Question

Explain ferromagnetism on the basis of domain theory.

Answer 1

Hint: There are different kinds of magnetic materials such as paramagnetic, diamagnetic and ferromagnetic. Paramagnetic materials and diamagnetic materials have temporary magnetic properties while ferromagnetic materials have permanent magnetic properties which can be explained on the basis of domain theory.

Complete step by step answer:
The domain theory was proposed by Weiss in 1907. According to this theory, ferromagnetic material consists of a large number of tiny regions, and each region gets spontaneously magnetized to saturation. The domains are free to move among those tiny regions. The spin magnetic moments of all the atoms in a domain are oriented in a particular direction. These domains are prone to the influence of external magnetic fields. Initially the direction of these domains is such that they are randomly oriented and the magnetization due to these cancel out each other, so that the resultant magnetization of the material is zero in the absence of an external magnetic field. Thus, we get weak magnetization.
But in the presence of a strong magnetic field, these domains get aligned in one particular direction and as a result strong magnetization gets produced.

Note:
In case of ferromagnetic materials, after all the domain gets aligned in one particular direction and the external field is removed, the domain boundaries do not change their orientation. Thus, the ferromagnetic materials do not get demagnetized and that’s why they are used widely to make permanent magnets. Ferromagnetic materials get strongly attracted towards the external field.