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Showing papers on "Curie–Weiss law published in 1975"


Journal ArticleDOI
TL;DR: In this paper, a wide range of temperatures on concentrated amorphous transition-metal aluminosilicate glasses (11.8-33.5-at.% Co, 12.3-41.7-At.% Mn) are reported.
Abstract: Susceptibility measurements over a wide range of temperatures on concentrated amorphous transition-metal aluminosilicate glasses (11.8-33.5-at.% Co, 12.3-41.7-at.% Mn) are reported. In the high-temperature regime (g\ensuremath{\sim}50 K), these glasses show Curie-Weiss behavior with large negative paramagnetic Curie temperatures, indicating the presence of strong antiferromagnetic exchange interactions. The slope of ${\ensuremath{\chi}}^{\ensuremath{-}1}$ vs $T$ curves shows a slight dependence on the transition-metal concentration, implying that the local environment of the magnetic ions is concentration dependent. The magnitude as well as the concentration dependence of the magnetic moments, as determined from the high-temperature data, can be understood for the cobalt glasses by appealing to the solidus surface diagram (which gives information concerning the local environment of the cobalt ions) of the glass system. In the low-temperature regime ($1lTl50$ K), the susceptibility of both systems is enhanced and furthermore exhibits an anomalously sharp peak below \ensuremath{\sim}10 K. The magnitude of this peak decreases with increasing magnetic-ion concentration, while the position at which it occurs shifts to higher temperatures. This low-temperature behavior can be explained satisfactorily by assuming that these glasses contain small (\ensuremath{\sim}50 \AA{}) regions of relatively high cobalt or manganese concentration (monodomains) which are ordered antiferromagnetically, and which are separated from one another by paramagnetic areas of lesser magnetic-ion content. Each monodomain has a net magnetic moment which freezes in the direction of its anisotropy field at the so-called blocking temperature, giving rise to the peak in the susceptibility. By calculating the susceptibility of the monodomains and properly averaging over the random directions of their anisotropy fields, remarkable agreement with the low-temperature data is obtained. The values of the anisotropy constants needed to fit the data are consistent with values found in various cobalt and manganese compounds.

105 citations


Journal ArticleDOI
TL;DR: In this paper, a newly modified thermodynamic theory was proposed to explain the nonlinear magnetoelectric effects arising from the electric field dependence of the macroscopic magnetic anisotropy energy.
Abstract: The application of a static magnetic field to a single crystal of synthetic magnetite (${\mathrm{Fe}}_{3}$${\mathrm{O}}_{4}$) at 42\ifmmode^\circ\else\textdegree\fi{}K is found to induce a static electric polarization which is a nonlinear function of the components of the magnetic field and exists even in the absence of an applied electric field A newly modified thermodynamic theory shows that these nonlinear magnetoelectric effects arise from the electric field dependence of the macroscopic magnetic anisotropy energy No such dependence has been observed previously at any temperature in any material The values of the electric field derivatives of two of the anisotropy constants are determined by means of experiments in saturating magnetic fields With the use of these two values, and without the use of adjustable parameters, the modified thermodynamic theory successfully predicts the measured curves of (a) the induced electric polarization as a function of the orientation of a nonsaturating magnetic field of constant magnitude and (b) the induced electric polarization as a function of the magnitude of a sufficiently large magnetic field of constant orientation After a brief discussion of the microscopic origin of the electric field derivatives of the anisotropy constants, appropriate symmetry arguments are used in conjunction with the experimental data to show for the first time that the point group of the crystallographic space group of magnetite at 42\ifmmode^\circ\else\textdegree\fi{}K is the group 1

84 citations


Journal ArticleDOI
TL;DR: In this article, the magnetic properties, the pressure dependence of the Curie temperature (Tc), and the initial compressibilities of the series of compounds LaCo5xNi5-x were determined.
Abstract: The magnetic properties, the pressure dependence of the Curie temperature (Tc) and the initial compressibilities of the series of compounds LaCo5xNi5-x were determined. The compounds with x>or=0.6 are ferromagnets whilst for the compounds with 0.2

42 citations


Journal ArticleDOI
TL;DR: In this article, the use of fractional distillation has been used for the synthesis and purification of GdN, both distilled and undistilled, with different magnetic properties.
Abstract: New procedures, employing the use of fractional distillation, have been developed for the synthesis and purification of GdN Distilled and undistilled GdN exhibit different magnetic behavior, both being sensitive to oxygen impurities The zero field magnetic moment of a virgin sample of distilled GdN is zero but with increasing field exhibits features of ferromagnetic behavior For distilled GdN, an increase in oxygen concentration from 08 to 58 at% decreases the paramagnetic Curie temperature from 90 to 60 K Undistilled GdN, having a large nitrogen deficiency, shows ferromagnetic behavior

38 citations


Journal ArticleDOI
TL;DR: The magnetic susceptibility of americium metal is almost temperature independent between room and liquid helium temperatures as discussed by the authors, and it shows Curie-Weiss paramagnetism with antiferromagnetic ordering around 52 K; its effective magnetic moment supports the hypothesis of localized 5∫ electrons and a metal valence of three.

