Showing papers on "Curie–Weiss law published in 1974"
TL;DR: In this paper, a modification of the ac calorimetric technique has been used to test the proportionality of the specific heat and temperature derivative of the basal-plane resistivity of gadolinium through the Curie point.
Abstract: A modification of the ac calorimetric technique has been used to test the proportionality of the specific heat and temperature derivative of the basal-plane resistivity of gadolinium through the Curie point. Because of a large temperature-dependent background to the resistivity derivative, a direct comparison of the critical contributions to the two quantities was impossible. It was found, however, that the background was insensitive to applied magnetic fields so that a direct comparison of the deviation of the specific heat at a finite field from its zero-field value with the similar deviation of the resistivity derivative demonstrated the proportionality of the two quantities. In applied fields below 585 Oe, a "kink point" was observed in the specific heat below ${T}_{C}$ which moved to lower temperatures with increasing fields. Such an effect has been predicted to occur at fields and temperatures for which the internal magnetic field vanishes. The specific heat in several fields above 585 Oe was compared with the predictions of scaling laws and with the linear approximation to the parametric equation of state. Reasonable agreement between the data and the specific-heat scaling function predicted by the linear model could only be obtained by using an unrealistic value of the critical exponent describing the zero-field specific heat.
56 citations
TL;DR: In this paper, it is shown that the spontaneous magnetization of small magnetic particles is rather different from the bulk magnetization, and the magnetization process can be accounted for by the Neel theory, if the correct spontaneous magnetisation of the particle is used.
Abstract: In earlier computer simulation small magnetic particles with nearest neighbor Heisenberg interactions in zero magnetic field have been studied. We now continue these investigations including next nearest neighbor exchange and non zero magnetic fieldsH. The particles treated have spherical shape with a number of spinsN in the range from 33 to 3071. It is shown that the spontaneous magnetization of the particles is rather different from the bulk magnetization. The magnetization process can be accounted for by the Neel theory, if the correct spontaneous magnetization of the particle is used. The distribution of local magnetizations (the magnetic “profile”) was also obtained in various cases. It is shown that the magnetization of very small particles is much more depressed than predicted by the mean field approximation. We introduce an “effective magnetic radius”\(\hat R\) accounting for the reduction of the local magnetization. This magnetic radius is important for the interpretation of experimental results. A distinct dependence of\(\hat R\) on the magnetic field, temperature and the fraction of next nearest neighbor exchange is found. Finally a brief comparison is made with the recent study of magnetic surface properties by Binder and Hohenberg.
34 citations
TL;DR: In this article, isothermal measurements of the magnetic entropy, magnetization, and differential susceptibility of Dy2Ti2O7 have been made and the results are consistent with the assumption of a nearly pure Jz equals + or - 15/2 ground-state Kramers doublet for the Dy(+++) ion.
Abstract: Isothermal measurements of the magnetic entropy, magnetization, and differential susceptibility of Dy2Ti2O7 have been made. Absolute values of magnetic entropy have been determined as a function of applied magnetic field for several temperatures in the range 2-20 K, and several isofield lines in the magnetic entropy-temperature plane have been determined. Magnetization measurements, which extended into the saturation region, yield a powder-average magnetic moment of about 4.7 Bohr magnetons per ion. A van Vleck contribution to M was also observed. The results are consistent with the assumption of a nearly pure Jz equals + or - 15/2 ground-state Kramers doublet for the Dy(+++) ion. Comments on the suitability of Dy2Ti2O7 for use in a magnetic refrigerator cycling between 4.2 and 20 K are included.
33 citations
TL;DR: For a large Fermi wave vector, the divergence is similar to that of specific heat both below and above the Curie temperature as discussed by the authors, but for a small wave vector the de Gennes-Friedel region appears at higher temperatures.
31 citations
TL;DR: Magnetic susceptibilities of uranium, plutonium, and neptunium trichlorides, tribomides, and triiodides were measured from 27°K to as high as 240°K with a vibrating sample magnetometer at applied fields up to 12 kOe as discussed by the authors.
