Showing papers on "Metamagnetism published in 1996"
TL;DR: A field-induced insulator-metal (I-M) transition in Pr 0.7 Ca 0.3 MnO 3 has been studied with neutron diffraction experiments and it has been established that an applied field enforces a ferromagnetic spin alignment and drives Pr 1.0 T to a metallic state by actuating the double exchange mechanism and destroying the charge ordering.
Abstract: A field-induced insulator-metal (I-M) transition in Pr 0.7 Ca 0.3 MnO 3 has been studied with neutron diffraction experiments. Over the whole temperature range, the resistivity of Pr 0.7 Ca 0.3 MnO 3 shows insulating behavior at zero field, but exhibits an I-M transition at around 4.0 T at 5 K. It has been established that an applied field enforces a ferromagnetic spin alignment and drives Pr 0.7 Ca 0.3 MnO 3 to a metallic state by actuating the double exchange mechanism and destroying the charge ordering. This I-M transition at 5 K is accompanied with a large hysteresis. By contrast, in the field dependence at 50 K, antiferromagnetic and charge-order components are gradually recovered below 2.0 T in a field-decreasing process. Furthermore, a reentrant I-M-I transition has been observed in the temperature dependence at 2.5 T.
93 citations
TL;DR: In this article, the authors performed an extensive dHvA effect study of CeRu 2 Si 2 to gain more insight into the nature of the metamagnetic transition and confirmed the transition of the Fermi surfaces of the up and down spin electrons from those of the itinerant f electron below H m to those of localized f electron above H m.
Abstract: We have performed an extensive dHvA effect study of CeRu 2 Si 2 to gain more insight into the nature of the metamagnetic transition. The angular dependence of the dHvA frequencies confirms the transition of the Fermi surfaces from those of the itinerant f electron below the metamagnetic transition field ( H m ) to those of the localized f electron above H m . The field dependence of the frequencies and effective masses are measured for all the frequencies observed with fields parallel to [001]. A waveform analysis suggests that the Fermi surfaces of the up and down spin electrons are similar in size, whereas the effective masses are significantly different. The amplitudes of the dHvA oscillations and their field dependence are anomalous above H m , implying that the dHvA oscillations above H m may possibly come from a state which is not well developed near H m .
86 citations
TL;DR: EuPdIn and EuAuIn were prepared by reaction of the elemental components in tantalum tubes and crystallized with the TiNiSi structure in space group Pnma and with Z= 4 formula units per unit cell.
Abstract: EuPdIn and EuAuIn were prepared by reaction of the elemental components in tantalum tubes. They crystallize with the TiNiSi structure in space group Pnma and with Z= 4 formula units per unit cell. Both structures were refined from single-crystal X-ray data: a= 748.30(13) pm, b= 447.20(8) pm, c= 853.50(14) pm, V= 0.28562(5) nm3, wR2 = 0.0408, 449 F2 values, 20 variables for EuPdIn; and a= 755.2(2) pm, b= 472.2(1) pm, c= 842.3(2) pm, V= 0.3004(2) nm3, wR2 = 0.0470, 524 F2 values, 20 variables for EuAuIn. Magnetic susceptibility measurements show Curie–Weiss behaviour above 40 K for both compounds with experimental magnetic moments of 7.6(1)µB/Eu (EuPdIn) and 7.5(1)µB/Eu (EuAuIn), which are close to that of the free Eu2+ ion, namely µeff= 7.94 µB/Eu. At an external field strength of 0.01 T, EuPdIn and EuAuIn order antiferromagnetically at 13.0(5) and 21.0(5) K, respectively. Magnetization measurements at 5 K indicate metamagnetism with a magnetic moment of 5.9(1)µB/Eu at 5.5 T for both compounds. The critical fields amount to 3.1(1) T for EuPdIn and 0.25(2) T for EuAuIn. Both compounds are good metallic conductors with specific resistivities of 23 (EuPdIn) and 96 µΩ cm (EuAuIn) at room temperature.
