi-liquids (SFLs) is used. Equations for the order parameter paramagnetic SFL with spin-triplet pairing in static and uniform (DC) moderately strong magnetic field are derived without taking into account strong-coupling (SC) effects. An integro-differential equation is deduced for the order parameter in the general case of spin-triplet pairing (spin of a pair is s = 1, orbital moment l of a pair is any odd number). It is valid in the approximation of small space inhomogeneities of the SFL for external DC magnetic field at temperatures near T c . In the case of spin-triplet p-wave pairing a Ginzburg-Landau (GL) equation is derived for the order parameter A αj (complex 3 x 3 matrix). Corrections to the coefficients in the GL eq. are resulted from taking into account the influence of moderately strong DC magnetic field and spin-exchange F-L interaction by the theory of permutations. In such fields these corrections can be of the same order of magnitude as the so-called > SC corrections to the GL eq. (or even exceed them) and are much higher than the particle-hole asymmetric contribution. The above corrections are connected with deformation of the order parameter in moderate magnetic fields and are of interest at description of 3 He - B at low pressures

  12. Coexistence of magnetic order and valence fluctuations in a heavy fermion system Ce{sub 2}Rh{sub 3}Sn{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Gamza, Monika [Jeremiah Horrocks Institute, University of Central Lancashire, Preston (United Kingdom); MPI CPfS, Dresden (Germany); Institute of Physics, University of Silesia, Katowice (Poland); Gumeniuk, Roman [Institute of Experimental Physics, Freiberg University of Mining and Technology, Freiberg (Germany); MPI CPfS, Dresden (Germany); Schnelle, Walter; Burkhardt, Ulrich; Rosner, Helge [MPI CPfS, Dresden (Germany); Slebarski, Andrzej [Institute of Physics, University of Silesia, Katowice (Poland)

    2016-07-01

    While most Ce-based intermetallics contain either trivalent or intermediate-valent Ce ions, only for a few compounds a coexistence of both species has been reported. Here, we present a combined experimental and theoretical study based on thermodynamic measurements and spectroscopic data together with ab-initio electronic structure calculations aiming at exploring magnetic properties of Ce ions in two nonequivalent sites in Ce{sub 2}Rh{sub 3}Sn{sub 5}. Ce L{sub III} XAS spectra give direct evidence for valence fluctuations. Magnetization measurements show an onset of an antiferromagnetic order at T{sub N}∼2.5 K. The electronic structure calculations suggest that the magnetic ordering is related only to one Ce sublattice. This is in-line with a small entropy associated with the magnetic transition S{sub mag}∼0.35 R ln2 per Ce atom as revealed by the specific heat measurement. Furthermore, the temperature dependence of the magnetic susceptibility can be well described assuming that there are fluctuating moments of Ce{sup 3+} ions in one sublattice, whereas Ce atoms from the second sublattice are in a nonmagnetic intermediate valence state.

  13. Discovery of a new phase with magnetic short range correlations and its possible relevance for the hidden order in URu{sub 2}Si{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Sykora, Steffen [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany); Becker, Klaus W. [Technische Universitaet Dresden, D-01062 Dresden (Germany)

    2016-07-01

    In this paper we discuss a new phase of the Kondo lattice model which arises from the competition of Kondo and RKKY energy scales. Normally the Kondo lattice model is used to capture the low-energy physics of heavy fermion systems. However, according to the so-called Doniach picture the Kondo state will be replaced by an antiferromagnetic state for the case that the Kondo energy scale becomes smaller than the magnetic interaction between magnetic ions. In the present study we start instead from a modified electronic one-particle dispersion which avoids nesting of particle-hole excitations. Thus the magnetic ordered state should be suppressed which provides an opportunity for the inset of a new low-energy state with competing Kondo and magnetic energies. As will be shown, this new state avoids magnetic symmetry breaking but leads to a number of physical properties which are relevant for the understanding of the hidden order state in URu{sub 2}Si{sub 2}.

  14. Minimisation of higher order harmonics for large aperture super-ferric quadrupole magnet

    International Nuclear Information System (INIS)

    Dutta, Atanu; Sharma, P.R.; Dey, M.K.; Bhunia, U.; Nandy, C.; Roy, S.; Pal, G.; Mallik, C.

    2011-01-01

    We have analysed the magnetic field of finite length (effective length of 1200 mm), large bore (pole radius of 350 mm) superconducting quadrupole magnets for use in Low Energy Branch of Super FRS with the program TOSCA. In particularly we have tried to minimize the 12-pole and 20-pole components, which would contribute to geometric aberrations. At the same time we have tried to keep the gradient field uniformity at reference radius 300 mm within ±8.0E-04. (author)

  15. The Problem of World Order in Western IR Studies

    OpenAIRE

    Maria Victorovna Soljanova

    2016-01-01

    The article "Problem of world order in modern Western studies" is the study of one of the most debated issues in the science of international relations - world order. Discussion of the structure of world order is underway in various countries, both at the state level and in the expert community. Some researchers insist on the fact that after the end of the cold war, the collapse of the bipolar model of international relations, the world has become unipolar. Others argue that the increase in t...

  16. The Magnetic Reconnection Code: Center for Magnetic Reconnection Studies

    Energy Technology Data Exchange (ETDEWEB)

    Amitava Bhattacharjee

    2007-04-20

    Understanding magnetic reconnection is one of the principal challenges in plasma physics. Reconnection is a process by which magnetic fields reconfigure themselves, releasing energy that can be converted to particle energies and bulk flows. Thanks to the availability of sophisticated diagnostics in fusion and laboratory experiments, in situ probing of magnetospheric and solar wind plasmas, and X-ray emission measurements from solar and stellar plasmas, theoretical models of magnetic reconnection can now be constrained by stringent observational tests. The members of the CMRS comprise an interdisciplinary group drawn from applied mathematics, astrophysics, computer science, fluid dynamics, plasma physics, and space science communities.

  17. Synergy of exchange bias with superconductivity in ferromagnetic-superconducting layered hybrids: the influence of in-plane and out-of-plane magnetic order on superconductivity

    International Nuclear Information System (INIS)

    Stamopoulos, D; Manios, E; Pissas, M

    2007-01-01

    It is generally believed that superconductivity and magnetism are two antagonistic long-range phenomena. However, as was preliminarily highlighted in Stamopoulos et al (2007 Phys. Rev. B 75 014501), and extensively studied in this work, under specific circumstances these phenomena instead of being detrimental to each other may even become cooperative so that their synergy may promote the superconducting properties of a hybrid structure. Here, we have studied systematically the magnetic and transport behavior of such exchange biased hybrids that are comprised of ferromagnetic (FM) Ni 80 Fe 20 and low-T c superconducting (SC) Nb for the case where the magnetic field is applied parallel to the specimens. Two structures have been studied: FM-SC-FM trilayers (TLs) and FM-SC bilayers (BLs). Detailed magnetization data on the longitudinal and transverse magnetic components are presented for both the normal and superconducting states. These data are compared to systematic transport measurements including I-V characteristics. The comparison of the exchange biased BLs and TLs that are studied here with the plain ones studied in Stamopoulos et al (2007 Phys. Rev. B 75 184504) enable us to reveal an underlying parameter that may falsify the interpretation of the transport properties of relevant FM-SC-FM TLs and FM-SC BLs investigated in the recent literature: the underlying mechanism motivating the extreme magnetoresistance peaks in the TLs relates to the suppression of superconductivity mainly due to the magnetic coupling of the two FM layers as the out-of-plane rotation of their magnetizations takes place across the coercive field where stray fields emerge in their whole surface owing to the multidomain magnetic state that they acquire. The relative in-plane magnetization configuration of the outer FM layers exerts a secondary contribution on the SC interlayer. Since the exchange bias directly controls the in-plane magnetic order it also controls the out-of-plane rotation of

  18. Transport Studies of Quantum Magnetism: Physics and Methods

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Minhyea [Univ. of Colorado, Boulder, CO (United States)

    2017-03-30

    The main goal of this project was to understand novel ground states of spin systems probed by thermal and electrical transport measurements. They are well-suited to characterize the nature of low-energy excitations as unique property of the ground state. More specifically, it was aimed to study the transverse electrical conductivity in the presence of non-collinear and non-coplanar spin ordering and the effects of gauge field as well as novel spin excitations as a coherent heat transport channel in insulating quantum magnets. Most of works done during the grant period focused on these topics. As a natural extension of the project's initial goals, the scope was broadened to include transport studies on the spin systems with strong spin-orbit coupling. One particular focus was an exploration of systems with strong magnetic anisotropy combined with non-trivial spin configuration. Magnetic anisotropy is directly related to implement the non-collinear spin ordering to the existing common geometry of planar devices and thus poses a significant potential. Work in this direction includes the comparison of the topological Hall signal under hydrostatic pressure and chemical doping, as well as the angular dependence dependence of the non-collinear spin ordered phase and their evolution up on temperature and field strength. Another focus was centered around the experimental identification of spin-originated heat carrying excitation in quasi two dimensional honeycomb lattice, where Kitaev type of quantum spin liquid phase is expected to emerge. In fact, when its long range magnetic order is destroyed by the applied field, we discovered anomalously large enhancement of thermal conductivity, for which proximate Kitaev excitations in field-induced spin liquid state are responsible for. This work, combined with further investigations in materials in the similar class may help establish the experimental characterization of new quantum spin liquid and their unique low energy

  19. 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.

  20. Coexistence of superconductivity and magnetism in Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2}. Universal suppression of the magnetic order parameter in 122 iron pnictides

    Energy Technology Data Exchange (ETDEWEB)

    Materne, Philipp; Kamusella, Sirko; Sarkar, Rajib; Klauss, Hans-Henning [IFP, TU Dresden, 01062 Dresden (Germany); Harnagea, Luminita [IFW Dresden, Postfach 270016, 01171 Dresden (Germany); Wurmehl, Sabine; Buechner, Bernd [IFP, TU Dresden, 01062 Dresden (Germany); IFW Dresden, Postfach 270016, 01171 Dresden (Germany); Luetkens, Hubertus [PSI, 5232 Villigen (Switzerland); Timm, Carsten [ITP, TU Dresden, 01062 Dresden (Germany)

    2016-07-01

    We examined Ca{sub 1-x}Na{sub x}Fe{sub 2}As{sub 2} single crystals with x=0.00, 0.35, 0.50, and 0.67 by means of muon spin relaxation and Moessbauer spectroscopy to investigate the electronic and structural properties of these compounds. CaFe{sub 2}As{sub 2} is a semimetal, which shows spin density wave order below 167 K. By hole doping via Ca→Na substitution, the magnetic order is suppressed and superconductivity emerges with T{sub c}∼34K at optimal doping including a substitution level region where both phases coexist. We have studied the interplay of order parameters in this coexistence region and found nanoscopic coexistence of both order parameters. This is proven by a reduction of the magnetic order parameter by 7% below the superconducting transition temperature. We present a systematic correlation between the reduction of the magnetic order parameter and the ratio of the transition temperatures, T{sub c}/T{sub N}, for the 122 family of the iron-based superconductors.

  1. Some neutron scattering studies on magnetic and molecular phase transitions

    International Nuclear Information System (INIS)

    Bevaart, L.

    1978-01-01

    In this thesis neutron-scattering investigations on two different systems are described. The first study is concerned with the magnetic ordering phenomena in pseudo two-dimensional (d = 2), two-component antiferromagnets K 2 Mnsub(1-x)Msub(x)F 4 (M = Fe, Co), as a function of the composition x and temperature T. For one of the samples in this series, K 2 Musub(0.978)Fesub(0.022)F 4 , the influence of an external magnetic field on the ordering characteristics was studied in addition. The second study deals with the rotational motions of the NH 4 + groups in NH 4 ZnF 3 in relation with the structural phase transition at Tsub(c) = 115.1 K. The experimental techniques were chosen according to the requirements of each of these two subjects. The former study was carried out by observing the elastic magnetic neutron scattering with a double-axis diffractometer, whereas for the latter study time-of-flight (TOF) techniques were applied to observe the inelastic and quasi-elastic incoherent neutron scattering by the protons of the rotating NH 4 + groups. (Auth.)

  2. 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

  3. Polar and Magnetic Layered A Site and Rock Salt B Site-Ordered NaLnFeWO6 (Ln = La, Nd) Perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Tetuerto, Maria [State University of New Jersey, The; Li, Mang-Rong [State University of New Jersey, The; Ignatov, Alexander [State University of New Jersey, The; Croft, Mark [State University of New Jersey, The; Ramanujachary, Kandalam V. [Rowan University; Chi, Songxue [ORNL; Hodges, Jason P [ORNL; Dachraoui, W. [University of Antwerp; Hadermann, Joke [University of Antwerp; Thao Tran, T. [University of Houston, Houston; Shiv Halasyamani, P. [University of Houston, Houston; Grams, C. [Universitat zu Koln, Koln, Germany; Hemberger, J. [Universitat zu Koln, Koln, Germany; Greenblatt, M. [State University of New Jersey, The

    2013-01-01

    We have expanded the double perovskite family of materials with the unusual combination of layered order in the A sublattice and rock salt order over the B sublattice to compounds NaLaFeWO6 and NaNdFeWO6. The materials have been synthesized and studied by powder X-ray diffraction, neutron diffraction, electron diffraction, magnetic measurements, X-ray absorption spectroscopy, dielectric measurements, and second harmonic generation. At room temperature, the crystal structures of both compounds can be defined in the noncentrosymmetric monoclinic P21 space group resulting from the combination of ordering both in the A and B sublattices, the distortion of the cell due to tilting of the octahedra, and the displacement of certain cations. The magnetic studies show that both compounds are ordered antiferromagnetically below TN 25 K for NaLaFeWO6 and at 21 K for NaNdFeWO6. The magnetic structure of NaNdFeWO6 has been solved with a propagation vector k = (1/2 0 1/2) as an antiferromagnetic arrangement of Fe and Nd moments. Although the samples are potential multiferroics, the dielectric measurements do not show a ferroelectric response.

  4. Marine magnetic studies in the northern Bay of Bengal, preliminary results

    Digital Repository Service at National Institute of Oceanography (India)

    Ramana, M.V.; Subrahmanyam, V.; Krishna, K.S.; Chaubey, A.K.; Sarma, K.V.L.N.S.; Murty, G.P.S.; Murty, P.S.N.; Rao, D.G.; Mittal, G.S.; Drolia, R.K.

    The bathymetric and total magnetic intensity data collected along six E-W tracks were analysed and presented as stacked anomaly profiles. A first order basement configuration model was generated across the Bay of Bengal. The model studies indicate...

  5. Identifying intestinal malrotation on magnetic resonance examinations ordered for unrelated indications

    International Nuclear Information System (INIS)

    Fay, Jill S.; Chernyak, Victoria; Taragin, Benjamin H.

