Showing papers on "Metamagnetism published in 2003"
TL;DR: In this article, the isothermal entropy change around a first-order structural transformation and in correspondence to the second-order Curie transition in the ferromagnetic Heusler alloy Ni2.15Mn0.85Ga was studied.
Abstract: We have studied the isothermal entropy change around a first-order structural transformation and in correspondence to the second-order Curie transition in the ferromagnetic Heusler alloy Ni2.15Mn0.85Ga. The results have been compared with those obtained for the composition Ni2.19Mn0.81Ga, in which the martensitic structural transformation and the magnetic transition occur simultaneously. With a magnetic field span from 0 to 1.6 T, the magnetic entropy change reaches the value of 20 J/kg K when transitions are co-occurring, while 5 J/kg K is found when the only structural transition occurs.
150 citations
TL;DR: In this paper, a large positive magnetic entropy change ΔSM is observed in the metallic antiperovskite Mn3GaC near its first-order metamagnetic transition temperature 159 K where the stoichiometric compound transforms from an antiferromagnetic to a canted ferromagnetic state accompanied by a discontinuous volume change of −0.46% without change of symmetry.
Abstract: A large positive magnetic entropy change ΔSM is observed in the metallic antiperovskite Mn3GaC near its first-order metamagnetic transition temperature 159 K where the stoichiometric compound transforms from an antiferromagnetic to a canted ferromagnetic state accompanied by a discontinuous volume change of −0.46% without change of symmetry. The unusual field dependence of the ΔSM of Mn3GaC shows a very rapid linear increase from zero to a saturation value within a field interval smaller than 1 T. The broadening of the peak of ΔSM to low temperature with increasing field change creates an ΔSM plateau in the temperature dependence of the MCE, which is of significance for practical application of these materials in the Ericsson-cycle magnetic refrigerator.
128 citations
TL;DR: In this article, a 3D molecular metamagnet was constructed by interlinking 2D azido-bridged and spin-canted antiferro-magnetic layers with semi-rigid organic pillars.
126 citations
TL;DR: The magnetic properties and magnetic entropy changes of La(Fe1−xMnx)11.3 have been studied in this article, where the authors showed that the Curie temperatures TC decrease monotonously with increasing Mn concentration from 188 to 127 K, and the saturation magnetization μS decreases from 23.9 μB/fu to 22.2μB/Fu respectively, as x increases from 0 to 0.03.
Abstract: The magnetic properties and magnetic entropy changes of La(Fe1−xMnx)11.7Si1.3 (x = 0–0.03) have been studied. The Curie temperatures TC decrease monotonously with increasing Mn concentration from 188 to 127 K, and the saturation magnetization μS decreases from 23.9 μB/fu to 22.2 μB/fu respectively, as x increases from 0 to 0.03. The maximal magnetic entropy changes |ΔS|, under a magnetic field change of 0–5 T, are 26.0 J kg−1K −1, 25.7 J kg−1K −1, 20.8 J kg−1K −1 and 17.1 J kg−1K −1 for x = 0, 0.01, 0.02 and 0.03, respectively. The appearance of negative slopes in the Arrott plots for all samples confirms the occurrence of a first-order field-induced itinerant-electron metamagnetic (IEM) transition. Furthermore, the full-width at half-maximum (FWHM) of |ΔS| peak, δTFWHM, increases obviously with increasing Mn content, which results in the decrease of the maximum magnetic entropy change.
113 citations
TL;DR: In this article, the authors report on peculiar metamagnetic transitions which take place in antiferromagnetic, charge and orbitally ordered manganites at very low temperatures, the virgin magnetization curves of some of these compounds exhibit several, sharp steps giving rise to a staircase-like shape.
78 citations
TL;DR: Two three-dimensional malonate bridged networks have been synthesized in H(2)O-DMF solution and exhibits ferromagnetic ordering below 2.6 K (T(c), and metamagnetic behavior below 3.2 K (N).
