Grain-size effect on coercivity of Nd–Fe–B nanomagnets: micromagnetics simulation based on a multi-grain model

The coercivity (Hc) of nanocrystalline Nd–Fe–B magnet was simulated by multi-grain models in combination with hybrid Monte Carlo method. The simulated grain size dependence of Hc with grain boundary (GB) model reproduces the available experiment nicely. The Hc of direct contact (DC) model increase with the decreasing grain size (SG). This fact suggests that the Hc of Nd–Fe–B magnets can be further increased by grain refinement even though the average SG down to several tens of nanometers. The difference of coercivity mechanism between GB-model and DC-model was understood by magnetization reversal analysis.