Magnetism and stability of the Co: TiO2(100) interface probed by X-ray photoemission and ex situ magnetometry

Ferromagnetic Co:TiO2 thin films have been grown by Co evaporation on a sputtered TiO2(100) surface. Annealing in ultra-high vacuum induced a recovery of the oxygen stoichiometry and consequently the oxidation of titanium to Ti4+ at the surface, while oxidation of the Co layer has not been observed. Room temperature ferromagnetism is observed, along with a paramagnetic contribution. Differences of the hysteresis cycle with respect to that usually observed for bulk cobalt are ascribed both to the reduced film thickness and to the disorder induced by the sputtering treatment.