Expansion research on half-metallic materials in double perovskites of Sr2BB'O6 (B = Co, Cu, and Ni; B' = Mo, W, Tc, and Re; and BB' = FeTc).

Calculations with full structural optimization were conducted by generalized gradient approximation (GGA) with correlation effect correction (GGA + U) based on density functional theory. The stable structures, magnetic stable phases, and electronic structures of the double perovskites of Sr2BB'O6 (B = Co, Cu, and Ni; B' = Mo, W, Tc, and Re; and BB' = FeTc) were investigated. All compounds, except for Sr2NiMoO6 and Sr2NiWO6, can be half-metallic (HM) materials in the GGA scheme; Sr2NiMoO6 and Sr2NiWO6 are ferromagnetic (FM) insulators. Sr2FeTcO6, Sr2CoWO6, and Sr2NiTcO6 are stable ferrimagnetic (FiM)-HM compounds in the GGA and GGA + U schemes. Given the small energy difference between their antiferromagnetic and FiM states, Sr2CoTcO6, Sr2CuMoO6, Sr2NiMoO6, Sr2NiWO6, and Sr2NiReO6 can coexist. The mechanisms of the HM-FiM properties can be described by d-d' hybridization with double-exchange interaction. [ABSTRACT FROM AUTHOR]