D-Type Anti-Ferromagnetic Ground State in Ca₂Mn₂O₅

We study the electronic and magnetic properties of an oxygen-deficient perovskite Ca₂Mn₂O₅ based on the first principle calculations. The calculations show that the ground state of Ca₂Mn₂O₅ is a D-type anti-ferromagnetic structure with the anti-ferromagnetic spin coupling along the c-direction. The corresponding electronic structure of the D-type state is investigated, and the results display that Ca₂Mn₂O₅ is an insulator with an indirect energy gap of ~2.08 eV. By the partial density-of-state analysis, the valence band maximum is mainly contributed to by the O-2p orbitals and the conduction band minimum is contributed to by the O-2p and Mn-3d orbitals. Due to the Coulomb repulsion interaction between electrons, the density of state of Mn-3d is pulled to -6--4.5 eV. .