Co K-edge XANES and spin-state transition of RCoO3 (R=La, Eu)

Co K-edge X-ray absorption near-edge spectra at 300 K and magnetic studies for the rhombohedral LaCoO3 with low-spin state to intermediate-spin (IS) state transition Ts≅105 K and orthorhombic EuCoO3 (Ts≅295 K) are reported. The small pre-edge feature observed is from 1s-3d dipole transition, which is weakly allowed through the hybridization of Co 4p states with 3d states of neighboring Co atoms. For both samples in the IS state, pre-edge can be fitted using three peaks with energy separation P2-P1=2.0 eV for R=La and Eu, and P3-P2=1.5 eV for R=La and 1.3 eV for R=Eu. Since the thermally excited IS state is a mixed t2g5eg1 and d7L-bar (t2g6eg1 or t2g5eg2), with almost filled t2g↑ states. From reported band structure calculation, the three peaks P1, P2, P3 are probably corresponding to the unfilled t2g↓, eg↑ and eg↓ states, respectively