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Showing papers on "Curie–Weiss law published in 1981"



Journal ArticleDOI
TL;DR: The magnetic susceptibility of RB2C2 has been measured in the temperature range of 3-300 K and Curie-Weiss fits to the susceptibilities led to effective moments in agreement with those expected for R3+ ions as mentioned in this paper.

58 citations


Journal ArticleDOI
TL;DR: In this article, measurements of the magnetization, magnetic susceptibility and NMR have been made for (Co 1- x Mn x ) 2 P single crystal compounds, and the magnetocrystalline anisotropy constants are both negative and their absolute values take maxima at x = 0.5.
Abstract: Measurements of the magnetization, magnetic susceptibility and NMR have been made for (Co 1- x Mn x ) 2 P single crystal compounds. The compounds with orthorhombic structure are ferromagnetic for 0.06< x <0.63, ferromagnetic at high temperatures and screw antiferromagnetic at low temperatures for 0.63 ≤ x ≤0.73 and antiferromagnetic for 0.73 ≤ x ≤0.80. The magnetic moments of Mn I and Mn II are expected to have about 1 and 3 µ B , respectively, from the measurement of NMR. The magnetocrystalline anisotropy constants K 1 and K 2 are both negative and their absolute values take maxima at x =0.5. The Curie temperatures and saturation magnetic moments for x ≤0.5 compounds are briefly discussed with the exchange interaction and the local environment of Mn II site.

53 citations



Journal ArticleDOI
TL;DR: Magnetic properties of recently prepared spherical hematite (α•Fe2O3) particles of narrow size distributions with average diameters (d) varying between 20 and 300 nm are reported in this article.
Abstract: Magnetic properties are reported of recently prepared spherical hematite (α‐Fe2O3) particles of narrow size distributions with average diameters (d) varying between 20 and 300 nm. Mass magnetization (σ) of these particles has been determined as a function of temperature (T) up to 1000 K and of magnetic field (H) as high as 22 kOe. Specifically, magnetic behavior of α‐Fe2O3 particles of d = 300 nm is described in detail. Their Curie (Neel) temperature has been determined to be 960 K. The Bean‐Livingston plot indicates a change in magnetic anisotropy from higher symmetry at room temperatures to unidirectional behavior at elevated temperatures. This observation is consistent with the change of saturation and remanent magnetization with T. The measurements of σ on different size particles indicate that below 100 nm the particle magnetic susceptibility increases with decreasing size.

51 citations


Journal ArticleDOI
TL;DR: The effect of structure on the magnetic properties of amorphous alloys is discussed in this article, with emphasis on the effect of fluctuations in the local atomic structure, and the role of structural defects on the last three properties is also discussed.
Abstract: The effect of structure on the magnetic properties of amorphous alloys is discussed, with emphasis on the effect of fluctuations in the local atomic structure. It is pointed out that the structural fluctuations are best described by the internal stresses of long, medium or atomic range, and some of the magnetic properties are discussed in terms of these stresses. The properties discussed include the Curie temperature, saturation magnetization, magnetostriction, spin wave stiffness, paramagnetic susceptibility, changes in the Curie temperature, induced anisotropy and magnetic after-effect. The role of the structural defects on the last three is also discussed.

48 citations


Journal ArticleDOI
TL;DR: In this paper, the results of neutron paramagnetic scattering measurements obtained between 300 K and 870 K on CeFe2 were reported, and strong ferromagnetic correlations were found to persist up to the highest temperature used in this study.
Abstract: Below 230 K CeFe2 orders with a saturation magnetic moment of 1.15 μB/Fe at 4.2 K. The paramagnetic effective moment deduced from the Curie‐Weiss law is 3.7 μB. Reported here are the results of neutron paramagnetic scattering measurements obtained between 300 K and 870 K on CeFe2. The technique of polarization analysis has been used to obtain a unique measurement of the magnetic cross‐section. The Fe moment determined in this way is about 1 μB, close to that observed in the ferromagnetic state. However, strong ferromagnetic correlations are found to persist up to the highest temperature used in this study, i.e., 870 K. The results are in complete agreement with recent theories which tend to reconcile 3d band magnetism with the persistence of a moment in the paramagnetic state. In conclusion, effective moments derived from susceptibility measurements do not allow an understanding of the 3d magnetism in the paramagnetic state.

