Arrott plot

Fig. 2. Arrott plots (M versus H/M) of the magnetization of UNij (Fournier )...

In the case of very weak ferromagnets, like UNi2 and UPt , the anisotropy is very small but problems are connected with M(H). There is of course no saturation of the magnetization due to the very large superimposed susceptibility in the ordered state. Spontaneous magnetization may be conveniently obtained from Arrott plots (linear versus H/M for small M values) and extrapolation to H = 0. Such results for UNi2 are shown on Fig. 2. 

Arrott plots of M r versus H/Mh t should be straight lines over a wide range of temperature not only near the Curie temperature. 

The magnetic phase diagram for the Co system is shown in fig. 25 and table 13 lists the important properties. The ferromagnetic alloys are regarded as itinerant because of the linearity of the Arrott plots over a wide range of temperature and also of the Mathon plots of M02 as a function of x (Hilscher and Kirchmayr 1975). Calculations of the density of states (Terao and Shimizu 1983) show that the itinerant-electron model gives a volume magnetostriction consistent with the experimental value (Muraoka et al. 1980, 1983). 

This system has been discussed in terms of spin fluctuations (Fluitman et al. 1973). Arrott plots suggest that ferromagntism may occur at > 76 at.% Ni (de Boer et al. 1969), but there is a lack of saturation at 4.2 K in fields up to 200 kOe. The... 

The Arrott plot analysis of the magnetic isotherms measured up to 15 T at different temperatures reveals straight lines above 3 T. They indicate a transition at... 

A magnetic study of magnetron-sputtered amorphous U27Fe73 films was performed by Freitas et al. (1988). Arrott plots indicate magnetic ordering below 32 K. The freezing phenomena found at low temperatures were interpreted in terms of random-anisotropy ferromagnetism. 

Fig. 116. Arrott plots of the Sc(Feo,5Si(,2s)2 compound. Inset the low-temperature magnetisation in an M vs. representation. The spin wave stiflhess (hus obtained is 66meVA (Kotur et aL 1998).

Finally, the spin-glass sample a-GdAl (fig. 107c) clearly exhibits no spontaneous magnetization, a small value for the initial susceptibility ( g = 13.7), and the curvature remains positive for all measmed temperatures in the Arrott plot. Thus, the spin glass a-GdAl shows many similarities to the speromagnet a-DyCu. 

From eq. (14.23) one obtains a quadratic temperature dependence of the reciprocal susceptibility and a linear dependence of versus HIM over a large temperature region (so-called Arrott plots). Mathon discussed the concentration dependence of Af(0,0), Tc and yo by using the Landau theory for weak ferromagnets in the critical region. There exists a close analogy between what happens for a fixed concentration when the temperature is varied and what happens for a fixed temperature when the concentration is varied A T, x) =... 

Fig. 14.118. Composition dependence of the Curie temperature of La(Co, Cu) . The open circles refer to permeability measurements, while the black dots refer to magnetization measurements (Arrott plots). (Brouha and Buschow, 1975b),...

Arrott plots (M H/M) are more or less straight lines ... 

A non-linear Arrott plot is a characteristic of all nearly ferromagnetic and weak ferromagnetic Y(Coi tAl c)2 compounds (Sakakibara et al. 1986 and Due et al. 1993a see fig. 22). This behaviour exists up to r 80K. At higher temperatures, the Arrott plots become almost linear. As already mentioned in sect. 2.1.1, in the case of the unusual Arrott plot, the description of the magnetization curves needs the higher power terms in the equation of state ... 

Figure 2. The Arrott plots of versus HIM for the sample Lao.yPbo.BMnOa.

Experimentally, to obtain these parameters, we followed the modified Arrott plots [18], Firstly, Ms(r,0) and Xo iT) data were determined by plotting versus from trial... 

With the critical parameters of Tc, P and y, we have performed the scaling plots of ln(M/ versus ln(77/ for the samples at temperatures around their phase transition Tc-The results of this performance reveal that the M-H data fall on two branches, one for temperatures TTc, as can be seen in Figure 5. This is in good agreement with the descriptions of Eq. (6) as detailed above, revealing the reliability of the critical parameters obtained in our case when using the modified Arrott plots. The successful determination of the critical parameters based on the critical equations, i.e., Eqs. (3-5), proves an existence of the second-order phase transition in our samples of Lai. Pb rMnOs (x = 0.1-0.3), in accordance with the preliminary judgment based on the Banerjee criterion. 

Koh] Magnetization isotherms, modified Arrott plots, the method of Kouvel and Fisher, scaling plots and ln(7) versus In (>F/o) plots Magnetic phase transition... 

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