Showing papers on "Metamagnetism published in 2002"
TL;DR: The magnetocaloric effect (MCE) originated from the itinerant-electron metamagnetic transition for La(FexSi1−x)13 compounds has been investigated as discussed by the authors.
Abstract: The magnetocaloric effect (MCE) originated from the itinerant-electron metamagnetic transition for La(FexSi1−x)13 compounds has been investigated. With increasing Fe concentration, the MCE is enhanced and both the isothermal magnetic entropy change ΔSm and the adiabatic temperature change ΔTad for the compound with x=0.90 are −28 J/kg K and 8.1 K, respectively, by changing the magnetic field from 0 to 2 T. Similar large MCE values are achieved around room temperature by controlling the Curie temperature by means of hydrogen absorption. Consequently, La(FexSi1−x)13 compounds are promising as magnetic refrigerant materials working in relatively low magnetic fields.
458 citations
TL;DR: In this article, a metamagnetic transition is observed just above the Curie temperature (TC) of compounds having a first order phase transition, i.e. ErCo2, HoCo2-, and DyCo2-based ones.
Abstract: Magnetisation and magnetoresistance isotherms were measured for a number of (R,R′)Co2, (R,Y)Co2 and R(Co,Si)2 (R,R′=rare earth) compounds. A metamagnetic transition is observed just above the Curie temperature (TC) of compounds having a first order phase transition, i.e. ErCo2-, HoCo2-, and DyCo2-based ones. Both 4f- and 3d-sublattice magnetic moments contribute to a sharp change of the magnetisation at this transition. The concurring suppression of the magnetoresistance can be considered to be due to quenching of spin fluctuations. In addition, the magnetic entropy change ΔSm is estimated from the magnetisation data by using a Maxwell equation. The resulting giant magnetocaloric effects are discussed in terms of the 4f(R)-localised spin and the 3d(Co)-spin fluctuations as well as the nature of the phase transition.
162 citations
TL;DR: In this article, the electronic structure of perovskite La1−xSrxCoO3 has been obtained as a function of Sr substitution and volume from a series of generalized-gradient-corrected, full-potential, spin-density-functional band-structure calculations.
Abstract: The electronic structure of the perovskite La1−xSrxCoO3 has been obtained as a function of Sr substitution and volume from a series of generalized-gradient-corrected, full-potential, spin-density-functional band-structure calculations. The energetics of different spin configurations are estimated using the fixed-spin-moment (FSM) method. From the total energy versus spin magnetic moment curve for LaCoO3 the ground state is found to be nonmagnetic with the Co ions in a low-spin (LS) state, a result that is consistent with the experimental observations. Somewhat higher in energy, we find an intermediate-spin (IS) state with spin moment ∼1.2μB/%f.u. From the anomalous temperature dependent susceptibility along with the observation of an IS state we predict metamagnetism in LaCoO3 originating from an LS-to-IS transition. The IS state is found to be metallic and the high-spin (HS) state of LaCoO3 is predicted to be a half-metallic ferromagnet. With increasing temperature, which is simulated by a corresponding ...
85 citations
TL;DR: Curie-Weiss law fits of the high-temperature data yield magnetic moments in close agreement with those expected for noninteracting Gd(3+) ions, suggesting that the behavior seen is due to a magnetic transition rather than superparamagnetism.
Abstract: Gadolinium nanoparticles have been produced at subambient temperature by alkalide reduction. The nanoparticles display maxima in the temperature dependence of their magnetization, cooled in the absence of an applied external field, at Tmax of 5.0 and 17.5 K for unheated samples and samples annealed at 1000 °C for 4 h, respectively. Field cooled behavior deviates at temperatures slightly above Tmax, increasing at lower temperature. Curie−Weiss law fits of the high-temperature data yield magnetic moments in close agreement with those expected for noninteracting Gd3+ ions, suggesting that the behavior seen is due to a magnetic transition rather than superparamagnetism. Magnetization is linearly dependent on field at temperatures higher than 7−8 times Tmax and shows remanence-free hysteresis at lower temperature, suggesting metamagnetism. Some annealed samples show evidence of additional ferromagnetic interactions below ∼170 K. Magnetic entropy curves generated from magnetization data are consistent with that...
