Curie-Weiss fit

Fig. II. (a) Temperature dependence of the magnetization for 200-nm thick Ga, MnrAs with x =0.053. The magnetic field is applied perpendicular to the sample surface (hard axis). The inset shows the temperature dependence of the remanent magnetization (0 T) and the magnetization at 1 T in a field parallel to the film surface, (b) Temperature dependence of the saturation magnetization determined from the data shown in (a) by using ArTott plots (closed circles). Open circles show inverse magnetic susceptibility and the Curie-Weiss fit is depicted by the solid straight line (Ohno and Matsukura 2001).

Allah and coworkers (1969, 1970) performed susceptibility and thermoelectric power measurements on (Ag, Au)Yb alloys. They found that for Au concentrations > 5 at.% a Curie-Weiss fit to the magnetic susceptibility yielded an effective moment of around 4.3 pe, as shown in fig. 11.13. For Au concentrations <5 at.% the effective moment rapidly goes to zero. For Au concentrations >30 at.% the Curie-Weiss temperature 0 is approximately constant and equal to -10 K due to CEF effects. A small composition-dependent anomaly in the Curie-Weiss temperature occurs for Au concentrations between 5 and 30 at.%... 

The DC magnetic susceptibihty of die complex measured at 1000 Oe from 1.8 to 300 K suggests diat at low temperature, a well-defined high-spin groimd state is almost exclusively thermally populated. The Curie Weiss fitting result of xmT versus T above 30 K indicates dominant antiferromagnetic interactions between spin carriers. The AC susceptibility of the complex over 1-1500 Hz from 1.8 to 3K indicates that the out-of-phase susceptibility displays frequency dependence, but none of the curves reaches a peak at 1.8 K. The DC magnetization decay method determined the effective barrier of 18.4 K and the relaxation time constant of 2 X 10 s. As Gd ion is an isotropic spin ion, the major anisotropy contribution comes from the Mn + ion, which is the most important anisotropy source of SMMs and SCMs. 

Fig. 207. CaCu(CHjC00)4-6H20 single crystal. Temperature dependence of z i, Xml- Th dahed curves illustrate the Curie-Weiss fit using...

Figure 2.21 Some magnetic properties of volborthite. Left, the Curie-Weiss fit showing = —115 K and right, the broad maximum at 20 Reprinted with permission from Hiroi et al., 2001 [50]. Copyright (2001) Physical Society of Japan...

Frequently the magnetic behavior of a paramagnetic solid does not follow the Curie law exactly but is rather better fitted by the Curie-Weiss law ... 

The above statements apply to an assembly of independent spins. Deviation from proportionality, if any is observed, suggests the presence of cooperative magnetic phenomena, i.e. ferro-, antiferro-, ferri-, meta-, micto-magnetism, and so on. The magnetic susceptibility at above the spinordering temperature (Tq) can be usually fitted by the Curie-Weiss expression (18) with the Weiss temperature 0 > 0 for the sample with dominant... 

Figure 6.40. Temperature dependence of x The line denotes the fit to the Curie-Weiss law. Reprinted with permission from Tamura et al, 2003.

Very often, experimental data are well fitted by the so called modified Curie-Weiss Law ... 

Yamada et al. [9,10] demonstrated that the copolymers were ferroelectric over a wide range of molar composition and that, at room temperature, they could be poled with an electric field much more readily than the PVF2 homopolymer. The main points highlighting the ferroelectric character of these materials can be summarized as follows (a) At a certain temperature, that depends on the copolymer composition, they present a solid-solid crystal phase transition. The crystalline lattice spacings change steeply near the transition point, (b) The relationship between the electric susceptibility e and temperature fits well the Curie-Weiss equation, (c) The remanent polarization of the poled samples reduces to zero at the transition temperature (Curie temperature, Tc). (d) The volume fraction of ferroelectric crystals is directly proportional to the remanent polarization, (e) The critical behavior for the dielectric relaxation is observed at Tc. 

From fits of the high temperature (150 K < T < 250 K) magnetic susceptibilities of RAIB14 (Tb, Dy, Ho, Er), relatively large Curie-Weiss temperatures of 0 10 K were determined by Korsukova et al. (1989). However, the existence of magnetic transitions were not reported. An anomaly is that the Tb phase is reported to have 0 = 10 K, which indicates ferromagnetic interaction. 

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