    2017-01-01

    Anatomical imaging findings indicating normal bowel rotation can be identified on cross-sectional imaging, including magnetic resonance imaging (MRI) performed for non-related indications. The goal of our study was to assess whether non-targeted MRI can accurately assess intestinal malrotation. Four anatomical landmarks were assessed on MRIs of the chest, spine or abdomen performed from January 2006 to June 2014, on patients who also had upper gastrointestinal series (UGI) performed within 10 years of the MRI date: 1) retroperitoneal duodenum, 2) left upper quadrant duodenojejunal junction, 3) superior mesenteric artery to the left of the superior mesenteric vein, and 4) right lower quadrant cecum. Two attending radiologists, one pediatric and one abdominal radiologist, independently reviewed the MR images. The pediatric radiologist reviewed images from UGI (considered the gold standard) to determine the intestinal rotation for each case. Validation of the criteria was performed on new patients imaged through January 2016. The original cohort included 109 MRIs (15 chest, 41 spine and 53 abdomen) done on 109 patients (42% males, mean age: 10.2 years). If each of the 4 anatomical questions were answered ''yes'' (4-YES), specificity was 100% for each radiologist and malrotation was appropriately excluded. Using the 4-YES criteria, the pediatric radiologist excluded malrotation in 71 patients (65%) and the abdominal radiologist excluded it in 65 (60%), with concurrence for 57 patients. Validation of the 4-YES criteria in 23 new patients appropriately proved the 4-YES rule, with neither labeling the one new malrotation case 4-YES. If a radiologist can confidently answer ''yes'' to the four questions evaluated in this study, then intestinal rotation can be safely considered normal. Normal bowel rotation should be commented upon in MRI reports when these four anatomical locations are imaged, thus helping patients avoid unnecessary

  6. Identifying intestinal malrotation on magnetic resonance examinations ordered for unrelated indications

    Energy Technology Data Exchange (ETDEWEB)

    Fay, Jill S.; Chernyak, Victoria; Taragin, Benjamin H. [Montefiore Medical Center, Department of Diagnostic Radiology, Bronx, NY (United States)

    2017-10-15

    Anatomical imaging findings indicating normal bowel rotation can be identified on cross-sectional imaging, including magnetic resonance imaging (MRI) performed for non-related indications. The goal of our study was to assess whether non-targeted MRI can accurately assess intestinal malrotation. Four anatomical landmarks were assessed on MRIs of the chest, spine or abdomen performed from January 2006 to June 2014, on patients who also had upper gastrointestinal series (UGI) performed within 10 years of the MRI date: 1) retroperitoneal duodenum, 2) left upper quadrant duodenojejunal junction, 3) superior mesenteric artery to the left of the superior mesenteric vein, and 4) right lower quadrant cecum. Two attending radiologists, one pediatric and one abdominal radiologist, independently reviewed the MR images. The pediatric radiologist reviewed images from UGI (considered the gold standard) to determine the intestinal rotation for each case. Validation of the criteria was performed on new patients imaged through January 2016. The original cohort included 109 MRIs (15 chest, 41 spine and 53 abdomen) done on 109 patients (42% males, mean age: 10.2 years). If each of the 4 anatomical questions were answered ''yes'' (4-YES), specificity was 100% for each radiologist and malrotation was appropriately excluded. Using the 4-YES criteria, the pediatric radiologist excluded malrotation in 71 patients (65%) and the abdominal radiologist excluded it in 65 (60%), with concurrence for 57 patients. Validation of the 4-YES criteria in 23 new patients appropriately proved the 4-YES rule, with neither labeling the one new malrotation case 4-YES. If a radiologist can confidently answer ''yes'' to the four questions evaluated in this study, then intestinal rotation can be safely considered normal. Normal bowel rotation should be commented upon in MRI reports when these four anatomical locations are imaged, thus helping patients avoid unnecessary

  7. Intralayer Cation Ordering in a Brownmillerite Superstructure: Synthesis, Crystal, and Magnetic Structures of Ca2FeCoO5

    International Nuclear Information System (INIS)

    Ramezanipour, Farshid; Greedan, John E.; Grosvenor, Andrew; Britten, James; Cranswick, Lachlan M.D.

    2010-01-01

    The synthesis, crystal, and magnetic structures and the bulk magnetic properties of Ca2FeCoO5, a brownmillerite type oxide, are presented. The crystal structure, solved and refined from single crystal X-ray and powder neutron diffraction data, is described in Pbcm with cell parameters, a = 5.3652(3), b = 11.0995(5), c = 14.7982(7) . Thus, one axis, b in this setting, is doubled in comparison with the standard brownmillerite structure description giving rise to two sets of octahedral and tetrahedral sites. Aided by the strong scattering contrast between Fe and Co for neutrons, a nearly perfect intralayer cation site ordering, not observed for any brownmillerite before, is detected in the tetrahedral layers. There is a lesser degree of cation site ordering in the octahedral sites. Overall, the Fe/Co site ordering is of the NaCl type both within and between the tetrahedral and octahedral layers. There are also both intra- and interlayer ordering of tetrahedral chain orientations. The left- and right-handed orientations alternate within each tetrahedral layer as well as between the closest tetrahedral layers. The occurrence of the rare Pbcm space group in Ca2FeCoO5 is not consistent with a recently proposed structure-field map for brownmillerite oxides. The magnetic structure is G-type antiferromagnetic, with preferred orientation of magnetic moments parallel to the longest axis between 3.8 K to 100 K which switches to the shortest axis between 225 K and 550 K. The neutron diffraction data indicate different site specific ordering temperatures at about 450(5) K and 555(5) K. The refined ordered moments at 3.8 K are somewhat smaller than expected for Fe3+ and Co3+(high spin) but are similar to those found in Sr2FeCoO5. There is evidence for spin canting from isothermal magnetization data that shows well pronounced hystereses and remnant magnetizations at 5 K and 200 K.

  8. Study of the magnetic interaction in nanocrystalline Pr–Fe–Co–Nb–B permanent magnets

    International Nuclear Information System (INIS)

    Dospial, M.; Plusa, D.; Ślusarek, B.

    2012-01-01

    The magnetic properties of an isotropic, epoxy resin bonded magnets made from Pr–Fe–Co–Nb–B powder were investigated. The magnetization reversal process and magnetic parameters were examined by measurements of the initial magnetization curve, major and minor hysteresis loops and sets of recoil curves. From the initial magnetization curve and the field dependencies of the reversible and irreversible magnetization components derived from the recoil loops it was found that the magnetization reversal process is the combination of the nucleation of reversed domains and pinning of domain walls at the grain boundaries and the reversible rotation of magnetization vector in single domain grains. The interactions between grains were studied by means of δM plots. The nonlinear behavior of δM curve approve that the short range intergrain exchange coupling interactions are dominant in a field up to the sample coercivity. The interaction domains and fine magnetic structure were revealed as the evidence of exchange coupling between soft α-Fe and hard magnetic Nd 2 Fe 14 B grains. - Highlights: ► Coercivity of the Pr–Fe–Co–Nb–B magnet is determined by the pinning of domain walls at the grain boundaries. ► Rotation of magnetization vector and domain walls bowing also give the contribution to the initial and demagnetization process. ► δM behavior shows that the dominant interaction is the short range exchange one among soft magnetic α-Fe and hard magnetic Pr 2 Fe 14 B grains.

  9. The Optimization of Magnetic Resonance Imaging Pulse Sequences in Order to Better Detection of Multiple Sclerosis Plaques.

    Science.gov (United States)

    Farshidfar, Z; Faeghi, F; Haghighatkhah, H R; Abdolmohammadi, J

    2017-09-01

    Magnetic resonance imaging (MRI) is the most sensitive technique to detect multiple sclerosis (MS) plaques in central nervous system. In some cases, the patients who were suspected to MS, Whereas MRI images are normal, but whether patients don't have MS plaques or MRI images are not enough optimized enough in order to show MS plaques? The aim of the current study is evaluating the efficiency of different MRI sequences in order to better detection of MS plaques. In this cross-sectional study which was performed at Shohada-E Tajrish in Tehran - Iran hospital between October, 2011 to April, 2012, included 20 patients who suspected to MS disease were selected by the method of random sampling and underwent routine brain Pulse sequences (Axial T2w, Axial T1w, Coronal T2w, Sagittal T1w, Axial FLAIR) by Siemens, Avanto, 1.5 Tesla system. If any lesion which is suspected to the MS disease was observed, additional sequences such as: Sagittal FLAIR Fat Sat, Sagittal PDw-fat Sat, Sagittal PDw-water sat was also performed. This study was performed in about 52 lesions and the results in more than 19 lesions showed that, for the Subcortical and Infratentorial areas, PDWw sequence with fat suppression is the best choice, And in nearly 33 plaques located in Periventricular area, FLAIR Fat Sat was the most effective sequence than both PDw fat and water suppression pulse sequences. Although large plaques may visible in all images, but important problem in patients with suspected MS is screening the tiny MS plaques. This study showed that for revealing the MS plaques located in the Subcortical and Infratentorial areas, PDw-fat sat is the most effective sequence, and for MS plaques in the periventricular area, FLAIR fat Sat is the best choice.

  10. Spiral magnetic order, non-uniform states and electron correlations in the conducting transition metal systems

    Science.gov (United States)

    Igoshev, P. A.; Timirgazin, M. A.; Arzhnikov, A. K.; Antipin, T. V.; Irkhin, V. Yu.

    2017-10-01

    The ground-state magnetic phase diagram is calculated within the Hubbard and s-d exchange (Kondo) models for square and simple cubic lattices vs. band filling and interaction parameter. The difference of the results owing to the presence of localized moments in the latter model is discussed. We employ a generalized Hartree-Fock approximation (HFA) to treat commensurate ferromagnetic (FM), antiferromagnetic (AFM), and incommensurate (spiral) magnetic phases. The electron correlations are taken into account within the Hubbard model by using the Kotliar-Ruckenstein slave boson approximation (SBA). The main advantage of this approach is a correct qualitative description of the paramagnetic phase: its energy becomes considerably lower as compared with HFA, and the gain in the energy of magnetic phases is substantially reduced.

  11. Two dimensional electron transport in disordered and ordered distributions of magnetic flux vortices

    International Nuclear Information System (INIS)

    Nielsen, M.; Hedegaard, P.

    1994-04-01

    We have considered the conductivity properties of a two dimensional electron gas (2DEG) in two different kinds of inhomogeneous magnetic fields, i.e. a disordered distribution of magnetic flux vortices, and a periodic array of magnetic flux vortices. The work falls in two parts. In the first part we show how the phase shifts for an electron scattering on an isolated vortex, can be calculated analytically, and related to the transport properties through the differential cross section. In the second part we present numerical results for the Hall conductivity of the 2DEG in a periodic array of flux vortices found by exact diagonalization. We find characteristic spikes in the Hall conductance, when it is plotted against the filling fraction. It is argued that the spikes can be interpreted in terms of ''topological charge'' piling up across local and global gaps in the energy spectrum. (au) (23 refs.)

  12. Chemical elements in invertebrate orders for environmental quality studies

    International Nuclear Information System (INIS)

    Magalhaes, Marcelo R.L.; Franca, Elvis J.; Paiva, Jose D.S.; Hazin, Clovis A.; Fonseca, Felipe Y.; Fernandes, Elisabete A. de Nadai; Bacchi, Marcio A.

    2013-01-01

    Among the biomonitors of environmental quality, there is a lack of studies on using invertebrates to evaluate quantitatively chemical elements in ecosystems. This group of animals is quite numerous, widely distributed and adaptable to the most diverse environmental conditions. These features are very useful for the environmental quality assessment, as well as the several occurring insect-plant interactions performing essential functions in ecosystems. The objective of this work is to study the variability of chemical composition of invertebrate orders for using in environmental quality monitoring studies. Instrumental neutron activation analysis - INAA was applied to determine some nutrients and trace elements in invertebrate samples. Sampling by pitfall traps was carried out in riverine ecosystems from the urban area from the Piracicaba Municipality, State of Sao Paulo, Brazil. Invertebrate and reference material samples were irradiated in the nuclear research reactor IEA-R1, Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN. Fragments of a Ni-Cr alloy were irradiated for monitoring the thermal neutron flux. Hymenoptera order was considered the most representative according to the total number of sampled species (about 60%). Significant amounts of Ba, Br, Fe and Sc were found in invertebrates of the order Opiliones. Potassium, rubidium and zinc were highly accumulated in species from Blattodea order, indicating a consistent pattern of accumulation for this invertebrate order. Taking into account the abundance of Hymenoptera order, the chemical composition of its species was significant different at the 95% confidence level for Br and Na in the sampled locals. (author)

  13. Chemical elements in invertebrate orders for environmental quality studies

    Energy Technology Data Exchange (ETDEWEB)

    Magalhaes, Marcelo R.L.; Franca, Elvis J.; Paiva, Jose D.S.; Hazin, Clovis A., E-mail: marcelo_rlm@hotmail.com, E-mail: ejfranca@cnen.gov.br, E-mail: dan-paiva@hotmail.com, E-mail: chazin@cnen.gov.br [Centro Regional de Ciencias Nucleares do Nordeste (CRCN-NE/CNEN-PE), Recife, PE (Brazil); Fonseca, Felipe Y.; Fernandes, Elisabete A. de Nadai; Bacchi, Marcio A., E-mail: felipe-yamada@hotmail.com, E-mail: lis@cena.usp.br, E-mail: mabacchi@cena.usp.br [Centro de Energia Nuclear na Agricultura (CENA/USP), Piracicaba, SP (Brazil)

    2013-07-01

    Among the biomonitors of environmental quality, there is a lack of studies on using invertebrates to evaluate quantitatively chemical elements in ecosystems. This group of animals is quite numerous, widely distributed and adaptable to the most diverse environmental conditions. These features are very useful for the environmental quality assessment, as well as the several occurring insect-plant interactions performing essential functions in ecosystems. The objective of this work is to study the variability of chemical composition of invertebrate orders for using in environmental quality monitoring studies. Instrumental neutron activation analysis - INAA was applied to determine some nutrients and trace elements in invertebrate samples. Sampling by pitfall traps was carried out in riverine ecosystems from the urban area from the Piracicaba Municipality, State of Sao Paulo, Brazil. Invertebrate and reference material samples were irradiated in the nuclear research reactor IEA-R1, Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN. Fragments of a Ni-Cr alloy were irradiated for monitoring the thermal neutron flux. Hymenoptera order was considered the most representative according to the total number of sampled species (about 60%). Significant amounts of Ba, Br, Fe and Sc were found in invertebrates of the order Opiliones. Potassium, rubidium and zinc were highly accumulated in species from Blattodea order, indicating a consistent pattern of accumulation for this invertebrate order. Taking into account the abundance of Hymenoptera order, the chemical composition of its species was significant different at the 95% confidence level for Br and Na in the sampled locals. (author)

  14. Learning word order at birth: A NIRS study

    Directory of Open Access Journals (Sweden)

    Silvia Benavides-Varela

    2017-06-01

    Full Text Available In language, the relative order of words in sentences carries important grammatical functions. However, the developmental origins and the neural correlates of the ability to track word order are to date poorly understood. The current study therefore investigates the origins of infants’ ability to learn about the sequential order of words, using near-infrared spectroscopy (NIRS with newborn infants. We have conducted two experiments: one in which a word order change was implemented in 4-word sequences recorded with a list intonation (as if each word was a separate item in a list; list prosody condition, Experiment 1 and one in which the same 4-word sequences were recorded with a well-formed utterance-level prosodic contour (utterance prosody condition, Experiment 2. We found that newborns could detect the violation of the word order in the list prosody condition, but not in the utterance prosody condition. These results suggest that while newborns are already sensitive to word order in linguistic sequences, prosody appears to be a stronger cue than word order for the identification of linguistic units at birth.

