→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.