Showing papers on "Curie–Weiss law published in 1996"
TL;DR: The paramagnetic insulator to ferromagnetic metal transition in Lanthanum manganites and the associated magnetoresistive phenomena is treated by considering the localization due to random hopping induced by slowly fluctuating spin configurations and electron-electron interactions.
Abstract: The paramagnetic insulator to ferromagnetic metal transition in lanthanum manganites and the associated magnetoresistive phenomena is treated by considering the localization due to random hopping induced by slowly fluctuating spin configurations and electron-electron interactions. The transition temperature and its variation with composition is derived. The primary effect of the magnetic field on transport is to alter the localization length, an effect which is enhanced as the magnetic susceptibility increases. Expressions for the conductivity, its variation with magnetic field, and its connection with magnetic susceptibility in the paramagnetic phase are given, and can be tested with further experiments. \textcopyright{} 1996 The American Physical Society.
181 citations
TL;DR: The magnetic properties of the nine title compounds were studied by magnetic susceptibility measurements with a SQUID magnetometer between 2 and 300 K as mentioned in this paper, with the exception of the cerium and samarium compounds showing Curie-Weiss behavior.
162 citations
TL;DR: In this article, the Curie temperature of single-phase material is shown to be sensitive to the state of nonconvergent cation order, with a difference in Te of more than 70°C being observed between a sample quenched from 1400 °C and the same sample after heating to 650°C.
Abstract: Curie temperatures (Td of the (Fe304)x(MgA1204)1-xsolid solution have been determined from measurements of magnetic susceptibility (x) vs. temperature. The trend in Te vs. composition extrapolates to 0 K at x = 0.27. This behavior is rationalized in terms of the trend in cation distribution vs. composition suggested by Nell and Wood (1989), with Fe occurring predominantly on tetrahedral sites for x < 0.27. High-temperature x-T curves are nonreversible because of the processes of cation ordering and exsolution, which occur in the temperature range 400-650 0c. The Curie temperature of single-phase material is shown to be sensitive to the state of nonconvergent cation order, with a difference in Te of more than 70°C being observed between a sample quenched from 1400 °C and the same sample after heating to 650°C. This interaction between magnetic and chemical ordering leads to thermal hysteresis behavior such that Te measured during heating experiments is approximately 10°Chigherthan that measured during cooling. The hysteresis is due to a reversible difference in the state of cation order during heating and cooling caused by a kinetic lag in the cation-ordering behavior. Samples with compositions in the range 0.55 < x < 0.7 undergo exsolution to a mixture of ferrimagnetic and paramagnetic phases after heating to 650°C. Room-temperature hysteresis loops of the starting material and the high-temperature experiment products are compared. All starting materials are multidomain with coercivities He < 1.26 mT and Mr/ M, < 0.051. Samples that exsolved during the experiments have coercivities up to 20 mT and Mr/M, up to 0.36. This change in hysteresis properties is caused by grain subdivision during exsolution and implies a transition in the magnetic domain state from multito single-domain.
51 citations
TL;DR: In this paper, the authors report results of quantitative magnetization studies on epitaxial thin films of La 0.60Y0.07Ca0.33MnO3−δ and La 1−x⧠xMn O3 −δ, with ⧠ standing for vacancy on the La site.
Abstract: We report results of quantitative magnetization studies on epitaxial thin films of La0.60Y0.07Ca0.33MnO3−δ and La1−x⧠xMnO3−δ, with ⧠ standing for vacancy on the La site. The magnetization in all samples shows significant field dependent broadening of the ferromagnetic transition. Classical mean‐field analysis of magnetization data in applied fields above a few Tesla leads to a magnetic cluster size of the order of a few unit cells. The density of such a magnetic cluster correlates with the doping concentration x in the compound series La1−x⧠xMnO3−δ. In thin films of La0.60Y0.07Ca0.33MnO3−δ, a magnetic field dependent, non‐Curie–Weiss susceptibility was found in the paramagnetic state, indicating local ferromagnetic cluster formation above macroscopic ferromagnetic ordering temperature.
46 citations
TL;DR: Analytical results are obtained based on a mean-field approximation and a Monte Carlo simulation of the exchange interactions between ferromagnetic grains dispersed in a paramagnetic amorphous matrix for Fe77B18Nb4Cu nanocrystalline alloy.