  15. Learning word order at birth: A NIRS study.

    Science.gov (United States)

    Benavides-Varela, Silvia; Gervain, Judit

    2017-06-01

    In language, the relative order of words in sentences carries important grammatical functions. However, the developmental origins and the neural correlates of the ability to track word order are to date poorly understood. The current study therefore investigates the origins of infants' ability to learn about the sequential order of words, using near-infrared spectroscopy (NIRS) with newborn infants. We have conducted two experiments: one in which a word order change was implemented in 4-word sequences recorded with a list intonation (as if each word was a separate item in a list; list prosody condition, Experiment 1) and one in which the same 4-word sequences were recorded with a well-formed utterance-level prosodic contour (utterance prosody condition, Experiment 2). We found that newborns could detect the violation of the word order in the list prosody condition, but not in the utterance prosody condition. These results suggest that while newborns are already sensitive to word order in linguistic sequences, prosody appears to be a stronger cue than word order for the identification of linguistic units at birth. Copyright © 2017. Published by Elsevier Ltd.

  16. Study of the performance of Micromegas detectors in magnetic field

    Science.gov (United States)

    Dimitrios, Sampsonidis

    2018-02-01

    Resistive Micromegas (MICRO MEsh GAseous Structure) detectors have been chosen by the ATLAS collaboration at LHC for the high luminosity upgrade, due to their capability to maintain full efficiency and high spatial resolution at high occupancy, for tracking muons in the forward region of the detector. The Inner Muon Station, in the high-rapidity region, the so called New Small Wheel (NSW), will be composed of micromegas detectors that will have to maintain good performance in the presence of magnetic field of up to about 0.3 T. The response of micromegas detectors is affected by the magnetic field, where the deflection of the drift electrons is described by the Lorentz angle, resulting in a bias in the reconstructed track position. Several test-beam campaigns have been performed to test the behaviour of small size resistive micromegas prototypes (10×10 cm2) in magnetic fields up to 1 T, using high momentum muon and hadron beams at CERN. These studies are performed in order to validate the capability of the chambers to provide unbiased tracks in the NSW conditions. Measurements of the Lorentz angle and drift velocity as a function of the magnetic field are presented and both are compared to expectations based on Garfield-Magboltz simulations. Several methods to correct the position bias are applied, based on the chamber configuration or on the knowledge of the local value of the magnetic field. The results of these studies are presented together with an overall discussion of the Micromegas tracking capability in magnetic field.

  17. Study of the performance of Micromegas detectors in magnetic field

    Directory of Open Access Journals (Sweden)

    Dimitrios Sampsonidis

    2018-01-01

    Full Text Available Resistive Micromegas (MICRO MEsh GAseous Structure detectors have been chosen by the ATLAS collaboration at LHC for the high luminosity upgrade, due to their capability to maintain full efficiency and high spatial resolution at high occupancy, for tracking muons in the forward region of the detector. The Inner Muon Station, in the high-rapidity region, the so called New Small Wheel (NSW, will be composed of micromegas detectors that will have to maintain good performance in the presence of magnetic field of up to about 0.3 T. The response of micromegas detectors is affected by the magnetic field, where the deflection of the drift electrons is described by the Lorentz angle, resulting in a bias in the reconstructed track position. Several test-beam campaigns have been performed to test the behaviour of small size resistive micromegas prototypes (10×10 cm2 in magnetic fields up to 1 T, using high momentum muon and hadron beams at CERN. These studies are performed in order to validate the capability of the chambers to provide unbiased tracks in the NSW conditions. Measurements of the Lorentz angle and drift velocity as a function of the magnetic field are presented and both are compared to expectations based on Garfield-Magboltz simulations. Several methods to correct the position bias are applied, based on the chamber configuration or on the knowledge of the local value of the magnetic field. The results of these studies are presented together with an overall discussion of the Micromegas tracking capability in magnetic field.

  18. Nuclear magnetic resonance studies of lens transparency

    International Nuclear Information System (INIS)

    Beaulieu, C.F.

    1989-01-01

    Transparency of normal lens cytoplasm and loss of transparency in cataract were studied by nuclear magnetic resonance (NMR) methods. Phosphorus ( 31 P) NMR spectroscopy was used to measure the 31 P constituents and pH of calf lens cortical and nuclear homogenates and intact lenses as a function of time after lens enucleation and in opacification produced by calcium. Transparency was measured with laser spectroscopy. Despite complete loss of adenosine triphosphate (ATP) within 18 hrs of enucleation, the homogenates and lenses remained 100% transparent. Additions of calcium to ATP-depleted cortical homogenates produced opacification as well as concentration-dependent changes in inorganic phosphate, sugar phosphates, glycerol phosphorylcholine and pH. 1 H relaxation measurements of lens water at 200 MHz proton Larmor frequency studied temperature-dependent phase separation of lens nuclear homogenates. Preliminary measurements of T 1 and T 2 with non-equilibrium temperature changes showed a change in the slope of the temperature dependence of T 1 and T 2 at the phase separation temperature. Subsequent studies with equilibrium temperature changes showed no effect of phase separation on T 1 or T 2 , consistent with the phase separation being a low-energy process. 1 H nuclear magnetic relaxation dispersion (NMRD) studies (measurements of the magnetic field dependence of the water proton 1/T 1 relaxation rates) were performed on (1) calf lens nuclear and cortical homogenates (2) chicken lens homogenates, (3) native and heat-denatured egg white and (4) pure proteins including bovine γ-II crystallin bovine serum albumin (BSA) and myoglobin. The NMRD profiles of all samples exhibited decreases in 1/T 1 with increasing magnetic field

  19. Contribution of different Erbium sublattices in magnetic ordering of the reentrant superconductor [Snsub(1-x)Ersub(x)]Er4Rh6Sn18

    International Nuclear Information System (INIS)

    Hodeau, J.L.; Marezio, M.; Pannetier, J.; Benoit, A.

    1984-01-01

    The compound [Sn(1)sub(1-x)Er(1)sub(x)]Er(2) 4 Rh 6 Sn 18 with x = 1/3 is a reentrant superconductor; it belongs to a series of compounds whose formula is MRhsub(x)Snsub(y), M = rare earth. We have determined by X-ray diffraction the structure of these compounds and we have also studied the magnetic ordering by neutron diffraction of the reentrant superconductor [fr

  20. Efficiency enhancement of slow-wave electron-cyclotron maser by a second-order shaping of the magnetic field in the low-gain limit

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Si-Jia; Zhang, Yu-Fei; Wang, Kang [School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Li, Yong-Ming [Information Science and Engineering College, XinJiang University, Urumqi XinJiang 830046 (China); Jing, Jian, E-mail: jingjian@mail.buct.edu.cn [School of Science, Beijing University of Chemical Technology, Beijing 100029 (China)

    2017-03-15

    Based on the anomalous Doppler effect, we put forward a proposal to enhance the conversion efficiency of the slow-wave electron cyclotron masers (ECM) under the resonance condition. Compared with previous studies, we add a second-order shaping term in the guild magnetic field. Theoretical analyses and numerical calculations show that it can enhance the conversion efficiency in the low-gain limit. The case of the initial velocity spread of electrons satisfying the Gaussian distribution is also analysed numerically.

  1. Mixed hyperfine interaction - a tool to investigate the short range order and the strange magnetic behaviour of amorphous Fe-based binary alloys

    International Nuclear Information System (INIS)

    Fries, S.M.; Crummenauer, J.; Gonser, U.; Schaaf, P.; Chien, C.L.

    1989-01-01

    The Moessbauer study of the mixed magnetic dipole and electric quadrupole interaction in the paramagnetic state of amorphous Fe-Zr and Fe-Hf alloys is presented. Strong evidence for chemical short range order of the iron-pure alloys is found. The hyperfine parameters of the iron-rich alloys are marked by a complex applied field and temperature dependence, suggesting a not negligible spin-correlation well above Tc. (orig.)

  2. Experimental study of induced staggered magnetic fields in dysprosium gallium garnet (DGG)

    International Nuclear Information System (INIS)

    Steiner, M.; Corliss, L.M.; Hastings, J.M.; Blume, M.; Giordano, N.; Wolf, W.P.

    1979-01-01

    Neutron diffraction techniques have been used to study induced staggered magnetic field effects in DGG. The application of a uniform magnetic field at temperatures much greater than the Neel temperature induces a significant amount of antiferromagnetic order. The temperature and field dependences of this effect are in good agreement with recent theoretical predicions

  3. Gilbert's De Magnete: An early study of magnetism and electricity

    Science.gov (United States)

    Malin, Stuart; Barraclough, David

    Four hundred years might seem an excessively long time to wait for a book review, but there are reasons why a prompt review would have been difficult. Not only is De Magnete written in Latin, but it is also in the form of a scientific textbook. The language problem was overcome by Paul Fleury Mottelay and Silvanus P. Thompson, who translated the book into English in 1893 and 1900, respectively. The latter was published in connection with a beautiful tercentenary limited edition by the Chiswick Press that retains much of the flavor and appearance of the original. But the notion of a scientific textbook was unfamiliar when De Magnete first appeared in 1600. Certainly, scientific subjects and even geomagnetism had been written about (for example, by Petrus Peregrinus in his Epistola De Magnete, 1269), but as reports of equipment and phenomena rather than as in-depth investigations of a subject with experimental evidence and interpretation.

  4. Contribution to magnetic refrigeration study at liquid helium study

    International Nuclear Information System (INIS)

    Lacaze, A.

    1985-10-01

    An experimental prototype of magnetic refrigerator operates, following a Carnot cycle, with gallium gadolinium garnet, from liquid helium at 4.2 0 K. Analysis of the cyle and heat exchanges allowed to improve performance up to get more than 50% of Carnot yield at 1.8 0 K and nearly 80% at 2.1 0 K. Operation conditions of a regenerator refrigerator between 4 and 20 0 K are studied. The association of a magnetic refrigerator and a gas refrigerator is analyzed. Among different ways to realize the magnetic stage, an active regenerator cycle is chosen. An experimental device is described [fr

  5. Low-temperature magnetic ordering in the perovskites Pr1-xAxCoO3 (A=Ca, Sr)

    International Nuclear Information System (INIS)

    Deac, Iosif G.; Tetean, Romulus; Balasz, Istvan; Burzo, Emil

    2010-01-01

    The magnetic and electrical properties of polycrystalline Pr 1-x A x CoO 3 cobaltites with A=Ca, Sr and 0≤x≤0.5 were studied in the temperature range 4 K≤T≤1000 K and field up to 7 T. The X-ray analyses show the presence of only one phase having monoclinic or orthorhombic symmetry. The magnetic measurements indicate that the Ca-doped samples have at low temperatures, similar properties to the frustrated magnetic materials. PrCoO 3 is a paramagnetic insulator in the range from 4 to 1000 K. The Sr-doped cobaltites exhibit two phase transitions: a paramagnetic-ferromagnetic (or magnetic phase separated state) phase transition at about 240 K and a second one at about 100 K. The magnetic measurements suggest the presence of magnetic clusters and a change in the nature of magnetic coupling between Co ions at low temperatures. A semiconducting type behavior and high negative magnetoresistance was found for the Ca-doped samples, while the Sr-doped ones were metallic and with negligible magnetoresistance. The results are analyzed in the frame of a phase separation scenario in the presence of the spin-state transitions of Co ions.

  6. Polarized neutron scattering study of the multiple order parameter system NdB4

    Science.gov (United States)

    Metoki, N.; Yamauchi, H.; Matsuda, M.; Fernandez-Baca, J. A.; Watanuki, R.; Hagihala, M.

    2018-05-01

    Neutron polarization analysis has been carried out in order to clarify the magnetic structures of multiple order parameter f -electron system NdB4. We confirmed the noncollinear "all-in all-out" structure (Γ4) of the in-plane moment, which is in good agreement with our previous neutron powder diffraction study. We found that the magnetic moment along the c -axis mc showed diagonally antiferromagnetic structure (Γ10), inconsistent with previously reported "vortex" structure (Γ2). The microscopic mixture of these two structures with q⃗0=(0 ,0 ,0 ) appears in phase II and remains stable in phases III and IV, where an incommensurate modulation coexists. The unusual magnetic ordering is phenomenologically understood via Landau theory with the primary order parameter Γ4 coupled with higher-order secondary order parameter Γ10. The magnetic moments were estimated to be 1.8 ±0.2 and 0.2 ±0.05 μB at T =7.5 K for Γ4 and Γ10, respectively. We also found a long-period incommensurate modulation of the q⃗1=(0 ,0 ,1 /2 ) antiferromagnetic structure of mc with the propagation q⃗s 1=(0.14 ,0.14 ,0.1 ) and q⃗s 2=(0.2 ,0 ,0.1 ) in phase III and IV, respectively. The amplitude of sinusoidal modulation was about mc=1.0 ±0.2 μB at T =1.5 K. The local (0 ,0 ,1 /2 ) structure consists of in-plane ferromagnetic and out-of-plane antiferromagnetic coupling of mc, opposite to the coexisting Γ10. The mc of Γ10 is significantly enhanced up to 0.6 μB at T =1.5 K, which is accompanied by the incommensurate modulations. The Landau phenomenological approach indicates that the higher-order magnetic and/or multipole interactions based on the pseudoquartet f -electron state play important roles.

  7. 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.)

  8. Electrical transport and magnetic ordering in R2Ti3Ge4 (R = Dy, Ho ...

    Indian Academy of Sciences (India)

    CCR) in the temperature range of 15 K–300 K. The ac magnetic susceptibility measurements were per- formed in a bath-type cryostat down to 4.2 K. The thermoelectric power was measured by employing conventional differential technique using ...

  9. Leading-order hadronic contributions to the electron and tau anomalous magnetic moments

    International Nuclear Information System (INIS)

    Burger, Florian; Hotzel, Grit

    2015-01-01

    The leading hadronic contributions to the anomalous magnetic moments of the electron and the τ-lepton are determined by a four-flavour lattice QCD computation with twisted mass fermions. The continuum limit is taken and systematic uncertainties are quantified. Full agreement with results obtained by phenomenological analyses is found.

  10. X-ray holographic imaging of magnetic order in meander domain structures

    Directory of Open Access Journals (Sweden)

    Jaouen Nicolas

    2013-01-01

    Full Text Available We performed x-ray holography experiments using synchrotron radiation. By analyzing the scattering of coherent circularly polarized x-rays tuned at the Co-2p resonance, we imaged perpendicular magnetic domains in a Co/Pd multilayer. We compare results obtained for continuous and laterally confined films.