47 citations
TL;DR: There is a marked relationship between the resistivity and the magnetic state of the material as discussed by the authors, and magnetic correlations from either paramagnetic or antiferromagnetic to ferromagnetic.
Abstract: In zero field, shows thermally activated behaviour for all values of x. For charge ordering occurs at 250 K, with long-range antiferromagnetic ordering at lower temperatures. For a range of compositions a first-order magnetic-field-induced insulator - metal transition produces changes in resistivity of up to 12 orders of magnitude at low temperatures. These conducting states are metastable, resulting in a large hysteresis in resistivity with changes in both magnetic field and temperature. There is a marked relationship between the resistivity and the magnetic state of the material. Below the charge-ordering temperature, metamagnetic transitions occur which transform the magnetic correlations from either paramagnetic or antiferromagnetic to ferromagnetic. The range of compositions for which these metamagnetic transitions occur, the fields required to induce the ferromagnetic state, and the irreversible changes in the nature of the magnetic ordering all correlate with the field-induced changes in resistivity.
44 citations
TL;DR: In this paper, the temperature dependence of the electrical resistivity, the magnetic susceptibility and the high-field magnetization of CeNi 2 Ge 2 was studied and it was shown that it exhibits metamagnetic behavior at H M ∼42 T as in CeRu 2 Si 2.
Abstract: We have studied the temperature dependence of the electrical resistivity, the magnetic susceptibility and the high-field magnetization of CeNi 2 Ge 2 . Quadratic temperature dependence of the resistivity is observed below 0.7 K. The susceptibility exhibits a broad maximum at 28 K. Magnetization shows metamagnetic behavior at H M ∼42 T as in CeRu 2 Si 2 . These results indicate that CeNi 2 Ge 2 is a new heavy-fermion compound showing the metamagnetic behavior in the nonmagnetic ground state.
43 citations
TL;DR: The field dependence of the Hall resistivity has been measured below and above a metamagnetic-like transition (MT) at 50 mK-2 K in a high quality single crystal CeRu2Si2 as discussed by the authors.
Abstract: Field dependence of the Hall resistivity has been measured below and above a metamagnetic-like transition (MT) at 50 mK-2 K in a high quality single crystal CeRu
2Si2. The MT in the Fermi-liquid region is regarded as a continuous modification of resonance quasi-particle band near the Fermi level and no drastic change of carrier density is observed. In contrast, the MT in the incoherent region exhibits no clear change of effective mass or inelastic scattering time. The strong modification of the MT by the coherent effect is discussed.
34 citations
TL;DR: In this article, the authors measured the magnetic susceptibility and magnetization of PrCu 2, which are highly anisotropic due to the orthorhombic crystalline electric field (CEF).
Abstract: We have measured the magnetic susceptibility and the magnetization of PrCu 2 . These magnetic properties are highly anisotropic, which are mainly due to the orthorhombic crystalline electric field (CEF). The energy scheme of the 4 f levels in PrCu 2 has been estimated by fitting the CEF theory to the susceptibility data. A new metamagnetism has been observed in the wide temperature range of \(1.3\;{\rm K}\) to \(50\;{\rm K}\). The transition field increases almost linearly from \(10\;{\rm T}\) to \(32 \;{\rm T}\) with the increase of temperature from \(1.3\;{\rm K}\) to \(50\;{\rm K}\).
33 citations
TL;DR: In this article, the stability of different magnetic structures is discussed and the results are compared with those of the LaMn 2− x Cu x Ge 2 and NdMn2− x Fe x Ge2 systems.
25 citations
TL;DR: In this article, ising metamagnets in a field with weak ferromagnetic intralayer interactions and highly coordinated antiferromagnetic interlayer couplings are studied using mean field theory and Monte Carlo simulations.
