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

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.

Automated summary

The simulation results using multi-grain models and hybrid Monte Carlo method demonstrate that the coercivity of nanocrystalline Nd-Fe-B magnets can be further increased by grain refinement. This finding is supported by the experimental validation of the grain size dependence of coercivity. The difference in coercivity mechanism between grain boundary model and direct contact model was understood through magnetization reversal analysis.