Computer simulation of coercivity improvement due to microstructural refinement

The effect of the presence of a non-magnetic phase at multi-junctions of Nd2Fe14B grains on the demagnetization process of Nd-Fe-B magnets was investigated by micromagnetic simulations, while varying the size of the non-magnetic phase and the Nd2Fe14B grains. While the demagnetizing field created by the non-magnetic phase assisted the nucleation of a reverse domain, its effect was only significant when its size exceeded a critical value. This critical size effect can be explained by a change in the spatial distribution of the demagnetizing field. In addition, the calculations indicated that microstructural refinement would also increase the coercivity. This increase in coercivity could also be attributed to a change in the spatial distribution of the demagnetizing field due to the presence of a non-magnetic phase. Changes in the spatial distribution of the demagnetizing field due to such a non-magnetic phase could represent a mechanism by which microstructural refinement leads to increased coercivity.