Showing papers on "Curie–Weiss law published in 1992"
TL;DR: It is proposed that this deviation arises due to short-range correlations between polar regions, and that these correlations at high temperatures are the precursor to a freezing of the polarization fluctuations into a glassy state.
Abstract: The deviation from Cure-Weiss behavior has been investigated in lead magnesium niobate relaxor ferroelectrics. At high temperatures, the susceptibility was found to follow the Curie-Weiss relationship. A Curie constant and temperature of 1.2\ifmmode\times\else\texttimes\fi{}${10}^{5}$ and 398 K, respectively, were obtained. With decreasing temperature the deviation was found to increase. It is proposed that this deviation arises due to short-range correlations between polar regions, and that these correlations at high temperatures are the precursor to a freezing of the polarization fluctuations into a glassy state. A local (glassy) order parameter was calculated from the susceptibility by analogy to spin glasses [D. Sherrington and S. Kirkpatrick, Phys. Rev. Lett. 35, 1972 (1975)]. These results are compared to the rms polarization [G. Burns and F. Dacol, Solid State Commun. 48, 853 (1983)] and to the measured remanent polarization. The frequency and field dependence has also been investigated.
491 citations
TL;DR: In this paper, the authors studied the Curie temperature of ferroelectric films described by the transverse Ising model under the mean-field theory and obtained the film layer number, the surface interaction and the surface layer number dependence of the curie temperature.
Abstract: The Curie temperature of ferroelectric films described by the transverse Ising model was studied under the mean-field theory. The film layer number, the surface interaction and the surface layer number dependence of the Curie temperature were obtained. There is a critical surface interaction strength, which is JSC=1.25 J for single-surface-layer films, and JSC=1.078 J for multiple-surface-layer films. If the surface interaction strength exceeds the critical value, there exists an optimum film thickness which possesses the maximum Curie temperature; then the surface interaction strength is weaker than the critical value, the Curie temperature decreases monotonically with increasing film thickness, and there exist critical sizes or critical thicknesses at which the ferroelectricity will disappear if the surface interaction is weak enough.
98 citations
74 citations
TL;DR: In this article, the spontaneous magnetization of ferromagnetic clusters of various structures and sizes has been modeled with the Heisenberg model, and a self-consistent spinwave-spectrum is found by direct diagonalization of the equation of motion of S+.
65 citations
TL;DR: In this paper, LiUO3 was prepared and its magnetic susceptibility was measured in the 4.2-300 K temperature range, where the magnetic transition occurred at 16.9 K and below this temperature large field dependence was observed.
48 citations
47 citations
TL;DR: In this paper, the properties of seven equiatomic ternary RNiSn and RRhSn compounds have been studied in fields of up to 20 kOe in the temperature range 4.2-200 K.
45 citations
TL;DR: In this paper, the magnetic anisotropy in UTX compounds is found to be closely connected with the coordination of U atoms in the crystal lattice, where the easy magnetization direction is oriented perpendicular to the highest coordination plane or direction.
Abstract: The huge magnetic anisotropy in UTX compounds is found to be closely connected with the coordination of U atoms in the crystal lattice. Generally, the easy magnetization direction is oriented perpendicular to the highest coordination plane or direction. The magnetization behaviour in ordered state yields effective anisotropy fields in the range 100–400 T. The anisotropy persists in the paramagnetic state where the values of the paramagnetic Curie temperature for the easy and hard magnetization directions differ by 100–400 K. The results are discussed in the framework of a model considering the anisotropic two-ion exchange interaction mediated by the 5f-ligand hybridization.
44 citations
TL;DR: In this article, the magnetic properties of Gd 2 Fe 17− x M x compounds with M=Al or Mn were investigated, and it was shown that substitution of Al or Mn, although it reduces the Fe magnetization in different ways, has only little influence on the intersublattice coupling strength.
39 citations
TL;DR: In this paper, an approach to the definition of infinite-volume Gibbs states for the (quenched) random-field Ising model is considered in the case of a Curie-Weiss ferromagnet.
Abstract: An approach to the definition of infinite-volume Gibbs states for the (quenched) random-field Ising model is considered in the case of a Curie-Weiss ferromagnet. It turns out that these states are random quasi-free measures. They are random convex linear combinations of the free product-measures “shifted” by the corresponding effective mean fields. The conditional self-averaging property of the magnetization related to this randomness is also discussed.