Abstract: Ising metamagnets in a field with weak ferromagnetic intralayer interactions and highly coordinated antiferromagnetic interlayer couplings are studied using mean field theory and Monte Carlo simulations. In the antiferromagnetic phase anomalies in the magnetization and the specific heat are observed, reflecting the competing ordering tendencies of the external field and the interlayer couplings. Results are compared to recent experimental findings on FeBr2.
24 citations
TL;DR: In this article, the magnetic field effects on the intermediate valence of the Eu system were studied and the excitation energy to convert an Eu 3+ ion into Eu 2+ was estimated based on the interconfigurational fluctuation model.
Abstract: In order to study the magnetic field effects on the intermediate valence of the Eu system, magnetization was measured for EuPd 2 Si 2 and Eu(Pd 0.95 Pt 0.05 ) 2 Si 2 up to 100 T. A first-order metamagnetic transition was observed for both samples under high magnetic fields. The transition field is 93T for EuPd 2 Si 2 at 6 K. The saturation magnetization close to 7µ B indicates that this metamagnetism is a field-induced valence transition from an intermediate valence state to a divalent state of the Eu ion. Based on the interconfigurational fluctuation (ICF) model, the excitation energy to convert an Eu 3+ ion into Eu 2+ was estimated. Temperature dependence of the metamagnetic transition field of EuPd 2 Si 2 was also studied.
24 citations
TL;DR: In this article, a metamagnetic transition from low to high moment state was observed at 21 T in Ce(Co 0.9 Ni 0.1 ) 5, and the Co moment was found to be in the high moment states for CeCo 5 and in the low moment state for x ≥ 0.3.
TL;DR: The field-induced magnetic transition in GdSi has been investigated in this article, where the critical field of the metamagnetic transition decreases linearly with the square of temperature T 2 for the GdM (M=Si, Al and Ge) equiatomic compounds.
Abstract: The field-induced magnetic transition in GdSi has been investigated. The Neel temperature and the paramagnetic Curie temperature are 55 K and -8 K, respectively. The metamagnetic transition occurs at a magnetic field of 197 kOe at 4.2 K. The critical field of the metamagnetic transition decreases linearly with the square of temperature T 2 . For the GdM ( M=Si, Al and Ge) equiatomic compounds, the linear relationship between the critical field and the Neel temperature has been confirmed.
TL;DR: In this article, the frequency field relations below T N turned out to be quite different among the above materials and were analyzed by the model which was used previously to interpret the two successive metamagnetic transitions observed in the magnetization process of R 2 Cu 2 O 5.
Abstract: Antiferromagnetic resonances (AFMR) and EPR of R 2 Cu 2 O 5 (R=Y, Lu, In) powders have been observed from 1.8 K to 265 K by submillimeter wave ESR in the frequency region 90 to 383 GHz using pulsed magnetic field up to 16 T. The frequency field relations below T N turned out to be quite different among above materials. AFMR modes have been analyzed by the model which was used previously to interpret the two successive metamagnetic transitions observed in the magnetization process of R 2 Cu 2 O 5 .
TL;DR: In this paper, the effects of external pressure and the substitution of S by Se on the ferromagnetic phase transtion in CoS 2 were studied by magnetization measurements, and the experimental results are consistently interpreted on the basis of the variation of the fourth coefficient (F 4 ) from a small positive value through zero to a negative value by varying Se-concentration or applying pressure.
Abstract: The effects of external pressure and the substitution of S by Se on the ferromagnetic phase transtion in CoS 2 were studied by magnetization measurements. Both operations reduced T c , made the magnetic phase transition discontinuous and gave rise to the metamgnetic transition immediately above T c . In terms of the phenomenological Landau theory, our experimental results are consistently interpreted on the basis of the variation of the fourth coefficient ( F 4 ) from a small positive value through zero to a negative value by varying Se-concentration or applying pressure. The appearance of weak metamagnetic transition in CoS 2 at ambient pressure also supports that F 4 is nearly equal to zero under the external field. Therefore, the anomalous critical exponents in CoS 2 reflect the tricritical behavior, as in the previous argument.
