Paramagnetic materials

PARAMAGNETIC MATERIALS

In the case of paramagnetic materials, the spins in two opposite directions will not be equal. There exists some unpaired electrons (Fig. 1.7) which gives rise to spin magnetic moment. Hence the resultant magnetic moment will not be equal to zero.

However in the absence of external field the magnetic moments are oriented randomly. Due to its random orientation some magnetic moments get cancelled and the material possess very less magnetisation in it.

Effect of external field

When an external field is applied, the magnetic moments of individual molecules reorient itself along the direction of the magnetic field and the material is magnetised.

Properties

1. The magnetic lines of force pass through the material (Fig. 1.8)

2. Magnetic susceptibility is positive and it is given by

 χ= C / T‒θ

(also called Curie‒Weiss law)

where

C‒Curie constant

T‒ Absolute temperature

θ-Curie temperature

3. Permeability is greater than one.

4. They possess permanent dipole moment.

5. When the temperature is less than curie temperature, paramagnetic materials becomes diamagnetic material.

Examples: CuSO₄, MnSO₄, Platinum etc.