Question

Explain the following with suitable examples:

Ferromagnetism

Answer 1

1. The substances that can be permanently magnetised even in the absence of a magnetic field are called ferromagnetic substances, and the mechanism is called ferromagnetism.
2. Some examples of ferromagnetic substances are iron, cobalt, nickel, gadolinium, and CrO­₂.
3. In solid state, the metal ions of ferromagnetic substances are grouped together into small regions called domains, and each domain acts as a tiny magnet.
4. In an unmagnetized piece of a ferromagnetic substance, the domains are randomly oriented, and so their magnetic moments get cancelled.
5. However, when the substance is placed in a magnetic field, all the domains get oriented in the direction of the magnetic field.
6. As a result, a strong magnetic effect is produced. This ordering of domains persists even after the removal of the magnetic field. Thus, the ferromagnetic substance becomes a permanent magnet.

Schematic alignment of magnetic moments in ferromagnetic substances