Micromagnetic study on the effect of grain size distribution in hot-deformed Nd–Fe–B magnets

Hot deformation is a potential technique to fabricate anisotropic rare earth permanent magnets required for high-performance electric motors. The magnetic properties of hot-deformed Nd–Fe–B magnets are closely related to the microstructure and can be improved by controlling microstructural factors. In this study, the effect of standard deviation of grain size distribution, a good measure of the inhomogeneity of the material, is tested via a micromagnetic simulation. In the case of the non-ferromagnetic GB phase, on increasing the standard deviation, the coercivity significantly decreases. This implies that the inhomogeneity of the grain size plays an important role in enhancing the coercivity and can be a dominant microstructural feature. The simulated results will contribute partially to the development of hot-deformed magnets, providing an insight into the relationship between the homogeneity of materials and the coercivity.