Garcia March, M. A.Jimenez Villacorta, F.Quesada, A.de la Venta, J.Carmona Tejero, NoemíLorite, I.LLopis, J.Fernández, J. F.2023-06-202023-06-202010-01-150021-897910.1063/1.3294649https://hdl.handle.net/20.500.14352/44716© 2010 American Institute of Physics. Lucas Pérez and Manuel Plaza are acknowledged for the help with the magnetic measurements. M.S. Martín-González and J. L. Costa-Krämer are acknowledged for fruitful discussions. This work was supported by the Spanish Council for Scientific Research through Project Nos. CSIC 2006-50F0122 and CSIC 2007-50I015 and Spanish Ministry of Science and Education through Project Nos. MAT2007- 66845-C02-01 and FIS-2008-06249. We acknowledge the European Synchrotron Radiation Facility for provision of synchrotron radiation facilities and we would like to thank the SpLine CRG beamline staff for assistance during x-ray absorption experiments.We recently reported the observation of room temperature ferromagnetism in mixtures of ZnO and Co_3O_4 despite the diamagnetic and antiferromagnetic character of these oxides, respectively. Here, we present a detailed study on the electronic structure of this material in order to account for the unexpected ferromagnetism. Electrostatic interactions between both oxides lead to a dispersion of Co_3O_4 particles over the surface of ZnO larger ones. As a consequence, the reduction Co^(+3) -> Co^(2+) at the particle surface takes place as evidenced by x-ray absorption spectroscopy measurements and optical spectroscopy. This reduction allows explaining the observed ferromagnetic signal within the well established theories of magnetism in oxides.engjournal articlehttp://dx.doi.org/10.1063/1.3294649http://scitation.aip.orgopen access538.9Room-temperatureDoped ZnOSol-gelFerromagnetismOxideFísica de materialesFísica del estado sólido2211 Física del Estado Sólido