Comparative analysis on the structure, electronic and magnetic properties of SrRuO3 and PbRuO3

Abstract

The structure, electronic and magnetic properties of SrRuO3 and PbRuO3 are studied by using density functional theory in the local spin density approximation. The lattice constants of orthorhombic SrRuO3 and PbRuO3 with a Pbnm space group have a > b, different from most of other ABO3 structures with a < b. We obtain two reasons about a > b for SrRuO3 and PbRuO3: One is that the horizontal middle plane of the oxygen octahedra deforms from square to rectangle, resulting in the side length of rectangle along x direction, aoct, is larger than that along y direction, boct; The other is the tilting angle of the oxygen octahedra having θ < arccos (boct/aoct). SrRuO3 and PbRuO3 with similar structure should have similar magnetic ground states. But SrRuO3 is ferromagnetic, while PbRuO3 is paramagnetic. Our results show that the orbital hybridization of Pb–O is much stronger than that of Sr–O, which lead to the broaden bandwidth near Fermi level. This is the main reason for the different magnetic ground states of SrRuO3 and PbRuO3. The calculations for PbRuO3 with Pbnm and Imma structures have considered the spin-orbit coupling effect, the calculated results show that the ground states of Pbnm and Imma PbRuO3 are both paramagnetic metals.