Abstract: Two three-dimensional (3D) malonate bridged networks, [Cu(mal)(DMF)]n (1) and {[Cu(mal)(0.5pyz)]·H2O}n (2), have been synthesized in H2O−DMF solution. Compound 1 exhibits ferromagnetic ordering below 2.6 K (Tc), and 2 displays a metamagnetic behavior below 3.2 K (TN).
73 citations
TL;DR: In this paper, the authors show that the magnetic entropy changes of all hydrides can be attributed to the first-order itinerant-electron metamagnetic transition confirmed by the Arrott plots.
Abstract: LaFe11.5Si1.5Hy interstitial compounds have been prepared by hydrogen absorption and subsequent desorption. The Curie temperatures are easily tunable for a wide temperature range from ~ 195 to ~ 340 K by hydrogen content. The maximal magnetic entropy changes, under a magnetic field change of 0?5 T, are as large as 16.8? 20.5 J kg?1 K?1, exceeding that of Gd (|?S| ~ 9.8 J kg?1 K?1 at TC = 293 K) by 70?110% in the vicinity of room temperature. The large magnetic entropy change of all hydrides may be attributed to the first-order itinerant-electron metamagnetic transition confirmed by the Arrott plots. Large |?S|, convenient adjustment of TC and small thermal and magnetic hystereses, make LaFe11.5Si1.5Hy interstitial hydrides promising candidates for magnetic refrigerants in the corresponding temperature range.
69 citations
TL;DR: In this paper, the magnetocaloric effect in Dy(Co1-x6)2 compounds has been calculated and correlated with the strength of itinerant electron metamagnetism, and the domain wall pinning effect was found to be dominant at low temperatures.
67 citations
TL;DR: Magnetization measurements of URu2Si2 in pulsed magnetic fields of 44 T reveal that the hidden order phase is destroyed before appearing in the form of a reentrant phase between approximately 36 and 39 T as mentioned in this paper.
Abstract: Magnetization measurements of URu2Si2 in pulsed magnetic fields of 44 T reveal that the hidden order phase is destroyed before appearing in the form of a reentrant phase between approximately 36 and 39 T. Evidence for conventional itinerant electron metamagnetism at higher temperatures suggests that the reentrant phase is created in the vicinity of a quantum critical end point.
65 citations
TL;DR: An ion-pair complex [FBzPyNH2][Ni(mnt)2] has been obtained by I2 oxidation of the corresponding dianion complex, and exhibits antiferromagnetic ordering below 2.5 K.
Abstract: An ion-pair complex [FBzPyNH2][Ni(mnt)2] {[FBzPyNH2]+ = [1-(4′-fluorobenzyl)-4-amino]pyridinium and mnt2− = maleonitriledithiolate} has been obtained by I2 oxidation of the corresponding dianion complex. It forms a wellsegregated stacking column structure in the solid state, and exhibits antiferromagnetic ordering below 2.5 K. It is the first complex in this series of complexes containing a maleonitriledithiolate dianion that exhibits metamagnetism. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
58 citations
TL;DR: In this article, structural and magnetic properties of La1−yNdy(Fe0.88Si0.12)13 compounds have been investigated by means of X-ray diffraction and magnetization measurements.
TL;DR: In this paper, the effects of interstitial carbon atoms on the magnetic properties of the LaFe11.5Si1.5 compound have been studied and X-ray diffraction patterns reveal a monotonous increase of the lattice constant with the concentration of carbon.
