Question
Explain hard ferromagnetic and soft ferromagnetic materials.

Answer

In some ferromagnetic materials, the magnetisation persists even when the external field is removed. Such materials are called hard ferro magnetic materials (or hard ferro magnets.) Example : Alnico, an alloy of iron, aluminium, nickel cobalt and copper is one such material.
Naturally occurring lode stone is also one such material.
Such materials form permanent magnets to be used in other things as compass needle.
The ferromagnetic materials in which magnetisation disappears on removal of external field, are called soft ferromagnetic. Example : Soft iron.

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