La_1-xSr_xCoO₃のX線磁気円二色性と第一原理計算

抄録

The electronic and magnetic structure of La_1-xSr_xCoO₃ (0.0≤x≤0.6) has been studied by X-ray magnetic circular dichroism (XMCD) at the Co K absorption edge. A negative XMCD peak was clearly observed for pure LaCoO₃ at E=7.719 keV within the threshold region, suggesting the existence of the intermediate-spin state of Co³⁺. A positive XMCD peak at E=7.723 keV was assigned to Co⁴⁺, having the double-exchange interaction between Co³⁺ and Co⁴⁺. In order to verify the origin of XMCD, the electronic structure of ground and is core-hole states was calculated by a DV-Xα Hartree-Fock-Slater method, using several cluster models up to the fifth neighbor shell. The first-principles calculations well reproduced the experimental XMCD spectra, where a hybridization of Co 3d, 4p and O 2p orbits stabilizes a magnetic state of La_1-xSr_xCoO₃.