  11. Two-flavor QCD correction to lepton magnetic moments at leading-order in the electromagnetic coupling

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Xu [DESY, Zeuthen (Germany). NIC; Muenster Univ. (Germany). Inst. fuer Theoretische Physik; Jansen, Karl; Renner, Dru B. [DESY, Zeuthen (Germany). NIC; Petschlies, Marcus [Humboldt Univ. Berlin (Germany). Inst. fuer Physik

    2011-03-15

    We present a reliable nonperturbative calculation of the QCD correction, at leading-order in the electromagnetic coupling, to the anomalous magnetic moment of the electron, muon and tau leptons using two-flavor lattice QCD. We use multiple lattice spacings, multiple volumes and a broad range of quark masses to control the continuum, in nite-volume and chiral limits. We examine the impact of the commonly ignored disconnected diagrams and introduce a modi cation to the previously used method that results in a well-controlled lattice calculation. We obtain 1.513(43).10{sup -12}, 5.72(16).10{sup -8} and 2.650(54).10{sup -6} for the leading-order QCD correction to the anomalous magnetic moment of the electron, muon and tau respectively, each accurate to better than 3%. (orig.)

  12. Two-flavor QCD correction to lepton magnetic moments at leading-order in the electromagnetic coupling

    Energy Technology Data Exchange (ETDEWEB)

    Dru Renner, Xu Feng, Karl Jansen, Marcus Petschlies

    2011-08-01

    We present a reliable nonperturbative calculation of the QCD correction, at leading-order in the electromagnetic coupling, to the anomalous magnetic moment of the electron, muon and tau leptons using two-flavor lattice QCD. We use multiple lattice spacings, multiple volumes and a broad range of quark masses to control the continuum, infinite-volume and chiral limits. We examine the impact of the commonly ignored disconnected diagrams and introduce a modification to the previously used method that results in a well-controlled lattice calculation. We obtain 1.513 (43) 10^-12, 5.72 (16) 10^-8 and 2.650 (54) 10^-6 for the leading-order QCD correction to the anomalous magnetic moment of the electron, muon and tau respectively, each accurate to better than 3%.

  13. Magnetic ordering in single crystals of PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta

    CERN Document Server

    Uma, S; Gmelin, E; Rangarajan, G; Skanthakumar, S; Lynn, J W; Walter, R; Lorenz, T; Büchner, B; Walker, E; Erb, A

    1998-01-01

    Heat capacity measurements on pure but twinned single crystals of PrBa sub 2 Cu sub 3 O sub 7 sub - subdelta reveal a sharp peak at T sub N sup P sup sub T =16.6 K, which according to thermal expansion, neutron diffraction, and magnetic susceptibility measurements originates from an antiferromagnetic ordering of the Pr-ion moments. A modest coupling to the Cu(2) spin system is observed. Below T sub N sup P sup sub T a first-order transition in the magnetic structure of the Pr spin system (at 13.4 K in warming; approx. 11 K in cooling) is found. Field-dependent heat capacity data show anisotropic temperature dependences of the c sub p -peaks and recover a Schottky-like anomaly due to the crystal-field-split ground state of the Pr sup 3 sup +. (author). Letter-to-the-editor

  14. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

      The magnet was operated without any problem until the end of the LHC run in February 2013, apart from a CERN-wide power glitch on 10 January 2013 that affected the CMS refrigerator, causing a ramp down to 2 T in order to reconnect the coldbox. Another CERN-wide power glitch on 15 January 2013 didn’t affect the magnet subsystems, the cryoplant or the power converter. At the end of the magnet run, the reconnection of the coldbox at 2.5 T was tested. The process will be updated, in particular the parameters of some PID valve controllers. The helium flow of the current leads was reduced but only for a few seconds. The exercise will be repeated with the revised parameters to validate the automatic reconnection process of the coldbox. During LS1, the water-cooling services will be reduced and many interventions are planned on the electrical services. Therefore, the magnet cryogenics and subsystems will be stopped for several months, and the magnet cannot be kept cold. In order to avoid unc...

  15. Polarized-neutron-scattering study of the spin-wave excitations in the 3-k ordered phase of uranium antimonide.

    Science.gov (United States)

    Magnani, N; Caciuffo, R; Lander, G H; Hiess, A; Regnault, L-P

    2010-03-24

    The anisotropy of magnetic fluctuations propagating along the [1 1 0] direction in the ordered phase of uranium antimonide has been studied using polarized inelastic neutron scattering. The observed polarization behavior of the spin waves is a natural consequence of the longitudinal 3-k magnetic structure; together with recent results on the 3-k-transverse uranium dioxide, these findings establish this technique as an important tool to study complex magnetic arrangements. Selected details of the magnon excitation spectra of USb have also been reinvestigated, indicating the need to revise the currently accepted theoretical picture for this material.

  16. Effect of carbon on interstitial ordering and magnetic properties of epsilon-Fe-2(N,C)(1-z)

    Czech Academy of Sciences Publication Activity Database

    Brink, B. K.; Stahl, K.; Christiansen, T. L.; Frandsen, C.; Hansen, M. F.; Beran, Přemysl; Somers, M. A. J.

    2017-01-01

    Roč. 694, FEB (2017), s. 282-291 ISSN 0925-8388 R&D Projects: GA MŠk LM2015056 Institutional support: RVO:61389005 Keywords : neutron diffraction * vibrating sample magnotometry * Epsilon iron nitride * thermal expansion * interstitial order Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 3.133, year: 2016

  17. An effect of the fringing field in sector bending magnets: the coupling of the transverse planes in the solutions of the equation of motion at second-order

    International Nuclear Information System (INIS)

    Roy, G.

    1988-11-01

    Second order coupling terms for sector bending magnets due to edge effects at high energy are reviewed. Motion in the horizontal plane (bending plane) and in the vertical (nonbending) plane is considered. The model of Heaviside's function is outlined. The case of the complete bending magnet is treated. Three second order coupling terms between the vertical and horizontal planes in a complete bending magnet are found. Their origin is the fringing field, i.e., the intensity difference of the magnetic field between the outside and the inside of the magnet

  18. Case Studies on Superconducting Magnets for Particle Accelerators

    International Nuclear Information System (INIS)

    Ferracin, P

    2014-01-01

    During the CERN Accelerator School 'Superconductivity for accelerators', the students were divided into 18 groups, and 6 different exercises (case studies), involving the design and analysis of superconducting magnets and RF cavities, were assigned. The problems covered a broad spectrum of topics, from properties of superconducting materials to operation conditions and general dimensions of components. The work carried out by the students turned out to be an extremely useful opportunity to review the material explained during the lectures, to become familiar with the orders of magnitude of the key parameters, and to understand and compare different design options. We provide in this paper a summary of the activities related to the case studies on superconducting magnets and present the main outcomes

  19. Case Studies on Superconducting Magnets for Particle Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Ferracin, P [European Organization for Nuclear Research, Geneva (Switzerland)

    2014-07-01

    During the CERN Accelerator School 'Superconductivity for accelerators', the students were divided into 18 groups, and 6 different exercises (case studies), involving the design and analysis of superconducting magnets and RF cavities, were assigned. The problems covered a broad spectrum of topics, from properties of superconducting materials to operation conditions and general dimensions of components. The work carried out by the students turned out to be an extremely useful opportunity to review the material explained during the lectures, to become familiar with the orders of magnitude of the key parameters, and to understand and compare different design options. We provide in this paper a summary of the activities related to the case studies on superconducting magnets and present the main outcomes.

  20. 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

  1. Magneto-optic studies of magnetic oxides

    Energy Technology Data Exchange (ETDEWEB)

    Gehring, Gillian A., E-mail: g.gehring@shef.ac.uk [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Alshammari, Marzook S.; Score, David S.; Neal, James R.; Mokhtari, Abbas; Fox, A. Mark [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom)

    2012-10-15

    A brief review of the use of magneto-optic methods to study magnetic oxides is given. A simple method to obtain the magnetic circular dichroism (MCD) of a thin film on a transparent substrate is described. The method takes full account of multiple reflections in the film and substrate. Examples of the magneto-optic spectra of Co-doped ZnO, Fe{sub 3}O{sub 4}, and GdMnO{sub 3} are given. The Maxwell-Garnett method is used to describe the effects of metallic cobalt inclusions in Co:ZnO samples, and the change of the MCD spectra of Fe{sub 3}O{sub 4} at the Verwey temperature is discussed. Data showing different MCD signals at different energies is presented for GdMnO{sub 3}.

  2. Magneto-optic studies of magnetic oxides

    International Nuclear Information System (INIS)

    Gehring, Gillian A.; Alshammari, Marzook S.; Score, David S.; Neal, James R.; Mokhtari, Abbas; Fox, A. Mark

    2012-01-01

    A brief review of the use of magneto-optic methods to study magnetic oxides is given. A simple method to obtain the magnetic circular dichroism (MCD) of a thin film on a transparent substrate is described. The method takes full account of multiple reflections in the film and substrate. Examples of the magneto-optic spectra of Co-doped ZnO, Fe 3 O 4 , and GdMnO 3 are given. The Maxwell–Garnett method is used to describe the effects of metallic cobalt inclusions in Co:ZnO samples, and the change of the MCD spectra of Fe 3 O 4 at the Verwey temperature is discussed. Data showing different MCD signals at different energies is presented for GdMnO 3 .

  3. Satellite to study earth's magnetic field

    Science.gov (United States)

    1979-01-01

    The Magnetic Field Satellite (Magsat) designed to measure the near earth magnetic field and crustal anomalies is briefly described. A scalar magnetometer to measure the magnitude of the earth's crustal magnetic field and a vector magnetometer to measure magnetic field direction as well as magnitude are included. The mission and its objectives are summarized along with the data collection and processing system.

  4. Magnetic order and spin dynamics in the heavy Fermion system YbNi{sub 4}P{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Spehling, Johannes; Guenther, Marco; Yeche, Nicholas; Klauss, Hans-Henning [Institut fuer Festkoerperphysik, TU Dresden (Germany); Luetkens, Hubertus; Baines, Chris [Laboratory for Muonm Spin Spectroscopy, Paul Scherrer Institut, Villigen (Switzerland); Krellner, Cornelius; Geibel, Christoph; Steglich, Frank [Max-Planck-Institut fuer Chemische Physik Fester Stoffe, Dresden (Germany)

    2012-07-01

    A longstanding question in the field of quantum criticality relates to the possible existence of a ferromagnetic (FM) quantum critical point (QCP). At a QCP, collective quantum fluctuations tune the system continuously from a magnetically ordered to a non-magnetic ground state. However, so far no 4f-material with a FM QCP is found. Recently, in the HF metal YbNi{sub 4}P{sub 2} with a quasi 1D-electronic structure, FM quantum criticality above a low FM transition temperature of T{sub C}=170 mK was suggested. Our zero field muon spin relaxation on YbNi{sub 4}P{sub 2} proves static magnetic order with a strongly reduced ordered Yb{sup 3+} moment below T{sub C}. Above T{sub C}, the muon asymmetry function P(t,B) is dominated by quasi homogeneous spin fluctuations and exhibits a time-field scaling relation P(t,B)=P(t/B{sup {gamma}}) indicating cooperative critical spin dynamics. At T=190 mK, slightly above T{sub C}, {gamma}=0.81(5) K suggesting time-scale invariant power-law behavior for the dynamic electronic spin-spin autocorrelation function. The results are discussed in comparison with the AFM compound YbRh{sub 2}Si{sub 2}.

  5. A structural study of effects of NiP seed layer on the magnetic properties of CoCrPt/Ti/NiP perpendicular magnetic films

    CERN Document Server

    Sun, C J; Wang, J P; Soo, E W; Noh, D Y; Je, J H; Hwu, Y K

    2003-01-01

    The CoCrPt/Ti/NiP films for perpendicular magnetic recording were studied using X-ray scattering and anomalous X-ray scattering. When the NiP seed layer was used, the long range order of the texture peak of the magnetic film decreased and less Co was associated with this Bragg order. The structural results were consistent with the observed increased coercivity and decreased magnetization due to the increased magnetic grain isolation caused by the presence of NiP seed layer.

  6. Unusual magnetic excitations in the weakly ordered spin- 12 chain antiferromagnet Sr2CuO3: Possible evidence for Goldstone magnon coupled with the amplitude mode

    International Nuclear Information System (INIS)

    Sergeicheva, E. G.; Sosin, S. S.; Prozorova, L. A.; Gu, G. D.; Zaliznyak, I. A.

    2017-01-01

    We report on an electron spin resonance (ESR) study of a nearly one-dimensional (1D) spin-1/2 chain antiferromagnet, Sr 2 CuO 3 , with extremely weak magnetic ordering. The ESR spectra at T > T N , in the disordered Luttinger-spin-liquid phase, reveal nearly ideal Heisenberg-chain behavior with only a very small, field-independent linewidth, ~1/T. In the ordered state, below T N , we identify field-dependent antiferromagnetic resonance modes, which are well described by pseudo-Goldstone magnons in the model of a collinear biaxial antiferromagnet. Additionally, we observe a major resonant mode with unusual and strongly anisotropic properties, which is not anticipated by the conventional theory of Goldstone spin waves. Lastly, we propose that this unexpected magnetic excitation can be attributed to a field-independent magnon mode renormalized due to its interaction with the high-energy amplitude (Higgs) mode in the regime of weak spontaneous symmetry breaking.

  7. Study of pitting corrosion in line-pipe steel under the influence of remanent magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Espina-Hernandez, J H; Caleyo, F; Hallen, J M [Instituto Politecnico Nacional (IPN), Zacatenco (Mexico)

    2009-07-01

    The influence of remanent magnetization on pitting corrosion in line-pipe steels is studied. Pitting corrosion experiments have been carried out on samples of an API 5L grade 52 steel under a magnetization level of the same order of magnitude of the remanent magnetization in the pipeline wall after in-line inspection based on magnetic flux leakage. The samples were magnetized using rings of the same grade as the investigated steel. Immediately after magnetization, the investigated samples were subjected to pitting by immersing them in a solution containing dissolved Cl{sup -} and SO{sup 2-}{sub 4} and ions. The pitting experiments were conducted during a seven days period. The pit depth distribution and the maximum pit depth in each sample were recorded and used to conduct extreme value analyses of the pitting process in magnetized and non-magnetized control samples. The statistical assessment of the pitting corrosion data collected during this study shows that the magnetic field reduces the average depth of the pit population and also the extreme pit depth values that can be predicted from the maximum values observed in the magnetized samples in comparison with to the non-magnetized control samples. Scanning electron microscopy observations show that the magnetic field alters the pit morphology by increasing the pit mouth opening. (author)

  8. Coupling between Spin and Charge Order Driven by Magnetic Field in Triangular Ising System LuFe2O4+δ

    Directory of Open Access Journals (Sweden)

    Lei Ding

    2018-02-01

    Full Text Available We present a study of the magnetic-field effect on spin correlations in the charge ordered triangular Ising system LuFe2O4+δ through single crystal neutron diffraction. In the absence of a magnetic field, the strong diffuse neutron scattering observed below the Neel temperature (TN = 240 K indicates that LuFe2O4+δ shows short-range, two-dimensional (2D correlations in the FeO5 triangular layers, characterized by the development of a magnetic scattering rod along the 1/3 1/3 L direction, persisting down to 5 K. We also found that on top of the 2D correlations, a long range ferromagnetic component associated with the propagation vector k1 = 0 sets in at around 240 K. On the other hand, an external magnetic field applied along the c-axis effectively favours a three-dimensional (3D spin correlation between the FeO5 bilayers evidenced by the increase of the intensity of satellite reflections with propagation vector k2 = (1/3, 1/3, 3/2. This magnetic modulation is identical to the charge ordered superstructure, highlighting the field-promoted coupling between the spin and charge degrees of freedom. Formation of the 3D spin correlations suppresses both the rod-type diffuse scattering and the k1 component. Simple symmetry-based arguments provide a natural explanation of the observed phenomenon and put forward a possible charge redistribution in the applied magnetic field.

