Abstract in Englisch:

We combine theoretical and experimental X-ray absorption near-edge spectroscopy (XANES) to probe the local environment around cationic sites of bulk spinel cobalt tetraoxide (Co₃ O₄ ). Specifically, we analyse the oxygen K-edge spectrum. We find an excellent agreement between our calculated spectra based on the density functional theory and the projector augmented wave method, previous calculations as well as with the experiment. The oxygen K-edge spectrum shows a strong pre-edge peak which can be ascribed to dipole transitions from O 1s to O 2p states hybridized with the unoccupied 3d states of cobalt atoms. Also, since Co₃ O₄ contains two types of Co atoms, i.e., Co³⁺ and Co²⁺, we find that contribution of Co²⁺ ions to the pre-edge peak is solely due to single spin-polarized t₂g orbitals (dₓz, dyz, and dₓy ) while that of Co³⁺ ions is due to spin-up and spin-down polarized eg orbitals (dₓ₂ −y² aⁿdd z² ⁾. Furthermore, we deduce the magⁿetⁱc momeⁿts oⁿ the Co³⁺ and Co²⁺ to be zero and 3.00 µB respectively. This is consistent with an earlier experimental study which found that the magnetic structure of Co₃ O₄ consists of antiferromagnetically ordered Co²⁺ spins, each of which is surrounded by four nearest neighbours of oppositely directed spins.