Half-metallic ferrimagnetism driven by Coulomb-enhanced spin-orbit coupling in PdCrO3

Abstract

Recently, in the seemingly narrow gap insulating NiCrO3 with the trigonally distorted (R (3) over barc) perovskite-like structure, a compensated half-metal (CHM) is predicted, as applying a modest pressure. Using ab initio calculations including both Coulomb correlations and spin-orbit coupling (SOC), we investigate the as-yet-unsynthesized PdCrO3, isostructural and isovalent to NiCrO3. Upon applying the on-site Coulomb repulsion U to both Pd and Cr ions, the Cr spin moment is precisely compensated with the antialigned spin moments of Pd and oxygens. Coincidentally only one spin channel remains metallic due to the twice larger width of the Pd 4d bands than the Ni 3d bands in NiCrO3, indicating CHM in ambient pressure. Inclusion of SOC as well as correlation effects (LDA + U + SOC) produces a SOC constant enhanced twice over the value of LDA + SOC, leading to unusually large orbital moment of -0.25 mu(B) on Pd. However, the half-metallicity still survives, so that a transition of CHM to a half-metallic ferrimagnet occurs due to Coulomb enhanced SOC. On the other hand, an isovalent, but presumed cubic double perovskite La2PdCrO6, is expected to be a half-metal ferromagnet with tiny orbital moments.