  9. Two-order parameters theory of the metal-insulator phase transition kinetics in the magnetic field

    Science.gov (United States)

    Dubovskii, L. B.

    2018-05-01

    The metal-insulator phase transition is considered within the framework of the Ginzburg-Landau approach for the phase transition described with two coupled order parameters. One of the order parameters is the mass density which variation is responsible for the origin of nonzero overlapping of the two different electron bands and the appearance of free electron carriers. This transition is assumed to be a first-order phase one. The free electron carriers are described with the vector-function representing the second-order parameter responsible for the continuous phase transition. This order parameter determines mostly the physical properties of the metal-insulator transition and leads to a singularity of the surface tension at the metal-insulator interface. The magnetic field is involved into the consideration of the system. The magnetic field leads to new singularities of the surface tension at the metal-insulator interface and results in a drastic variation of the phase transition kinetics. A strong singularity in the surface tension results from the Landau diamagnetism and determines anomalous features of the metal-insulator transition kinetics.

  10. On the study of the magnetic domain pattern via the initial magnetization curve

    International Nuclear Information System (INIS)

    Wu, T.

    1997-01-01

    This study inquires into the relationships between the initial magnetization curve and the magnetic domain pattern in the demagnetized states for amorphous TbFeCo as well as multilayered Co/Pd thin film samples. This was done specifically through an investigation of different demagnetized states of samples demagnetized by a variety of methods. The magnetic domain pattern for the sample demagnetized by an in-plane magnetic field and for the sample demagnetized by a perpendicular magnetic field was found to be quite different even though both states have zero magnetization. The former state has denser and finer domains than the latter. In addition, both states were studied in light of the initial magnetization curves obtained by measurements of the magneto-optic Kerr effect and the extraordinary Hall effect. Moreover, the initial magnetization for the fine domains increases with an increase in magnetic field, while for the coarse domains, the initial magnetization remains at zero for magnetic field below coercivity H c , then rises sharply to saturated magnetization when magnetic field is nearly equal to H c . copyright 1997 American Institute of Physics

  11. Defect-induced magnetic order in pure ZnO films

    Science.gov (United States)

    Khalid, M.; Ziese, M.; Setzer, A.; Esquinazi, P.; Lorenz, M.; Hochmuth, H.; Grundmann, M.; Spemann, D.; Butz, T.; Brauer, G.; Anwand, W.; Fischer, G.; Adeagbo, W. A.; Hergert, W.; Ernst, A.

    2009-07-01

    We have investigated the magnetic properties of pure ZnO thin films grown under N2 pressure on a -, c -, and r -plane Al2O3 substrates by pulsed-laser deposition. The substrate temperature and the N2 pressure were varied from room temperature to 570°C and from 0.007 to 1.0 mbar, respectively. The magnetic properties of bare substrates and ZnO films were investigated by SQUID magnetometry. ZnO films grown on c - and a -plane Al2O3 substrates did not show significant ferromagnetism. However, ZnO films grown on r -plane Al2O3 showed reproducible ferromagnetism at 300 K when grown at 300-400°C and 0.1-1.0 mbar N2 pressure. Positron annihilation spectroscopy measurements as well as density-functional theory calculations suggest that the ferromagnetism in ZnO films is related to Zn vacancies.

  12. Leading-order hadronic contributions to the electron and tau anomalous magnetic moments

    Energy Technology Data Exchange (ETDEWEB)

    Burger, Florian; Pientka, Grit [Humboldt-Universitaet zu Berlin, Institut fuer Physik, Berlin (Germany); Jansen, Karl [NIC, DESY, Zeuthen (Germany); Petschlies, Marcus [The Cyprus Institute, P.O.Box 27456, Nicosia (Cyprus); Rheinische Friedrich-Wilhelms-Universitaet Bonn, Institut fuer Strahlen- und Kernphysik, Bonn (Germany)

    2016-08-15

    The leading hadronic contributions to the anomalous magnetic moments of the electron and the τ-lepton are determined by a four-flavour lattice QCD computation with twisted mass fermions. The results presented are based on the quark-connected contribution to the hadronic vacuum polarisation function. The continuum limit is taken and systematic uncertainties are quantified. Full agreement with results obtained by phenomenological analyses is found. (orig.)

  13. Effects of atomic and magnetic order on electronic transport in Pd-richPd-Fe alloys

    Czech Academy of Sciences Publication Activity Database

    Kudrnovský, Josef; Drchal, Václav; Khmelevskyi, S.; Turek, Ilja

    2011-01-01

    Roč. 84, č. 21 (2011), "214436-1"-"214436-8" ISSN 1098-0121 R&D Projects: GA ČR(CZ) GAP204/11/1228 Institutional research plan: CEZ:AV0Z10100520; CEZ:AV0Z20410507 Keywords : residual resistivity * anisotropic magnetoresistance * anomalous Hall effect * PdFe-alloys * spin-orbit coupling * theory Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.691, year: 2011

  14. Positive muon studies of magnetic materials

    International Nuclear Information System (INIS)

    Patterson, B.D.

    1975-01-01

    Polarized positive muons (μ + ) are stopped in magnetic materials, and the μ + precession is observed via the muons's asymmetric decay to a positron. The precession frequency is a measure of the local magnetic field at the μ + . Relaxation of the μ + spin is caused by spatially or time-varying local fields. The local field at a stopped μ + in ferromagnetic nickel is measured. From this measurement, the hyperfine field seen by an interstitial μ + due to its contact interaction with polarized screening electrons is inferred to be -0.66kG. A discussion of this value in terms of a simple model for the screening configuration is presented. Critical spin fluctuations in Ni at temperatures just above the Curie point rapidly relax the μ + spin. The temperature and external magnetic field dependence of the relaxation rate is determined experimentally. A theory for the relaxation rate is presented which demonstrates the importance of the hyperfine and dipolar interactions of the μ + with its Ni host. Preliminary results on μ + studies in ferromagnetic iron and cobalt are also discussed. (U.S.)

  15. Moessbauer spectroscopic studies of the magnetic and structural properties of novel nanophase magnetic materials

    International Nuclear Information System (INIS)

    Milford, G.H.

    2000-08-01

    57 Fe Moessbauer Spectroscopy and complementary techniques have been used to characterise the physical and magnetic properties of a variety of novel nanophase iron containing magnetic particles, over a range of temperatures, and applied magnetic fields. Two series of commercially produced advanced metal particle pigments and tapes intended for use as magnetic recording media have been characterised using Transmission and Conversion Electron Moessbauer Spectroscopy at 4.2K, 77K and 293K. Moessbauer Spectra at 4.2K and 293K have identified two different forms of iron within the samples, an iron alloy core and an Fe 3+ oxide passivation layer. The first series of metal particle pigments studied is split into two separate groups, the core of the first group consists of a disordered Fe/Co alloy. Whereas the second group of metal particle pigments studied within the series have shown different characteristics than the previous samples, as the core is no longer a simple Fe/Co alloy. In addition to this the particle size is significantly reduced in the final sample within the series. This may be due to the presence of an Fe 2+ component, which appears to reduce the amount of Fe 3+ component necessary to passivate the particles by approximately half. The second series of samples have been used in part to investigate the out of plane angle of the metal particle pigments and its relationship with the squareness of the metal particle tapes. It is vital to minimise the out of plane angle of the metal particle tapes to obtain the optimum magnetic properties of the metal particle pigment. It has been shown that a decreasing out of plane angle leads to an increase in the squareness of the tapes. As a consequence of this the switching field distribution can be narrowed on metal particle tapes by reducing the out of plane angle. A further investigation has been carried out on the metal particle pigments coated onto tapes using Conversion Electron Moessbauer Spectroscopy, in order to

  16. Magnetic order of Y{sub 3}NiSi{sub 3}-type R{sub 3}NiSi{sub 3} (R=Gd–DY) compounds

    Energy Technology Data Exchange (ETDEWEB)

    Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation); Yapaskurt, V.O. [Department of Petrology, Faculty of Geology, Moscow State University, Leninskie Gory, Moscow 119992 (Russian Federation); Nirmala, R. [Indian Institute of Technology Madras, Chennai 600036 (India); Malik, S.K.; Quezado, S. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59082-970 (Brazil); Yao, Jinlei; Mozharivskyj, Y. [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 (Canada); Nigam, A.K. [Tata Institute of Fundamental Research, Mumbai 400005 (India); Isnard, O. [Université Grenoble Alpes, Inst NEEL, BP166, F-38042 Grenoble (France); CNRS, Institut NEEL, 25 rue des martyrs, F-38042 Grenoble (France)

    2016-01-15

    Magnetic measurements and neutron powder diffraction investigations on the Y{sub 3}NiSi{sub 3}-type R{sub 3}NiSi{sub 3} compounds (R=Gd, Tb, Dy) reveal their complex antiferromagnetic ordering. Magnetic measurements on Gd{sub 3}NiSi{sub 3}, Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} indicate antiferromagnetic-like transition at temperatures 260 K, 202 K and 140 K, respectively. Also, the Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} compounds show spin-reorientation transition at 132 K and 99 K, respectively. Below the spin-reorientation transition, the isothermal magnetization curves indicate the metamagnetic-like behavior of Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3}. The magnetocaloric effect of Dy{sub 3}NiSi{sub 3} is calculated in terms of isothermal magnetic entropy change and it reaches a maximum value of −1.2 J/kg K and −1.1 J/kg K for a field change of 50 kOe near 146 K and 92 K, respectively. The neutron diffraction studies of Tb{sub 3}NiSi{sub 3} suggest the magnetic ordering of the Tb2 4j sublattice and no magnetic ordering of the Tb1 2a sublattice. Tb{sub 3}NiSi{sub 3} transforms from the high temperature paramagnetic state to the commensurate high-temperature a- and c-axis antiferromagnet of I′2/m magnetic space group below 250 K. Below 150 K, the high-temperature antiferromagnet transforms into the low-temperature a-, b- and c-axis antiferromagnet of I′i magnetic space group. At 1.5 K, the terbium magnetic moment in Tb2 sublattice and its a-, b- and c-axis components reach the values of M{sub Tb2}=8.2(1) μ{sub B}, M{sub aTb2}=5.9(1) μ{sub B}, M{sub bTb2}=4.3(2) μ{sub B} and M{sub cTb2}=3.7(2) μ{sub B}, respectively. - Highlights: • Gd{sub 3}NiSi{sub 3}, Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} have Neel points of 260. 202 and 140 K. • Tb{sub 3}NiSi{sub 3} and Dy{sub 3}NiSi{sub 3} show spin-reorientation transition at 132 and 99 K. • Tb{sub 3}NiSi{sub 3} exhibits the commensurate magnetic ordering of Tb2 4j sublattice

  17. Interfaces exchange bias and magnetic properties of ordered CoFe_2O_4/Co_3O_4 nanocomposites

    International Nuclear Information System (INIS)

    Zhang, B.B.; Xu, J.C.; Wang, P.F.; Han, Y.B.; Hong, B.; Jin, H.X.; Jin, D.F.; Peng, X.L.; Li, J.; Yang, Y.T.; Gong, J.; Ge, H.L.; Wang, X.Q.

    2015-01-01

    Graphical abstract: - Highlights: • CoFe_2O_4 nanoparticles were well-dispersed anchored in mesopores of Co_3O_4. • The magnetic behavior of nanocomposites changed greatly at low temperature. • CoFe_2O_4 nanoparticles reinforced the interfaces magnetic interaction of nanocomposites. • M increased with the doping of CoFe_2O_4 and the decreasing temperature. • Exchange bias effect was observed at 100 K and increased with the doping of CoFe_2O_4. - Abstract: Cobalt ferrites (CoFe_2O_4) nanoparticles were implanted into the ordered mesoporous cobaltosic oxide (Co_3O_4) nanowires to synthesize magnetic CoFe_2O_4/Co_3O_4 nanocomposites. X-ray diffraction (XRD), N_2 physical absorption–desorption, transmission electron microscope (TEM) and energy disperse spectroscopy (EDS) were used to characterize the microstructure of mesoporous Co_3O_4 and CoFe_2O_4/Co_3O_4 nanocomposites. The percent of pore-volume of mesoporous Co_3O_4 nanowires was calculated to be about 41.99% and CoFe_2O_4 nanoparticles were revealed to exist in the mesopores of Co_3O_4_. The magnetic behavior of both samples were investigated with superconducting quantum interference device (SQUID). Magnetization increased with the doping CoFe_2O_4 and decreasing temperature, while coercivity hardly changed. The exchange bias effect was obviously observed at 100 K and enhanced with the doping CoFe_2O_4. CoFe_2O_4 nanoparticles reinforced the interfaces magnetic interaction between antiferromagnetic Co_3O_4 and ferrimagnetic CoFe_2O_4.

  18. Study on magnetic field mapping within cylindrical center volume of general magnet

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Li; Lee, Sang Jin [Uiduk University, Gyeongju (Korea, Republic of)

    2016-06-15

    For the magnetic field analysis or design, it is important to know the behavior of the magnetic field in an interesting space. Magnetic field mapping becomes a useful tool for the study of magnetic field. In this paper, a numerical way for mapping the magnetic field within the cylindrical center volume of magnet is presented, based on the solution of the Laplace's equation in the cylindrical coordinate system. The expression of the magnetic field can be obtained by the magnetic flux density, which measured in the mapped volume. According to the form of the expression, the measurement points are arranged with the parallel cylindrical line (PCL) method. As example, the magnetic flux density generated by an electron cyclotron resonance ion source (ECRIS) magnet and a quadrupole magnet were mapped using the PCL method, respectively. The mapping results show the PCL arrangement method is feasible and convenience to map the magnetic field within a cylindrical center volume generated by the general magnet.

  19. Magnetic resonance studies of atomic hydrogen gas at low temperatures

    International Nuclear Information System (INIS)

    Hardy, W.N.; Morrow, M.; Jochemsen, R.; Statt, B.W.; Kubik, P.R.; Marsolais, R.M.; Berlinsky, A.J.; Landesman, A.

    1980-01-01

    Using a pulsed low temperature discharge in a closed cell containing H 2 and 4 He, we have been able to store a low density (approximately 10 12 atoms/cc) gas of atomic hydrogen for periods of order one hour in zero magnetic field and T=1 K. Pulsed magnetic resonance at the 1420 MHz hyperfine transition has been used to study a number of the properties of the gas, including the recombination rate H + H + 4 He→H 2 + 4 He, the hydrogen spin-exchange relaxation rates, the diffusion coefficient of H in 4 He gas and the pressure shift of the hyperfine frequency due to the 4 He buffer gas. Here we discuss the application of hyperfine frequency shifts as a probe of the H-He potential, and as a means for determining the binding energy of H on liquid helium

  20. Preliminary study of an integral harmonic analysis magnetic field measurement system for long SSC magnets

    International Nuclear Information System (INIS)

    Green, M.I.

