Influence of impurities on dynamic hysteresis of magnetization reversal

The effects of impurities on driving-rate-dependent energy loss in ferromagnets are investigated by analyzing several well-defined models for magnetization reversal. The random-field Ising models are analyzed using a mean-field approximation and Monte Carlo simulation. The hysteresis loop area A is found to obey a universal scaling relation with respect to the linear driving rates h of the applied field, A-A0∞hβ. The scaling exponent β is found independent of the disorder strength D. In a random-field spherical model, the energy loss increases as a power law with the driving rate A∞hβ(D). The scaling exponent β(D) increases with increasing D. These results indicate that the scaling and universality for the field-driven first-order phase transition can be understood in the framework of dynamic hysteresis.