69 citations
TL;DR: The critical field at which the antiferromagnetic ground state switches to a ferrimagnetic ground-state is ∼48 Oe for 1 and 185Oe for 2 at about 2 K.
Abstract: Compounds [NH3(CH2)4NH3]Cu3(hedp)2·2H2O (1) and [NH3(CH2)3NH3]Cu3(hedp)2·3.5H2O (2), where hedp represents 1-hydroxyethylidenediphosphonate, exhibit two-dimensional structures closely related to each other. The anionic layers with composition {Cu3(hedp)2}n2n- contain four- and eight-membered rings assembled from vertex-sharing {CuO4} units and {CPO3} tetrahedra. The protonated diamines and lattice water fill the interlayer spaces. Crystal data for 2: space group P1, a = 8.0315(4), b = 11.3713(6), c = 13.3117(7) A, α = 97.122(1), β = 103.187(1), γ = 108.668(1)°, V = 1095.5(1) A3, Z = 2. Magnetic properties of the two compounds have been investigated. Both show typical metamagnetic behaviors at low temperature. The critical field at which the antiferromagnetic ground-state switches to a ferrimagnetic state is ∼48 Oe for 1 and 185 Oe for 2 at about 2 K.
60 citations
TL;DR: In this paper, the authors focused on the macroscopic and microscopic experimental works realized during a decade on the clear case of itinerant metamagnetism in the heavy fermion paramagnetic compound CeRu2Si2.
Abstract: Focus is given on the macroscopic and microscopic experimental works realized during a decade on the clear case of itinerant metamagnetism in the heavy fermion paramagnetic compound CeRu2Si2. Emphasis is made on the feedback between the band structure, the exchange coupling and the lattice instability. Sweeps in magnetic field, pressure and temperature feel the pseudogap of this strongly correlated electronic system as well as its equivalent CeRu2Ge2 at a fictitious negative pressure. Some mysteries persist as the complete observation of the Fermi surface above the metamagnetic field HM and the detection of the dynamical ferromagnetic fluctuation near HM. The novelty of the bilayer ruthenate Sr3Ru2O7 is discussed by comparison. Despite differences in spin and electronic dimensionality many common trends emerge.
57 citations
TL;DR: In this article, a metamagnetic transition is observed just above the Curie temperature (T C ) of compounds having a first-order phase transition, i.e. ErCo 2, HoCo 2 and (Dy, Y)Co 2.
57 citations
TL;DR: In this paper, the synthesis, structures and magnetism of cyanide-bridged bimetallic network compounds are discussed, and the strategies for gaining high Tc magnetic material and modulating magnetic nature by a change in network structure are described.
Abstract: This account concerns the synthesis, structures and magnetism of cyanide-bridged bimetallic network compounds. The study aims at the development of molecular-based magnetic materials. Different network structures, from one-dimensional to three-dimensional, are synthesized by the reaction of [M(CN)6]n- with a cationic constituent such as [Ni-(diamine)2]2+, [Ni(triamine)]2+, [Mn(salen)]+, [Mn(en)]2+, etc., in the absence or presence of an appropriate counter ion. Magnetostructural studies for those bimetallic compounds have clarified fundamental factors contributing to magnetic ordering in bulk, magnetic nature (ferromagnetism or metamagnetism) and magnetic phase-transition temperature (Tc). The strategies for gaining high Tc magnetic material and modulating magnetic nature by a change in network structure are described.
50 citations
TL;DR: In this article, the magnetic properties and magnetic phase diagrams of Mn2−xCoxSb are explained by the itinerant magnetism of d-electrons and by peculiarities of electronic structure.
