Abstract
Structural, magnetic, and Co K-edge X-ray absorption near-edge structure (XANES) spectroscopic studies for the stoichiometric La 1-x Eu x CoO 3 (0 ≤ x ≤ 1) system with trivalent Co 3+ are reported. The thermally-excited spin-state transition from low-spin (LS) to intermediate-spin (IS) state increases from T s ∼ 105 K for LaCoO 3 (x = 0) to ∼140 K for x = 0.25, to ∼200 K for x = 0.5, and extrapolates to ∼295 K for EuCoO 3 (x = 1), where the IS state is a mixture of d 6 (t 2g 5 e g 1 ) and d 7 L (t 2g 5 e g 2 with a ligand hole) with filled t 2g majority spin states. The small pre-edge feature observed in room temperature XANES for the system in the IS state is from the 1s-3d quadrupole transition, which is weakly allowed through the hybridization of Co 4p states with 3d states of the neighboring Co atoms. For LaCoO 3 , the pre-edge can be fitted using three Gaussian peaks with energy separations ΔE(P 2 -P 1 ) = 2.0 eV and ΔE(P 3 -P 2 ) = 1.5 eV, where P 1 , P 2 , and P 3 presumably correspond to the unfilled t 2g minority, e g majority, and e g minority spin states, respectively.