Abstract: We study the exchange interactions between ferromagnetic grains dispersed in a paramagnetic amorphous matrix. This interaction becomes very important for high-density packing of the grains and also when the amorphous matrix is near its Curie temperature. We obtain analytical results based on a mean-field approximation and also perform a Monte Carlo simulation. We use both procedures to estimate the ordering temperature as a function of the effective intergrain separation. The theoretical predictions are compared with experimental results for the Fe77B18Nb4Cu nanocrystalline alloy.
44 citations
TL;DR: In this paper, a linear relationship between the change of Curie temperature per unit stress and the reciprocal of the curie temperature itself was shown. But this relationship was not shown for the case of pure FeZr glasses.
Abstract: FeZrB(Cu) metallic glasses present the same Invar (like) properties as the pure FeZr ones, in particular a large dependence of the Curie temperature on pressure. Magnetic and M\"ossbauer measurements show a decrease of the Invar character as the boron concentration increases, with a linear relationship between the change of Curie temperature per unit stress and the reciprocal of the Curie temperature itself. The influence of boron is shown to greatly enhance the weak itinerant ferromagnetism of FeZr glasses leading to stronger ferromagnetic behavior. \textcopyright{} 1996 The American Physical Society.
44 citations
TL;DR: In this paper, an investigation on magnetocaloric effects, magnetic entropy, Curie temperature, and specific heat of nanocomposite binary gadolinium alloys was carried out with an applied magnetic field of 1 T and in a temperature range of 233-313 K.
Abstract: Investigation on magnetocaloric effects, magnetic entropy, Curie temperature, and specific heat of nanocomposite binary gadolinium alloys Gd–Tb, Gd–Zn, and Gd–Y has been carried out with an applied magnetic field of 1 T and in a temperature range of 233–313 K. Compared with the respective bulk alloys, the as‐prepared nanocomposite alloys were found to have higher specific heat and lower Curie temperature. The nanocomposite Gd–Y alloy exhibited distinctive enhancement of both magnetocaloric effect and magnetic entropy over that of the bulk alloy. The finding is of importance for developing new materials for magnetic refrigeration at room temperature. A discussion concerning the enhanced magnetic entropy in nanometer superparamagnetic systems is presented in detail.
41 citations
TL;DR: In this paper, the magnetic properties of materials with La 2 NiO 4+δ composition have been investigated, ranging between 0 and 0.25, and their electrical conductivity, thermoelectric power, and magnetic susceptibility behaviors are reported.
40 citations
TL;DR: In this article, the structural and intrinsic magnetic properties of the Pr member of the newly discovered class of R3(Fe,Ti)29 compounds and its nitride were investigated.
26 citations
TL;DR: In this paper, large single crystals of the bronze Na 2+ x P 4 Nb 6 O 26 were grown by chemical vapor transport technique with either NH 4 Cl or NaCl as the transporting agent.
20 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: In this paper, magnetic susceptibility measurements were carried out on the intermetallic compounds Dy0.73Tb0.27Fe2−xNix and Ho0.85Tb 0.15Fe2+yNiy [x = y = 0−] in the temperature range 14-300 K.
TL;DR: Data show that the critical longitudinal ~along the wave vector qO spin fluctuations above and below the Curie temperature are similar, an experimental proof of this similarity.
Abstract: We present zero-field muon-spin-relaxation data on the ferromagnetic fluctuations near the Curie temperature of the intermetallic GdNi5, which is a Heisenberg magnet with strong dipolar interaction. Our data show that the critical longitudinal ~along the wave vector qO spin fluctuations above and below the Curie temperature are similar. They are an experimental proof of this similarity. This result is explained using the dynamical scaling theory of Halperin and Hohenberg. Although the transition from the paramagnetic to the ordered state of a simple ferromagnet is an archetypical second-order phase transition, the dramatic effect of the dipolar interaction on the nature of the critical paramagnetic spin fluctuations has been fully understood only recently. An almost quantitative agreement has been achieved between the experimental data from magnetization, 1 neutron, 2 and local probe 3,4 techniques and mode coupling theory. 5 In contrasts below the Curie temperature TC the experimental data are scarce 6,7 and a complete theory is still lacking. 8 This report presents a detailed study on crystals of the spin dynamics for a dipolar Heisenberg ferromagnet by a local
TL;DR: In this article, the temperature-dependent magnetic properties of room-temperature grown fcc iron films on Cu(001) were investigated by means of spin-polarized appearance potential spectroscopy.
TL;DR: A series of new compounds RNi5 − xSn1 + x, where R = Y, Sm, Gd, Yb, has been synthesized by X-ray powder diffraction.