Abstract: The magnetization of Mn2−xCoxSb system with 0⩽x⩽0.35 has been measured under high magnetic fields up to 100 T and high pressure up to 12 kbar . Mn 2 Sb is a ferrimagnet and substitution of Co for Mn at 0.18⩽x⩽0.35 results in the appearance of the spontaneous first-order magnetic phase transition from ferrimagnetic (FRI) to antiferromagnetic (AF) state at T=Tt with decreasing temperature at a critical Co concentration. Below Tt a first-order field-induced AF–FRI transition is observed at a critical field Bc. The critical field Bc is found to decrease with increasing pressure applied at T=4.2 K . The AF state which appeared for the compound with the critical concentration x=0.18 can be transformed to the FRI one by the application of the high pressure of about 16 kbar by increasing the amount of FRI phase. Using the experimental data, the magnetic phase diagrams Bc–T–x and Bc–p–x are determined. The observed magnetic properties and magnetic phase diagrams of Mn2−xCoxSb are explained by the itinerant magnetism of d-electrons and by peculiarities of electronic structure. The itinerant nature of AF–FRI transition is confirmed by specific heat measurements in AF- and field-induced FRI states.
33 citations
TL;DR: In this article, the magnetization of the polycrystalline manganese cluster Mn 4 Br was measured down to 0.13 K under a magnetic field of ±15 kOe.
Abstract: The magnetization of the polycrystalline manganese cluster Mn 4 Br was measured down to 0.13 K under a magnetic field of ±15 kOe. It shows a gradual drop at around 1.5 K and the heat capacity measurement at 0 kOe reveals a sharp anomaly at 1.33 K, indicating the occurrence of a second-order antiferromagnetic (AFM) phase transition. The M – H curve well below the transition temperature T N shows a step around 2.5 kOe, which probably corresponds to the transition from the AFM phase to metamagnetic (MM) phase. The observed field agrees with that estimated from T N for the MM transition, using a simple molecular field theory. This is the first observation of a well-defined AFM and also a MM phase among the many manganese clusters with a high-spin ground state that function as molecular nanomagnets.
32 citations
TL;DR: In this paper, a spin-glass to ferromagnet transition in a modest applied magnetic field has been found in the single-valent perovskite system LaMn1−xScxO3 as in the analogous system LaN 1−xGaxO3, which supports the existence of a ferromagnetic vibronic-superexchange interaction between octahedral-site, high-spin Mn(III) with fluctuating e-orbitals.
TL;DR: The magnetic phase diagram of the Lu 2 Fe 17 intermetallics was determined at temperatures below 300 k under hydrostatic pressure up to 1.2 GPa using a SQUID magnetometer.
TL;DR: In this article, the magnetization and electrical resistivity of antiferromagnetic CePdAl were measured at 0.5 -k in steady fields up to 10 -k along the c -axis.
TL;DR: In this article, the lattice constant and magnetic properties of compounds Nd1-xTbxCo2 were investigated by x-ray power diffraction and magnetic measurements, and it was shown that these compounds exhibit a field-induced metamagnetic transition from a weak ferrimagnetism to a strong ferrimagnetic transition in the vicinity of x(c).
Abstract: The lattice constant and magnetic properties of compounds Nd1-xTbxCo2 were investigated by x-ray power diffraction and magnetic measurements. The lattice constant and Curie temperature show linear variations with the Tb concentration, while the saturation moment exhibits an anomaly at a critical concentration x(c)approximate to0.33. The compounds exhibit a field-induced metamagnetic transition from a weak ferrimagnetism to a strong ferrimagnetism in the vicinity of x(c). (C) 2002 American Institute of Physics.
TL;DR: In this article, the authors present results of a dc magnetization study which show interesting thermomagnetic history effects across the antiferromagnetic-to-ferromagnetic transition in Ce(Fe 0.96 Al 0.04 ) 2 pseudobinary alloy.