47 citations



Journal ArticleDOI
TL;DR: In this article, the authors proposed a magnetic phase diagram in which, for x < 0.91, long-range magnetic order undergoes a transition to a cluster-glass state.
Abstract: Magnetic susceptibility and Mossbauer measurements are reported for amorphous (Fe1-xNix)77Si10B13 in a Ni concentration range 0.85

37 citations


Journal ArticleDOI
Masao Shimizu1
TL;DR: In this article, the effects of spin fluctuations on the paramagnetic spin susceptibility, magnetization and specific heat are calculated in gaussian statistics as a power series of k B T, and the results are applied to nickel and iron.

35 citations



Journal ArticleDOI
TL;DR: The anomalous Hall effect (AHE) as mentioned in this paper measures the magnetic properties of thin Pd films with Fe surface impurities and is sufficiently sensitive to investigate Fe coverages down to 0.01 atomic layers (atola).
Abstract: The magnetic properties of thin Pd films with Fe surface impurities are investigated by means of the anomalous Hall effect (AHE). The AHE measures the $z$ component (perpendicular to the surface) of the magnetization and is sufficiently sensitive to investigate Fe coverages down to 0.01 atomic layers (atola). The magnetization varies strongly nonlinearly with magnetic field. For small Fe coverages, in the range from 0.01 to 0.1 atola the susceptibility is temperature independent. The author concludes that the Fe has lost its moment and represents a local spin-fluctuating system. For Fe coverages above 0.5 atola the magnetization shows a hysteresis which disappears with increasing temperature. In this range of coverage the Fe atoms possess a magnetic moment. The moments prefer the orientation perpendicular to the film and form an Ising ferromagnet. In the intermediate range around 0.3-atola Fe the susceptibility follows a Curie law. The large value of the susceptibility either requires the existence of super large moments of about $100{\ensuremath{\mu}}_{B}$ or is due to an indirect exchange enhancement of the magnetic field. Covering the dilute Fe-surface atoms with a few layers of Pd changes the magnetic behavior of the Fe completely. The magnetization follows a Brillouin function with $S=8$ and $g=2$ and describes the magnetization of free giant moments.

Journal ArticleDOI
TL;DR: In this article, the authors measured the heat capacity of the weak itinerant electron ferromagnet Sc 3 In in magnetic fields up to ∼ 10 T and showed that it is completely quenched at 12 T. This depression of the spin fluctuation contibution to heat capacity occurs at lower magnetic fields than had been considered possible heretofore.

Journal ArticleDOI
TL;DR: In this article, magnetic measurements performed on the amorphous Fe10Ni70B19Si1 alloy in the critical region (145-210 K) in fields up to 10 kOe reveal that this alloy exhibits a well-defined magnetic phase transition at 186.5±0.3 K with the critical exponents β=0.42± 0.02, γ=1.35± 0.04 and δ=4.49±0.
Abstract: Magnetic measurements performed on the amorphous Fe10Ni70B19Si1 alloy in the critical region (145–210 K) in fields up to 10 kOe reveal that this alloy exhibits a well-defined magnetic phase transition at 186.5±0.3 K with the critical exponents β=0.42±0.02, γ=1.35±0.04 and δ=4.49±0.05 satisfying an equality relation resulting from the static scaling hypothesis and with the reduced magnetization and field following a magnetic equation of state derived for the second-order phase transition over a wide temperature range. A reasonably good agreement between the present exponent values and those derived from the theories based on the Heisenberg spin model has been observed. Long range forces (such as dipole forces) are shown to have negligible influence on the critical fluctuations of magnetization. A detailed analysis of the magnetization versus field isotherms taken above the Curie temperature demonstrates the existence of giant super-paramagnetic clusters.

Journal ArticleDOI
TL;DR: In this paper, the magnetization for H ⊥ c (c; the c-axis) shows a field-induced phase transition from a small magnetic moment state ( ∼ 0.6μ B ) at lower fields to a larger moment one ( 2.2 - 2.5μ B ), above 25kG.

Journal ArticleDOI
TL;DR: The local magnetic moment at the Curie temperature in the 35 at% Ni-Fe alloy retains still a half value of the magnetic moments at 0 K as discussed by the authors, and new formulas are proposed, which describe reasonably the phenomena of spontaneous volume magnetostriction and forced volume magnetstriction.
Abstract: The local magnetic moment at the Curie temperature in the 35 at% Ni-Fe alloy retains still a half value of the magnetic moment at 0 K. Taking into consideration this fact, new formulas are proposed, which describe reasonably the phenomena of spontaneous volume magnetostriction and forced volume magnetostriction. The magnetovolume coupling constant determined by the new formulas is approximately 1.2 ×10 -8 cm 6 /emu 2 for Fe-Ni Invar alloys, which is independent of the Ni concentration.

