X-ray Absorption Near-Edge Structure (XANES) at the O <i>K</i>-Edge of Bulk Co<sub>3</sub>O<sub>4</sub>: Experimental and Theoretical Studies
Stephane Kenmoe,
Dick Hartmann Douma,
Abdulrafiu Tunde Raji,
Bernard M’Passi-Mabiala,
Thomas Götsch,
Frank Girgsdies,
Axel Knop-Gericke,
Robert Schlögl,
Eckhard Spohr
Affiliations
Stephane Kenmoe
Department of Chemistry, University of Duisburg-Essen, Universitätsstr. 2, 45141 Essen, Germany
Dick Hartmann Douma
Groupe de Simulations Numériques en Magnétisme et Catalyse, Faculté des Sciences et Techniques, Université Marien Ngouabi, Brazzaville B.P. 69, Congo
Abdulrafiu Tunde Raji
Department of Physics, College of Science, Engineering and Technology (CSET), University of South Africa (UNISA), Corner of Christiaan de Wet Road & Pioneer Avenue, Florida 1709, South Africa
Bernard M’Passi-Mabiala
Groupe de Simulations Numériques en Magnétisme et Catalyse, Faculté des Sciences et Techniques, Université Marien Ngouabi, Brazzaville B.P. 69, Congo
Thomas Götsch
Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
Frank Girgsdies
Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
Axel Knop-Gericke
Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
Robert Schlögl
Department of Inorganic Chemistry, Fritz-Haber-Institut der Max-Planck Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany
Eckhard Spohr
Department of Chemistry, University of Duisburg-Essen, Universitätsstr. 2, 45141 Essen, Germany
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 unoccupied 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 t2g orbitals (dxz, dyz, and dxy) while that of Co3+ ions is due to spin-up and spin-down polarized eg orbitals (dx2−y2 and dz2). 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 Co3O4 consists of antiferromagnetically ordered Co2+ spins, each of which is surrounded by four nearest neighbours of oppositely directed spins.