Abstract: Magnetic susceptibilities of uranium, plutonium, and neptunium trichlorides, tribomides, and triiodides were measured from 27°K to as high as 240°K with a vibrating‐sample magnetometer at applied fields up to 12 kOe Antiferromagnetic transitions were observed in UCl3, TN=220±10°K; in UBr3, TN=150±05°K; in UI3, TN=34±02°K; and in PuCl3, TN=45±05°K A ferromagnetic transition at Tc=475±01°K was found for PuI3, and a slight hysteresis was measured at 27°K Temperature‐independent paramagnetism was observed for NpCl3 below 50°K, for α‐NpBr3 below 30°K, and for NpI3 below 15°K All these latter compounds, and PuBr3, exhibited Curie‐Weiss paramagnetism at higher temperatures, with effective moments near the free‐ion moments The experimental magnetic susceptibility of PuCl3 from 10 to 100°K agrees with the susceptibility calculated from crystal field energy levels and wavefunctions
29 citations
TL;DR: In this paper, the authors measured the isothermal magnetization of a TbAl, single crystal in static magnetic fields up to 150 kOe and in the temperature range from 1.5 to 300 K.
Abstract: The isothermal magnetization of a TbAl, single crystal has been measured along the main symmetry directions in static magnetic fields up to 150 kOe and in the temperature range from 1.5 to 300 K. (111) is the easy direction of magnetization a t all field strengths and for a11 temperatures below the Curie point T, = 105 K. The spontaneous magnetization along (111) follows a Brillouin law; however, there is a strong magnetization anisotropy. By neglecting magnetostriction, the thermal variations of the anisotropy parameters of 4th and 6th order have been obtained: They are of the same type as those anticipated by Callen and Callen. Nous avons mesure les variations isothermes de l'aimantation d'un monocristal de Tb AI, suivant les principales directions cristallographiques dans des champs statiques atteignant 150 kOe, entre 1,5 et 300 K. L'axe (111) est de facile aimantation b toutes temperatures infkrieures b la tempkrature de Curie T, = 105 K. Selon cet axe la variation thermique de l'aimantation spontanke obkit b une loi de Brillouin; il apparait cependant une forte ani-sotropie de l'aimantation. E n n6gligeant la magn6tostriction, les variations thermiques des constantes d'anisotropie d'ordres 4 et 6 ont pu atre obtenues: elles sont du type de celles pr6vues par Callen et Callen.
26 citations
TL;DR: A 12-layer hexagonal perovskite BaFeO 3 with a=5.700 and c=28.03 A has been synthesized at high oxygen pressures and temperatures as mentioned in this paper.
18 citations
TL;DR: In this paper, the magnetic behavior of disordered alloys was described in terms of a "spin glass" matrix with magnetic clusters, and the gradual freezing of the spin orientations on cooling, time dependence, and thermomagnetic history effects characteristic of mictomagnetism were found.
17 citations
TL;DR: In this article, the magnetic properties of disordered Pd-Ni alloys with low nickel content have been studied at high magnetic fields and high pressures, and the variation of the saturation magnetization and Curie temperature with the concentration and pressure are described.
17 citations
TL;DR: In this paper, the canted ferromagnetism of manganese(II) phthalocyanine (PcMn) was studied by torque and magnetization measurements.
Abstract: The canted ferromagnetism of manganese(II) phthalocyanine (PcMn) was studied by torque and magnetization measurements. The experimental results were interpreted in terms of a two sublattice-four domain model. Below the Curie temperature, the magnetic moments on two sublattices which form ferromagnetic linear chains are aligned nearly along the molecular axes and make an angle about 90° with each other resulting in the canted ferromagnetism. This spin structure gives four kinds of domain as observed in the torque measurement. From the analysis on the basis of the molecular field approximation the large and negative crystalline field parameter, D , was found to be responsible to the spin structure in PcMn.
16 citations
TL;DR: In this article, the low temperature field dependent magnetization and susceptibility of the linear ferromagnet CsNiF 3 were compared with calculations for a one-dimensional classical spin field model.
TL;DR: In this paper, the critical magnetic behavior of a weakly ferromagnetic Ni-Rh alloy was found to resemble the anomalous behavior recently reported for dilute Fe in Pd, and it was shown that the elementary moments involved in the Curie-point transition are those of giant polarization clouds rather than of individual atoms.
TL;DR: In this paper, the magnetic properties of the CsCl type compounds GdMg1-xZnx were studied and the authors observed a hyperfine field at the Zn nuclei which remains unaltered with composition x. All these results, together with the complex character of the Gd NMR resonances observed for low x values, were interpreted in terms of an increasing interchange of the magnetic and nonmagnetic sites in the csCl structure.
Abstract: The magnetic properties of the CsCl type compounds GdMg1-xZnx were studied. All these compounds show ferromagnetic behaviour with the asymptotic Curie temperatures close to their ferromagnetic Curie temperatures. In spite of the fact that the nominal number of conduction electron concentration does not change in this series, the authors observed a decrease of the asymptotic Curie temperature with decreasing x and in GdMg is 20% lower than the free ion value. In contrast to these results, which are apparently in conflict with the RKKY approach, the authors observed a hyperfine field at the Zn nuclei which remains unaltered with composition x. All these results, together with the complex character of the Gd NMR resonances observed for low x values (even in the binary compound GdMg are interpreted in terms of an increasing interchange of the magnetic and nonmagnetic sites in the CsCl structure.
