Electronic structure of the high‐spin Co4+ system Ba2CoO4

Abstract

AbstractThe electronic structure of the semiconductor Ba2CoO4 has been investigated using x‐ray absorption spectroscopy at the Co‐L2,3 and O‐K edges as well as soft x‐ray valence band photoemission. The spectra can be accurately reproduced by a combination of full atomic‐multiplet configuration‐interaction cluster calculations and ab‐initio band structure analysis. The large negative O 2p to Co 3d charge‐transfer energy has been established as well as the high stability of the S=5/2 high‐spin state of the Co4+ ion. The band gap of this high‐oxidation state material is sizeable and can be attributed to the joint effect of electron correlations, the local tetrahedral coordination of the Co ions, and the poor electronic connection between the CoO4 tetrahedra.