Showing papers on "Metamagnetism published in 2000"
TL;DR: A terephthalate-based cobalt hydroxide, Co2(OH)2(C8H4O4), was synthesized by the hydrothermal method.
Abstract: A new terephthalate-based cobalt hydroxide, Co2(OH)2(C8H4O4), was synthesized by the hydrothermal method. Its crystal structure has been determined by ab-initio XRPD methods (monoclinic, C2/m, a = 19.943(1), b = 3.2895(1), c = 6.2896(3) A, β = 95.746(3)°) and fully refined by the Rietveld technique down to Rp = 0.15 for 9301 observed data (178 independent reflections). The terephthalates are coordinated and pillared directly to the cobalt hydroxide layers and thus a three-dimensional framework is formed. Because of the bonds with the terephthalates, two crystallographically inequivalent cobalt sites are found inside the hydroxide layers, with different octahedral orientations. Magnetic studies show that the intralayer exchange interaction between Co(II) ions is ferromagnetic but the whole system orders antiferromagnetically at 48 K with a metamagnetic transition above a threshold field of 0.2 T. The existence of conjugated π electrons in terephthalates explains the antiferromagnetic interactions between t...
202 citations
TL;DR: In this paper, it was shown that the possibility of a first-order phase transition is connected to features of the electronic structure rather than to the magnitude of the transition temperature as conjectured earlier.
Abstract: It has been found experimentally that the order of the magnetic phase transitions in RCo2 compounds (R standing for rare-earth metals) at Tc changes from second order for the light-rare-earth series up to TbCo2 to first order for the heavier-rare-earth compounds DyCo2, HoCo2 and ErCo2. On the basis of results of fixed-spin-moment band-structure calculations for the isostructural compound YCo2 at different lattice constants, we propose an explanation for this behaviour. In contrast to the widely accepted Inoue-Shimizu theory for this class of compounds, our explanation also includes Pr, Nd which were thought to behave differently due to the influence of crystal-field effects. We show that an itinerant-electron metamagnetic transition in these compounds can occur only over a certain range of lattice constants and that the possibility of a first-order phase transition is connected to features of the electronic structure rather than to the magnitude of the transition temperature as conjectured earlier. The influence of the latter is only important if the transition takes place at elevated temperatures, where effects of spin fluctuations can suppress a first-order transition.
115 citations
TL;DR: In this article, a low-field metamagnetic transition in UGe 2 close to the critical pressure at which the Curie temperature is suppressed to zero was discovered, which provides a unique opportunity to test theoretical models of metamagnetism.
Abstract: We have discovered a low-field metamagnetic transition in UGe 2 close to the critical pressure at which the Curie temperature is suppressed to zero. The systematic evolution of the transition with pressure provides a unique opportunity to test theoretical models of metamagnetism.
48 citations
TL;DR: In this article, magnetization measurements in the Ln(Mn1−xCox)O3+λ (Ln=Eu, Nd; 0⩽x<1) and Y(mn 1−xcox) O3 (0.5Mn 0.5) perovskites as a function of temperature and magnetic field were reported.
Abstract: We report magnetization measurements in the Ln(Mn1−xCox)O3+λ (Ln=Eu, Nd; 0⩽x<1) and Y(Mn1−xCox)O3 (0.35⩽x⩽0.5) perovskites as a function of temperature and magnetic field. Compositions in the range of 0.35⩽x⩽0.8 (Ln=Eu), 0.4⩽x⩽0.6 (Ln=Nd), and 0.35⩽x⩽0.45 (Ln=Y) exhibit metamagnetic behavior associated with a transformation of the magnetic structure from ferrimagnetic, where the magnetic moments of Co2+ and Mn4+ ions are antiparallel, to ferromagnetic where they are parallel. A ferromagnetic state is observed for the 0.1⩽x⩽0.15 (Ln=Nd) and 0.45
44 citations
TL;DR: In this article, the authors examined magnetocaloric effects of DyMn 2 Ge 2, which shows two successive first-order phase transitions at 36 and 40 K. The magnetization measurements for single crystals have revealed that the intermediate state appearing between 36-40 K in zero field is essentially the same as the high-field phase, which is induced by a magnetic field of 7 T at 4.2 K.
43 citations
TL;DR: In this paper, the properties of the compounds Ce 2 Fe 17− x Mn x (x = 0-3) were studied and their structure and magnetic properties were studied, showing that Mn prefers the 6 c site and avoids completely the 9 d site, whereas the 18 f and 18 h sites are occupied almost randomly.