    1991-04-01

    We described the research and development required to design and build a prototype system capable of making integrated magnetic multipole measurements of warm and cryogenic 50 mm bore SSC dipole and quadrupole magnets utilizing a warm probe in a warm finger. Our experience and some preliminary studies indicate that it is highly unlikely that a 16 meter long probe can be fabricated that will have a twist below several milliradians at any temperature. Consequently we describe a segmented 16 meter long probe for which we intend to calibrate the phase of each segment to within 0.1 milliradians. The data for all segments will be acquired simultaneously, and integrated data will be generated from the vector sums of the individual segments. The calibration techniques and instrumentation required to implement this system are described. The duration of an integral measurement at one current is less than ten seconds, which is three orders of magnitude shorter than that required by the mole technique presently being used. The system is based on an extrapolation of the techniques used at LBL to measure cryogenic 1 meter models of SSC magnets with a cryogenic probe. 3 refs., 3 figs

  1. Magnetic relaxation phenomena in the chiral magnet Fe1 -xCoxSi : An ac susceptibility study

    Science.gov (United States)

    Bannenberg, L. J.; Lefering, A. J. E.; Kakurai, K.; Onose, Y.; Endoh, Y.; Tokura, Y.; Pappas, C.

    2016-10-01

    We present a systematic study of the ac susceptibility of the chiral magnet Fe1 -xCoxSi with x =0.30 covering four orders of magnitude in frequencies from 0.1 Hz to 1 kHz, with particular emphasis to the pronounced history dependence. Characteristic relaxation times ranging from a few milliseconds to tens of seconds are observed around the skyrmion lattice A phase, the helical-to-conical transition and in a region above TC. The distribution of relaxation frequencies around the A phase is broad, asymmetric, and originates from multiple coexisting relaxation processes. The pronounced dependence of the magnetic phase diagram on the magnetic history and cooling rates as well as the asymmetric frequency dependence and slow dynamics suggest more complicated physical phenomena in Fe0.7Co0.3Si than in other chiral magnets.

  2. Magnetic anisotropy and chemical long-range order in epitaxial ferrimagnetic CrPt sub 3 films

    CERN Document Server

    Maret, M; Köhler, J; Poinsot, R; Ulhaq-Bouillet, C; Tonnerre, J M; Berar, J F; Bucher, E

    2000-01-01

    Thin films of CrPt sub 3 were prepared by molecular beam epitaxy on both Al sub 2 O sub 3 (0 0 0 1) and MgO(0 0 1) substrates, either directly by co-deposition of Cr and Pt at high temperatures or after in situ annealing of superlattices [Cr(2 A)/Pt(7 A)]. In situ RHEED observations and X-ray diffraction measurements have allowed us to check the single-crystal quality of CrPt sub 3 films and to determine the degree of L1 sub 2 -type long-range order (LRO). In films co-deposited between 850 deg. C and 950 deg. C a nearly perfect LRO has been observed. As in bulk alloys, such ordering yields a ferrimagnetic order, while the disordered films are non-magnetic. In contrast with the ferromagnetic L1 sub 2 -type ordered CoPt sub 3 (1 1 1) films, the ferrimagnetic CrPt sub 3 (1 1 1) films exhibit perpendicular magnetic anisotropy with quality factors, K sub u /K sub d , as large as 5 and large coercivities around 450 kA/m. Such anisotropy could be related to the arrangement of Cr atoms, which owing to their large mag...

  3. An investigation on the role of texture evolution and ordered phase transition in soft magnetic properties of Fe–6.5 wt%Si electrical steel

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Guojun; Li, Changsheng, E-mail: lics@ral.neu.edu.cn; Cai, Ban; Wang, Qiwen

    2017-05-15

    Fe–6.5 wt%Si electrical steel characterized with excellent soft magnetic properties such as almost zero magnetostriction, low eddy current and hysteresis losses characteristics has been widely applied in high frequency fields. In this work, the role of texture evolution and ordered phase transition in soft magnetic properties of annealed sheets was explored using EBSD, XRD and TEM. The results demonstrate that accompanied with the increase of annealing temperatures, an increase on the B8 is attributable to a contribution combining the sizes of recrystallization grains with APBs of ordered phases as pinning the migration of magnetic domain wall. Whereas B50 declines to a minimum value (1.479 T) and then increases to a certain value (1.695 T) due to different types and intensities of textures affecting on the magnetocrystalline anisotropy energy. Meanwhile, the dislocation density gradually decreases and corresponding to a gradual decline in the internal stress, which makes the coercive force (H{sub c}) decrease monotonically. - Highlights: • Role of texture and ordered phase in Fe–6.5 wt%Si were studied. • With increasing annealing temperatures, H{sub c} decreases monotonically. • Combining grain sizes with APBs in B8 measurements. • Increasing annealing temperatures, B50 declines and then increases due to texture.

  4. MATLAB-based algorithm to estimate depths of isolated thin dike-like sources using higher-order horizontal derivatives of magnetic anomalies.

    Science.gov (United States)

    Ekinci, Yunus Levent

    2016-01-01

    This paper presents an easy-to-use open source computer algorithm (code) for estimating the depths of isolated single thin dike-like source bodies by using numerical second-, third-, and fourth-order horizontal derivatives computed from observed magnetic anomalies. The approach does not require a priori information and uses some filters of successive graticule spacings. The computed higher-order horizontal derivative datasets are used to solve nonlinear equations for depth determination. The solutions are independent from the magnetization and ambient field directions. The practical usability of the developed code, designed in MATLAB R2012b (MathWorks Inc.), was successfully examined using some synthetic simulations with and without noise. The algorithm was then used to estimate the depths of some ore bodies buried in different regions (USA, Sweden, and Canada). Real data tests clearly indicated that the obtained depths are in good agreement with those of previous studies and drilling information. Additionally, a state-of-the-art inversion scheme based on particle swarm optimization produced comparable results to those of the higher-order horizontal derivative analyses in both synthetic and real anomaly cases. Accordingly, the proposed code is verified to be useful in interpreting isolated single thin dike-like magnetized bodies and may be an alternative processing technique. The open source code can be easily modified and adapted to suit the benefits of other researchers.

  5. Corrections to the sixth-order anomalous magnetic moment of the muon

    International Nuclear Information System (INIS)

    Chlouber, C.; Samuel, M.A.

    1978-01-01

    The contribution to the muon anomaly from fourth-order electron vacuum polarization is determined to order m/sub e//m/sub μ/. The result, including the contribution from graphs containing two second-order lepton vacuum polarization subgraphs is (α/π) 3 [(2/9)ln(m/sub μ//m/sub e/) + (403/108 - 4π 2 / 9)ln(m/sub μ//m/sub e/) + zeta (3)/2 + 2π 2 /27 + 5/27 - 6.56m/sub e// m/sub μ/

  6. Thermo-sensitively and magnetically ordered mesoporous carbon nanospheres for targeted controlled drug release and hyperthermia application.

    Science.gov (United States)

    Chen, Lin; Zhang, Huan; Zheng, Jing; Yu, Shiping; Du, Jinglei; Yang, Yongzhen; Liu, Xuguang

    2018-03-01

    A multifunctional nanoplatform based on thermo-sensitively and magnetically ordered mesoporous carbon nanospheres (TMOMCNs) is developed for effective targeted controlled release of doxorubicin hydrochloride (DOX) and hyperthermia in this work. The morphology, specific surface area, porosity, thermo-stability, thermo-sensitivity, as well as magnetism properties of TMOMCNs were verified by high resolution transmission electron microscopy, field emission scanning electron microscopy, thermo-gravimetric analysis, X-ray diffraction, Brunauer-Emmeltt-Teller surface area analysis, dynamic light scattering and vibrating sample magnetometry measurement. The results indicate that TMOMCNs have an average diameter of ~146nm with a lower critical solution temperature at around 39.5°C. They are superparamagnetic with a magnetization of 10.15emu/g at 20kOe. They generate heat when inductive magnetic field is applied to them and have a normalized specific absorption rate of 30.23W/g at 230kHz and 290Oe, showing good potential for hyperthermia. The DOX loading and release results illustrate that the loading capacity is 135.10mg/g and release performance could be regulated by changing pH and temperature. The good targeting, DOX loading and release and hyperthermia properties of TMOMCNs offer new probabilities for high effectiveness and low toxicity of cancer chemotherapy. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Polarized neutron powder diffraction studies of antiferromagnetic order in bulk and nanoparticle NiO

    DEFF Research Database (Denmark)

    Brok, Erik; Lefmann, Kim; Deen, Pascale P.

    2015-01-01

    surface contribution to the magnetic anisotropy. Here we explore the potential use of polarized neutron diffraction to reveal the magnetic structure in NiO bulk and nanoparticle powders by applying the XYZ-polarization analysis method. Our investigations address in particular the spin orientation in bulk....... The results show that polarization analyzed neutron powder diffraction is a viable method to investigate magnetic order in powders of antiferromagnetic nanoparticles.......In many materials it remains a challenge to reveal the nature of magnetic correlations, including antiferromagnetism and spin disorder. Revealing the spin structure in magnetic nanoparticles is further complicated by the large incoherent neutron scattering cross section from water adsorbed...

  8. A Study of Thermocurrent Induced Magnetic Fields in ILC Cavities

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Anthony C. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Cooley, Victoria [Univ. of Wisconsin, Madison, WI (United States)

    2014-03-31

    The case of axisymmetric ILC-type cavities with titanium helium vessels is investigated. A first-order estimate for magnetic field within the SRF current layer is presented. The induced magnetic field is found to be not more than 1.4x10-8 Tesla = 0.14 milligauss for the case of axial symmetry. Magnetic fields due to symmetry breaking effects are discussed.

  9. Magnetic ordered mesoporous Fe3O4/CeO2 composites with synergy of adsorption and Fenton catalysis

    Science.gov (United States)

    Li, Keyan; Zhao, Yongqin; Song, Chunshan; Guo, Xinwen

    2017-12-01

    Magnetic Fe3O4/CeO2 composites with highly ordered mesoporous structure and large surface area were synthesized by impregnation-calcination method, and the mesoporous CeO2 as support was synthesized via the hard template approach. The composition, morphology and physicochemical properties of the materials were characterized by XRD, SEM, TEM, XPS, Raman spectra and N2 adsorption/desorption analysis. The mesoporous Fe3O4/CeO2 composite played a dual-function role as both adsorbent and Fenton-like catalyst for removal of organic dye. The methylene blue (MB) removal efficiency of mesoporous Fe3O4/CeO2 was much higher than that of irregular porous Fe3O4/CeO2. The superior adsorption ability of mesoporous materials was attributed to the abundant oxygen vacancies on the surface of CeO2, high surface area and ordered mesoporous channels. The good oxidative degradation resulted from high Ce3+ content and the synergistic effect between Fe and Ce. The mesoporous Fe3O4/CeO2 composite presented low metal leaching (iron 0.22 mg L-1 and cerium 0.63 mg L-1), which could be ascribed to the strong metal-support interactions for dispersion and stabilization of Fe species. In addition, the composite can be easily separated from reaction solution with an external magnetic field due to its magnetic property, which is important to its practical applications.

  10. Layered magnets: polarized neutron reflection studies

    Energy Technology Data Exchange (ETDEWEB)

    Zabel, H; Schreyer, A [Ruhr-Univ. Bochum, Lehrstuhl fuer Experimentalphysik/Festkoerperphysik, Bochum (Germany)

    1996-11-01

    Neutron reflectivity measurements from extended surfaces, thin films and superlattices provide information on the chemical profile parallel to the film normal, including film thicknesses, average composition and interfacial roughness parameters. Reflectivity measurements with polarized neutrons are particularly powerful for analyzing the magnetic density profiles in thin films and superlattices in addition to chemical profiles. The basic theory of polarized neutron reflectivity is provided, followed by some examples and more recent applications concerning polarized neutron reflectivity studies from exchange coupled Fe/Cr superlattices. (author) 5 figs., 13 refs.

  11. Magnetic resonance spectroscopy studies in migraine

    Energy Technology Data Exchange (ETDEWEB)

    Montagna, P.; Cortelli, P.; Barbiroli, B. (Inst. of Medical Pathology, Univ. of Bologna (Italy))

    1994-06-01

    The authors describe the method of [sup 31]phosphorus magnetic resonance spectroscopy and review the results when it is applied to the study of brain and muscle energy metabolism in migraine subjects. Brain energy metabolism appears to be abnormal in all major subtypes of migraine when measured both during and between attacks. Impaired energy metabolism is also documented in skeletal muscle. It is suggested that migraine is associated with a generalized disorder of mitochondrial oxidative phosphorylation and that this may constitute a threshold for the triggering of migraine attacks. 47 refs., 10 figs., 3 tabs.

  12. Magnetic ordering of YPd{sub 2}Si-type HoNi{sub 2}Si and ErNi{sub 2}Si compounds

    Energy Technology Data Exchange (ETDEWEB)

    Morozkin, A.V., E-mail: morozkin@tech.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow, 119992 (Russian Federation); Isnard, O. [CNRS, Insitut. Néel, 25 Rue Des Martyrs BP166 x, F-38042 Grenoble (France); Université Grenoble Alpes, Inst. Néel, F-38042 Grenoble (France); Nirmala, R. [Indian Institute of Technology Madras, Chennai 600 036 (India); Quezado, S.; Malik, S.K. [Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59082-970 (Brazil)

    2016-12-01

    Magnetic properties of YPd{sub 2}Si-type HoNi{sub 2}Si and ErNi{sub 2}Si were investigated via neutron diffraction and magnetisation measurements. HoNi{sub 2}Si and ErNi{sub 2}Si show ferromagnetic-like ordering at T{sub C} of 9 K and 7 K, respectively. The paramagnetic Weiss temperatures are 9 K and 11 K and the effective magnetic moments are 10.76 μ{sub B}/fu and 9.79 μ{sub B}/fu for HoNi{sub 2}Si and ErNi{sub 2}Si compounds, respectively. The HoNi{sub 2}Si and ErNi{sub 2}Si are soft ferromagnets with saturation magnetization of 8.1 μ{sub B}/fu and 7.5 μ{sub B}/fu, respectively at 2 K and in field of 140 kOe. The isothermal magnetic entropy change, ΔS{sub m}, has a maximum value of −15.6 J/kg·K at 10 K for HoNi{sub 2}Si and −13.9 J/kg·K at 6 K for ErNi{sub 2}Si for a field change of 50 kOe. Neutron diffraction study in zero applied field shows mixed ferromagnetic-antiferromagnetic ordering of HoNi{sub 2}Si at ~9 K and its magnetic structure is a sum of a-axis ferromagnetic F{sub a}, b-axis antiferromagnetic AF{sub b} and c-axis antiferrromagnetic AF{sub c} components of Pn′a2{sub 1}′={1, m_x′/[1/2, 1/2, 1/2], 2_y′/[0, 1/2, 0], m_z/[1/2, 0, 1/2]} magnetic space group and propagation vector K{sub 0}=[0, 0, 0]. The holmium magnetic moment reaches a value of 9.23(9) μ{sub B} at 1.5 K and the unit cell of HoNi{sub 2}Si undergoes isotropic contraction around the temperature of magnetic transition. - Graphical abstract: HoNi{sub 2}Si: mixed ferro-antiferromagnet (F{sub a}+AF{sub b}+AF{sub c}){sup K0} with Pn′a2{sub 1}′ magnetic space group and K{sub 0}=[0, 0, 0] propagation vector below 10 K. - Highlights: • Ferro-antiferromagnetic ordering is observed in HoNi{sub 2}Si at 9 K and in ErNi{sub 2}Si at 7 K. • HoNi{sub 2}Si is soft ferromagnet with ΔS{sub m} of −15.6 J/kg·K at 10 K in field of 0–50 kOe. • ErNi{sub 2}Si is soft ferromagnet with ΔS{sub m} of −13.9 J/kg·K at 6 K in field of 0–50 kOe. • HoNi{sub 2}Si shows mixed F

  13. Ferrimagnetic resonance study on photo-induced magnetism in hybrid magnetic semiconductor V(TCNE)x, x ˜2 film

    Science.gov (United States)

    Yoo, Jung-Woo; Shima Edelstein, R.; Lincoln, D. M.; Epstein, A. J.

