The electronic structure and magnetic properties of stable Sr₂BB′O₅ (B = Fe, Co, Ni and B′ = Co, Ni, Mn) with the brownmillerite structure

First-principles calculations have been performed to investigate the structural, electronic, and magnetic properties of Sr₂BB′O₅ (B = Fe, Co, Ni; B′ = Co, Ni, Mn) brownmillerite materials. By considering the atomic arrangements and the tetrahedral rotated modes, including typical magnetic configurations, the ground states are found by comparing their total energy. The thermodynamic and dynamic stability studies revealed that two compounds, Sr₂FeCoO₅ and Sr₂NiMnO₅, could be stable in the brownmillerite structure. Further electronic structure calculations show that the ground state of Sr₂FeCoO₅ is a G-AFM insulator, while the ground state of Sr₂NiMnO₅ is an A-AFM half-metal with a half-metallic bandgap of about 1 eV, exhibiting excellent half-metallic properties. In addition, the magnetic interactions are analyzed, which suggest that Sr₂FeCoO₅ could suffer from the influence of the B-site atomic disorder to maintain the G-AFM state, while Sr₂NiMnO₅ is more sensitive to atomic disorder, so its A-AFM state would be easily destroyed by the B-site disorder. These results would be helpful for further research.