Curie-Weiss law

The Curie-Weiss law will apply only when the temperature is well above the Curie temperature.

While some substances obey the Curie law, others obey the Curie-Weiss law.

Both Curie's Law and the Curie-Weiss law fail as the temperature approaches 0K.

For other substances μ is temperature dependent, but the dependence is small if the Curie-Weiss law holds and the Curie temperature is low.

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.

Materials that are called 'paramagnets' are most often those that exhibit, at least over an appreciable temperature range, magnetic susceptibilities that adhere to the Curie or Curie-Weiss laws.

The word paramagnet now merely refers to the linear response of the system to an applied field, the temperature dependence of which requires an amended version of Curie's law, known as the Curie-Weiss law:

Some are paramagnetic down to absolute zero and their susceptibility is inversely proportional to the temperature (see Curie's law); others are magnetically ordered below a critical temperature and the susceptibility increases as it approaches that temperature (see Curie-Weiss law).

Magnetization data for an isolated LaC isomer were obtained using a SQUID magnetometer at temperatures ranging from 3 to 300 K. For LaC the inverse susceptibility as a function of temperature was observed to follow a Curie-Weiss law.