Ferromagnetism decreases with rise in temperature
Ferromagnetic substances are strongly attracted by a magnet, show all properties of a
paramagnetic substance to a much higher degree. While paramagnetic substances are
feebly attracted by a magnet. When ferromagnetic substance is heated, then at a definite temperature the ferromagnetic property of the substance suddenly disappears and the substance becomes paramagnetic. The temperature above which a ferromagnetic substance becomes paramagnetic is called the curie temperature (point) of the substance.
The susceptibility of a paramagnetic substance varies inversely as the Kelvin
temperature of the substance, that is
$\chi_{m} \,\propto \frac{1}{T}$
This is known as Curie’s law.