Strain and spin-orbit coupling induced orbital ordering in the Mott insulator BaCrO3

Abstract

Using ab initio calculations, we have investigated an insulating tetragonally distorted perovskite BaCrO3 with a formal 3d(2) configuration, the volume of which is apparently substantially enhanced by a strain due to SrTiO3 substrate. Inclusion of both correlation and spin-orbit coupling (SOC) effects leads to a metal-insulator transition and in-plane zigzag orbital ordering (OO) of alternating singly filled d(xz) + id(yz) and d(xz) - id(yz) orbitals, which results in a large orbital moment M-L approximate to -0.78 mu(B) antialigned to the spin moment M-S approximate to 2 vertical bar M-L vertical bar in Cr ions. Remarkably, this ordering also induces a considerable M-L for apical oxygens. Our findings show metal-insulator and OO transitions, driven by an interplay among strain, correlation, and SOC, which is uncommon in 3d systems.