Journal ArticleDOI
TL;DR: In this article, the first synthetized MnSiTe3 has been grown by the vapor phase transport and X-ray studies show that the crystal structure is hexagonal with a=7.02 A and c=14.26 A.


Journal ArticleDOI
TL;DR: In this article, the authors measured the low field magnetic susceptibility and the high field magnetic moment of D-Er2Si2O7 at low temperatures by an inductance method and showed that it undergoes a transition from a paramagnetic to an antiferromagnetic ordered state at TN=1.9 +-0.1 K.
Abstract: The low field magnetic susceptibility and the high field magnetic moment of D-Er2Si2O7 at low temperatures are measured by an inductance method. The susceptibility results show that D-Er2Si2O7 undergoes a transition from a paramagnetic to an antiferromagnetically ordered state at TN=1.9 +-0.1 K. The magnetic moment data is analysed on the basis of a four-sublattice antiferromagnetic spin model. The g-values obtained from magnetic susceptibility and moment experiments are compared with those of optical measurements.

Journal ArticleDOI
TL;DR: In this article, the magnetic susceptibility χ a in the two-dimensional ferromagnet K 2 CuF 4 has been measured near T c =6.25 K with the magnetic field H applied in the direction parallel to the a -axis in the easy plane.
Abstract: The magnetic susceptibility χ a in the two-dimensional ferromagnet K 2 CuF 4 has been measured near T c =6.25 K with the magnetic field H applied in the direction parallel to the a -axis in the easy plane. The field and temperature dependences of χ a are determined and the static scaling hypothesis is examined. Above T c , it is found that χ a is described by a scaling function, χ∼ H - λ Ψ( H / t 1/ µ ), where t =| T / T c -1|, λ=0.82 ±0.05 and µ=0.83 ±0.05. The critical exponents of magnetization and susceptibility, β and γ, are estimated as β=0.22 ±0.05 and γ=0.99 ±0.05 from the relations β=(1 -λ)/µ and γ=λ/µ. The susceptibility χ a has a broad peak in an external magnetic field above T c which shifts to higher temperatures as the mannetic field increases. This broad peak corresponds to the appearance of the magnetic-field-induced ferromagnetic state.

Journal ArticleDOI
TL;DR: In this paper, the anomalous behavior of the heat of transition for compositions near the morphotropic boundary is discussed on the basis of an extended phenomenological theory for the PbZrO3:PbTiO3 system.
Abstract: The perovskite structure solid solutions between antiferroelectric PbZrO3 and ferroelectric PbTiO3 embrace a number of technologically important piezoelectric compositions grouped near the morphotropic phase boundary (composition close to Zr:Ti ratio 1:1). Heats of transition Q(J/m3) and ferroelectric transition temperature Tc(K) for a series of carefully prepared (chemically coprecipitated) composition in the Pb(ZrxTi1-x)O3 solid solution system in the range 0.0 < x ≤ 0.6 were measured using a Perkin Elmer DSC2 thermal analyser under computer control. The composition dependence of the transition entropy S(J/m3/deg) and the Curie Weiss constant were deduced from a combination of calorimetric and phenomenological data. The anomalous behaviour of the heat of transition for compositions near the morphotropic boundary is discussed on the basis of an extended phenomenological theory for the PbZrO3:PbTiO3 system(1).

Journal ArticleDOI
TL;DR: In this article, the upper critical magnetic field (H c2 ) of the pseudoternary system La 1.2−x Eu x Mo 6 S 8 was measured at temperatures above 1.5 K. The results were attributed to an increase of the orbital critical field with increasing x, compensation of the applied magnetic field by a negative exchange field due to an antiferromagnetic exchange interaction between the conduction electron spins and the Eu magnetic moments, and exchange scattering of conduction electrons by the rare earth magnetic moments.


Journal ArticleDOI
E. Uhl1
TL;DR: In this paper, new quarternary Heusler alloys of composition (Cu 1− x Co x ) 2 MnSn (x = 0−1) were prepared with the cubic L2 1 structure.

Journal ArticleDOI
TL;DR: An analogue of the Curie-Weiss model ferromagnet is introduced in this article, which is based on a two sublattice description in which spins of spins of the spins of...
Abstract: An analogue, for ferrimagnetism, of the Curie–Weiss model ferromagnet is introduced. The resulting structure, the Curie–Weiss–Neel model, is based on a two sublattice description in which spins of ...

Journal ArticleDOI
TL;DR: In this paper, the magnetic susceptibility of Cd 1-x Mn x Te and cd 1 -x Mn X Se was measured as a function of magnetic field, temperature, and concentration.

