Curie-Weiss expression

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... 

This is the Curie law (Pierre, not Marie), C being a constant for a given sample. Better agreement with experimental data is obtained with the modified Curie-Weiss expression ... 

The sum runs over an infinite amount of terms, of which only a limited number can be calculated due to the rapidly increasing computational demand. However, a sufficiently high order of the series is a requirement in order to describe the susceptibility in proximity to a critical temperature and determine the exchange parameters. If the series is cut short to zeroth order, a Curie expression follows for the susceptibility if the series is developed to first order, the Curie-Weiss law follows. Thus, both Curie and Curie-Weiss expressions can be regarded as development stages in the high-temperature expansion, which also implies that these expressions should be valid only for high temperatures. 

If a solution of UCI4 in anhydrous formic acid is reduced with Zn/Hg crystals of U(III) formate separate. They are rhombohedral, belonging to the space group R3m, like Gd formate. Their magnetic susceptibility follows the Curie-Weiss expression in the temperature interval 50-250 K. The data yield fietr of 3.70 (xb (79, 80). It is antiferro-magnetic below 12 K. 

ORD measurement, deg cm /dmol temperature (c.g., in Curie—Weiss expressions) metric ton triplet (spectra) triton... 

It should be noticed that the contribution of the core regitm to the magnetic susceptibility reduced to the Curie-Weiss expression only in the paramagnetic regime. On the other hand, the absence of spin correlations evidenced by the Curie law implies that, at any temperature, including below the Neel temperature Tf ... 

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