What are permanent magnets? What is an efficient way of preparing a permanent magnet?

Permanent Magnets:The magnets prepared from ferromagnetic materials which retain their magnetic properties for a long time are called permanent magnets. 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. 

The materials used for permanent magnet must have the following characteristic properties : 

(i) High retentivity so that the magnet may cause strong magnetic field. 

(ii) High coercivity so that the magnetisation is not wiped out by strong external fields, mechanical ill-treatment and temperature changes. The loss due to hysteresis is immaterial because the magnet in this case is never put to cyclic changes.

Permanent Magnets: The magnets prepared from ferromagnetic materials which retain their magnetic properties for a long time are called permanent magnets. 

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. The materials used for permanent magnet must have the following characteristic properties: 

(i) High retentivity so that the magnet may cause strong magnetic field. 

(ii) High coercivity so that the magnetisation is not wiped out by strong external fields, mechanical ill-treatment and temperature changes. The loss due to hysteresis is immaterial because the magnet in this case is never put to cyclic changes.