Curie Temperature - Curie-Weiss Law

Curie-Weiss Law

A simple theory predicts that, above the Curie temperature, the magnetic susceptibility, χ, is given by the Curie-Weiss law:

where C is a material-specific Curie constant, T is absolute temperature and T_c is the Curie temperature, both measured in kelvin. Thus, the susceptibility approaches infinity as the temperature approaches T_c.

In many materials the Curie-Weiss law fails to describe the susceptibility in the immediate vicinity of the Curie point, since it is based on a mean-field approximation. Instead, there is a critical behavior of the form

with the critical exponent γ. However, at temperatures T >> T_c the expression of the Curie-Weiss law still holds, but with T_c replaced by a temperature Θ that is somewhat higher than the actual Curie temperature. Some authors call Θ the Weiss constant to distinguish it from the temperature of the actual Curie point.