Domain wall depinning in hard-soft composites - art. no. 140419

We study the optimization of the energy product of nanocomposites of hard m agnetic material with soft magnetic material. In bulk magnets, nucleation c enters exist on surfaces and along grain boundaries. The coercive field of the composite may not be the intrinsic coherent rotation nucleation field H -n but may be the depinning field H-d of domain walls. We study H-d as well as H-n by finite-temperature Monte Carlo simulation for a model of the com posites. The dependence of H-d On the amount of the soft phase is different from that of H-n. As the amount of the soft material is increased, the dep inning field increases, exhibits a maximum, and then decreases whereas H-n always decreases. H-d is much smaller than H-n. The optimum design paramete rs and the optimum energy product are different in the two cases.