Distinguish between ferromagnetic and paramagnetic materials, mentioning at least one example of each.

Ferromagnetic Materials: These are materials wherein magnetic dipoles interact in a manner which they aim to line up in parallel. Ferromagnetic substances have a number of domains or regions that are spontaneously magnetized. This direction of magnetization varies by domain to domain. And the resultant magnetization is zero or may nearly zero. The relative permeability is extremely high. Presence of external magnetic field, the ferromagnetic materials find strongly magnetised and exhibit hysterisis loop. The susceptibility of these is specified by

 χ = C / T - T_C , here C is curie constant, T_C is the curie temperature above that the ferromagnetic material exhibits paramagnetic behaviour. The ferromagnetic materials are broadly used in industries. Examples are: Iron, nickel and cobalt.

Paramagnetic Materials: The atoms of these materials have permanent magnetic dipoles. Individual dipoles are oriented in random fashion therefore resultant magnetic field is negligible or zero. For these materials relative permeability is slightly greater than unity and this is independent of magnetizing force. In presence of external magnetic field, paramagnetic materials find weakly magnetised into the field direction and the susceptibility is specified by

 χ = C /T , here C is a curie constant and T is the temperature. Examples are: Chromium chloride, manganese sulphate, chromium oxide and air.