Compositional dependence of X-ray absorption spectra on magnetic circular dichroism and near-edge structure at Co K edge in La1-xSrCoO3 (0 ≤ x ≤ 0.6)

We have studied the effect of Sr doping on the magnetic structure of La1-xSrxCoO3 (x = 0, 0.2, 0.3, 0.4, 0.5 and 0.6) by X-ray magnetic circular dichroism (XMCD) at Co K absorption edges. A negative XMCD peak was clearly observed for pure LaCoO3 at E = 7.719 keV within the threshold region of the main edge, suggesting the existence of the intermediate-spin state of Co3+. A positive XMCD peak appeared at E = 7.723 keV by Sr substitution of La in LaCoO3 (X greater than or equal to 0.2) in accordance with the low-spin state of Co4+ and X-ray absorption near-edge-structure (XANES) spectra. A negative XMCD peak was also observed at the pre-edge, which can be explained as the hybridization with the neighboring Co4+ in the dipole transition. The dispersion-type XMCD signals at the main edge may be rationalized with the hypothetical double-exchange interaction between Co3+ and Co4+.