TL;DR: The Jahn-Teller effect and metamagnetic transition in single crystalline PrCu 2 have been studied by thermal expansion and magnetostriction measurements in the paramagnetic state as discussed by the authors.
Abstract: The Jahn-Teller effect and metamagnetic transition in single crystalline PrCu 2 have been studied by thermal expansion and magnetostriction measurements in the paramagnetic state. The linear thermal expansion in the temperature range from 1.8 to 300 K is found to be quite anisotropic in the whole temperature range, which is due to the highly anisotropic crystalline electric field. The magnetostrictions along the three crystallographic axes in the field along the c -axis also indicate anisotropic behavior with an extremely large length change and large hysteresis. It is clarified that the metamagnetic transition with the conversion of the Ising axis in PrCu 2 is due to the large modification of the crystalline electric field by the field-induced structural phase transition.
TL;DR: In this paper, the field dependence of the magnetic anisotropy of rock samples has been studied using a new computer-controlled automatic torque magnetometer, and the hypothesis is introduced that field-induced magnetic coupling (metamagnetism) occurs at higher fields in the paramagnetic sheet silicates well above their previously reported Neel temperature.
TL;DR: In this article, the magnetic properties of R6Fe11Al3 and 6Fe12Al2 compounds with R = Pr and Nd have been investigated by measuring the magnetization of free powder particles at 4.2 K in high magnetic fields.
TL;DR: In this paper, the NdPtSb structure of DyCuSn was refined from single crystal X-ray data of an inversion twin: P63mc, a = 450.75m, c = 724.78m, V = 0.60(5) T.
TL;DR: In this paper, the magnetic properties of Ce 2 CuGe 6 and Pr 2CuGe 6, both of which exhibit a ferrimagnetic order around 15 K, were reported. But they were not shown to have a small residual magnetization, and the peak of specific heat and sharp decrease of electrical resistivity near their ordering temperature are consistent with observed magnetic orders.
Abstract: We report the magnetic properties of Ce 2 CuGe 6 and Pr 2 CuGe 6 , both of which exhibit a ferrimagnetic order around 15 K. Hysteretic curves with small residual magnetization, 7.8×10 -4 µ B / f.u. and 1.1×10 -2 µ B / f.u., are observed for Ce 2 CuGe 6 and Pr 2 CuGe 6 , respectively. The peak of specific heat and the sharp decrease of electrical resistivity near their ordering temperature are consistent with observed magnetic orders.
TL;DR: In this article, the authors investigated magnetization as a function of external magnetic field H in the U -infinite Anderson lattice model within the leading-order approximation in the 1/N -expansion.
Abstract: We investigate magnetization as a function of external magnetic field H in the U -infinite Anderson lattice model within the leading-order approximation in the 1/ N -expansion. At T =0, at H = H M where the Zeeman energy is equal to a certain characteristic energy of the system, the magnetization curve has a kink and the differential susceptibility d M / d H shows a jump. At finite temperature, d M / d H shows a peak around H M . Its maximum value increases with decreasing T and saturates to a finite value at T →0. When H H M , the bands reform such that they are free from the Luttinger sum rule, eventually leading to a small Fermi surface at H ≫ H M . These results are consistent with the metamagnetic properties observed in the heavy fermion compound CeRu 2 Si 2 .
TL;DR: In this paper, the authors measured the magnetization and specific heat below the antiferromagnetic (AF) transition temperature T N =10 K in the magnetic field along [100] and [110] axis.