39 citations
TL;DR: In this article, the magnetic properties of thin ferromagnetic films were studied using a mean-field model and the thickness dependent film Curie temperature Tc(d) was calculated for different surface magnetic moments μs as well as for different lattice types and -faces.
TL;DR: In this paper, a spin-one-half Ising model of an alternating magnetic superlattice was used to study the effects of surface modification on the Curie temperature on the film thickness.
Abstract: The authors study a spin-one-half Ising model of an alternating magnetic superlattice. They use the mean-field approximation and express their results for the Curie temperature in terms of two types of determinants. The dependence of the Curie temperature on the film thickness is obtained. The effects of surface modification on finite superlattices are studied numerically for two types of modification to the surface exchange constants.
TL;DR: In this article, the magnetization and magnetic susceptibility have been measured on the PrRu2Si2 single crystal compound, which is a ferromagnet with a Curie temperature of 14 K and saturation moment of 2.7μB/f.
TL;DR: The magnetic properties of Ni-Zn ferrites have been upgraded by preparing hot-pressed Ni0.4Zn0.6−2xLixFe2+xO4 ferrites wherein 2xZn2+ ions have been substituted byxLi1+ andxFe3+ ions.
Abstract: The magnetic properties of Ni-Zn ferrites have been upgraded by preparing hot-pressed Ni0.4Zn0.6−2xLixFe2+xO4 ferrites wherein 2xZn2+ ions have been substituted byxLi1+ andxFe3+ ions. This results in an increase of saturation magnetization, Curie temperature and dielectric constant, whereas resistivity and initial permeability are reduced. The values of saturation magnetization, Curie temperature and dielectric constant are improved due to hot pressing in which grain growth and densification are controlled simultaneously. The variations of saturation magnetization and Curie temperature can be explained by the preferential site occupancy of Li1+ and Ni2+ ions at the tetrahedral site, sublattice magnetization with canted spin structure, and magnetic exchange interactions. The inferences drawn from the bulk magnetic properties of these ferrites conform with the conclusions drawn from variations of internal magnetic field, obtained from Mossbauer studies of these samples. The decrease in d.c. resistivity due to substitution of Li1+ ions is attributed to increased hopping due to formation of Fe2+ and Ni3+ ions.
TL;DR: In this article, the crystal structure and the magnetic properties, especially the magnetocrystalline anisotropy of (Sm1−xYx)2Fe17Ny compounds (x=0, 0.2, 0., 4, 0, 8, and 1.0, 2
Abstract: A study of the crystal structure and the magnetic properties, especially the magnetocrystalline anisotropy of (Sm1−xYx)2Fe17Ny compounds (x=0, 0.2, 0.4, 0.6, 0.8, and 1.0, 2
TL;DR: In this article, a direct determination of the magnetocrystalline anisotropy field (HA) of various polycrystalline materials of the type Nd2Fe14B, Sm2Fe17Cx, Sm 2Fe17Nx and R(Fe, T)12 by using the singular-point-detection technique in the temperature range from 4.2 K up to the Curie temperature is demonstrated.
Abstract: A direct determination of the magnetocrystalline anisotropy field (HA) of various polycrystalline materials of the type Nd2Fe14B, Sm2Fe17Cx, Sm2Fe17Nx and R(Fe, T)12 by using the singular-point-detection technique in the temperature range from 4.2 K up to the Curie temperature is demonstrated. Some recent results on determining the critical first order magnetization process (FOMP) field (Hcr) using the same technique are also presented.
TL;DR: In this article, the properties of the Cr2S3−xSex and Cr2Te3−ySey systems were investigated, and an interesting result was found in a relation between the paramagnetic Curie temperature θp and the lattice parameter ratio c / a.
TL;DR: In this article, the curie temperatures of rare earth metals have been calculated ab initio using the local pin density approximation, which is necessary allow for disordered local 5d moments above T c and to calculate the local susceptibility.
TL;DR: In this paper, the magnetic properties of a series of Co-containing polymers of general formula X = NO 3, ClO 4 and (SO 4 ) t 2, and [Co(C13H17N3)Cl2·3H2O]n.
