Electronic states of LaCoO3: Co K-edge and La L-edge x-ray absorption studies

Room-temperature Co K-edge and La L-edge x-ray absorption studies have been carried out on LaCoO3. Experimental near-edge structures have been analysed by theoretical LDA+U density of states (DOS) and multiple scattering (MS) calculations. Use of both MS and DOS calculations yields additional information about hybridization of the states of the central atom with neighbouring atoms responsible for producing the near-edge structures. Absorption processes at the CoK-edge, and the La L1-, L2-, and L3-edges have been attributed to electronic transitions from Co {1s to Co};4p, La {2s to La}; 6p, La &2 {p}_{1 / 2} to {La}; 5d, and La &2 {p}_{3 / 2} to {La}; 5d, respectively. All the pre-edge and post-edge features including the shape of the main absorption edge have been generated by taking the convolution of the calculated DOS, indicating that single particle approximation is sufficient to express all experimentally observed major structures. Two pre-edge structures observed in the CoK-edge spectrum are attributed to Co{1s to e_{g}{uparrow }}; and {e_{g}{ downarrow }}; quadrupole transitions in contrast to earlier identification of the same to Co{1s to t_{2g}}; and eg transitions. The influence of La6p states on the Co4p states is such that the inclusion of La atoms in the MS calculations is necessary to generate post-edge structures in the CoK-edge spectrum. The importance of the hybridization of the O2p state with La6p and 5d in the L-edge absorption processes is also discussed. A 10% contribution of the quadrupole channel has been estimated in the La L-edges.