Showing papers on "Metamagnetism published in 1998"
TL;DR: In this paper, a study of the magnetic properties of several (Gd1−xErx)NiAl alloys (where x = 0, 0.30, 0., 30, 0, 30, 40, 45, 50, 55, 60, 70, 80, and 90) was performed using both ac and dc magnetic and heat capacity measurements in an attempt to understand the table-like magnetocaloric effect previously observed in Gd0.54Er0.46NiAl.
Abstract: A study of the magnetic properties of several (Gd1−xErx)NiAl alloys (where x=0, 0.30, 0.40, 0.46, 0.50, 0.55, 0.60, 0.80, and 1.00) was undertaken using both ac and dc magnetic and heat capacity measurements in an attempt to understand the table-like magnetocaloric effect previously observed in (Gd0.54Er0.46)NiAl. Results indicate the presence of both antiferromagnetic and ferromagnetic ordering processes in all alloys containing Gd. For ErNiAl, a metamagnetic transition from an antiferromagnetic ground state was observed. Within each alloy, several magnetic transitions occur over a temperature range from 10 K [in (Gd0.20Er0.80)NiAl] up to 35 K (in GdNiAl), with all but the lowest temperature transition shifting to higher temperatures with increasing Gd content. The change in magnetic entropy (ΔSmag) induced by a change in field is observed to peak around the Neel temperature for ErNiAl while gradually broadening and shifting toward the Curie temperature as the Gd content is increased. For Gd-rich alloys,...
107 citations
TL;DR: In this paper, the authors investigated the metamagnetic anomaly observed in several heavy-fermion compounds, and found that MA is closely related to a sharp peak in the density of states of the hybridized quasiparticle bands.
75 citations
TL;DR: In this article, the Eu T In compounds were investigated by magnetic susceptibility measurements and 151 Eu Mossbauer spectroscopy, showing that the isomer shifts are linearly correlated with the closest Eu-Eu distance in the structure.
63 citations
TL;DR: In this paper, a simple slave-boson representation combined with the Hartree-Fock approximation for Hund's rule coupling is introduced for a doubly degenerate narrow band, which bears a direct relation to that introduced previously in the nondegenerate case.
Abstract: A simple slave-boson representation combined with the Hartree-Fock approximation for Hund's rule coupling is introduced for a doubly degenerate narrow band, which bears a direct relation to that introduced previously in the nondegenerate case. Namely, one keeps the fermion representation of the spin operator to recover properly the energy of fermionic quasiparticles in the presence of an applied magnetic field. A simple two-parameter mean-field analysis of the metamagnetism is provided, with the emphasis on the role of Hund's rule coupling. We also analyze the appearance of the spin-split effective masses in the applied field and for the non-half-filled band situation. The Mott-Hubbard boundary is determined at nonzero temperature $(Tg0)$; it shifts towards lower interactions with increasing $T$ and the field signaling the precursory localization effects, explicitly exhibited in the behavior of the magnetic susceptibility calculated in the Appendix. We also formulate a more general two-parameter rotationally invariant approach for an arbitrary degeneracy $d$ of equivalent orbitals and show that the Mott-Hubbard transition at zero temperature and at any integer filling $ng~1$ is always discontinuous. A brief overview of the experimental situation is also given.
47 citations
TL;DR: The reaction of Eu with molten lithium polyselenide produced a new rare-earth dichalcogenide, EuSe2 as mentioned in this paper, which cannot be obtained via direct combination of the elements and is therefore an exam...
Abstract: The reaction of Eu with molten lithium polyselenide produced a new rare-earth dichalcogenide, EuSe2. This compound cannot be obtained via direct combination of the elements and is therefore an exam...
38 citations
TL;DR: In this paper, the magnetization and magnetostriction of Mn 3 GaC were measured under pulsed high magnetic fields up to 37 T and under steady magnetic field and pressure up to 0.82 GPa.
Abstract: We have measured the magnetization and magnetostriction of Mn 3 GaC in pulsed high magnetic fields up to 37 T and the magnetization under steady magnetic field and pressure up to 0.82 GPa. Mn 3 GaC is antiferromagnetic (AF) at low temperatures. It exhibits successive transitions to an intermediate (I), to a ferromagnetic (F) and to a paramagnetic phase. The transition between the AF and I phases is first order and the others are second order. The transition temperature between the I and F phases does not change greatly with increasing magnetic field. At low temperatures, a metamagnetic transition from the AF to the I state is observed. Volume magnetostriction measurement at 4.2 K indicates that the volume is abruptly decreased by the metamagnetic transition and then gradually shrinks with increasing field. High pressure stabilizes the F phase and enhances the Mn moment.