TL;DR: In this paper, the polarized crystal spectrum of CsMnBr3 and manganous ion doped into the isostructural magnesium salt, csMgBr3, has been investigated in the 15 000 −30 000 cm−1 region.
Abstract: The polarized crystal spectrum of CsMnBr3 and manganous ion doped into the isostructural magnesium salt, CsMgBr3, have been investigated in the 15 000–30 000 cm−1 region. The general spectral features are very similar to those reported for (CH3)4NMnCl3. The intensities of the ligand field transitions appear to be strongly affected by exchange interactions, since these intensities are quite dependent on the manganese ion concentration. The magnetic susceptibilities of powdered samples of CsMnBr3 and CsMg0.92Mn0.08Br3 have been investigated in the 77–300°K range. The CsMnBr3 obeys the Curie& Weiss law above 190°K, but deviates significantly at lower temperatures. The dilute sample, CsMg0.92Mn0.08Br3, shows near Curie law behavior. The magnetic properties indicate the presence of strong antiferromagnetic coupling in CsMnBr3.
TL;DR: The temperature dependence of the AC susceptibility and the coercive field of gadolinium has been studied near the Curie temperature as mentioned in this paper, and it has been shown that AC susceptibility is positively associated with coercive field.
Abstract: The temperature dependence of the AC susceptibility and the coercive field of gadolinium has been studied near the Curie temperature.
TL;DR: In this article, the influence of order-disorder transitions on the paramagnetic Curie temperature of alloys with dilute concentrations of Mn has been measured and the sign of the contribution to θ which is linearly dependent upon Mn concentration is reversed.
TL;DR: Magnetic susceptibility and magnetization measurements on V3O7 from 4,2 to 600 K characterize a paramagnetic behaviour above 18 K as discussed by the authors, with a Curie constant in good agreement with a spin only value S = 1 2 per V4+.
TL;DR: In this article, the magnetic susceptibility and high-field magnetization have been measured for powdered samples of Ce x La 1-x Bi. These characteristics were discussed on the basis of the crystal field and molecular field interactions.
Abstract: The magnetic susceptibility and high-field magnetization have been measured for powdered samples of Ce x La 1- x Bi. In the range of x >0.5 the Neel temperature depends linearly on the cerium concentration and it deviates downward from this linear relation for x <0.5. No antiferromagnetic ordering could be observed for x =0.35 above 2.5 K. All antiferromagnetic samples investigated here showed metamagnetic behavior. The saturation magnetization corresponding to the magnetic moment of Ce 3+ decreases remarkably with decreasing Ce concentration. These characteristics were discussed on the basis of the crystal field and molecular field interactions.
TL;DR: In this paper, the spontaneous volume magnetostriction and the pressure dependences of the magnetization and of the Curie temperature are formulated, and the magnetic contribution to thermal expansion is obtained as the temperature derivative of the spontaneous volumetric magnetization.
Abstract: Stoner model is extended by taking account of the volume dependence of the exchange parameter and the band width. On the basis of this model, the spontaneous volume magnetostriction and the pressure dependences of the magnetization and of the Curie temperature are formulated. The magnetic contribution to thermal expansion is obtained as the temperature derivative of the spontaneous volume magnetostriction. In the numerical calculations, the use is made of the step-type density-of-states curve, which is reasonable and the simplest one for fcc Fe-Ni alloys. Calculated results of the magnetovolume effects are plotted as function of the temperature or the composition. Those are qualitatively similar to experimental results in fcc Fe-Ni alloy system.
TL;DR: The most important contributions to the magnetic susceptibility are the Curie-Weiss term, expressing the paramagnetism of localized f-electrons, and a temperature independent term for which all the contributions were estimated.
Abstract: NMR and magnetic susceptibility of CeCu6 intermetallic compound were investigated. The most important contributions to the magnetic susceptibility are the Curie-Weiss term, expressing the paramagnetism of the localized f-electrons, and a temperature independent term for which all the contributions were estimated. The phenomenological exchange constantJsf between 4f — electron spins and conduction — electron spins is derived to be −0·012 eV. The Knight shift and Curie temperature are discussed in terms of the Ruderman-Kittel-Kasuya-Yosida theory and in the Rocher's virtual bound states model. The s — f exchange integralΓ and the Fermi wavevectorkF are derived to be — 0·8 eV and 1·32 A−1, respectively.
