Curie-Weiss plot

The magnetic susceptibility versus temperature behavior is typically interpreted using three types of plots. One is the so-called Curie-Weiss plot of 1/x versus T (Fig. 2). The Brillouin form of magnetization given earlier reduces to a simple form when H T in energy terms the Curie law (Equation (3)), in... 

The Weiss constant applies a minor perturbation of the Curie Law a small FM exchange yields 6 > 0 K and an AFM exchange yields 9 < 0 K. In a Curie-Weiss plot, a negative x-intercept means AFM interactions are present, and a positive x-intercept means FM interactions. For large enough 9, these plots deviate from linearity at lower temperatures (upward for 9 < 0, downward for 9 > 0). It is best not to overinterpret small Weiss constants where 9 < 0.5 K or so, save to note that they imply nearly isolated paramagnetic behavior. From mean-field theory, one can approximate 9 = 2z JMF/k,46 where is an... 

Fig. 3. Curie-Weiss plot for AgjF8 Q.5 kG , 40 kG (Reprinted with permission from J. Am. Chem. Soc.. 113, May 1991, pp. 4192-4198. Copyright 1991 American Chemical Society.)...

Figure 2. Magnetic susceptibiiity of SrjCrNbOssj as a function of temperature. Inset - inverse susceptibility as a function of temperature along with the Curie-Weiss plots.

If a straight line is not obtained from the Curie-Weiss plot, then it is clear that more detailed theory is necessary for data analysis, and the Van Vleck equation or other more sophisticated theory must be used. 

Figure 5. Magnetic susceptibiliiy data ai two fields (A 5 kg, 40 kg) as a function of temperature (K) for (a) F-NiFs, (b) //-NiFs, and (c) F-Nip3 (a Curie-Weiss plot).

Fignre 2. Curie—Weiss plot of the magnetic susceptibility of Ag(Bip6)2. 

The values of and 0 are usually determined graphically from the straight line which fits best to the experimental l/xj data plotted versus temperature (Curie-Weiss plot). In addition, the term Net may be incorporated into Eq. (28), its numerical value being calculated on the basis of crystal field theory [89,96]. There are also methods available to determine No. empirically in the same procedure which results in values of and 0p [93,108],... 

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