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

摘要

The coercivity (H (c)) 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 H (c) with grain boundary (GB) model reproduces the available experiment nicely. The H (c) of direct contact (DC) model increase with the decreasing grain size (S (G)). This fact suggests that the H (c) of Nd-Fe-B magnets can be further increased by grain refinement even though the average S (G) down to several tens of nanometers. The difference of coercivity mechanism between GB-model and DC-model was understood by magnetization reversal analysis.