Magnetization in a multidomain crystal

after the material has been magnetically saturated to the value Bs, the field is reduced to zero, the magnetization vectors rotate out of line with the field towards the nearest preferred direction which is determined in part by magnetocrystalline anisotropy. The magnetization is thus prevented from complete relaxation to the virgin curve and hence, for zero field, there is a remanent induction Bx. In order to reduce the induction to zero a reverse field II,. has to be applied. The coercive field or coercivity II,. depends in part on crystalline anisotropy, as might be expected. 

Because of hysteresis, energy is dissipated as heat in a magnetic material as it is taken round a complete B-H loop, and the hysteresis energy loss Wh per unit volume of material is 

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