Abstract: Effects of the interstitial carbon atoms on the magnetic properties, especially on the magnetic entropy change, of the LaFe11.5Si1.5 compound, have been studied. X-ray diffraction patterns reveal a monotonous increase of the lattice constant with the concentration of carbon, while the cubic NaZn13-type structure remains unchanged. The Curie temperatures TC of LaFe11.5Si1.5Cy are ∼195, 225, and 241 K for y=0, 0.2, and 0.5, respectively, increasing with the increase of carbon concentration. The maximal magnetic entropy changes |ΔS| of LaFe11.5Si1.5Cy at the respective TC under a magnetic field change of 0–5 T are ∼24.6, ∼22.8, and ∼12.7 J/kg K for y=0, 0.2, and 0.5, respectively, notably exceeding that of Gd (|ΔS| ∼9.8 J/kg K at TC=293 K). The |ΔS| of LaFe11.5Si1.5C0.2 is nearly as giant as that of the parent alloy LaFe11.5Si1.5 due to the first-order field-induced itinerant-electron metamagnetic transition that occurs in both compounds clearly observed for the LaFe11.5Si1.5C0.5 compound. With the increase ...
TL;DR: In this paper, two 3d−5d Cu(II)−W(V) cyano-bridged compounds, [Cu(tn)]3[W(CN)8]2·3H2O (1) and [Cu[pn]3[CN]2 ·3H 2O (2), have been synthesized and characterized structurally and magnetically, and X-ray analyses of the two complexes reveal that they exhibit two-dimensional layer structures.
Abstract: Two novel 3d−5d Cu(II)−W(V) cyano-bridged compounds, [Cu(tn)]3[W(CN)8]2·3H2O (1) and [Cu(pn)]3[W(CN)8]2·3H2O (2), where tn is 1,3-diaminopropane and pn is 1,2-diaminopropane, have been synthesized and characterized structurally and magnetically. The X-ray analyses of the two complexes reveal that they exhibit two-dimensional layer structures with the following crystal data: space group P21/c, a = 24.459(5) A, b = 9.6426(19) A, c = 18.037(4) A, β = 90.45(3)°, V = 4253.9(15) A3, Z = 4 for 1; and space group P21/c, a = 24.126(5) A, b = 9.8889(19) A, c = 18.077(3) A, β = 90.204(4)°, V = 4312.9(14) A3, and Z = 4 for 2. Magnetic properties of the two compounds have also been investigated. Both show typical metamagnetic behavior. The critical field at which the interlayer antiferromagnetic ground-state switches to a ferromagnetic state is ∼1.25 T for 1 and 0.35 T for 2 at 1.8 K.
TL;DR: In this article, solid solutions of Dy 1− x Ca x MnO 3 (0.00⩽ x ⩽0.60) were prepared by solid state reaction of oxides and carbonates.
TL;DR: In this paper, the influence of pressure on the itinerant electron metamagnetic (IEM) transition has been investigated for a La(FexSi1−x)13 compound.
Abstract: The influence of pressure on the itinerant electron metamagnetic (IEM) transition has been investigated for a La(FexSi1−x)13 compound. The critical temperature T0 defined as the disappearance point of the IEM transition decreases with increasing hydrostatic pressure. Since the pressure dependence of T0 is smaller than that of TC, the temperature range for appearance of the IEM transition becomes wider with increasing hydrostatic pressure. These results are consistent with the theoretical model based on the Landau expansion of free energy including the influence of spin fluctuations and the magnetovolume effect. On applying pressure, the critical field Bc for the IEM transition increases proportionally with temperature in low pressures, whereas it exhibits a quadratic temperature dependence with lowering the Curie temperature in high pressures. The change in the temperature dependence of Bc is explained by a change in the thermal growth rate of spin fluctuations.
TL;DR: In this paper, the mapping transformation technique is applied to obtain exact results for the spin-1/2 and spin-S (S = 1/2, 1) Ising-Heisenberg antiferromagnetic chain in the presence of an external magnetic field.
Abstract: The mapping transformation technique is applied to obtain exact results for the spin-1/2 and spin-S (S = 1/2, 1) Ising–Heisenberg antiferromagnetic chain in the presence of an external magnetic field. Within this scheme, a field-induced first-order metamagnetic phase transition resulting in multiplateau magnetization curves is investigated in detail. It is found that the scenario of the plateau formation depends fundamentally on the ratio between Ising and Heisenberg interaction parameters, as well as on the strength of the XXZ Heisenberg exchange anisotropy.
