Showing papers on "Curie–Weiss law published in 1972"

New Magnetic Material Having Ultrahigh Magnetic Moment

Abstract: The change of the saturation magnetization of Fe films with the pressure of nitrogen during deposition ranging from 2 × 10−5 to 7 × 10−3 Torr has been investigated systematically. We found a new magnetic material which has the highest saturation magnetization at room temperature, 2050 G, among those of all the magnetic materials. This was attributed to Fe16N2, which has a bct structure, and the magnetic moment associated with Fe atoms of Fe16N2 was deduced to be 3.0 μB.

The magnetic properties of rare earth-Pd3 phases

Abstract: Magnetic measurements from 1.5 to 300 K on the complete series of Cu3Au-type R Pd3 phases have been made. LaPd3 and LuPd3 are diamagnetic at room temperature. CePd3 shows Pauli-type paramagnetism indicative of a nonmagnetic virtual bound state. PrPd3 and NdPd3 are affected at low temperatures by the presence of the crystal field. The magnetic properties of SmPd3 and EuPd3 are determined by the energy levels of the lowest multiplet. GdPd3 and (possibly) TbPd3 become antiferromagnetic at 7.5 and 2.5 K respectively. DyPd3-ErPd3 obey the Curie law. The magnetic properties of these phases are discussed in relation to crystal field effects and a possible band structure.

Magnetic properties of Clb compounds; CoVSb,CoTiSb and NiTiSb

Abstract: Experimentally CoVSb is found to be a ferromagnetic compound with a ferromagnetic and a paramagnetic Curie temperature of 58 K and 75 K, respectively. The saturation magnetic moment per formula at 0 K is 0.18µ B . and the paramagnetic moment per formula 1.26µ B . The relations of the Curie temperature and magnetic moment between ferromagnetic and paramagnetic states are very different from that of usual ferromagnetic materials. CoTiSb and NiTiSb are found to be temperature independent paramagnetic compounds with the susceptibility per gram of 5×10 -7 and 6×10 -7 emu/g, respectively. It should be a noticeable fact that CoVSb has a spontaneous magnetic moment while CoTiSb and NiTiSb have not.

Spontaneous magnetization curves and curie points of spinels containing two types of magnetic ion

Abstract: Weiss molecular field theory has been applied to spinels containing two types of ions carrying magnetic moment. By neglecting AA and BB interactions and considering only the four AB interactions between the two types of ion in the two types of site, it is shown that anomalous spontaneous magnetization curves can arise, some of which are more varied than those described by Neel. Calculated curves for titanomagnetites with Fe2+ and Fe2+ ions as carriers of magnetic moment are similar to the Neel P type for some cation distributions, in agreement with experimental data. Spinel systems containing Fe3+ Co2+ and Fe3+ Ni2+ have also been considered and a general expression for the Curie point of spinels containing two types of ions carrying magnetic moment is given as a function of the cation concentration on the A and B sites and the lattice parameter.

Effect of crystal field anisotropy on the Curie temperature of an Ising ferromagnet: HTS expansion method

Abstract: A high temperature expansion is obtained for the zero field susceptibility of a generalized Ising model which contains a single-ion anisotropy term commuting with Ising hamiltonian. The first five coefficients of the series are obtained for general spin and all three cubic lattices. Estimates of the critical temperature are made and compared with the predictions of molecular field theory and previous results. Estimations of the critical exponent of the susceptibility are in favour of the hypothesis that it is the same as for the pure Ising model.

Spin Relaxation on Yttrium Iron Garnet near Curie Temperature Studied by High Frequency Magnetic Susceptibility

Abstract: The high frequency magnetic susceptibilities in yttrium iron garnet are observed in the temperature range from 546 K and 553 K in the high frequency range from 100 kHz to 100 MHz and the low frequency range lower than 100 Hz. The anomalous sharp peak appears in the temperature dependence curves of the imaginary part of the magnetic susceptibility in MHz range and is broadened with increasing frequency. From frequency dependence of the magnetic susceptibilities it is made clear that the relaxation of spin system occurs in the above two frequency ranges and relaxation process near the Curie temperature is not monodispersive but polydispersive. The temperature dependence of the relaxation time in spin system is obtained near the Curie temperature and is corresponding with the critical slowing down phenomena.

