Datensatz

Zusammenfassung

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 (Co₃O₄). 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 unoccu-
pied 3d states of cobalt atoms. Also, since Co₃O₄ 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
t_2g orbitals (d_xz, d_yz, and d_xy) while that of Co³⁺ ions is due to spin-up and spin-down polarized e_g
orbitals (d_x²−y² and d_z² ). Furthermore, we deduce the magnetic moments on the Co³⁺ and Co²⁺ to
be zero and 3.00 μ_B respectively. This is consistent with an earlier experimental study which found that the magnetic structure of Co₃O₄ consists of antiferromagnetically ordered Co²⁺ spins, each of which is surrounded by four nearest neighbours of oppositely directed spins.