## Weiss’s Theory of Ferromagnetism

### HYPOTHESIS:

1.                A specimen of ferromagnetic material contains a number of small regions called domains which are spontaneously magnetized. The magnitude of the spontaneous magnetization is given by the vector sum of the magnetic moments of individual domains.
2.              The spontaneous magnetization of each domain is due to the pressure of an exchange field, BE, which tends to produce a parallel alignment of the atomic dipoles.

BE  λM

Where,
λ = Weiss field constant
BE  = Weiss field
M = Spontaneous magnetization