Curie-Weiss law

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The Curie-Weiss law describes the magnetic susceptibility of a ferromagnet in the paramagnetic region above the Curie point:

$\chi = \frac{C}{T - T_{c}}$

where

χ

is the magnetic susceptibility

C is a material-specific Curie constant

T is absolute temperature, measured in kelvins

T_c is the Curie temperature, measured in kelvins

The susceptibility has a singularity at T = T_c. At this temperature and below there exists a spontaneous magnetization.

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

$\chi \sim \frac{1}{(T - T_{c})^\gamma}$

with the critical exponent $\gamma\,$ . However, at temperatures $T \gg T_c$ the expression of the Curie-Weiss law still holds, but with $T_c\,$ representing a temperature which is somewhat higher than the actual Curie temperature.