38 citations
TL;DR: The field dependence of specific heat has been measured at low temperatures in order to study two different types of f-electron metamagnetic systems as discussed by the authors, and the results showed that in the low-field state, ferromagnetic spin-fluctuation dominates in an anomalous temperature dependence of C.
Abstract: The field dependence of specific heat has been measured at low temperatures in order to study two different types of f-electron metamagnetic systems. The antiferromagnet PrFe4P12 with Neel temperature of 6.4 K shows a sharp peak structure in C/T at the spin flip metamagnetic transition. In the high field state, the magnetic contribution Cm/T shows an anomalous huge value ∼1.4 J/K 2 mol . UCoAl shows the metamagnetic transition from paramagnetic ground state at ∼1 T, where C/T at 0.5 K shows an apparent decrease reflecting a change of the density of states. In the low-field state, ferromagnetic spin-fluctuation dominates in an anomalous temperature dependence of C.
29 citations
TL;DR: In this article, electrical resistivity ρ( T ), magnetic susceptibility χ( T ) and magnetization M ( B ) on single crystals for x = 0.13 and 0.18.
Abstract: Highly anisotropic properties of CeTe 2- x with the layered Cu 2 Sb-type structure have been found by the measurements of electrical resistivity ρ( T ), magnetic susceptibility χ( T ) and magnetization M ( B ) on single crystals for x =0.15–0.18. Both M ( B ∥ c ) and M ( B ⊥ c ) at 2 K exhibit a metamagnetic transition at 0.04 T. M ( B ∥ c ) saturates rapidly to a value of 1.06 µ B /f.u. at around B =0.2 T, whereas M ( B ⊥ c ) gradually increases to a value of 0.75 µ B /f.u. at 5.5 T. The absence of hysteresis and remanence in M ( B ) indicates an antiferromagnetic ground state. The resistivity ratio ρ ∥ c /ρ ⊥ c increases from 3 to 150 on cooling from 300 K to 1.5 K. Both ρ ∥ c and ρ ⊥ c exhibit a sharp peak at 6 K before the onset of long-range magnetic order at T N =4.3 K, where χ( T ) exhibits a sharp peak. Measurements of the Hall coefficient R H ( T ), specific heat C ( T ), magnetoresistance ρ( B ) and electron tunneling have been done for polycrystals with x =0.13 and 0.18. Electron-tunneling spec...
26 citations
TL;DR: In this paper, the HfFe6Ge6-type YMn 6Ge6−xGax solid solution (0.25⩽x2.00) has been studied by magnetization measurements.
24 citations
TL;DR: In this article, the magnetic properties of La 0.9 Sr 0.1 MnO 3 samples prepared by the floating-zone technique have been studied and the results were interpreted within the framework of a mixed ferromagnetic-antiferromagnetic ground state model.
23 citations
TL;DR: In this paper, the non-collinear antiferromagnetic structure exhibits field-induced magnetic phase transitions of a first-order type along all principal axes, accompanied by a strongly anisotropic giant magnetoresistance and by a change of the Sommerfeld coefficient of the specific heat.
Abstract: Electrical resistivity and calorimetric measurements on Dy 3 Coshow that below the Neel temperature (TN=44 K) the non-collinear antiferromagnetic structure exhibits field-induced magnetic phase transitions of a first-order type along all principal axes, accompanied by a strongly anisotropic giant magnetoresistance and by a change of the Sommerfeld coefficient of the specific heat Quantum tunnelling of the magnetization appears to be possible for T < 06 K
TL;DR: In this paper, a two sublattice model consisting of antiferromagnetic order between ferromagnetic layers is proposed with an estimation of the ferro- and antiferromeagnetic interactions, and the effect of cobalt on the superexchange interactions is also discussed.
TL;DR: In this article, the molecular structure of [Ni(edt)2]− is reported for the first time, consisting of an array of parallel alternating donors, [Fe(Cp*)2]•+, and acceptors.
