Curie–Weiss law

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

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

where $C$ is a material-specific Curie constant, $T$ is absolute temperature, measured in kelvins, and $T c$ is the Curie temperature, measured in kelvins. The law predicts a singularity in the susceptibility at $T = T c$ . Below this temperature the ferromagnet has 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 $γ$ . 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.

References

Introduction to Solid State Physics 7th ed. (1996) by Charles Kittel

Curie–Weiss law

See also

References