First Principles Investigation of Half-Metallic Ferromagnetism in Alkaline-Earth Oxides Doped with Group VII Elements

Alkaline-earth oxides (AeO; Ae = Mg, Ca and Sr) doped with group VII (F, Cl, Br and I) elements as promising spin-injector materials have been investigated by using first principles full-potential linearized augmented plane-wave method. The substitution of group VII elements turns the insulator host AeO into ferromagnetic and some of them exhibit half-metallic ferromagnetic property with an integer magnetic moment of 3.00 μ_B/cell. The spin-resolved electronic band structure and density of states show that the Ae_0.875M_0.125O compounds exhibit spin-dependent transport properties, in which the conduction proceeds entirely via the minority spin state in F-doped AeO and through majority spin state in Cl, Br and I-doped CaO and SrO. The comparison of local spin density approximation and generalized gradient approximation is also carried out. The results show that the origin of ferromagnetism in Ae_0.875M_0.125O is attributed to the p-p hybridization interaction betwwn group VII elements and oxygen.