36 citations
TL;DR: In this article, structural and magnetic properties of the RCuAl (R=rare earth) intermetallic compounds were studied by means of X-ray diffraction, susceptibility, magnetization and specific heat measurements.
36 citations
TL;DR: In this article, a semiquantitative analysis of (B,T) magnetic phase diagrams in the hexagonal region of the MnFeP1−xAsx (0.15⩽x0.66) series of compounds was carried out.
Abstract: On the basis of the relation T(σ,H) derived within the framework of the Bean–Rodbell model a semiquantitative analysis of (B,T) magnetic phase diagrams in the hexagonal region of the MnFeP1−xAsx (0.15⩽x⩽0.66) series of compounds was carried out. It was found that the first order transition line in the (B,T) plane is terminated by the isolated critical point for x=0.33 and x=0.5 contents. The positive value of dBC/dT and the saturation of the magnetization was found to be in agreement with the experiment. Thus the Bean–Rodbell model and the molecular field approximation can be applied to describe the discontinuous Ferro–Para magnetoelastic phase transition. Semiquantitative agreement between the theoretical and the experimental (B,T) magnetic phase diagrams was obtained. For the MnFeP0.67As0.33 compound the electronic structure calculations were performed by the Korringa–Kohn–Rostoker with the coherent potential approximation method. The density of states (DOS) curve calculated in the nonmagnetic state sho...
35 citations
TL;DR: In this paper, ground-state energies and magnetization curves in the one-dimensional ε-XXZ model with next-to-nearest neighbor coupling were investigated. And the magnetization curve is discontinuous at a critical field.
Abstract: We investigate ground-state energies and magnetization curves in the one-dimensional $\mathrm{XXZ}$ model with next-to-nearest neighbor coupling $\ensuremath{\alpha}g0$ and anisotropy $\ensuremath{\Delta}$ $(\ensuremath{-}1l~\ensuremath{\Delta}l~1)$ at $T=0$. In between the familiar ferro- and antiferromagnetic phase we find a transition region---called the metamagnetic phase---where the magnetization curve is discontinuous at a critical field ${B}_{c}(\ensuremath{\alpha},\ensuremath{\Delta})$.
33 citations
TL;DR: In this paper, the Anderson lattice model was used to investigate the metamagnetism of heavy fermions using the anisotropy of the hybridization matrix element, together with electron-lattice coupling.
Abstract: Metamagnetism of heavy fermions is investigated using the Anderson lattice model in which the anisotropy of the hybridization matrix element, together with electron-lattice coupling, is taken into account. Within the leading-order approximation in the 1/ N -expansion, it is found that the incoherent part of the f electron becomes relevant above a critical field H M , while it is irrelevant below H M . Consequently, both magnetization and magnetostriction show abrupt increases with increasing H at H M . The results are in good agreement with the experimental data of CeRu 2 Si 2 .
33 citations
TL;DR: In this paper, the authors studied the origin of the cooperative Jahn-Teller effect and the metamagnetic transition in the orthorhombic compound PrCu 2, and determined the anisotropic ferroquadrupole phase diagram by measuring the specific heat and thermal expansion under magnetic fields.
Abstract: We have studied the origin of the cooperative Jahn-Teller effect and the metamagnetic transition in the orthorhombic compound PrCu 2 . We have determined the anisotropic ferroquadrupole phase diagram by measuring the specific heat and thermal expansion under magnetic fields. With increasing the field, the Jahn-Teller transition temperature increases slightly for the field along a - and c -axes, while it decreases intensively along the b -axis. The phase diagram can be explained quantitatively by including the quadrupolar interaction of - K JT O x y in the crystalline electric field and Zeeman Hamiltonian. The metamagnetic transition, which brings about the conversion between the easy ( a )- and hard ( c )-axes magnetization, has been also studied through the magnetostriction. This phenomenon is also explained quantitatively on the basis of the quadrupolar interaction of - K M O 2 2 . The sign of is found to be negative in the state where the c -axis is the hard one, while it ...
TL;DR: In this article, the magnetovolume coupling constant in the paramagnetic state is nearly constant up to about x = 0.05 and then decreases with increasing x and the value of is considerably reduced by the metamagnetic transition.