TL;DR: The magnetic susceptibilities of twelve samples in the alloy system, with x ranging from to 19.4% Mn, are measured in the temperature range, in applied fields in the range Oe, after cooling in zero field and in the measuring field as discussed by the authors.
Abstract: The magnetic susceptibilities of twelve samples in the alloy system , with x ranging from to 19.4% Mn, are measured in the temperature range , in applied fields in the range Oe, after cooling in zero field and in the measuring field. The field dependence of the magnetization M(H) is measured at T = 5 K in the range kOe. The magnetic behaviour is characteristic of a spin glass, with hysteresis of M(H) and also hysteresis between the field-cooled and zero-field-cooled states, a peak in for the zero-field-cooled state, and relaxation of M as the logarithm of time when H is changed at low temperature. Unlike a typical spin glass, however, the peak in in the zero-field-cooled state is at roughly the same temperature (between 25 and 40 K) for all concentrations, and Curie - Weiss paramagnetism is seen at higher temperatures only for Mn. The Curie constant increases by an order of magnitude between x = 11.2 and 13.5% Mn, corresponding perhaps to a change in the atomic short-range order.
TL;DR: In this paper, the magnetic properties of very thin ferromagnetic films were investigated within a modified spin-wave theory and the non-uniform magnetization distribution was calculated, and the Curie temperature demonstrates a sharp decrease with decreasing L. In this case dynamic and kinematic interactions of magnons turn out to be important.
TL;DR: In this article, the magnetic properties of solid 3He using Monte Carlo simulation exchange energy values for a large number of exchange processes in solid3He have become available, and it has become feasible to calculate magnetic properties using these as given, rather than to try to fit a limited number of energies to experimental properties of the solid.
Abstract: Since Monte Carlo simulation exchange energy values for a large number of exchange processes in solid3He have become available, it has become feasible to calculate the magnetic properties of solid3He using these as given, rather than to try to fit a limited number of energies to experimental properties of the solid. The magnetization is calculated in the paramagnetic and CNAF phase, using the mean field approximation, and the consequences for the melting curve in high magnetic field are discussed.
TL;DR: In this article, the volume effects on the Curie temperature of R2Fe17−xMx compounds have been studied by comparing the change of the curie temperature and volume before and after nitrogenation.
Abstract: Structure and magnetic properties of the R2Fe17‐based quasiternary compounds (R=Sm, Er, Gd, Y, Pr, Nd; M=Al, Ga) and their nitrides have been investigated. The saturation magnetization of R2Fe17−xMx compounds decreases with the increasing M content, while the M concentration dependence of the Curie temperature exhibits a maximum at about x=3.0 for the parent compounds. By nitrogenation the lattice parameters, the saturation magnetization, and the Curie temperature all have a corresponding increase compared with the parent alloys. The volume effects on the Curie temperature of these compounds have been studied. The d ln Tc/d ln V values were derived by comparing the change of the Curie temperature and volume before and after nitrogenation and show a linear dependence on the Curie temperatures for these systems investigated. This behavior can be quite well understood in terms of a combined model of localized and itinerant electrons suggesting more than 90% d electrons are localized, The same conclusion can ...
TL;DR: In this paper, the temperature dependence of the AC magnetic susceptibility of antiferromagnetic Cr - x% V (x = 0, 0.67, 1.0, 6.5 and 20.0 kOe) has been investigated in the vicinity of the Neel transition.
Abstract: The temperature dependence of the AC magnetic susceptibility of antiferromagnetic Cr - x% V (x = 0, 0.1, 0.67, 1.0, 1.5) has been investigated in the vicinity of the Neel transition. The behaviour of Cr - 0.1% V is similar to that reported previously for the alloys containing 0.2 and 0.4% V, in that the susceptibility above the Neel transition has a component with a temperature dependence that obeys the Curie - Weiss (CW) law. This CW paramagnetism was not however seen in the samples containing higher concentrations of V. The DC susceptibility of Cr - 0.2% V was also measured in fields of 2.0, 6.5 and 20.0 kOe, and the high field was found to suppress the CW paramagnetism.
TL;DR: In this paper, the temperature behavior of the local magnetic fields at 139 La nuclei in various ferromagnetic LaMnO 3 -based compounds has been studied and a qualitative correlation has been found: the greater the degree of spatially non-uniform magnetic ordering, the higher are the values of local field and the Curie temperature.
TL;DR: In this article, the dielectric properties of single-crystal CH 3 NH 3 AlBr 4 have been studied and the spontaneous polarization measured by means of 50 Hz hysteresis loop at 64 K is 6.6×10 -3 C/m 2.
