Role of N in the Permanent Magnet Material Sm2Fe17Nx

The magnetic properties of the permanent magnet material Sm2Fe17Nx are discussed in terms of the change in the electronic structure caused by the insertion of N into the system. The magnetic moments are mainly determined by the Fe-d states: On insertion of N, the d states at Fe near N hybridize with the N-p states and acquire an electronic structure similar to that of Co. As a result, the magnetic moments at these sites decrease. The magnetic moments at other Fe sites increase because of the hybridization with the thus-changed d states of Fe near N. The Sm-f states also hybridize with N; however, these states in the absence of N would have nearly an atomlike electronic structure. This change affects the band energy and causes a large uniaxial magnetocrystalline anisotropy. We also discuss the cases where N is replaced by other typical elements.