Abstract: High-field magnetization and magnetostriction measurements have been performed for typical metamagnetic itinerant-electron systems and with at 4.2 K in pulsed magnetic fields up to 40 T. The substitution of Al or Ga for Co significantly decreases the critical field of the metamagnetic transition. The magnetovolume coupling constant in the paramagnetic state is nearly constant up to about x = 0.05 and then decreases with increasing x. Moreover, the value of is considerably reduced by the metamagnetic transition. The variation of produced by the change of x or the metamagnetic transition is considered to originate from the change of the spin fluctuation spectrum.
TL;DR: In this paper, the magnetic properties of the Gd 1− x La x Mn 2 Ge 2 system with the ThCr 2 Si 2 type structure were investigated for x = 0.1.
TL;DR: The results of magnetic, transport and dilatometric studies of the Er(Co1− x6)2 compounds (for x ⩽ 0.15) in ambient and elevated pressures are presented in this paper.
TL;DR: In this article, the magnetic properties of quasiternary UCo 1− x Pt x Al compounds were investigated. But the initial substitutions of Pt for Co (x ≤ 0.05) cause gradual suppression of the UCoAl-type metamagnetism.
TL;DR: In this article, a changeover from first-to second-order transition at about x c = 0.60 was observed in the framework of the generalized Inoue-Shimizu phenomenological model.
TL;DR: In this paper, lattice constants and magnetization in MnAs were measured under pressures up to 24 kbar at room temperature and 10kbar at 80 K. Magnetic moment of Mn ion was about 1.6 μB under 8-10 kbar.
TL;DR: In this paper, the properties of hexagonal Th 7 Fe 3 -type R 7 Rh 3 compounds (R=La, Ce, Pr and Nd) have been studied by measuring a.c. magnetic susceptibility, magnetization, electrical resistivity, thermoelectric power and thermal expansion.
TL;DR: GMR Δϱ ϱ of about 10% was observed in bulk-MnAu 2 at 300 K in a field of 70 kOe as mentioned in this paper, which is a tetragonal material with a spiral spin structure of Mn and shows a metamagnetic transition from a spiral to a ferromagnetic structure.
TL;DR: The magnetic properties of these compounds were determined with a SQUID magnetometer between 2 and 300 K with magnetic flux densities up to 5.5 T as mentioned in this paper, and the highest ordering temperature occurs for Gd3Si2C2 with a Neel temperature TN=50(±1) K.
TL;DR: In this paper, the entire feature of H-T magnetic phase diagram has been obtained, for the first time, with three distinct ordered phases observed, with a strong uniaxial anisotropy along the tetragonal c -axis.
Abstract: The magnetic, transport, and thermal properties have been studied in UPd 2 Si 2 single crystals by various experiments including neutron diffraction and ultra-high-field ( H < 1 MOe) magnetization. The entire feature of H – T magnetic phase diagram has been obtained, for the first time. Three distinct ordered phases are observed, with a strong uniaxial anisotropy along the tetragonal c -axis. One of the notable features revealed in the ordered phases is a formation of an incommensurate-longitudinal-sine-wave (ICLSW) modulation in the temperature range 108 K < T < 135 K, where the propagation vector Q (∼0.71 c * at 135 K) varies continuously as a function of temperature, with no admixture of harmonics. The magnetic susceptibility exhibits an unusual ferromagnetic enhancement in this antiferromagnetically ordered state. The entropy analyses using a non-5 f analog ThPd 2 Si 2 have confirmed that the anomalous magnetic properties of UPd 2 Si 2 are ascribed to the 5 f moments of uranium ions, which are replace...
TL;DR: In this paper, a careful analysis of neutron diffraction experiments under magnetic field performed on a single crystal of tetragonal is presented, which shows that the zero-field-low-temperature magnetic phase is not the natural compensated antiphase structure proposed so far for the Q = (3/13, 0, 0) propagation vector, but a mixed phase where the moment of two of the 26 Tb sites of the unit cell vanishes.