    2007-03-01

    The V(TCNE)x, x˜2 is a fully spin-polarized magnetic semiconductor, whose magnetic order exceeds room temperature (Tc > 350 K), and electronic transport follows hopping mechanism through the Coulomb energy split &*circ; subband. In addition, it was determined that this material has thermally reversible persistent change in both magnetism and conductivity driven by the optical excitation [1]. Here, we report detailed investigation on photo-induced magnetism in V(TCNE)x by employing ferrimagnetic resonance (PIFMR) study with an in-situ light illumination. Upon optical excitation (λ˜ 457.9 nm), the FMR spectra display substantial change in their linewidth and resonance field. Angular dependence analyses of line shift indicate the increase of unixial anisotropy field in the film caused by the light irradiation. The results demonstrated that the change in overall magnetic anisotropy by the illumination plays an important role in inducing photo- induced magnetism in (TCNE) class magnet. [1] J.-W. Yoo, et al. to be published in Phys. Rev. Lett.

  14. X-ray scattering studies of non-equilibrium ordering processes

    International Nuclear Information System (INIS)

    Nagler, S.E.

    1991-01-01

    We report on the progress of the project entitled ''X-ray Scattering Studies of Non-Equilibrium Ordering Processes.'' The past year has seen continued progress in the study of kinetic effects in metallic binary alloys and polymers. In addition, work has begun on a low dimensional CDW system: blue bronze. A sample chamber has been constructed to perform small angle neutron scattering measurements on a model quantum system with phase separation: solid He3/He4. Work is continuing on magnetic systems. Planned future experiments include an investigation of crystallization in Rubidium

  15. Low temperature Mössbauer studies on magnetic nanocomposites

    Indian Academy of Sciences (India)

    Unknown

    in the recording industry for achieving high density infor- mation storage and in the refrigeration industry ( ... by an ultra fine grain size (< 50 nm) have created a great deal of interest in recent years by virtue of their ... The reduction in size modifies the magnetic order in these materials. The magnetic nanocomposites can be ...

  16. Study of the maguemite-hematite transformation by magnetic resonance

    International Nuclear Information System (INIS)

    Portella, P.D.

    1979-08-01

    The conversion of γ-Fe 2 O 3 powders to α-Fe 2 O 3 has been studied with the magnetic resonance technique. The residual fraction of γ-Fe 2 O 3 was measured for several times and temperatures of isothermal treatments, in the range 450 0 C - 550 0 C. The transformation can be described by a first order Kinetic equation and the apparent activation energy is about 200 kJ/mol (48 kcal/mol). This value is independent of temperature and particle size. The experimental data suggest that the reaction is growth-controlled and nucleation occurs preferably at the particle surface. (Author) [pt

  17. Study of one dimensional magnetic system via field theory

    International Nuclear Information System (INIS)

    Talim, S.L.

    1988-04-01

    We present a study of one-dimensional magnetic system using field theory methods. We studied the discreteness effects in a classical anisotropic one dimensional antiferromagnet in an external magnetic field. It is shown that for TMMC, at the temperatures and magnetic fields where most experiments have been done, the corrections are small and can be neglected. (author)

  18. Fundamental studies of superconductors using scanning magnetic imaging

    Science.gov (United States)

    Kirtley, J. R.

    2010-12-01

    In this review I discuss the application of scanning magnetic imaging to fundamental studies of superconductors, concentrating on three scanning magnetic microscopies—scanning SQUID microscopy (SSM), scanning Hall bar microscopy (SHM) and magnetic force microscopy (MFM). I briefly discuss the history, sensitivity, spatial resolution, invasiveness and potential future developments of each technique. I then discuss a selection of applications of these microscopies. I start with static imaging of magnetic flux: an SSM study provides deeper understanding of vortex trapping in narrow strips, which are used to reduce noise in superconducting circuitry. Studies of vortex trapping in wire lattices, clusters and arrays of rings and nanoholes show fascinating ordering effects. The cuprate high-Tc superconductors are shown to have predominantly d-wave pairing symmetry by magnetic imaging of the half-integer flux quantum effect. Arrays of superconducting rings act as a physical analog for the Ising spin model, with the half-integer flux quantum effect helping to eliminate one source of disorder in antiferromagnetic arrangements of the ring moments. Tests of the interlayer tunneling model show that the condensation energy available from this mechanism cannot account for the high critical temperatures observed in the cuprates. The strong divergence in the magnetic fields of Pearl vortices allows them to be imaged using SSM, even for penetration depths of a millimeter. Unusual vortex arrangements occur in samples comparable in size to the coherence length. Spontaneous magnetization is not observed in Sr2RuO4, which is believed to have px ± ipy pairing symmetry, although effects hundreds of times bigger than the sensitivity limits had been predicted. However, unusual flux trapping is observed in this superconductor. Finally, unusual flux arrangements are also observed in magnetic superconductors. I then turn to vortex dynamics: imaging of vortices in rings of highly underdoped

  19. Fundamental studies of superconductors using scanning magnetic imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kirtley, J R [Center for Probing the Nanoscale, Stanford University, Stanford, CA (United States)

    2010-12-01

    In this review I discuss the application of scanning magnetic imaging to fundamental studies of superconductors, concentrating on three scanning magnetic microscopies-scanning SQUID microscopy (SSM), scanning Hall bar microscopy (SHM) and magnetic force microscopy (MFM). I briefly discuss the history, sensitivity, spatial resolution, invasiveness and potential future developments of each technique. I then discuss a selection of applications of these microscopies. I start with static imaging of magnetic flux: an SSM study provides deeper understanding of vortex trapping in narrow strips, which are used to reduce noise in superconducting circuitry. Studies of vortex trapping in wire lattices, clusters and arrays of rings and nanoholes show fascinating ordering effects. The cuprate high-T{sub c} superconductors are shown to have predominantly d-wave pairing symmetry by magnetic imaging of the half-integer flux quantum effect. Arrays of superconducting rings act as a physical analog for the Ising spin model, with the half-integer flux quantum effect helping to eliminate one source of disorder in antiferromagnetic arrangements of the ring moments. Tests of the interlayer tunneling model show that the condensation energy available from this mechanism cannot account for the high critical temperatures observed in the cuprates. The strong divergence in the magnetic fields of Pearl vortices allows them to be imaged using SSM, even for penetration depths of a millimeter. Unusual vortex arrangements occur in samples comparable in size to the coherence length. Spontaneous magnetization is not observed in Sr{sub 2}RuO{sub 4}, which is believed to have p{sub x} {+-} ip{sub y} pairing symmetry, although effects hundreds of times bigger than the sensitivity limits had been predicted. However, unusual flux trapping is observed in this superconductor. Finally, unusual flux arrangements are also observed in magnetic superconductors. I then turn to vortex dynamics: imaging of vortices

  20. Thermodynamics of the Heat-Flux Avalanches at the First-Order Magnetic Transition in Magnetocaloric Materials

    Science.gov (United States)

    Piazzi, Marco; Bennati, Cecilia; Basso, Vittorio

    2017-10-01

    We investigate the kinetics of first-order magnetic phase transitions by measuring and modeling the heat-flux avalanches corresponding to the irreversible motion of the phase-boundary interface separating the coexisting low- and high-temperature stable magnetic phases. By means of out-of-equilibrium thermodynamics, we encompass the damping mechanisms of the boundary motion in a phenomenological parameter αs. By analyzing the time behavior of the heat-flux signals measured on La (Fe -Mn -Si )13-H magnetocaloric compounds through Peltier calorimetry temperature scans performed at low rates, we relate the linear rise of the individual avalanches to the intrinsic-damping parameter αs.

  1. Varying Eu2+ magnetic order by chemical pressure in EuFe2(As1-xPx)2

    Science.gov (United States)

    Zapf, S.; Wu, D.; Bogani, L.; Jeevan, H. S.; Gegenwart, P.; Dressel, M.

    2011-10-01

    Based on low-field magnetization measurements on a series of single crystals, we present a scheme of the Eu2+ spin alignment in EuFe2(As1-xPx)2. We explain observations of the Eu2+ ordering previously reported, reconciling different existing phase diagrams. The magnetic moments of the Eu2+ ions are slightly canted, yielding a ferromagnetic contribution along the c direction that becomes stronger with pressure, until superconductivity sets in. The spin-density wave as well as the superconducting phase coexist with an antiferromagnetic interlayer coupling of the canted spins. Reducing the interlayer distance finally leads to a ferromagnetic Eu2+ interlayer coupling and to the suppression of superconductivity.

  2. EXPERIMENTAL STUDY OF MAGNETIC FLUID SEAL

    Directory of Open Access Journals (Sweden)

    V. G. Bashtovoi

    2006-01-01

    Full Text Available Dependences of critical pressure drop, being held by magnetic fluid seal, on time in a static state and shaft rotation velocity in dynamics have been experimentally determined. The significant influence of particles’ redistribution in magnetic fluid on static parameters of magnetic fluid seal has been established.

  3. Birth order and mortality: a population-based cohort study.

    Science.gov (United States)

    Barclay, Kieron; Kolk, Martin

    2015-04-01

    This study uses Swedish population register data to investigate the relationship between birth order and mortality at ages 30 to 69 for Swedish cohorts born between 1938 and 1960, using a within-family comparison. The main analyses are conducted with discrete-time survival analysis using a within-family comparison, and the estimates are adjusted for age, mother's age at the time of birth, and cohort. Focusing on sibships ranging in size from two to six, we find that mortality risk in adulthood increases with later birth order. The results show that the relative effect of birth order is greater among women than among men. This pattern is consistent for all the major causes of death but is particularly pronounced for mortality attributable to cancers of the respiratory system and to external causes. Further analyses in which we adjust for adult socioeconomic status and adult educational attainment suggest that social pathways only mediate the relationship between birth order and mortality risk in adulthood to a limited degree.

  4. The Problem of World Order in Western IR Studies

    Directory of Open Access Journals (Sweden)

    Maria Victorovna Soljanova

    2016-01-01

    Full Text Available The article "Problem of world order in modern Western studies" is the study of one of the most debated issues in the science of international relations - world order. Discussion of the structure of world order is underway in various countries, both at the state level and in the expert community. Some researchers insist on the fact that after the end of the cold war, the collapse of the bipolar model of international relations, the world has become unipolar. Others argue that the increase in the number of centers of power and the need for a multilateral approach to solving global problems (terrorism, proliferation of weapons of mass destruction, environmental and climate issues talking about the formation of multipolarity. However, it should be recognized that currently no widely accepted theoretical and conceptual apparatus, which complicates not only the study of the world order, but makes it impossible to search for common approaches of the international community in solving the problems associated with global development, new challenges and threats. The author of this article seeks to research and analyze the various theoretical paradigms (neo-realism, neo-liberalism, institutionalism, neo-marxism, etc. and concepts to form a coherent picture of the structure of the world system, its main features and to offer readers the vision of the concept of "world order". Thus, the article notes that the multidimensional structure of the modern system of international relations established after the end of the cold war is so complex that none of the concepts can claim to accurate interpretation of the world order. The modern system differs from systems of the past centuries. Characteristics inherent in it (on the one hand, the increasing global processes in economy, politics, culture, etc., on the other, the attraction to return to the concept of "nation state", the closure of borders, the disintegration, require new approaches to the study of world

  5. Magnetic ordering and spin excitations in Mn(dca) sub 2 (pyz) [dca=N(CN) sub 2 sup - , pyz=pyrazine

    CERN Document Server

    Manson, J L; Argyriou, D N; Bordallo, H N; Lynn, J W; Huang, Q; Feyerherm, R; Loose, A

    2002-01-01

    We have studied the T- and H-dependent magnetism in Mn(dca) sub 2 (pyz) [dca=N(CN) sub 2 sup - , pyz=pyrazine] using neutron-scattering methods. The crystal structure can be viewed as a molecular analog of ReO sub 3 , where 1D Mn-pyz-Mn chains connect 2D Mn(dca) sub 2 square sheets to form a 3D network. In zero field, the Mn sup 2 sup + moments order antiferromagnetically below 2.53(2) K along the ac diagonal with a magnitude of 4.15(6) mu B at 1.35 K. The field-dependent response of the [111] magnetic reflection is consistent with spin-flop and induced ferromagnetic phase transitions as previously observed in magnetization measurements. Diffuse-scattering studies indicated no evidence for low-dimensional spin correlations. Using quasielastic neutron scattering, a low-energy spin-wave excitation was observed at propor to 0.23 meV, which is propor to 1/6 the momentum transfer observed in Mn(dca) sub 2 owing to a reduced number of magnetic nearest neighbors. (orig.)

  6. Higher-order Stark effect on magnetic fine structure of the helium atom

    Energy Technology Data Exchange (ETDEWEB)

    Magunov, A.; Pal' chikov, V.; Pivovarov, V. [National Research Inst. for Physical-Technical and Radiotechnical Measurements (VNIIFTRI), Mendeleevo, Moscow Region (Russian Federation); Ovsiannikov, V. [Dept. of Physics, Voronezh State Univ. (Russian Federation); Oppen, G. von [Inst. fuer Analytische und Atomare Physik at Technische Univ. Berlin (Germany)

    2001-07-01

    We have calculated the scalar and tensor dipole polarizabilities ({beta}) and hyperpolarizabilities ({gamma}) of excited 1s2p {sup 3}P{sub 0}, 1s2p {sup 3}P{sub 2}- states of helium. Our theory includes fine structure of triplet sublevels. Semiempirical and accurate electron-correlated wave functions have been used to determine the static values of {beta} and {gamma}. Numerical calculations are carried out using sums of oscillator strengths and, alternatively, with the Green function for the excited valence electron. Specifically, we present results for the integral over the continuum, for second- and fourth-order matrix elements. The corresponding estimations indicate that these corrections are of the order of 23% for the scalar part of polarizability and only of the order of 3% for the tensor part.

