Nitrogen-induced ferromagnetism in BaO

Abstract

Density functional theory with local spin density approximation has been used to propose possible room temperature ferromagnetism in N-doped NaCl-type BaO. Pristine BaO is a wide bandgap semiconductor, however, N induces a large density of states at the Fermi level in the non-magnetic state, which suggests magnetic instability within the Stoner mean field model. Spin-polarized calculations show that N-doped BaO is a true half-metal, where N has a large magnetic moment, which is mainly localized around the N atoms, and a small polarization at the O sites is also observed. The origin of magnetism is linked to the electronic structure. The ferromagnetic (FM) and antiferromagnetic (AFM) coupling between the N atoms in BaO reveal that doping N atoms have a FM ground state, and the calculated transition temperature (T_C), within the Heisenberg mean field theory, theorizes possible room temperature FM in N-doped BaO. Nitrogen also induces ferromagnetism when doping occurs at the surface O sites and it has a smaller defect formation energy than bulk N-doped BaO. The magnetism of N-doped BaO has also been compared to that of Co-doped BaO, and we believe that N has a greater potential for tuning the magnetism in BaO than Co.