Corecivity (oc):

The value of –H which has to be applied to a magnetic material so as to reduce residual magnetism to zero.  The area of hysteresis loop is proportional to the thermal energy loss per unit volume for one hysteresis cycle of magnetization & demagnetization. Thus in order to minimize the energy losses that material must be selected which have minimum area of the hysteresis loop. e.g.  Soft iron is preferred over steel.

The hysteresis curve allows us to select suitable materials for permanent magnets.