Abstract: We present results of a dc magnetization study which show interesting thermomagnetic history effects across the antiferromagnetic-to-ferromagnetic transition in Ce(Fe 0.96 Al 0.04 ) 2 pseudobinary alloy. Specifically, we observe (i) the degree of ZFC/FC irreversibility rising with increasing field; (ii) the virgin curve lying outside the envelope M-H curve. Some of the key results are supported by magneto-transport measurements. We argue that these effects are quite different from the characteristics seen in spin glasses or in hard ferromagnets. They can be understood in terms of kinetic arrest of a first-order transition.
TL;DR: A cyanide-bridged bimetallic compound, [Ni(1,1-dmen)2]2[Fe(CN)6](BPDS)0.5·4H2O (1) (1, 1dmen = 1, 1-dimethylethylenediamine, BPDS2− = biphenyl-4, 4,4,4′-disulfonate), has been prepared.
Abstract: A cyanide-bridged bimetallic compound, [Ni(1,1-dmen)2]2[Fe(CN)6](BPDS)0.5·4H2O (1) (1,1-dmen = 1,1-dimethylethylenediamine, BPDS2− = biphenyl-4,4′-disulfonate), has been prepared. It has a pseudo 2-D network structure based on a Fe4Ni4 square unit with two Fe–CN–Ni–NC–Fe and two Fe–CN···H2O–Ni–NC–Fe linkages and shows a metamagnetic ordering with TC = 3.3 K. The dehydration of 1 at 150 °C has afforded [Ni(1,1-dmen)2]2[Fe(CN)6](BPDS)0.5 (1a). It has a definite 2-D network structure based on a Fe4Ni4 square unit with four Fe–CN–Ni–NC–Fe linkages and shows essentially a ferromagnetic ordering with TC = 10.7 K under weak applied field (> 250 G). 1a is hygroscopic and adsorbed atmospheric moisture to afford [Ni(1,1-dmen)2]2[Fe(CN)6](BPDS)0.5·2H2O (1b), which has a pseudo 2-D network structure similar to that of 1 and shows a metamagnetic ordering with TC = 4.0 K. 1a and 1b can be interconverted by dehydration at 150 °C and hydration in open air at room temperature, producing a unique molecular magnetic system ...
TL;DR: In this article, the magnetization and magnetoresistance for a series of rare earth (R=Er,Ho,Dy) plumbide intermetallic compounds, R 2 Ni 2 Pb, were measured.
Abstract: We have measured the magnetization and magnetoresistance for a series of rare-earth (R=Er,Ho,Dy) plumbide intermetallic compounds, R 2 Ni 2 Pb. These materials form in an unusual orthorhombic structure with space group Cmmm. After multiple magnetic transitions, the ground state exhibits a steplike series of large-moment metamagnetic transitions in low fields (1-2 T) concomitant with switchinglike properties of the magnetoresistance where sharp changes of up to 30% are found. We relate these properties to the layered magnetic structure of the compound.
TL;DR: In this article, temperature-induced itinerant-electron metamagnetism has been observed in the concentration range 0.0⩽ x ⩽ 0.4 where the Co sublattice is in the strong ferromagnetic state at low temperatures.
Abstract: X-ray thermal expansion, magnetic and electrical resistivity measurements of the pseudo-binary Ho 1− x Y x Co 3 system with PuNi 3 -type structure have been performed in a wide temperature range. Temperature-induced itinerant-electron metamagnetism has been observed in the concentration range 0.0⩽ x ⩽0.4 where the Co sublattice is in the strong ferromagnetic state at low temperatures. The transition was found to be sharper in the diluted compounds with a lower value of the transition temperature, which is in accordance with the nature of the observed effect. The temperatures of the spin-reorientation transition have been determined from low-field magnetisation measurements and the magnetic phase diagram of this system has been constructed.
