In ferromagnetic materials when magnetic field intensity H is increased and then decreased to its original value the magnetization I does not return to its original value. This phenomenon is known as hysteresis.

Unlike ferromagnetic materials paramagnetic and diamagnetic materials have no residual magnetization after the external magnetic field is removed. And hence they have very less retentivity.

Also, loss of dissipation of energy is more in case of para and diamagnetic materials.

Therefore, paramagnetic and diamagnetic materials do not form hysteresis loops.