First-principles study on the role of Nd6Fe13Ga in Nd-Fe-B magnets

Abstract

We study the magnetic anisotropy around the interface of Ga-added Nd-Fe-B magnets by first-principles calculations. In general, the subphases of Nd-Fe-B magnets are amorphous or other complicated crystal structures which have not been identified yet. On the other hand, the existence of crystalline Nd6Fe13Ga with tetragonal structure around the main grains of Nd-Fe-B magnets is confirmed in the case of Ga-added Nd-Fe-B magnets. Nevertheless, the relationship between Nd6Fe13Ga existence around the main grains and the coercivity improvement still remains an open question. In order to clarify the magnetic structures around the interface of Ga-added Nd-Fe-B magnets, we performed first-principles calculations for Nd2Fe14B/ Nd6Fe13Ga grain-boundary model structures using the computational code OpenMX. From our analysis, we find that the crystal structures around the interface become complicated after structural optimization. When we see the charge distribution of Nd at the interface, we find that the charge distribution of Nd 5d electrons tends to stretch to the longitudinal direction due to Nd6Fe13Ga existing around the interface, which leads to increasing K1 of Nd.