TL;DR: R CrO 4 oxides (R =Pr, Gd, Tb, Tm, and Yb) have been synthesized at 773 K using the corresponding nitrates as precursors as mentioned in this paper.
TL;DR: In this paper, the temperature and field dependences of the magnetization of a UCoAl single crystal under hydrostatic pressures up to 1.2 GPa were analyzed based on the theory of itinerant electron metamagnetism.
Abstract: UCoAl is an itinerant $5f$-electron metamagnet. Just 2% substitution of Fe for Co in UCoAl stabilizes a ferromagnetic ground state. We studied the temperature and field dependences of the magnetization of a ${\mathrm{UCo}}_{0.98}{\mathrm{Fe}}_{0.02}\mathrm{Al}$ single crystal under hydrostatic pressures up to 1.2 GPa. The reentrant metamagnetism of the UCoAl type was observed under pressures above 0.4 GPa. The experimental data have been analyzed based on the theory of itinerant electron metamagnetism, which considers anisotropic thermal fluctuations of the magnetic moment.
TL;DR: The magnetic properties of La 1− x Sm x Mn 2 Si 2 (0≤ x ≤ 1) quasi-ternary layered intermetallic compounds have been studied by magnetic measurements.
TL;DR: In this article, a quasi-low-dimensional TM-based oxy compound was synthesized by using a single crystal X-ray diffraction and magnetic susceptibility measurements, which revealed that the compounds are antiferromagnetic with the negative Weiss constants θ=−76.99 K (1) and −33.85 K (2).
TL;DR: In this article, the authors measured the high-field magnetization of USn 3 and UPb 3 grown by the self-flux method, and observed the broad metamagnetic transition in a heavy fermion paramagnetic compound USn3 at about 30 T, which is similar to the metamagnetism of UPt 3.
Abstract: UX 3 (X=Si, Ge, Sn and Pb) compounds with the cubic crystal structure are interesting in relation with the lattice constant and the electronic state of 5 f electrons.We measured the high-field magnetization of USn 3 and UPb 3 grown by the self-flux method.The broad metamagnetic transition was observed in a heavy fermion paramagnetic compound USn 3 at about 30 T, which is similar to the metamagnetism of UPt 3 . On the other hand, the sharp metamagnetic transitions were observed in an antiferromagnetic compound UPb 3 .
TL;DR: In this article, the properties of YMn6Sn6−xTix (0.8⩽x1.0) compounds with HfFe6Ge6-type structure were investigated in the temperature range of 5-400 K.
Abstract: Magnetic and transport properties of YMn6Sn6−xTix (0⩽x⩽1.0) compounds with HfFe6Ge6-type structure were investigated in the temperature range of 5–400 K. The compounds with low Ti content (x⩽0.2) display antiferromagnetic behavior (317 K⩽TN⩽327 K). The Ti-rich compounds (0.8⩽x⩽1.0) behave as ferromagnetic in their whole magnetic ordered range (293 K⩽TN⩽334 K). The intermediate compounds (0.4⩽x⩽0.6) undergo an antiferro- to ferromagnetic transition with increasing temperature. The metamagnetic transition from antiferro- to ferromagnetism can be also induced by an applied field for the antiferromagnetic compounds. The metamagnetic transition field decreases with increasing Ti concentration. The large magnetoresistance of up to 35% is observed at 5 K under 50 kOe for the compounds (0.4⩽x⩽0.6) with metamagnetic behavior. The evolution of the magnetic properties is discussed.
TL;DR: In this article, temperature-dependent magnetic susceptibility measurements on single crystals indicate that EuSnP is an antiferromagnet with a Neel temperature of 21 K, consistent with the assignment of a 2+ valence to the Eu ions, seven unpaired electrons.
TL;DR: The magnetisation and the magnetoresistance of the LuMn6Ge6−xGax compounds (x=0.2, 0.4 and 0.6) at 10 and 295 K in applied magnetic fields up to 9 T is presented in this paper.