Abstract: To investigate the 4f magnetic state of Eu 3 Ir 4 Sn 13 , we have measured the magnetization and specific-heat below the antiferromagnetic (AF) transition temperature T N =10 K in the magnetic field along [100] and [110] axis. The magnetic entropy approaching R ln 8 indicates 2+ valence of Eu ion at low temperatures. The existence of antiferromagnetic short-range interaction above T N is inferred from suppressed magnetic entropy at T N . The observed nuclear specific heat is mainly attributable to Eu nucleus. The electronic specific heat coefficient γ decreases continuously with increasing field, while the magnetic specific heat is enhanced around the metamagnetic transition field of B M =2.8 T for B //[100].
TL;DR: In this paper, it was shown that UCuSn does not form in the hexagonal CaIn2 structure, but is an ordered ternary compound and forms in an orthorhombic structure (space group: P21cn).
Abstract: Crystallographic analysis shows that UCuSn does not form in the hexagonal CaIn2 structure as reported previously, but is an ordered ternary compound and forms in an orthorhombic structure (space group: P21cn). Bulk and neutron‐diffraction measurements reveal that UCuSn orders antiferromagnetically below 62 K. At 4.2 K, high‐field magnetization reveals a complex magnetization process with two metamagnetic transitions. Furthermore, bulk investigations show an additional anomaly at 25 K, but a smooth temperature dependence of various magnetic peaks down to the lowest temperature gives no evidence for a second magnetic transition. Possible scenarios responsible for the drastic changes in the electronic properties around 25 K are discussed.
TL;DR: In this paper, the electronic origin of metamagnetism in strongly anisotropic antiferromagnets is examined and the infinite-dimensional Hubbard model with easy axis is investigated both analytically and numerically.
Abstract: The electronic origin of metamagnetism in strongly anisotropic antiferromagnets is examined. To this end the infinite-dimensional Hubbard model with easy axis is investigated both analytically and numerically. At weak coupling a first order transition and at strong coupling a second order phase transition is found. To determine the transition behavior at intermediate coupling Quantum Monte Carlo techniques are used to calculate the field versus temperature phase diagram. The apparent similarities to the phase diagram of FeBr2 and to mean field results for the Ising model with competing interactions are discussed.
TL;DR: In this paper, the anisotropy of the antiferromagnetic phase of the hexagonal heavy-fermion superconductor has been studied via the magnetic torque, with the field rotated in the a-b-plane, at temperatures between 4.2 and 30 K and in fields of up to 20 T.
Abstract: The basal-plane anisotropy of the antiferromagnetic phase of the hexagonal heavy-fermion superconductor has been studied via the magnetic torque. Torque measurements were performed as functions of magnetic field and angle, with the field rotated in the a - b-plane, at temperatures between 4.2 and 30 K and in fields of up to 20 T. We interpret our results within a mean-field model and derive expressions for the basal-plane anisotropy energy. Further, we studied the anisotropy and temperature dependence of the metamagnetic transition of at 18 T and we discuss its nature.
TL;DR: In this article, the de Haas-van Alphen experiments were used to clarify the drastic change of Fermi surfaces and scattering lifetimes of conduction electrons at the metamagnetic transition in f-electron systems.
Abstract: We have done de Haas—van Alphen experiments to clarify the drastic change of Fermi surfaces and scattering lifetimes of conduction electrons at the metamagnetic transition in f-electron systems. We present three examples of NdIn 3 , PrCu 2 and CeRu 2 Si 2 .
TL;DR: In this paper, the bulk electronic properties of polycrystalline UPtSi were reported in conjunction with results of neutron-powder-diffraction studies performed at low temperatures, and it was shown that the magnetic structure determined by means of neutron powder diffraction at low temperature (T = 1.5 K) is collinear, incommensurate with the crystallographic structure.