Magnetic behavior of hexagonal U2N3 in the temperature range from 77 to 300 °K

Abstract: The magnetic properties of hexagonal U2N3 are investigated in various magnetic fields in the temperature range from 77 to 300 °K. The magnetization versus temperature curves exhibit a pronounced maximum which shifts to lower temperatures with increasing magnetic field strength. On the other hand, in the case of cooling the sample through the Curie temperature in magnetic field, no peak in magnetization versus temperature curves occurs. These behaviors seem to be associated with a high anisotropy field below the Curie temperature. Large magnetic hysteresis effect at 77 °K confirms these arguments. The paramagnetic susceptibility obeys the Curie-Weiss law having a Weiss constant of 182 °K and a paramagnetic moment of 2.88 BM. The anisotropy and the paramagnetic moment are qualitatively discussed in terms of crystal field theory. Die magnetischen Eigenschaften von hexagonalem U2N3 werden bei verschiedenen Magnetfeldern im Temperaturbereich zwischen 77 und 300 °K untersucht. Die Kurven der Magnetisierung uber der Temperatur zeigen ein ausgepragtes Maximum, das sich mit steigendem Magnetfeld zu niedrigen Temperaturen verschiebt. Auf der anderen Seite tritt kein Maximum in der Magnetisierungs–Temperatur-Kurve auf, wenn die Probe im Magnetfeld unter die Curie-Temperatur abgekuhlt wird. Diese Verhaltensweisen scheinen mit einem hohen Anisotropiefeld unterhalb der Curietemperatur verbunden zu sein. Grose magnetische Hystereseeffekte bei 77 °K bestarken diese Argumente. Die paramagnetische Suszeptibilitat befolgt das Curie-Weissche Gesetz, mit einer Weisschen Konstante von 182 °K und einem paramagnetischen Moment von 2,88 BM. Die Anisotropie und das paramagnetische Moment werden qualitativ mit der Kristallfeldtheorie diskutiert.

Magnetic properties of UTe2 and U7Te12

Abstract: Magnetic measurements on UTe2 and U7Te12 have been performed in the temperature range 4.2 to 1000 K and in magnetic fields up to 80 kOe. U7Te12 appears to be a ferromagnet with the Curie point equal to 73 K. A maximum of the magnetization of U7Te12 is found in magnetic fields below 30 kOe. An attempt of explaining the value of the magnetic susceptibility for both compounds is made on the assumption that the ground state is a singlet. [Russian Text Ignored]

Tunneling Study of EuS Magnetization

Abstract: Ferromagnetic EuS crystals have Curie temperatures which increase rapidly as a function of electron concentration due to strong indirect exchange between the impurity electron and the localized 4f states Using measurements of indium vs EuS tunnel junctions, we have obtained the temperature and field dependence of the long range magnetic order (spontaneous moment) and short range fluctuations in this order (magnetic fluctuations) The long range magnetic order splits the conduction band and the resulting band edge shift is reflected in a change in the tunneling barrier height Thus measurement of the tunneling conductance, dominated below Tc (215 K) in the low concentration samples by the barrier height change, is a measure of the temperature and field dependence of the spontaneous moment Moment data obtained by this method agree to within 5% with Mossbauer and demagnetizing field measurements on the same material Magnetic fluctuations in the sample cause scattering of the electrons in the barrier whic

The magnetic susceptibility of dilute CuFe alloys in the temperature range 1.7 300 K

Abstract: The paramagnetic susceptibility ofCuFe alloys (100–300 ppm Fe) has been measured in the temperature range 1.7 to 300 K. The susceptibility is very well represented by the expression $$\chi = \chi _0 + \frac{{C_1 }}{{T - \theta _1 }} + \frac{{C_2 }}{{T - \theta _2 }}$$ the first and second Curie Weiss terms being associated with single and paired iron atoms respectively. A Cu0-9 Au0-1 Fe alloy was also studied.

Magnetic properties of semiconducting glasses

Abstract: The paper reports the temperature and compositional dependence of the magnetic susceptibility in some semiconducting glasses. The susceptibility is always negative and is given as a sum of a diamagnetic and of a paramagnetic term. The diamagnetic term is temperature independent, but depends strongly upon composition; the paramagnetic term is of Curie type. Results are explained using a following model. A semiconducting glass is formed from atoms bound together by covalent bonds. This glass is considered as a big molecule having no magnetic moment in the ground state and having some unsaturated bonds. This model enables to interpret the nature of bond between the atoms, the dependence of susceptibility upon composition, the nature of paramagnetic centers and their relation to energy spectrum.