Abstract: New electron-transfer salts, [M(Cp*)2][Ni(edt)2], with M = Fe and Cr, were prepared and shown to be isostructural by X-ray crystallographic studies. The molecular structure of [Ni(edt)2]− is reported here for the first time. The solid-state structure consists of an array of parallel alternating donors, [Fe(Cp*)2]•+, and acceptors, [Ni(edt)2]•−, ··DADADA·· stacks along [101]. At high temperatures (T > 50−100 K), the magnetic susceptibility obeys the Curie−Weiss expression, with the θ values of −5 and −6.7 K for the Ni and Cr compounds respectively, revealing dominant AFM interactions. At low temperatures metamagnetic behavior was observed in case of [Fe(Cp*)2][Ni(edt)2], with TN = 4.2 K and HC = 14 kG at 2 K, resulting from high magnetic anisotropy, due to the coexistence of strong FM DA intrachain interactions and strong AFM (DA and AA) interchain interactions. Single-crystal magnetization measurements with [Fe(Cp*)2][Ni(edt)2] showed that the transition from the AFM state to the FM high-field state was induced by the application of a magnetic field parallel to the stacking axis. In these compounds the AFM interchain (DA and AA) interactions play a dominant role, due to the large spin density on the periphery of the acceptor and the close AA and DA interchain contacts. Above 4.2 K the 57Fe Mossbauer spectra of [Fe(Cp*][Ni(edt)2] exhibit the classical low spin FeIII ferrocenium singlet. Below this temperature a poorly resolved hyperfine pattern is observed (estimated hyperfine field ca. 350 kG at 3.5 K). The analysis of the spectra obtained in applied fields of 20 kG and 50 kG is consistent with a strongly anisotropic g tensor. A pronounced temperature dependence of the spectra in a field of 50 kG suggests the presence of spin-lattice relaxation effects.
TL;DR: In this paper, the magnetization of single crystals of Y1−xCaxTiO3 ( x=0, 0.01, 0.02, 0., 0.05, 0, 0.10 ) grown by a floating-zone method was measured.
Abstract: YTiO3 has been known as a Mott-insulating ferromagnet with the Curie temperature Tc=30 K. We have measured the magnetization of single crystals of Y1−xCaxTiO3 ( x=0, 0.01, 0.02, 0.05, 0.10 ) grown by a floating-zone method. In YTiO3, a metamagnetic-like transition was observed for B||a and B||c (easy axis) at 1.5 and 7.5 mT, respectively, only after zero-field cooling. For B||b (hard axis), however, no metamagnetic behavior appears. From the magnetization measurements of alloys, it is found that the anisotropy in magnetization for B||a and B||c vanishes with increasing x up to 0.1.
TL;DR: In this paper, the phase diagrams of UPd 2 Al 3, URu 2 Si 2 and UPt 3 were determined and the metamagnetic transitions for these compounds were observed up to the characteristic temperatures showing the maxima of the magnetic susceptibilities.
Abstract: The high-field magnetization masurements in UPd 2 Al 3 , URu 2 Si 2 and UPt 3 were carried out up to 55 T at various temperatures. We determined their phase diagrams. The metamagnetic transitions for these compounds were observed up to the characteristic temperatures showing the maxima of the magnetic susceptibilities.
TL;DR: In this article, the specific heat and resistivity of high purity needle crystals and the magnetization of a 300-mg piece of a Czochralski-process single crystal of UPt3 aligned so that B⊥c were measured at 0, 18, 19, 20, 22, and 24 T applied fields between 0.5 and 10 K, where B metamag.
TL;DR: In this article, a universal linear relation between the critical field of the metamagnetic transition, BC, and the inverse of susceptibility-maximum, χ(T max ) −1, was demonstrated.
TL;DR: In this paper, the magnetic properties of the polymeric compound Fe(thiazole) 2 Cl 2 (1 ) have been measured as a function of temperature and magnetic field.
TL;DR: In this paper, the magnetic order in the metamagnetic phases of ErNi2B2C has been determined with the magnetic field applied parallel to the [0 1 0] and [1 1 0 ] crystallographic axes.
TL;DR: In this paper, the magnetic properties of itinerant electron magnets La 2 Ni 7 and related compounds with a hexagonal crystal structure were measured and a phase diagram of the H-T phase diagram was determined.
Abstract: Magnetizations of itinerant electron magnets La 2 Ni 7 and related compounds with a hexagonal crystal structure were measured. Successive metamagnetic transitions were observed in La 2 Ni 7 , and H-T phase diagram of La 2 Ni 7 was determined. The zero-field state may be antiferromagnetic for T < T t1 = 54 K, and is a state of some kind (probably antiferromagnetic) with a very small ferromagnetic moment in T t1 < T < T t2 = 66K. Substitutions of Co or Cu for Ni show that the band structure of La 2 Ni 7 tends to produce both ferromagnetic and antiferromagnetic states, favoring the application of the theory of Moriya and Usami. Their theory is applicable assuming a tendency to form two types of antiferromagnetic states and a tendency to form a ferromagnetic state.
