First-principles study of the electronic structure and magnetism of SrFe0.5Ru0.5O2

We study the electronic structures and magnetism of SrFe0.5Ru0.5O2 by first-principles calculations in the framework of density functional theory (DFT) with generalized gradient approximation plus on site repulsion (GGA+U). The DFT calculations were carried out with ten kinds of Fe-site doping form. Calculations show that the d-orbital electronic configurations of Fe2+ and Ru2+ ions are (dz2)2(dyzdxz)2(dxy)2(dx2−y2)1 and (dz2)2(dyzdxz)3(dxy)1(dx2−y2) , respectively, which are independent of the doping form. The degenerated (dxzdyz) orbitals of Ru2+ ions are occupied by three electrons, so it gives rise to the Jahn-Teller distortion. The calculated magnetic moments of Fe2+ and Ru2+ ions are 3.7 μB and 1.6 μB, respectively. The exchange parameters including nearest neighbor (NN) ions and next nearest neighbor (NNN) ions are calculated by using Heisenberg model and the magnetic frustration in the ordered structure is explained by the competition of the exchange parameters. We also study the external pressure effect on the compound. A pressure-induced orthorhombic to tetragonal structure transition accompanied by an insulator to half-metal transition and an antiferromagnetic (or spin glass) to ferromagnetic state transition is observed.