Distinguish between ferromagnetic and diamagnetic 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.

Diamagnetic Materials: These are the materials whose atoms do not carry permanent magnetic dipoles. When an external magnetic field is applied to a diamagnetic material, this induces a magnetization into the direction reverse to the applied field intensity. For such materials the relative permeability is negative. These are hardly utilized as magnetic material in electrical/electronic engineering applications. Examples are: Aluminium oxide, copper, barium chloride and gold.