TL;DR: In this article, the de Haas-van Alphen (dHvA) and ac-susceptibility experiments were performed on a ferromagnetic UGe2 under pressure for the field along the easy a-axis.
Abstract: We have performed the de Haas-van Alphen (dHvA) and ac-susceptibility experiments on a ferromagnet UGe2 under pressure for the field along the easy a-axis. The p-H phase diagram was determined, indicating three kinds of phase: paramagnetic and weakly and strongly polarized phases. The detected dHvA frequencies as well as the cyclotron masses are found to be very different between the weakly and strongly polarized states. A change of the Fermi surface occurs when the weakly polarized phase is changed into the strongly polarized phase with increasing magnetic field.
TL;DR: In this article, the magnetic transitions and magnetoresistance properties of the HfFe6Ge6-type Y05Ho05Mn6Sn6 compound have been investigated in the temperature range of 5-380 K.
Abstract: Magnetic transitions and magnetoresistance of the HfFe6Ge6-type Y05Ho05Mn6Sn6 compound have been investigated in the temperature range of 5–380 K It was found that the compound displays paramagnetism, ferrimagnetism, antiferromagnetism, and reentrant ferrimagnetism with decreasing temperature The temperature range of the antiferromagnetic state can be narrowed by increasing the magnetic field, and the metamagnetic transition from the antiferro- to ferrimagnetic state can be induced by a fairly small threshold field (<6 kOe) The antiferro-ferrimagnetic transition is accompanied by a large magnetoresistance effect of about −16% at 100 K The magnetic transitions with temperature and magnetic field are both of the second order
TL;DR: In this paper, the magnetoelastic behavior of single-crystalline ErNi2B2C in the temperature range 1.8K T 16 K and for external magnetic field in the tetragonal ab-plane µ0H 6T.
Abstract: Using a capacitive dilatometer we investigated the magnetoelastic behaviour of single-crystalline ErNi2B2C in the temperature range 1. 8K T 16 K and for external magnetic field in the tetragonal ab-plane µ0H 6T . For T TN = 6.4 K the longitudinal magnetostriction coefficient is negative, whereas the transverse one is positive. The thermal evolution of the lattice distortion e γ = (λ⊥ − λ� )/ √ 2 is in agreement with that of the previously reported spontaneous tetragonal-to-orthorhombic distortion determined by neutron diffraction. The behaviour is influenced by the distribution of the magnetic domains in the crystal. The H –T phase diagram, constructed from the magnetostriction curves, shows the well-known cascade of metamagnetic transitions between several phases (antiferromagnetic AF1, ferrimagnetic F1, F2) in the field range 0 <µ 0 H< 2.1 T below TN . On the basis of a Hamiltonian consisting of an exchange, a crystal-field, a Zeeman, and a magnetoelastic term, we were able to reproduce reasonably well the H –T phase diagram as well as various forced magnetostriction curves. (Some figures in this article are in colour only in the electronic version)
TL;DR: In this paper, electrical resistivity measurements in a magnetic field are carried out on UGe2 which exhibits pressure-induced superconductivity from 1.06 to 1.44 GPa, and it is observed that the application of an external field along the a-axis increases the coefficient A of the Fermi-liquid behaviour (∝ AT2) abruptly.
Abstract: Electrical resistivity measurements in a magnetic field are carried out on UGe2 which exhibits pressure-induced superconductivity. The superconductivity is observed from 1.06 to 1.44 GPa. In the temperature and field dependences of the resistivity at P > PC where the ferromagnetic ordering disappears, it is observed that the application of an external field along the a-axis increases the coefficient A of the Fermi-liquid behaviour (∝ AT2) abruptly—corresponding to the metamagnetic transition. The characteristic enhancement of HC2 is reconfirmed for H ∥ a-axis. The upper critical field of HC2 is anisotropic: HC2 (T) exhibits positive curvature for H ∥ b-axis and H ∥ c-axis.