Engineering Physics

7.6 Theory of paramagnetism

The atoms of paramagnetic material possess permanent magnetic moment. In the absence of an applied external magnetic field, the magnetic dipoles of paramagnetic atoms are oriented in random directions, so that there is no resultant magnetism of the material. By applying an external magnetic field on a paramagnetic material, the dipoles are rotated by different extents proportional to the strength of field in the direction of the applied magnetic field, so that the material acquires magnetism.

To calculate magnetic susceptibility, we consider N number of magnetic dipoles per unit volume of material of which N_p dipoles are parallel to the applied field and N_a dipoles are anti-parallel when a magnetic field H applied ...