Diamagnetic material

DIAMAGNETIC MATERIAL

In a diamagnetic material, the electron orbits are more or less random, and mostly all the magnetic moments are cancelled. Similarly all the spin moments are almost paired i.e., they have even number of electrons and has equal number of electrons spinning in two opposite directions as shown in Fig. 1.5. Hence the net magnetic moment in the diamagnetic material is zero. Therefore most of these materials do not have magnetism in the absence of magnetic field.

Effect of external field

When an external magnetic field is applied, the electrons reorient in such a way that they align perpendicular to the field direction and their magnetic moments opposes the external magnetic field. This will reduce the magnetic induction present in the specimen.

Properties

1. They repel the magnetic lines of force (Fig. 1.6)

2. Susceptibility is negative and it is independent of temperature and applied magnetic field strength.

3. Permeability is less than 1.

4. There is no permanent dipole moment, so they are called weak magnets.

5. When temperature is less than critical temperature diamagnetics become normal material.

Examples. Gold, Germanium, Silicon etc.