Explain hard ferromagnetic and soft ferromagnetic materials.

Explanation

Hard ferromagnetic material : In some ferromagnetic materials, the magnetisation persists on removal of external magnetic field. Such material are called hard magnetic materials.
Alnico, an alloy of iron, aluminium, nickel, cobalt and copper is one such material. The naturally occurring lodestone is also ferromagnetic material. Its relative permeability is `lt 1000.`
Such material forms permanent magnet to be used among other thing as a compass needle.
Soft magnetic materials : There are some ferromagnetic material in which the magnetisation disappears on removal of external magnetic field. These material are called soft magnetic materials.
These materials are used in electric bell, crane, transformers etc.