33 citations


Journal ArticleDOI
TL;DR: In this article, the Curie temperature, the magnetocrystalline anisotropy, the spontaneous magnetization and the differential susceptibility at high magnetic fields were studied for single crystal manganese ferrites.
Abstract: The cation distribution of single crystal manganese ferrites Mn 1-y Fe y [Mn y Fe 2-y ]O 4 with 0.06 \leq y \leq 0.24 was modified by appropriate heat treatment at temperatures 300-600°C. With these samples the Curie temperature, the magnetocrystalline anisotropy, the spontaneous magnetization and the differential susceptibility at high magnetic fields were studied. The experiments enabled us to determine the magnitude of the molecular field coefficient N Mn(A)-Fe(B) = 89 and to estimate the main part of the contribution to the magnetocrystalline anisotropy in MnFe 2 O 4 which was found to come from Fe3+in octahedral sites. High field susceptibility measurements confirmed the applicability of the noncolinear arrangement of magnetic moments in MnFe 2 O 4 which supposes that Mn(B) spins make an angle of 53° with the direction of the total magnetization.

32 citations


Journal ArticleDOI
TL;DR: In this paper, the weak ferromagnetic saturation moment of the intermetallic compound UPt is reduced with respect to the atmospheric pressure value by more than 90% at 20 kbar.

30 citations


Journal ArticleDOI
TL;DR: In this paper, the theoretically observed moment of a magnet embedded in a permeable medium is applied to the case of titanomagnetite particles containing minor quantities of an exsolved magnetite-rich phase of higher Curie point such as are found in basalts.
Abstract: Summary The theoretically observed moment of a permeable magnet embedded in a permeable medium is applied to the case of titanomagnetite particles containing minor quantities of an exsolved magnetite-rich phase of higher Curie point such as are found in basalts. The effect of temperature on the observed moment as the Curie point of the titanomagnetite is reached is discussed, and is shown to qualitatively explain experimental results found by Petherbridge et al. who found that an increase in moment occurred on heating synthetic samples in zero field through the titanomagnetite Curie point, and that a corresponding decrease in moment occurred on cooling.

27 citations


Journal ArticleDOI
TL;DR: In this article, the magnetic properties of ThMn2Si2 and Thmn2Ge2 were studied using neutron diffraction, X-ray diffraction and magnetometric techniques.
Abstract: ThMn2Si2 and ThMn2Ge2 were studied using neutron diffraction, X-ray diffraction, and magnetometric techniques. Both the compounds have tetragonal CeAl2Ge2-type structure. Position parameters z for Si and Ge were determined. ThMn2Si2 is an antiferromagnet with a Neel temperature of 483 K, and ThMn2Ge2 exhibits a small ferromagnetic moment of 0.35μB with the Curie temperature of 400 K. The magnetic transition in ThMn2Ge2 is of first order. The magnetic structures for both compounds consist of ferromagnetic layers perpendicular to the c0-axis which are antiferromagnetically coupled to adjacent layers. The magnetic moment direction in ThMn2Si2 is parallel t o the c0-axis, and in ThMn2Ge2 the magnetic moment is slightly deviated from c0-axis. It is suggested that conduction. [Russian Text Ignore]

25 citations


Journal ArticleDOI
TL;DR: Magnetic susceptibility and torque measurements of FeS4, FeV2S4 and FeTi2Se4 were made using the powder and the single crystal samples as discussed by the authors, and the paramagnetic moment obtained for these compounds was in the range of 5.26-5.37 μB, close to that of the high spin state Fe2+.

24 citations


Journal ArticleDOI
TL;DR: The magnetic properties of GdCo 2 and Gd 1-x Y x Co 2 have been observed and discussed in terms of the molecular field approximation in this article, which suggests that the Co moment is suppressed by Y substitution and quite sensitive to magnetic environments.
Abstract: The magnetic properties of GdCo 2 and Gd 1- x Y x Co 2 have been observed and discussed in terms of the molecular field approximation. An appropriate set of interaction parameters reproduces the temperature dependence of the magnetization of GdCo 2 and the concentration dependence of the Curie temperature of Gd 1- x Y x Co 2 for x 0.2, suggests that the Co moment is suppressed by Y substitution and quite sensitive to magnetic environments. A stepwise anomaly in the temperature dependence of the magnetization previously reported could not be observed.

