- A property of certain metals and alloys, in which magnetic polarization occurs spontaneously. That is, the magnetic dipoles of the metal or alloy line up spontaneously due to their mutual interaction. Such materials have a very high relative permeability, which varies with the magnetizing force. Above the Curie temperature, the ferromagnetic properties of a material become paramagnetic. It is analogous to the spontaneous electric polarization occurring in ferroelectricity.