TL;DR: In this paper, a singlet-triplet model for cubic Laves PrT2 compounds was proposed, in which the induced moments interact with an enhanced d band in the compound.
Abstract: The cubic Laves PrT2 compounds, where T is a metal atom, are ferromagnets which display a variety of magnetic moments on the Pr3+ ion varying from 0.61 mu B to 2.2 mu B. Crystal field analysis shows that the free Pr3+ ion in some of these compounds must be in a singlet ( Gamma 1) state. Here the authors analyse a singlet-triplet model for Pr3+ in which the induced moments interact with an enhanced d band in the compound. Expressions are given for the zero temperature magnetization and the Curie temperature in this model and the spin dynamics are discussed. In particular it is shown that the lowest spin modes are paramagnons or spin waves typical of an itinerant paramagnet or ferromagnet respectively. Finally in agreement with Fulde (1972) none of the excitonic modes become soft at the transition point.
TL;DR: In this article, a method of calculating the static generalized susceptibility for the critical region in the constant coupling approximation has been formulated and applied to ferromagnets above the Curie point, leading to an anisotropic susceptibility.
TL;DR: In this paper, the authors measured the magnetic susceptibility at low temperatures (1.2-4.2 K) of a series of ZnMn alloys (20-2500 ppm Mn) and found that χ can be represented by a Curie-Weiss law, χ ω=C/(T+θ), where both C and θ vary with concentration n of Mn impurities.
Abstract: We have measured the magnetic susceptibility at low temperatures (1.2–4.2 K) of a series of ZnMn alloys (20–2500 ppm Mn) and have found that χ can be represented by a Curie‐Weiss law, χ = C/(T+θ), where both C and θ vary with concentration n of Mn impurities. As a function of n, θ goes through a minimum (θmin = 0.3 K) at about n=100 ppm Mn. We interpret this minimum in θ, which is here observed for the first time in a dilute magnetic alloy system, as resulting from the competition between single‐impurity (Kondo) and impurity‐impurity (RKKY) interactions. We also report on the concentration dependence of the Curie constant C.
01 Jan 1974
TL;DR: The magnetic mass susceptibility of Zn alloys containing 12, 19, 27, 47, 82, 155, and 275 ppm Mn has been investigated by means of a high-sensitive Faraday balance (sensitivity 1.7 × 1011 emu/g, maximum field 10 KG) in a temperature range from 2.7 to 300°K as mentioned in this paper.
Abstract: The magnetic mass susceptibility of Zn—Mn alloys containing 12, 19, 27, 47, 82, 155, and 275 ppm Mn has been investigated by means of a high-sensitive Faraday balance (sensitivity 1.7 × 1011 emu/g, maximum field 10 KG) in a temperature range from 2.7 to 300°K. The samples are thin strips of cold-rolled alloys, whose low-temperature resistivity anomalies were measured earlier.1 A pure Zn sample has been submitted to an equal preparation and deformation procedure to allow proper deduction of the influence of the matrix from the alloy data. Within the investigated temperature range the Zn is diamagnetic with a slight tendency to paramagnetism compared to the “as-received” Zn at low temperatures, resulting from the melting process.
TL;DR: In this article, the magnetic properties of NpAl3 have been studied by means of magnetization and Mossbauer effect measurements between 4 and 300°K, and it has been shown that the magnetization cannot be saturated by an applied field of 13.5 kOe at 4°K.
Abstract: We have studied the magnetic properties of NpAl3 by means of magnetization and Mossbauer‐effect measurements between 4 and 300°K. This compound, which has the AuCu3‐type structure with a lattice parameter of a = 4.260 A, orders ferromagnetically at 62.5 ± 0.5°K. The magnetization cannot be saturated by an applied field of 13.5 kOe at 4°K. However, the 237Np magnetic hyperfine field of 2630 kOe measured at 4.2°K indicates an Np magnetic moment of ∼1.2 μB. Although the magnetic susceptibility above Tc deviates strongly from Curie‐Weiss behavior, the temperature dependence can be reasonably well reproduced theoretically if it is assumed that the neptunium ion has a +4 charge (5f3) and is situated in a cubic crystal field of 12 negatively charged ligands.
TL;DR: In this paper, the variation of Curie temperature and effective moment are discussed in terms of a parameter n e -the mean concentration of conduction electrons of nonmagnetic components. But their work is limited to Ni-Cu-Al solutions.