Giant susceptibilities of La-Gd

Abstract: Giant susceptibilities have been observed in some crystalline systems containing Gd impurity. The inverse magnetic susceptibility, however, conforms to the general pattern of dilute alloys of Cu—Mn type where local moments interact via Ruderman-Kittel—Yosida indirect exchange but there is no long-range magnetic ordering: the susceptibility is Curie-Weiss in the limit of high temperatures, but departs from such behaviour at lower temperatures to yield a peak susceptibility max' which is typically less than XCurie-Weiss This deviation is studied by assuming the existence of statistical fluctuations that arise from a random impurity distribution. A formula for the paramagnetic susceptibility of random alloys, valid to very low temperatures, is developed (with specific application to La-Gd), including external field effects.

Pulsed Nuclear Resonance Investigation of the Susceptibility and Magnetic Interaction in Degenerate 3He Films

Abstract: Continuous-wave nuclear resonance measurements have been made recently of the susceptibility and spin—lattice relaxation times on film1,2 of pure 3He and 3He–4He mixtures in the temperature range between 1.5 and 0.4°K for various film thicknesses. In the region investigated the films either were classical, in the sense that their susceptibility followed a Curie law, or showed only small (up ~ 26%) Fermi degeneracy, depending on coverage and temperature. It was shown that the susceptibility was consistent with a statistical layer model in which the first two layers could be considered as magnetically independent of each other and of the rest of the film, and each layer region of the film exhibited the same susceptibility as that of bulk 3He at the same interatomic spacing. Such an interpretation is not necessarily unique, and it is expected to be an approximation. In the present report we show that there are large deviations from this model at lower temperatures down to 50 m°K, in such a direction as to indicate a lower Fermi temperature in the real film than in the model, or a larger ferromagnetically inclined exchange interaction.

Temperature-dependent magnetic properties of individual glass spherules Apollo 11, 12, and 14 lunar samples

Abstract: Magnetic susceptibility of 11 glass spherules from the Apollo 14 lunar fines have been measured from room temperature to 4 K. Data taken at room temperature, 77 K, and 4.2 K, show that the soft saturation magnetization was temperature independent. In the temperature range 300 to 77 K the temperature-dependent component of the magnetic susceptibility obeys the Curie law. Susceptibility measurements on these same specimens and in addition 14 similar spherules from the Apollo 11 and 12 mission show a Curie-Weiss relation at temperatures less than 77 K with a Weiss temperature of 3-7 degrees in contrast to 2-3 degrees found for tektites and synthetic glasses of tektite composition. A proposed model and a theoretical expression closely predict the variation of the susceptibility of the glass spherules with temperature.

Saturation magnetization of polycrystalline iron

Abstract: The magnetic moment per gram, sigma (H sub I, T), where H sub I is the internal field and T is the temperature, was measured for a polycrystalline iron sphere with the vibrating-sample magnetometer. The instrument was calibrated by using a method utilizing the high permeability of an iron sphere. The spontaneous moment, sigma(0, T),was obtained from plots of sigma(H sub I, T) as a function of H sub I for temperatures from 4.2 K to room temperature. The value of the spontaneous moment, sigma(0, T), at 298.9 K was 217.5 + or -0.4 emu/g. The extrapolated moment, sigma(0, 0),at absolute zero from a plot of sigma(0, T) as a function of T to 3/2 power was 221.7 + or - 0.4 emu/g.

Thermodynamics of the Heisenberg ferromagnet in an applied magnetic field.

Abstract: The anisotropic-Heisenberg-ferromagnet formalism developed previously is examined to include an applied magnetic field for the isotropic case in the random-phase approximation. Thermodynamic quantities such as magnetization, susceptibility, and the derivative of magnetization with respect to temperature are studied near the Curie point.

Magnetic investigation of the effect of small additions of cobalt and manganese on the martensite reversal in an Fe-Ni alloy

Abstract: Data on the temperature and composition dependence of the magnetic moment and Curie temperature of several Fe-Ni-Co and Fe-Ni-Mn alloys have been obtained. The temperature dependence of the magnetization was obtained for each alloy from 298 to 873 K, following the magnetization change through the transformation from martensite to austenite. The effect of cobalt and manganese additions to an Fe-29.9 at. pct Ni alloy on the reverse transition temperature,A s , the Curie temperature,T c , and the saturation magnetization at absolute zero, ρso, has been determined, Values forA s , T c , and ρso were obtained by fitting a Brillouin function to the respective contributions of austenite and martensite to the total magnetization. This technique represents a very sensitive method of obtaining transition temperatures and the respective amounts of each phase present in the alloys. A theoretical prediction of ρso andT c was in agreement with the experimentally determined values.