Calculation of X-ray Magnetic Circular Dichroism for Sr-Substituted LaCoO₃ by Discrete-Variational Hartree–Fock–Slater Method

The ground and 1s core-hole states have been calculated by a DV-Xα discrete-variational Hartree–Fock–Slater method for a 51-atom model of LaCoO₃ with Sr substitution within the fifth neighbor shell. First-principles calculations reproduced the experimental spectra of X-ray magnetic circular dichroism (XMCD) at the Co K-absorption edge, where a hybridization of Co 3d,4 p and O 2 p stabilizes a magnetic state of La_1-xSr_xCoO₃. It was found that the π bonding and σ^* antibonding orbitals exist near the Fermi level, which is consistent with the interpretation based on the ligand field theory. The XMCD calculation shows a change of Co 3d electrons between the low-spin and high-spin states within a narrow energy range of ±0.3 eV from the Fermi level, where the Co–O molecular orbital may contribute to produce an intermediate state.