TL;DR: The manganese-III complex has particularly interesting magnetic properties that include weak intra-chain antiferromagnetic coupling at higher temperatures and a magnetic phase transition, at TN = 6.1 K, to an ordered antiferromeagnetic phase as mentioned in this paper.
TL;DR: In this article, the magnetic properties of the Pr0.5Ca0.97Ga0.03O3 perovskite manganite were investigated and it was shown that the low T orbitally and charge ordered state has been destabilized by the nonmagnetic impurity substituted for Mn.
Abstract: An experimental study of the magnetic properties of the Pr0.5Ca0.5Mn0.97Ga0.03O3 perovskite manganite is presented. The ac magnetic susceptibility measurements show that the low T orbitally and charge ordered state has been destabilized by the nonmagnetic impurity substituted for Mn. In this compound, at 2.5 K, well-defined, sharp steps on the field-dependent magnetization curves are observed. This unusual metamagnetic transition is found to be sensitive to thermal cycling. The latter induces a training effect for the transition, which strongly supports the proposed martensitic-like physics of some phase-separated manganites.
TL;DR: In this article, a review of the recent advances of itinerant-electron metamagnetism (IEM) is presented by taking into account the magneto-volume effects, spin fluctuation model for IEM based on the Ginzburg-Landau theory is given.
Abstract: A review is presented on the recent advances of itinerant-electron metamagnetism (IEM). By taking into account the magneto-volume effects, spin fluctuation model for IEM based on the Ginzburg–Landau theory is given. A magnetic phase diagram in this system is obtained for the pressure and temperature. It is shown that the Curie temperature depends strongly on pressure near the boundary between the first-order and second-order transitions, while the spontaneous magnetization at 0 K does not depend so much on the pressure, which is a common property in this system. Other field-induced metamagnetic transitions, e.g., between weakly and strongly magnetic states, between antiferromagnetic and ferromagnetic states and between the narrow-gap semiconductor and the metallic ferromagnet observed in FeSi, are discussed based on the basis of electronic structures obtained by band calculations.
TL;DR: In this article, a weak ferromagnetic phase is shown in pressed pellets of partially doped poly~3-methylthiophene!~ P3MT! in the whole range from 1.8 to 300 K in magnetic measurements.
Abstract: A weak ferromagnetic phase is shown in pressed pellets of partially doped poly~3-methylthiophene !~ P3MT! in the whole range from 1.8 to 300 K in magnetic measurements. Thermoremanence data have been used to estimate the suppression of this phase to be around 815 K. We also show that instead of the classical antiferromagnetism for the first-order interaction that gives weak ferromagnetism as a second-order effect, metamagnetic behavior is observed. X-band electron spin resonance ~ESR! measurements and magnetization measurements allowed us to estimate that 8.1% of the total number of spins contributes to the weak ferromagnetism at room temperature. The doping level obtained from the ESR data is in good agreement with that estimated from electron dispersive spectroscopy measurements.
TL;DR: In this article, the magnetic structures of Mn1-xFexWO4 with x = 0.22 were refined from neutron powder diffraction data and the magnetic phase diagram could be completed in the coexistence range of different magnetic structures up to x ≥ 0.29.
