Co K-edge XANES and spin-state transition of RCoO 3 (R=La, Eu)

Abstract

Co K-edge X-ray absorption near-edge spectra at 300 K and magnetic studies for the rhombohedral LaCoO 3 with low-spin state to intermediate-spin (IS) state transition T s ≃105 K and orthorhombic EuCoO 3 (T s ≃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 P 2− P 1=2.0 eV for R=La and Eu, and P 3− P 2=1.5 eV for R=La and 1.3 eV for R=Eu. Since the thermally excited IS state is a mixed t 2g 5e g 1 and d 7 L ̄ ( t 2 g 6 e g 1 or t 2g 5e g 2), with almost filled t 2g↑ states. From reported band structure calculation, the three peaks P 1, P 2, P 3 are probably corresponding to the unfilled t 2g↓, e g↑ and e g↓ states, respectively.