What are permanent magnets ? Give the ways for preparing them.

Explanation

Substance which at room temperature retain their ferromagnetic property for a long period of time are called permanent magnets.
One can hold an iron rod in the north-south direction and hammer it repeatedly. (This method is shown in figure).

One can also hold a iron rod and stroke it with one end of a bar magnet a large number of times, always in the same sense to make a permanent magnet.
An efficient way to make a permanent magnet is to place a ferromagnetic rod in a solenoid and pass a current. The magnetic field of the solenoid magnetises the rod.