TL;DR: In this article, the effect of ternary magnetic additions (Fe and Co) on the antiferromagnetic behavior of MnAu2 ribbons has been investigated and it has been shown that with 5 at. % Co or Fe additions, no metamagnetic transition is observed in the temperature range between 10 and 300 K.
Abstract: Melt-spun MnAu2 ribbons modified by ternary magnetic additions (Fe and Co) show a large giant magnetoresistance (GMR) effect up to a magnetoresistance ratio MR={[R(H=7T)−R(0)/R(0)]} of the order of −10% at room temperature. Pure MnAu2 samples show a transition from positive magnetoresistance at low temperatures (e.g., MR=+23% at 10 K and μ0H=5 T) to a GMR behavior with values of about −8% at 295 K and 5 T. At 135 K the resistivity is nearly independent of the applied magnetic field. The strong increase of |MR| at room temperature is only found with applied fields larger than a threshold field, where a metamagnetic transition occurs. Alloying the compound with Co or Fe this threshold field can be reduced or suppressed. This effect is due to softening of the antiferromagnetic behavior of the (Mn; Co or Fe)Au2 samples. For an alloy with 5 at. % Fe as substitutes for Mn, no metamagnetic transition is observed in the temperature range between 10 and 300 K. For both 5 at. % Co or Fe additions a GMR behavior is ...
TL;DR: In this paper, the magnetic properties (magnetization, DC and AC susceptibility) of a new series of ternary rare-earth ruthenium germanides R2RuGe2, which crystallize in the monoclinic structure type Sc2CoSi2 (space group C2/m, No. 12), were investigated.
Abstract: We have investigated the magnetic properties (magnetization, DC and AC susceptibility) of a new series of ternary rare-earth ruthenium germanides R2RuGe2, which crystallize in the monoclinic structure type Sc2CoSi2 (space group C2/m, No. 12). The two compounds containing yttrium or lanthanum are Pauli-type paramagnets. All the remaining compounds undergo ferromagnetic transitions, except Gd2RuGe2 and Tb2RuGe2, which seem to possess an antiferromagnetic ground state. The former finally exhibits a metamagnetic transition above 2 T and the latter, however, proves to be a highly anisotropic narrow domain wall ferromagnet, the critical field being close to 3 T. In the paramagnetic region the effective moments deduced are comparable with the ideal tripositive R3+ ion moments and the θp values are generally positive. The temperature dependence of the electrical resistivity is metallic like and reveals pronounced changes of slope near the ordering temperatures. The maxima of the dρ/dT versus T plots are in agreement with the magnetic data (Tord). The resistivity of Ce2RuGe2 was found to be determined by an interplay of Kondo scattering and crystal-field effects. The temperature dependence of the spin disorder resistivity in the paramagnetic regime for the remaining samples could be attributed to the influence of the crystalline field split 4f levels. Not knowing the exact level schemes, we use a single spacing (δ) crystal-field model for an order of magnitude estimate.
TL;DR: The ferromagnetic YCo3 compound exhibits two successive field-induced itinerant metamagnetic transitions from the low magnetic moment state to higher ones at 60 and 82 T as mentioned in this paper.
Abstract: The ferromagnetic YCo3 compound exhibits two successive field-induced itinerant metamagnetic transitions from the low magnetic moment state to higher ones at 60 and 82 T. These transitions can also be induced by the substitution of Fe for Co in YCo3. The observed anomalous magnetic behavior can satisfactorily be explained in terms of the occurrence of two successive metamagnetic transitions on three different non-equivalent Co sites with different local anisotropies in sign and value.
TL;DR: In this paper, the synthesis and magnetic properties of a series of layered cobalt compounds have been reported, where the interlayer separation has been tuned from 9 to 28 A, and it is shown that the Brucite-type layered compounds of cobalt having octahedral sites only are metamagnets, while those adopting the triple-deck structure, Co 5 (OH) 8 (X) 2.xsolvent, containing both octagonal and tetrahedral sites are two-sublattice ferrimagnets.
Abstract: The synthesis and magnetic properties of a series of layered compounds, where the interlayer separation has been tuned from 9 to 28 A, are reported. It is shown that the Brucite-type layered compounds of cobalt having octahedral sites only. Co 2 (OH) 3 X. are metamagnets, while those adopting the triple-deck structure, Co 5 (OH) 8 (X) 2 .xsolvent, containing both octahedral and tetrahedral sites are two-sublattice ferrimagnets. The long range ordering (LRO), T C up to 60 K or T N of 38 K, in both structural types is brought about by dipolar interaction between layers and super-exchange interactions between nearest neighbors within a layer. The exceptional hardness of these two structural types, coercive field of 20,000 Oe for the ferrimagnets and greater than 50,000 Oe for the metamagnet, is due to the synergy of single-ion and crystalline shape anisotropies and, most importantly, the alignment of the moments perpendicular to the layer.
