Explain briefly domain theory to explain ferromagnetism.

Explanation

Domains are the small region in which the magnetic dipole moments are oriented in the same direction.

In the absence of external magnetic field, the magnetic dipole moments in small domains are oriented in different directions so that the net dipole moment is zero. When external magnetic field is applied, the magnetic dipole moments align themselves in the direction of applied field. Therefore ferromagnetic materials gets magnetised in the direction of applied magnetic field.