Abstract: A careful analysis of neutron diffraction experiments under magnetic field performed on a single crystal of tetragonal is presented. It shows that the zero-field-low-temperature magnetic phase is not the natural compensated antiphase structure proposed so far for the Q = (3/13, 0, 0) propagation vector, but a mixed phase where the moment of two of the 26 Tb sites of the unit cell vanishes. The magnetic structures of the first three field induced phases of the multistep metamagnetic process agree with previous analysis whereas the fourth field induced phase is not the non-mixed proposed one but a mixed one with two zero moments as in zero field. Contrary to previous interpretations, the transition at 4.7 K observed by specific heat and susceptibility corresponds to the change of the magnetic structure from the mixed low-temperature one to a slightly modulated non-mixed one. Numerical simulation allowed us to account for the main properties observed and emphasizes the crucial role of the crystal field.
TL;DR: In this paper, the magnetic structures in magnetic fields up to 6 T on a single crystal of Y 2 Cu 2 O 5 were determined from a single diffraction experiment, which showed strange metamagnetic transitions at H c 1 = 3.0T and H c 2 = 4.8T for H b = 0, but new diffraction peaks appeared at completely unexpected positions between H c1 and H b 2, which means a three-lattice period modulation along the b-axis but this structure change is mysterious from the crystallographic point of view.
TL;DR: In this article, electrical resistivity and ac magnetic susceptibility studies of the 5f-metamagnet UCoAl reveal the presence of strong spin fluctuation effects for temperatures below 30 K and magnetic fields below the critical metamagnetic field μ 0Hc≈1 T, where a non-Fermi liquid term ∼T3/2 is prominent in the electrical resistivities.
Abstract: Electrical resistivity and ac magnetic susceptibility studies of the 5f-metamagnet UCoAl reveal the presence of strong spin fluctuation effects for temperatures below 30 K and magnetic fields below the critical metamagnetic field μ0Hc≈1 T, where a non-Fermi liquid term ∼T3/2 is prominent in the electrical resistivity. A step-wise increase of the residual resistivity and an increasingly prominent Fermi liquid T2 term of the resistivity is observed as the field is increased though the metamagnetic transition.
TL;DR: In this article, high-field magnetizations of Y(Co0.925Al 0.075)2Hx have been measured for 0≤x≤3.44 and amorphized YCo2H3.06 in pulsed high magnetic fields up to 42 T.
TL;DR: In this paper, the results of structure and magnetization study of solid solutions UCoAl 1− x Ga x are presented, where the ZrNiAl-type structure of parent compounds persists over whole series and a rather weak concentration dependence of lattice parameters is observed.
TL;DR: In this article, the results of low temperature magnetization measurements carried out on the Dy 0.73 Tb 0.27 Fe 2− x Co x system and their hydrogenated compounds are presented.
TL;DR: In this article, the authors give a theoretical explanation for the phenomenon of the magnetic susceptibility showing a maximum at low temperature for those compounds that show itinerant-electron metamagnetism and derive the linear relation between the metamagnetic transition field and observed experimentally for, paying particular attention to the effects of the zero point quantum spin fluctuations and assuming the existence of almost energetically degenerate paramagnetic thermodynamic states.
Abstract: We give a theoretical explanation for the phenomenon of the magnetic susceptibility showing a maximum at low temperature for those compounds that show itinerant-electron metamagnetism. We also derive the linear relation between the metamagnetic transition field and observed experimentally for , paying particular attention to the effects of the zero-point quantum spin fluctuations and assuming the existence of almost energetically degenerate paramagnetic thermodynamic states.
TL;DR: In this article, the itinerant-electron metamagnetic transition under different annealing conditions has been investigated for Laves phase Lu(Co 1− x Al x ) 2 compounds with a C15-type structure.
TL;DR: In this paper, the antiferromagnetic non-superconducting compound TbNi2B2C has been shown to exhibit an upward curvature of the magnetization versus field curves.
Abstract: The antiferromagnetic non-superconducting compound TbNi2B2C crystallizes in the same LuNi2B2C-type structure as the superconducting rare-earth borocarbides Below 15 K the magnetization curves of polycrystalline TbNi2B2C show an upward curvature of the magnetization versus field curves, ie a metamagnetic behaviour At low temperatures the field dependence of resistivity ρ is non-monotonic and the magnetoresistance ratio MR=[ρ(H)−ρ(0)]/ρ(0) even changes its sign Near T=TN the value of MR is negative and its magnitude increases monotonically with increasing fields up to about 45% at the maximum available field of 16 T The magnetoresistance of this material is isotropic with respect to the angle between current and field The observed effects can be understood within a theoretical approach of the giant magnetoresistance developed for artificial as well as natural layered structures, taking into account topological changes of the Fermi surface caused by metamagnetic transitions, together with field-reduced spin-disorder scattering