X-ray Absorption Fine Structure Study of La_0.5Sr_0.5Co_1−yFe_yO₃ Cobaltites

Abstract

The local structure and electron configuration of Co and Fe ions in La_0.5Sr_0.5Co_1−yFe_yO₃ (y=0.3 and 0.6) cobaltites have been examined by the X-ray absorption fine structure (XAFS) study. It was observed that the average valence of cobalt ions changed while the valence of iron ions did not. The average Fe–O bonding distance in (Fe/Co)O₆ octahedra was higher than that of Co–O pairs. Based on the relationship between the Debye–Waller factor and bond strength, it was concluded that the strength of Co–O bond is stronger than that of Fe–O bond in the y=0.6 sample and weaker in the y=0.3 compound. The change of the Co-ion valence and the local structure of the perovskite cell with y are discussed in connection with the change of magnetic and transport properties of the cobaltites.