  We report here the observation of ferromagnetism (FM) at 300 K in mixtures of
TiO2 and Co3O4 powders despite the antiferromagnetic and diamagnetic character
of both oxides respectively. The ferromagnetic behavior is found in the early
stages of reaction and only for TiO2 in anatase structure; no FM is found for
identical samples prepared with rutile-TiO2. Optical spectroscopy and X-ray
absorption spectra confirm a surface reduction of octahedral Co+3->Co+2 in the
mixtures which is in the origin of the observed magnetism