  7. Size effect on magnetic properties of a nano-graphene bilayer structure: A Monte Carlo study

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R. [Laboratory of Materials, Process, Environment and Quality, Cady Ayyad University, National School of Applied Sciences, Safi (Morocco); Laboratoire de Magnetisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Universite Mohammed V-Agdal, Faculte des Sciences, B.P. 1014 Rabat (Morocco); Bahmad, L., E-mail: bahmad@fsr.ac.ma [Laboratoire de Magnetisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Universite Mohammed V-Agdal, Faculte des Sciences, B.P. 1014 Rabat (Morocco); Benyoussef, A. [Laboratoire de Magnetisme et Physique des Hautes Energies L.M.P.H.E.URAC 12, Universite Mohammed V-Agdal, Faculte des Sciences, B.P. 1014 Rabat (Morocco)

    2012-11-15

    In this paper we use the Monte Carlo simulations to investigate the magnetic properties of an Ising ferromagnetic-antiferromagnetic model. The system is based on a nano-graphene structure-like bilayer with two bloc sizes: N=24 and 42 spins. For each size N, the upper layer A is formed with spin -3/2, whereas the lower layer B is composed of spin -5/2. We only consider the first nearest-neighbor interactions between the sites i and j. The magnetic properties are studied, in the absence as well as in the presence of a crystal magnetic field, and an external magnetic field. The increasing temperature and crystal field as well as the inter-layer coupling constant, are also studied for this system sizes N=24 and 42 spins. The zero-field-cooled and the field cooled magnetization behaviors are investigated for different values of external magnetic field and a fixed value of exchange interaction between the two blocs. The magnetizations as well as the magnetic susceptibilities versus the temperature are used in order to obtain blocking temperature. The saturation magnetization and coercive field are also obtained for the two sizes of the studied system. It is found that the blocking temperature decreases on increasing the crystal magnetic field and/or the external magnetic field, for a fixed system size. On the other hand, it is found that the blocking temperature increases on increasing the system size from N=24 to 42 spins, for fixed values of external and the crystal magnetic fields. - Highlights: Black-Right-Pointing-Pointer Magnetic properties of an Ising ferromagnetic-antiferromagnetic bilayer is studied. Black-Right-Pointing-Pointer Monte Carlo simulations are used. Black-Right-Pointing-Pointer Zero-field-cooled (ZFC) and field cooled (FC) magnetization behaviors for nano-graphene are obtained.

  8. Spatially resolved modelling of inhomogeneous materials with a first order magnetic phase transition

    DEFF Research Database (Denmark)

    Nielsen, Kaspar Kirstein; Bahl, Christian; Smith, Anders

    2017-01-01

    , respectively and first order reversal effect as a function of temperature. We conclude that even a very little variation in local stoichiometry of less than a percent, corresponding to a standard deviation in of for has a significant impact on the overall properties and history dependence of a sample....

  9. The amygdala in schizophrenia: a trimodal magnetic resonance imaging study.

    Science.gov (United States)

    Kalus, Peter; Slotboom, Johannes; Gallinat, Jürgen; Wiest, Roland; Ozdoba, Christoph; Federspiel, Andrea; Strik, Werner K; Buri, Caroline; Schroth, Gerhard; Kiefer, Claus

    2005-03-03

    In schizophrenic psychoses, structural and functional alterations of the amygdala have been demonstrated by several neuroimaging studies. However, postmortem examinations on the brains of schizophrenics did not confirm the volume changes reported by volumetric magnetic resonance imaging (MRI) studies. In order to address these contradictory findings and to further elucidate the possibly underlying pathophysiological process of the amygdala, we employed a trimodal MRI design including high-resolution volumetry, diffusion tensor imaging (DTI), and quantitative magnetization transfer imaging (qMTI) in a sample of 14 schizophrenic patients and 14 matched controls. Three-dimensional MRI volumetry revealed a significant reduction of amygdala raw volumes in the patient group, while amygdala volumes normalized for intracranial volume did not differ between the two groups. The regional diffusional anisotropy of the amygdala, expressed as inter-voxel coherence (COH), showed a marked and significant reduction in schizophrenics. Assessment of qMTI parameters yielded significant group differences for the T2 time of the bound proton pool and the T1 time of the free proton pool, while the semi-quantitative magnetization transfer ratio (MTR) did not differ between the groups. The application of multimodal MRI protocols is diagnostically relevant for the differentiation between schizophrenic patients and controls and provides a new strategy for the detection and characterization of subtle structural alterations in defined regions of the living brain.

  10. Study of magnetic materials in Langmuir-Blodgett films

    International Nuclear Information System (INIS)

    Coronel, Philippe

    1990-01-01

    As one of the key issue in molecular electronics is the fabrication of organised systems with specific properties born by molecules, one of these properties being the possibility of information storage, this research thesis reports an exploratory study based on the development of a magnetic complex in a two-dimensional organisation in order to obtain a molecular magnetic memory. For this purpose, the chosen property for the complex was the molecular bi-stability which is a characteristic of magnetic materials which display a spin transition phenomenon. Two types of complex families have been studied: [(Phenanthroline)_2Fe'' (NCS)_2] and [Fe''' (8-quinolyl-salicyl-aldimine)_2](X''). The fabrication of a two-dimensional organised system is performed by using the Langmuir-Blodgett technique. With this technique, three synthesis ways are considered: an in-situ synthesis, a semi-amphiphilic way, and an amphiphilic way. Within this research, the author tried to see whether the existence of 3D (powder) spin transition phenomenon was transposable in 2D (case of a LB film) [fr

  11. Satelite structure in 59Co NMR spectrum of magnetically ordered Dysub(1-x)Ysub(x)Co2 intermetallic compound

    International Nuclear Information System (INIS)

    Yoshimura, Kazuyoshi; Hirosawa, Satoshi; Nakamura, Yoji

    1984-01-01

    The magnetic environment effect of cobalt in Dysub(1-x)Ysub(x)Co 2 has been studied by means of bulk magnetization and 59 Co spin-echo NMR measurements at 4.2K. Clearly resolved satellite structures of the NMR spectra have been observed. The hyperfine field distributions of 59 Co are decomposed into contributions of Co atoms in various nearest neighbor configurations of rare earth atoms. In this analysis the dipole field due to nearest neighbor rare earth moments plays an important role. The result indicates that the magnetic moment of Co in the RCo 2 cubic Laves phase pseudobinary compounds is quite sensitive to the nearest neighbor rare earth environment. (author)

  12. Magnetic structures of (Co2-xNix)(OH)PO4 (x = 0.1,0.3) spin glass-like state in antiferromagnetically ordered phases

    International Nuclear Information System (INIS)

    Pedro, I de; Rojo, J M; Pizarro, J L; Fernandez, J RodrIguez; Marcos, J Sanchez; Fernandez-DIaz, M T; Arriortua, M I; Rojo, T

    2006-01-01

    Compounds of the general formula Co 2-x Ni x (OH)PO 4 (x = 0.1, 0.3) have been synthesized under mild hydrothermal conditions. Neutron powder diffraction, susceptibility and heat capacity measurements were carried out on polycrystalline samples. The cobalt-nickel compounds are ordered as three-dimensional antiferromagnets with ordering temperatures of 70 and 64 K for x = 0.1 and x = 0.3, respectively. The magnetic study shows a spin glass-like state below 11 and 5 K for Co 1.9 Ni 0.1 (OH)PO 4 and Co 1.7 Ni 0.3 (OH)PO 4 , respectively. Specific heat data present peaks at 68 and 61 K for Co 1.9 Ni 0.1 and Co 1.7 Ni 0.3 , respectively. These peaks show broad shoulders between approximately 15 and 40 K. The lack of any distinguishable anomaly below 10 K supports the spin glass nature of the low temperature transitions. Refinement of room temperature neutron diffraction data indicates that the Ni(II) ions are in octahedral co-ordination with the practical absence of these ions in the trigonal bipyramidal sites. The magnetic structures of Co 2-x Ni x (OH)PO 4 consist of ferromagnetic arrangements between the octahedral chains and trigonal bipyramidal dimers within the xz plane with the magnetic moments along the z axis. The ferromagnetic layers are disposed antiparallel to one another along the y direction establishing the three-dimensional antiferromagnetic order (T N ∼70 K for Co 1.9 Ni 0.1 and ∼64 K for Co 1.7 Ni 0.3 ). The different exchange pathways, the anisotropy of the Co(II) ions and the frustration of the magnetic moments in the trigonal bipyramidal geometry could be responsible for the freezing process

  13. Design study of the KIRAMS-430 superconducting cyclotron magnet

    International Nuclear Information System (INIS)

    Kim, Hyun Wook; Kang, Joonsun; Hong, Bong Hwan; Jung, In Su

    2016-01-01

    Design study of superconducting cyclotron magnet for the carbon therapy was performed at the Korea Institute of Radiological and Medical Science (KIRAMS). The name of this project is The Korea Heavy Ion Medical Accelerator (KHIMA) project and a fixed frequency cyclotron with four spiral sector magnet was one of the candidate for the accelerator type. Basic parameters of the cyclotron magnet and its characteristics were studied. The isochronous magnetic field which can guide the "1"2C"6"+ ions up to 430 MeV/u was designed and used for the single particle tracking simulation. The isochronous condition of magnetic field was achieved by optimization of sector gap and width along the radius. Operating range of superconducting coil current was calculated and changing of the magnetic field caused by mechanical deformations of yokes was considered. From the result of magnetic field design, structure of the magnet yoke was planned.

  14. Design study of the KIRAMS-430 superconducting cyclotron magnet

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hyun Wook; Kang, Joonsun, E-mail: genuinei@kirams.re.kr; Hong, Bong Hwan; Jung, In Su

    2016-07-01

    Design study of superconducting cyclotron magnet for the carbon therapy was performed at the Korea Institute of Radiological and Medical Science (KIRAMS). The name of this project is The Korea Heavy Ion Medical Accelerator (KHIMA) project and a fixed frequency cyclotron with four spiral sector magnet was one of the candidate for the accelerator type. Basic parameters of the cyclotron magnet and its characteristics were studied. The isochronous magnetic field which can guide the {sup 12}C{sup 6+} ions up to 430 MeV/u was designed and used for the single particle tracking simulation. The isochronous condition of magnetic field was achieved by optimization of sector gap and width along the radius. Operating range of superconducting coil current was calculated and changing of the magnetic field caused by mechanical deformations of yokes was considered. From the result of magnetic field design, structure of the magnet yoke was planned.

  15. Magnetic and electric order in the spin-1/2 XX model with three-spin interactions

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Pradeep; Durganandini, P. [Department of Physics, University of Pune, Ganeshkhind, Pune - 411007 (India)

    2016-05-23

    We study the spin-1/2 XX model in the presence of three-spin interactions of the XZX+YZY and XZY-YZX types. We solve the problem exactly and show that there is both finite magnetization and electric polarization for low non-zero strengths of the three-spin interactions.

  16. Large Coil Program magnetic system design study

    International Nuclear Information System (INIS)

    Moses, S.D.; Johnson, N.E.

    1977-01-01

    The primary objective of the Large Coil Program (LCP) is to demonstrate the reliable operation of large superconducting coils to provide a basis for the design principles, materials, and fabrication techniques proposed for the toroidal magnets for the THE NEXT STEP (TNS) and other future tokamak devices. This paper documents a design study of the Large Coil Test Facility (LCTF) in which the structural response of the Toroidal Field (TF) Coils and the supporting structure was evaluated under simulated reactor conditions. The LCP test facility structural system consists of six TF Coils, twelve coil-to-coil torsional restraining beams (torque rings), a central bucking post with base, and a Pulse Coil system. The NASTRAN Finite Element Structural Analysis computer Code was utilized to determine the distribution of deflections, forces, and stresses for each of the TF Coils, torque rings, and the central bucking post. Eleven load conditions were selected to represent probable test operations. Pulse Coils suspended in the bore of the test coil were energized to simulate the pulsed field environment characteristic of the TNS reactor system. The TORMAC Computer Code was utilized to develop the magnetic forces in the TF Coils for each of the eleven loading conditions examined, with or without the Pulse Coils energized. The TORMAC computer program output forces were used directly as input load conditions for the NASTRAN analyses. Results are presented which demonstrate the reliability of the LCTF under simulated reactor operating conditions

  17. Heating ability and biocompatibility study of silica-coated magnetic ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 38; Issue 6. Heating ability and biocompatibility study of silica-coated magnetic nanoparticles as heating mediators for magnetic hyperthermia and magnetically triggered drug delivery systems. Meysam Soleymani Mohammad Edrissi. Volume 38 Issue 6 October 2015 ...

  18. Magnetic enzyme reactors for isolation and study of heterogeneous glycoproteins

    International Nuclear Information System (INIS)

    Korecka, Lucie; Jezova, Jana; Bilkova, Zuzana; Benes, Milan; Horak, Daniel; Hradcova, Olga; Slovakova, Marcela; Viovy, Jean-Louis

    2005-01-01

    The newly developed magnetic micro- and nanoparticles with defined hydrophobicity and porosity were used for the preparation of magnetic enzyme reactors. Magnetic particles with immobilized proteolytic enzymes trypsin, chymotrypsin and papain and with enzyme neuraminidase were used to study the structure of heterogeneous glycoproteins. Factors such as the type of carrier, immobilization procedure, operational and storage stability, and experimental conditions were optimized

  19. [Gastric magnetic resonance study (methods, semiotics)].

    Science.gov (United States)

    Stashuk, G A

    2003-01-01

    The paper shows the potentialities of gastric study by magnetic resonance imaging (MRI). The methodic aspects of gastric study have been worked out. The MRI-semiotics of the unchanged and tumor-affected wall of the stomach and techniques in examining patients with gastric cancer of various sites are described. Using the developed procedure, MRI was performed in 199 patients, including 154 patients with gastric pathology and 45 control individuals who had no altered gastric wall. Great emphasis is placed on the role of MRI in the diagnosis of endophytic (diffuse) gastric cancer that is of priority value in its morphological structure. MRI was found to play a role in the diagnosis of the spread of a tumorous process both along the walls of the stomach and to its adjacent anatomic structures.

  20. Experimental studies of the magnetized friction force

    International Nuclear Information System (INIS)

    Fedotov, A. V.; Litvinenko, V. N.; Gaalnander, B.; Lofnes, T.; Ziemann, V.; Sidorin, A.; Smirnov, A.

    2006-01-01

    High-energy electron cooling, presently considered as an essential tool for several applications in high-energy and nuclear physics, requires an accurate description of the friction force which ions experience by passing through an electron beam. Present low-energy electron coolers can be used for a detailed study of the friction force. In addition, parameters of a low-energy cooler can be chosen in a manner to reproduce regimes expected in future high-energy operation. Here, we report a set of dedicated experiments in CELSIUS aimed at a detailed study of the magnetized friction force. Some results of the accurate comparison of experimental data with the friction force formulas are presented