Abstract: The magnetic structures of Mn1-xFexWO4 with x = 0.0, 0.16, 0.21, 0.225, 0.232, 0.24, 0.27, 0.29, and 1.0 were refined from neutron powder diffraction data. The magnetic phase diagram could be completed in the coexistence range of different magnetic structures up to x = 0.29. For the magnetic state at 1.5 K a commensurate antiferromagnetic structure with a propagation vector k = (±1/4, 1/2, 1/2) was found for x ≥0.22 while the magnetic spins order with k = (1/2, 0, 0) for x ≥ 0.22. In the latter phase, additionally, weak magnetic reflections indexed to an incommensurate ordering with k = (- 0.214, 1/2, 0.457) occur in the diffraction pattern up to x = 0.29 indicating the occurence of a reentrant phase. For 0.12 ≤ x ≤ 0.29 the low temperature phases are separated from a magnetic high temperature phase showing only magnetic reflections indexed to a spin arrangement with k = (1/2, 0, 0). The magnetic phase diagram is discussed qualitatively considering random superexchange between the statistically distributed Mn2+- and Fe2+-ions in the coexistence range 0.12 ≤ x ≤ 0.29 of different magnetic structures related to those of pure MnWO4 and FeWO4.
TL;DR: In this article, a double metamagnetic transition in Sr 3 Ru 2 O 7 detected by magnetization and magnetic torque measurements was reported, exhibiting stronger anisotropy between inter-and intraplane field directions.
Abstract: We report a double metamagnetic transition in Sr 3 Ru 2 O 7 detected by magnetization and magnetic torque measurements. In addition to the reported metamagnetic transition [R. S. Perry, L. M. Galvin, S. A. Grigera, L. Capogna, A. J. Schofield, A. P. Mackenzie, M. Chiao, S. R. Julian, S. I. Ikeda, S. Nakatsuji, Y. Maeno, and C. Pfleiderer, Phys. Rev. Lett. 86, 2661 (2001)], an unexpected second transition started to appear in the higher-field region below 2 K, exhibiting stronger anisotropy between inter- and intraplane field directions. We shall discuss metamagnetism of Sr 3 Ru 2 O 7 based upon spin-fluctuation theory as well as possible origins of the second metamagnetic transition.
TL;DR: In this paper, it was shown that the observed antiferromagnetic to ferromagnetic metamagnetic transition originates from cation-ordered PrBaMn2O6 nanoregions.
Abstract: Magnetization and resisitivity steps under application of a magnetic field are evidenced in absence of charge ordering at low temperature (T=2.5 K), in the manganite Pr0.5Ba0.5MnO3. Electron microscopy observations emphasize the important role of phase separation, suggesting that the observed antiferromagnetic to ferromagnetic metamagnetic transition originates from cation-ordered PrBaMn2O6 nanoregions.
TL;DR: In this article, a simple method of enhancing the magnetocaloric effect (MCE) in ferromagnetic materials is described, where thin layers of pure Fe of 0.1- and 0.2-μm thickness were evaporated onto both sides of polished 0.6-mm, slices of the giant magnetoric material Gd5Si1.5Ge2.
Abstract: A simple method of enhancing the magnetocaloric effect (MCE)) in ferromagnetic materials is described. Thin layers of pure Fe of 0.1- and 0.2-μm thickness were evaporated onto both sides of polished 0.6-mm, slices of the giant magnetocaloric material Gd5Si1.5Ge2.5. The slices were stacked for magnetic measurement in the temperature range from 165 to 235 K to assess the MCE. Sample geometries with the iron layers oriented both parallel and perpendicular to the applied field were measured. In the metamagnetic transition temperature range, the Fe layer in the parallel geometry lowers the onset field of the metamagnetic transition by 4240 Oe for the 0.1-μm layer thickness and by 4940 Oe for the 0.2-μm layer thickness from the base value of 8700 Oe at 187 K in the absence of Fe layers. Furthermore, the 0.1-μm layer of Fe oriented perpendicular to the applied field is found to enhance the entropy change, and thus the magnetocaloric effect, by approximately 11% above its base value at 191.5 K; intriguingly, the ...
TL;DR: In this article, the influence of two treatments, high-temperature annealing and grinding, on the phenomenon of metamagnetic transition was investigated. But the results provided us with information about the origin of these jumps in magnetization.