Journal ArticleDOI
TL;DR: In this article, the authors measured the paramagnetic susceptibility and the saturation magnetic moment of a number of polycrystalline samples of all four europium monochalcogenides.
Abstract: We have measured the paramagnetic susceptibility and the saturation magnetic moment of a number of polycrystalline samples of all four europium monochalcogenides. Many of them exhibit a negative susceptibility at 2 K and magnetic fields of 70 kOe, rather than the expected saturation behaviour. These anomalies are believed to be due to lattice defects. Reproducible saturation moments have been obtained after subtraction of this linear high field magnetization. Since all materials were nonstoichiometric to within a few percent, the ratio between the Curie-Weiss constantC and the saturation momentM0 has been evaluated in order to eliminate the unreliably known numberN of the Eu+ + ions. The quantityR = gJ(J+1) extracted in this way should have the valueR0 = 9.00 forg = 2 andJ ≡S = 7/2. The measured values, 9.72, 9.33, 9.32 and 9.50 for EuO, EuS, EuSe and EuTe, respectively, can be correlated directly with the magnetic hyperfine fields, which are − 305, − 330, − 328 and − 315 kOe in the ferromagnetic aligned states. Both results together lead to the assumption that the magnetic moment per Eu-ion is enhanced over the8S7/2-value by spin contributions of outer 5d or 6s electrons.



Journal ArticleDOI
TL;DR: In this paper, the magnetic properties of the series LaCo5xCu5−5x were studied and all compounds were found to crystallize in the hexagonal CaCu5 structure type and the following properties were determined: the lattice constants, the Curie temperatures and their pressure dependence up to 40 kbar, the anisotropy fields, the saturation moments at 4.2 K, and the initial compressibilities.
Abstract: The magnetic properties of the series LaCo5xCu5−5x were studied. All compounds were found to crystallize in the hexagonal CaCu5 structure type. As a function of composition x the following properties were determined: the lattice constants, the Curie temperatures and their pressure dependence up to 40 kbar, the anisotropy fields, the saturation moments at 4.2 K, and the initial compressibilities. Attempts have been made to explain the variation of the magnetic properties in terms of the collective electron model with a 3d band shape that depends on Cu concentration, taking account, however, of a certain extent of localization of the 3d electrons.

Journal ArticleDOI
TL;DR: In this article, the upper limit for the Curie temperature T c (x ) of the dilute Heisenberg ferromagnet near percolation threshold is derived.

Journal ArticleDOI
TL;DR: In this article, the electrical conductivity, dielectric constant and magnetic susceptibility of erbium tungstate are measured for the temperature range 300 to 1000K. The known phase transition near 600K is in evidence in all these measurements.
Abstract: Measurements of the electrical conductivity, dielectric constant and magnetic susceptibility of pellets of erbium tungstate are reported for the temperature range 300 to 1000K. The known phase transition near 600K is in evidence in all these measurements. The conductivity data for T>600K have been analysed in terms of an exponential relation sigma = sigma 0 exp (-Eg/2kT), giving sigma 0=8.892*102 ohm-1 cm-1 and Eg=1.52 eV. There is a weak dispersion in the dielectric constant at around 104 Hz and a rapid increase above 600K. The high-temperature data for the susceptibility obey a Curie-Weiss law that gives a value of 9.50 Bohr magneton for Er3+ ions and a (ferromagnetic) Curie temperature of 160K.

Journal ArticleDOI
TL;DR: In this article, the ternary alloys Gd 1− x Th x Fe 2 and Gd 2− x Ce x Fe2 were introduced into the lattice in an effort to induce ferromagnetic GdFe coupling.

Journal ArticleDOI
TL;DR: In this paper, the magnetic properties of Gd7Rh3 were measured by the Faraday technique between 100 and 800 K on samples of a weak, fibrous texture, which showed orientation-dependent antiferromagnetic ordering at 142 ± 1 K Above 470 K, normal Curie-Weiss behaviour was observed corresponding to the effective moment of tripositive gadolinium, with θp = 175 ± 7 K
Abstract: Measurements of the magnetic properties of Gd7Rh3 by the Faraday technique between 100 and 800 K on samples of a weak, fibrous texture showed orientation-dependent antiferromagnetic ordering at 142 ± 1 K Above 470 K, normal Curie-Weiss behaviour was observed corresponding to the effective moment of tripositive gadolinium, with θp = 175 ± 7 K


Journal ArticleDOI
TL;DR: In this paper, the exchange interactions between the carrier spins and the spins of the magnetic atoms are attributed to the red-shift of the low energy region of the spectra (∼1.95 and ∼2.6 eV) below the Curie temperature.