Journal ArticleDOI
Fumihisa Ono1
TL;DR: In this article, a detailed comparison of the thermal expansion coefficient in Fe-Ni Invar alloys with the results of magnetization measurements has been made in a wide temperature range both below and above the Curie temperatures.
Abstract: A detailed comparison of the thermal expansion coefficient in Fe-Ni Invar alloys with the results of magnetization measurements has been made in a wide temperature range both below and above the Curie temperatures. A new method of determining the lattice term from the observed thermal expansion coefficient has been proposed and applied to the estimation of the magnetic contribution to the thermal expansion coefficient. It has been found that the magnetic contribution below the Curie temperature is well expressed with the factor M d M /d T and that it is proportional to dχ -1 /d T above the Curie temperature. These results can well be explained by the spin fluctuation theory developed by Moriya and Usami.

Journal ArticleDOI
Abstract: 2014 We have shown that the VPt3 (V0.25Pt0.75) alloy becomes ferromagnetic in each of both atomically ordered states with Cu3Au and TiAl3 crystalline structure, respectively. The atomically disordered VPt3 alloy (with a Cu like fcc structure), remains paramagnetic over the whole temperature range 4.2 K to 1 100 K. By means of remanent magnetization measurements, we found the ferromagnetic Curie points Tc ~ 240 K for VPt3 ordered in the Cu3Au like structure (VPt3 (1) sample) and Tc ~ 210 K for VPt3 ordered in the TiAl3 structure (VPt3 (2) sample). Magnetization measurements performed at low temperatures (4.2 K to 160 K) and in moderate fields (0 ~ H ~ 20 kOe) showed that both VPt3 (1) and (2) samples behave as classical ferromagnets. The high field (0 H ~ 150 kOe) magnetization measurements performed on both VPt3 (1) and (2) samples at 4.2 K, allowed an accurate determination of the saturation magnetization 03C3s (4.2 K) and of the high field ~H (4.2 K) susceptibility. The order of magnitude of the ~H susceptibility (at 4.2 K, ~H ~ 1 x 10-6 emu . g-1. Oe-1) is consistent with band paramagnetism of transition metals. Both VPt3 (1) and (2) may be considered as weak ferromagnets, in view of their small ferromagnetic moment (03BC0 ~ 0.1 03BCB per V atom-gram). The paramagnetic behaviour of VPt3 (1) and (2) above their respective Curie points, is well described by a Curie-Weiss law yielding small paramagnetic moment values (03BC’ ~ 0.7 03BCB per V atom-gram). In spite of all experimental results obtained in this work, we could not settle with certainty whether the ferromagnetic behaviour of both ordered VPt3 alloys has to be interpreted in a localized model of ferromagnetism rather than in an itinerant one. Nevertheless, we have interpreted the ferromagnetic behaviour of VPt3 (1) and (2) within a model of localized ferromagnetism : the ferromagnetism in VPt3 (1) and (2) is tentatively ascribed to a mechanism of indirect exchange interaction between the V moments through the conduction electrons of the Pt atoms. In this mechanism, the Pt electrons acquire a magnetic polarization antiparallel to the V moments. J. Physique 42 (1981) 1157-1166 AOÛT 1981,

Journal ArticleDOI
TL;DR: In this paper, amorphous alloys having the composition (Fe 1- x Mn x ) 80 B 20 (0 ≤ x ≤ 0.25) have been studied by Mossbauer spectroscopy and magnetization measurements.
Abstract: Amorphous alloys having the composition (Fe 1- x Mn x ) 80 B 20 (0 ≤ x ≤0.25) have been studied by Mossbauer spectroscopy and magnetization measurements. All the samples show ferromagnetic behaviors. The saturation magnetization at 0 K, the Curie temperature T C and the average hyperfine field decrease monotonically from 197 emu/g, 680 K and 286 kOe in x =0 to 107 emu/g, 383 K and 178 kOe in x =0.25. The concentration dependence of T C gives a conclusion for the exchange interaction that J Fe-Mn and J Mn-Mn are relatively small positive and negative values, respectively, compared with J Fe-Fe . The magnetic moments of the Fe and Mn atoms are discussed in connection with the exchange interaction.

Journal ArticleDOI
TL;DR: In this article, the demagnetizing field is calculated taking into account the effects of anisotropy and magnetization of iron whiskers, and the temperature range covered is from room temperature to within 0.5 deg of the Curie temperature.
Abstract: The temperature dependences of anisotropy and magnetization of iron are extracted from measurements of the field dependence of the ac susceptibility in [111] and [100] oriented iron whiskers. To do this the demagnetizing field is calculated taking into account the effects of anisotropy. The temperature range covered is from room temperature to within 0.5 deg of the Curie temperature.