Abstract: We report on bulk electronic properties of polycrystalline UPtSi in conjunction with results of neutron-powder-diffraction studies performed at low temperatures. Specific anomalies in the temperature dependencies of magnetic susceptibility, specific heat and electrical resistivity around 51 K indicate that UPtSi orders antiferromagnetically below this temperature. The antiferromagnetic ground state is documented by pure magnetic reflections in the neutron-powder-diffraction patterns collected below 51 K and by metamagnetic transitions in the magnetization at 4.2 K. The magnetization above the metamagnetic transitions measured on a field-oriented powder sample reaches 0.94μB/f.u. in 52 T. Higher fields are needed, however, to obtain saturation. Neutron-diffraction results in the paramagnetic range confirm that UPtSi crystallizes in the orthorhombic CeCu2-type structure (space group Imma). The magnetic structure determined by means of neutron powder diffraction at low temperatures (T = 1.5 K) is collinear, incommensurate with the crystallographic structure (propagation vector k = (0.535(2), 0, 0)) : this structure consists of sine-modulated U moments directed within the a-c plane, with maximum size of 1.30(5)μB/f.u..
TL;DR: In this paper, the alloys of PrCo13−x6 (1.5≤x≤4.0) have been prepared by arc melting and subsequent annealing.
Abstract: Alloys of PrCo13−xSix (1.5≤x≤4.0) have been prepared by arc melting and subsequent annealing. X‐ray powder diffraction proved that the alloys crystallized in the cubic NaZn13‐type structure for x=1.5, and in the tetragonal NaZn13‐derivative one for x≥2.0. Their Curie temperatures are almost independent of the Si content. Their magnetization curves exhibit a binary‐step characteristic. The ac susceptibility curve indicates that there exists a magnetic transition below room temperature. The anomalous binary‐step magnetization curves and the ac susceptibility curves versus temperature suggest a metamagnetic transition.
01 Jan 1996
TL;DR: In this paper, the temperature dependence of the electrical resistivity, the magnetic susceptibility and the high-field magnetization of CeNi 2 Ge 2 was studied and it was shown that it exhibits metamagnetic behavior at H M ∼42 T as in CeRu 2 Si 2.
Abstract: We have studied the temperature dependence of the electrical resistivity, the magnetic susceptibility and the high-field magnetization of CeNi 2 Ge 2 . Quadratic temperature dependence of the resistivity is observed below 0.7 K. The susceptibility exhibits a broad maximum at 28 K. Magnetization shows metamagnetic behavior at H M ∼42 T as in CeRu 2 Si 2 . These results indicate that CeNi 2 Ge 2 is a new heavy-fermion compound showing the metamagnetic behavior in the nonmagnetic ground state.
TL;DR: In this paper, the induced moments as a function of magnetic field are obtained for compounds with various numbers of d electrons, and, on the constituent transition-metal elements A and B, by performing calculations at more than 50 points on this plane.
Abstract: Electronic structures of d electrons under magnetic fields for the transition-metal compounds with the cubic Laves phase structure are calculated in the self-consistent tight-binding approximation. The induced moments as a function of magnetic field are obtained for compounds with various numbers of d electrons, and , on the constituent transition-metal elements A and B. Ferromagnetic and paramagnetic phases are obtained on the plane of and , by performing calculations at more than 50 points on this plane. In a narrow range along the boundary between the two phases a metamagnetic phase is found. The critical fields of the metamagnetic transition are calculated in this range. The calculated results are qualitatively in good agreement with the observed values for , and .
TL;DR: In this article, the authors studied a metamagnetic transition in PrCu2 where there is a cooperative Jahn-Teller effect occurring below 8 K. This transition brings about a conversion between an easy and a hard axis in magnetization, which is reflected in a drastic change of the de Haas-van Alphen amplitude.
Abstract: We have studied a metamagnetic transition in PrCu2 where there is a cooperative Jahn—Teller effect occurring below 8 K. This transition brings about a conversion between an easy and a hard axis in magnetization, which is reflected in a drastic change of the de Haas—van Alphen amplitude. The metamagnetic field decreases for the field along the c-axis when the transition is repeated. On the other hand, it is almost constant for the a-axis.