Journal ArticleDOI
TL;DR: In this paper, the properties of very dilute (7-120 at ppm) alloys of Cr, Mn, and Fe in Zn are presented, and the authors obtain peff=3.6 and 4.1 mu B, respectively, for Cr and Mn solute, and in both cases the Curie Weiss theta is about 0.5K.
Abstract: Magnetic and electrical properties of very dilute (7-120 at ppm) alloys of Cr, Mn, and Fe in Zn are presented. Both Cr and Mn display local moment behaviour with logarithmic temperature dependence in the low temperature (1.5-4.2K) resistivity and a Curie-Weiss susceptibility (1.3-15K). The authors obtain peff=3.6 and 4.1 mu B, respectively, for Cr and Mn solute, and in both cases the Curie Weiss theta is about 0.5K. Non interacting Fe atoms contribute a temperature independent enhanced Pauli component to the susceptibility of dilute ZnFe alloys which corresponds to the characteristic spin fluctuation temperature of 180K.


Journal ArticleDOI
TL;DR: In this article, the critical phenomena near the Curie temperature in a single crystal of manganese phosphide were studied by the magnetization measurement along the easy axis of the crystal.
Abstract: The critical phenomena near the Curie temperature in a single crystal of manganese phosphide are studied by the magnetization measurement. The magnetization along the easy axis is precisely measure...

Journal ArticleDOI
TL;DR: In this paper, it was shown that the splitting of the conduction electron spectrum into two spin sub-bands does not vanish at Curie point T c, and the height of the scattering maximum for the Conduction electron at T c was estimated.

Journal ArticleDOI
TL;DR: In this paper, the magnetic properties of pyrolusite, polianite, manganite, hausmannite, psilomelan and wad from different localities all over the world were studied; the measured values are statistically treated so that the given values are valid in general.
Abstract: The paper is devoted to the study of the magnetic properties, of the volume magnetic susceptibility in a weak magnetic field, of the specific magnetic susceptibility in a strong magnetic field, of natural remanent magnetization and its stability in A.C. fields, and of the temperature dependence of magnetic susceptibility of natural Mn-oxides. Samples of pyrolusite, polianite, manganite, hausmannite, psilomelan and wad from different localities all over the world were studied; the measured values are statistically treated so that the given values are valid in general. Hausmannite displayed typical values of the magnetic susceptibility, different from the values of the other Mn-oxides. In general, many natural Mn-oxides contain heterogeneous admixtures of Fe-oxides, which are responsible for their ferromagnetic properties. A high degree of magnetic hardness, predetermining the minerals for palaeomagnetic research, was proved with many of the natural Mn-oxides.

Journal ArticleDOI
TL;DR: In this paper, a thickness-dependent critical concentration of an Ising ferromagnetic thin film is predicted, and the calculated values of the Curie temperature are bounded by those known for diluted two-and threedimensional ferromagnets.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the resistivity anomalies of ferromagnetic metals near the Curie temperature using the itinerant model of magnetic electrons and the current theory describing these anomalies is based on the localized model of magnetoresceptors in magnetoric metals.
Abstract: We have investigated the resistivity anomalies of ferromagnetic metals near the Curie temperature T c using the itinerant model of magnetic electrons Current theory describing these anomalies is based on the localized model of magnetic electrons in ferromagnetic metals. We use the itinerant model to treat the spin correlation function. Using the second quantization techniques of field theory, the correlation function is found. Thence, the scattering cross section is obtained. The relaxation time and the resistivity are calculated for both the paramagnetic and the ferromagnetic regions. The temperature derivatives of the resistivity are then derived for temperatures approaching the Curie temperature from both below and above. Our results are positive infinite for T approaching T c from below and negative infinite for T approaching T c from above.


Journal ArticleDOI
TL;DR: A theory of anomalous Kondo effect in amorphous magnetic materials below the Curie temperature was presented in this paper, where it was found that whether a particular spin is a Kondo scatterer, when the long-range magnetic order prevails, depends on the ratio of its local temperature of magnetic ordering and the bulk curie temperature.
Abstract: A theory of the anomalous Kondo effect in amorphous magnetic materials below the Curie temperature is presented. It was found that whether or not a particular spin is a Kondo scatterer, when the long-range magnetic order prevails, depends on the ratio of its local temperature of magnetic ordering and the bulk Curie temperature. By changing the external magnetic field or temperature we can obtain information about higher correlations of spins.