TL;DR: A ferrimagnetic character with a uniaxial anisotropy has been observed through static and dynamic magnetic measurements in amorphous compounds of (1−2 x ) BiFeO 3 − x CuFe 2 O 4 (x = 0-0.3) prepared by the technique of rf sputtering.
TL;DR: In this article, the authors performed magnetization studies on the alloy system (Fe 0.65 Ni 0.35 ) 1− x Mn x (0 ≤ x ≤ 0.30) using a Faraday balance and a SQUID magnetometer.
TL;DR: In this paper, the temperature dependence of magnetic susceptibility and high field magnetization for a single crystal of anti-ferromagnetic PrZn2 was studied for the first time.
Abstract: Temperature dependence of magnetic susceptibility and high field magnetization are studied for a single crystal of anti-ferromagnetic PrZn2. The paramagnetic Curie temperatures are anisotropic: θa=19.6 K, θb=2.9 K and θc=-72.5 K. Different field-induced magnetic transitions are observed along each crystal axis direction.
TL;DR: In this paper, the structure and magnetic properties of Sm10Fe79Si11Nx have been studied and the Curie temperature was found to reach 641 K. There are also substantial increases in magnetization and magnetocrystalline anisotropy, showing suitable intrinsic magnetic properties for permanent magnet applications.
TL;DR: In this paper, the Curie temperature and the thermal expansion of the lattice parameters were studied for the ferromagnetic compound LaMn2Ge2 and the pressure derivative of TC was obtained to be dTC/dP = −0.2 K/kbar.
TL;DR: Magnetic susceptibility, high field magnetization and specific heat measurements on CeCu are presented in this paper, where an antiferromagnetic transition is observed at T N = 3.13 K, with some evidences of low dimensionality of the order parameter.
TL;DR: In this article, the magnetic phase transitions occuring in layered structures, such as sandwiches and superlattices, are studied within Ising model and analytical expressions for the Curie temperature as a function of the Hamiltonian parameters and the thickness of the slabs are given.
TL;DR: In this article, the electrical conductivity and magnetization of CuxMg1{xFe2O4 are measured and the activation energy in the paramagnetic region is found to be greater than that in the ferrimagnetic region.
Abstract: The electrical conductivity and magnetization of CuxMg1{xFe2O4 are measured. The electrical conductivity obeys the exponential behaviour characteristic of semiconducting materials. The activation energy in the paramagnetic region is found to be greater than that in the ferrimagnetic region. This is attributed to the change in magnetic ordering. It is observed that the plots of logQ vs 103/T exhibit a linear relationship throughout the temperature region studied (room temperature to 1000 K). The slope of the plot changes at a particular temperature recognized as Curie temperature. These temperatures agree well with the experimentally obtained Curie temperatures using Laroia technique. Hopping of polarons mechanism is used to explain the conduction behaviour in ferrites. The magnetic moment (nB) is calculated from the magnetization studies carried out at 78 K. The cation distribution is suggested on the basis of these magnetization data.
TL;DR: In this paper, the temperature dependence of the critical field of the FOMP, H(cr)(T), and the anisotropy field H(a)(T) of Nd2Fe14C were measured by using the SPD technique in the temperature range from 4.2 to the Curie temperature.
TL;DR: In this article, the authors measured the magnetization and Mossbauer effect on vapor-quenched amorphous Hf 1-x Ta x Fe 2 alloys prepared by sputtering for x = 0, 0.3, 0., 0.5, 0,0.7 and 1 from 4.2 to 300 K.
Abstract: We have measured the magnetization and Mossbauer effect on vapor-quenched amorphous Hf 1- x Ta x Fe 2 alloys prepared by sputtering for x =0, 0.3, 0.5, 0.7, 0.9 and 1 from 4.2 to 300 K. We observed the spontaneous magnetization for all the present samples except for x =1, where the ferromagnetic moment and Curie temperature monotonically decrease with increasing Ta concentration. A comparison between the ferromagnetic and paramagnetic moments suggests that the alloys are an itinerant-electron ferromagnet. The reduced low-temperature magnetization falls characteristically below that of crystalline HfFe 2 and follows a T 3/2 law. From the broad Mossbauer spectrum below the Curie temperature we estimate the average hyperfine field. Ta-concentration and temperature dependence of the average hyperfine field agrees with that of the magnetization.