Abstract: The dielectric properties of single-crystal CH 3 NH 3 AlBr 4 have been studied. The crystal belongs to the tetragonal system at room temperature. It shows ferroelectricity along the a -direction below the Curie temperature T c =76.6 K. The dielectric constant along the a -direction obeys a Curie Weiss law above T c with the Curie constant being 3.7×10 2 K. The spontaneous polarization measured by means of 50 Hz hysteresis loop at 64 K is 6.6×10 -3 C/m 2 . Besides the ferroelectric transition, a first order structural phase transition is found at about 250 K.
TL;DR: In this article, the Rietveld profile method was used for the x-ray powder diffraction measurements of cadmium-manganese mixed oxides to investigate their crystalline structures, and all the samples were found to be of sodium chloride structure with lattice constants a(x) slightly deviating from the Vegard law.
Abstract: Polycrystalline samples of cadmium - manganese mixed oxides were synthesized by ceramic technology in a wide range of concentrations . Their crystalline structures were investigated by the Rietveld profile method based on the x-ray powder diffraction measurements. All samples were found to be of sodium chloride structure type with lattice constants a(x) slightly deviating from the Vegard law. Thermogravimetric analysis shows that samples are unstable above 500 K owing to the absorption of oxygen by MnO. Magnetic susceptibility measurements made by the Faraday method indicated the presence of antiferromagnetic interactions between ions. In the paramagnetic region the Curie - Weiss law is obeyed with the linear dependence on the concentration of the effective paramagnetic temperature and Curie molar constant . From the analysis of the magnetic susceptibility data, values of the spin and the nearest-neighbour exchange integral were found to be and , respectively.
TL;DR: In this article, the influence of annealing time and stress on the induced magnetic anisotropy constant has been investigated in the temperature range 150-350°C, and the temperature stability of the magnetic properties of Fe 3 Co 67 Cr 3 Si 15 B 12 with stress-annealing an isotropy has been estimated.
TL;DR: In this paper, the magnetic properties of polycrystalline and single crystalline rare earth transition metal silicides Gd x La 1− x MSi(M = Fe, Co) were investigated.
TL;DR: In this paper, the magnetic ordering (Neel) temperatures for XMnCl3 (X= Na, K, Rb, and Cs) single crystals grown by the Czochralski method have been investigated in the paramagnetic and antiferromagnetic regions byemploying a superconducting quantum interference device magnetometer.
Abstract: The magnetic ordering (Neel) temperatures for XMnCl3 (X= Na, K, Rb, and Cs) single crystals grown by the Czochralski method have been investigated in the paramagnetic and antiferromagnetic regions byemploying a superconducting quantum interference device magnetometer From these results, the Neel temperatures, are (53± 02) K for NaMnCl3, (94±3) K for KMnCl3, (99±1) K for RbMnCl3, and (85±5) K for CsMnCl3
TL;DR: In this article, independent contributions of spin and orbital susceptibilities to the observed one are determined experimentally by analyzing the K -χ diagram. But the results do not account for the large transferred hyperfine coupling between the neighboring V 3+ ions rather than by covalency with O 2- ions.
Abstract: The magnetic susceptibility (χ) and the 51 V Knight shift ( K ) measurements are performed on the perovskite LaVO 3 in the paramagnetic state. By analyzing the K -χ diagram, independent contributions of spin and orbital susceptibilities to the observed one are determined experimentally. The spin susceptibility was found to be suppressed from the Curie-Weiss law for S =1 spins well above the Neel temperature. It was also found that the hyperfine coupling constant for d spin is largely reduced from the usual core-polarization contribution. The analysis based on a local-moment model shows that this reduction may be caused by a large transferred hyperfine coupling between the neighboring V 3+ ions rather than by covalency with O 2- ions. This accounts for all the NMR data rather quantitatively, though, the sign and the magnitude of the transferred hyperfine field are not compatible with any existing microscopic theories.
TL;DR: In this article, the temperature dependence of the magnetic susceptibility in Co 0.5 Al 0.11 is similar to that of Co 0, 5 Al 0, 0, 6 Pd x and demonstrates subsequently clusterglass, mictomagnetic and reentrant ferromagnetic behaviour.
TL;DR: The magnetic properties of a metastable iron-mercury alloy have been investigated in the temperature range from 5 to 200 K by Mossbauer spectroscopy and magnetization measurements as discussed by the authors.