Computational approach to the magnetic properties of Ga-added Nd-Fe-B sintered magnets

Abstract

As reported in several experimental studies for Nd-Fe-B magnets, adding Ga into Nd-Fe-Bmagnets increases the coercivity. Nd6Fe13Ga exists around the interface of coercivity-improved Nd-Fe-B magnets. We calculated the magnetic anisotropy K1 of Nd inNd2Fe14B/Nd6Fe13Ga grain-boundary (GB) model from first principles to understand therelationship between coercivity and the Nd6Fe13Ga existence around the interface of Nd-Fe-B magnets. We used the computational code OpenMX. From the analysis of the magneticanisotropy K1 of Nd at the interface, we find that K1 of GB model systems is much higherthan K1 of Nd which is exposed to vacuum at a surface. Especially K1 of the several GB modelsystems is comparable to that of the Nd2Fe14B bulk. This K1 improvement suggests theimportance of the Nd6Fe13Ga existence around the interface of Nd-Fe-B magnets to gethigher coercivity.