TL;DR: Tb 3 Rh single crystals were obtained by the Czochralski method from a levitated melt as mentioned in this paper, and the electronic structure, electrical resistivity, magnetization in strong magnetic fields up to 140kOe, AC and DC magnetic susceptibility along the principal crystallographic directions and temperature dependence of lattice parameter exhibit an ordering of the terbium moments to the spin-canted magnetic structure at 96k and a reorientation of them at about 20k.
Abstract: Tb 3 Rh single crystals were obtained by the Czochralski method from a levitated melt. The electronic structure, electrical resistivity, magnetization in strong magnetic fields up to 140 kOe, AC and DC magnetic susceptibility along the principal crystallographic directions and temperature dependence of lattice parameter exhibit an ordering of the terbium moments to the spin-canted magnetic structure at 96 K and a reorientation of them at about 20 K.
TL;DR: In this paper, the magnetic diagram of the orthorhombic compound NdCu2 was investigated for external magnetic fields up to 15 T parallel to the crystallographic c-direction.
Abstract: The magnetic (H
,
T)-phase diagram of the orthorhombic compound NdCu2 was investigated for external magnetic fields up to 15 T parallel to the crystallographic c-direction. Magnetization and magnetostriction measurements reveal an anomalous change of the magnetic properties as well as giant magnetostriction (GMS) and large hysteretic effects. This behaviour is similar to that observed in some other RCu2 compounds where it has been interpreted as a conversion of the magnetic Ising axis. In contrast to these other RCu2 compounds, however, the easy axis of magnetization in NdCu2 is the b-axis. The macroscopic measurements are compared with neutron diffraction experiments which reveal GMS along the b-axis and a new magnetic phase with propagation vector in the converted crystal.
TL;DR: In this article, the evolution of crystal structure parameters and the magnetic behavior in the UCoAl1−xSnx and uCoAl 1−xInx solid solutions was studied.
TL;DR: The magnetic and electrical properties of rare-earth silicides R5Si3 have not been systematically investigated as discussed by the authors, despite their simple chemical formula and hexagonal structure, they have not yet been systematically studied.
Abstract: Despite their simple chemical formula and hexagonal structure, the magnetic and electrical properties of the family of rare-earth silicides R5Si3 have not been systematically investigated. To begin our systematic study of this system, we have synthesized Ho5Si3 and completed magnetic and resistivity measurements on this sample. AC susceptibility measurements show Ho5Si3 to have μeff=10.5μB/Ho atom and θ=16.5 K. Magnetic measurements indicate that Ho5Si3 undergoes two transitions at low temperatures, the first at 24 K is an antiferromagnetic transition, while the second, at about 8 K, is ferromagnetic. Low temperature measurements as a function of field reveal a metamagnetic transition at Hc=2.2 T. The behavior of this sample is consistent with the complicated low temperature ordering found in other members of this series.
TL;DR: In this article, the authors present results of a direct-current magnetization study showing that the low-temperature antiferromagnetic state in various CeFe 2 -based pseudobinary alloys can be transformed into a ferromagnetic states through a magnetic field-induced phase transition.
Abstract: We present results of a direct-current magnetization study showing that the low-temperature antiferromagnetic state in various CeFe 2 -based pseudobinary alloys can be transformed into a ferromagnetic state through a magnetic field-induced phase transition. We highlight the presence of hysteresis and phase coexistence across this metamagnetic transition and argue that the observed phase transition is first order in nature.
TL;DR: In this article, high-field magnetization measurements in a heavy fermion antiferromagnet CeRh2Si2 were performed under high pressures at various temperatures to study the nature of the metamagnetism.
Abstract: High-field magnetization measurements in a heavy fermion antiferromagnet CeRh2Si2 were performed under high pressures at various temperatures to study the nature of the metamagnetism Metamagnetic transitions were observed not only in the antiferromagnetic state but also in the paramagnetic state at various pressures The metamagnetism in CeRh2Si2 does not originate from the rearrangement of antiferromagnetic moments but from the recovery of the local moment from the Kondo singlet state by applying high magnetic fields