Abstract: Substitutions in the Mn sublattice of antiferromagnetic, charge, and orbitally ordered manganites was recently found to produce intriguing metamagnetic transitions consisting of a succession of sharp magnetization steps separated by plateaus. The compounds exhibiting such features can be divided into two categories, depending on whether they are sensitive to thermal cycling effects or not. One compound in each category has been considered in the present study. This article reports on the influence of two treatments: high-temperature annealing and grinding. It is shown that both of these treatments can dramatically affect the phenomenon of magnetization steps. The results provide us with information about the origin of these jumps in magnetization.
TL;DR: In this paper, the temperature and magnetic field dependencies of the c-axis magnetization of a UCoAl single crystal under various uniaxial pressures exerted along the caxis were investigated.
Abstract: We present the temperature and magnetic-field dependencies of the c-axis magnetization of a UCoAl single crystal under various uniaxial pressures exerted along the c-axis. The main result obtained is the uniaxial-pressure-induced reduction of the critical field of the metamagnetic transition followed by the formation of ferromagnetism at higher uniaxial-pressures. These and other associated results are discussed in comparison with corresponding data obtained by applying hydrostatic pressure on the same material. A scenario considering a variation of the anisotropic 5f-ligand hybridization and its consequences induced by the two different types of applied pressure is an important base for the discussion. The pressure-induced variations of the 5f–3d hybridization within the basal plane of the ZrNiAl-type hexagonal structure seem to be the underlying aspect of the evolution of the magnetism in UCoAl.
TL;DR: In this article, the mixing effects of light and heavy rare earths in cubic Laves phase compounds Nd1-xHRxCO2 (HR = Gd, Tb) have been investigated by means of x-ray powder diffraction and magnetic measurements.
Abstract: The mixing effects of light and heavy rare earths in cubic Laves phase compounds Nd1-xHRxCO2 (HR = Gd, Tb) have been investigated by means of x-ray powder diffraction and magnetic measurements. In Nd1-xTbxCo2, the saturation moment M-S exhibits in anomaly and could be ascribed to an abrupt jump of the Co moment at a critical concentration x approximate to 0.33, whereas, in Nd1-xGdxCo2, M-S does not show such an anomaly and a relatively simple magnetic behaviour is observed at x(c) approximate to 0.43. The different behaviours of these two systems can be understood by considering the structural distortion of a cubic unit cell at low temperature. A field-induced metamagnetic transition from weak ferrimagnetism to strong ferrimagnetism is observed in both systems. This can be interpreted by the evolution of magnetization with the help of percolation theory. The compensation points are observed in both systems, which are well explained within the two-sublattice model. A double peak of the AC susceptibility observed in Nd1-xTbxCo2 near x(0) approximate to 0.19 does not necessarily mean the occurrence of a first-order phase transition. The observed second-order magnetic phase transition near x(0) can be well described by Landau theory of the phase transition.
TL;DR: In this article, the authors present resistivity, magnetization, specific heat and magnetoresistance data on single crystals of EuCo 2 Ge 2 which undergo antiferromagnetic transition below T N =23 K.
TL;DR: The phase transition of the RCo2 (R=Er, Ho and Dy) compounds is of first-order type and a metamagnetic transition is observed above the Curie temperature as discussed by the authors.
TL;DR: In this paper, a spin-dependent varistor-like electrical transport is found in Nd 2/3 Sr 1/3 MnO 3-δ compounds for δ ⩾ 0.1, for which the transport through magnetic grain or phase boundaries is responsible.
Abstract: Spin-dependent varistor-like electrical transport is found in Nd 2/3 Sr 1/3 MnO 3- δ compounds for δ ⩾0.1, for which the transport through magnetic grain or phase boundaries is responsible. Specifically, electrical-field-induced changes of the spin array orientations inside of and between the domains have to be concluded. Among those, we identify an E -field-induced metamagnetic transition.