Thin films of room temperature diluted magnetic oxides of Co doped CeO2 (Ce0.97Co0.03O2-δ) with a predominant orientation of (001) were deposited on Al2O3(00•1) substrates. An Ar+ sputtering process was applied to the as deposited films to investigate its effect on the films' ferromagnetic properties. With the aid of magnetic measurements, it was found that Ar+ bombardment had an obvious effect upon the magnetic properties of the as-deposited films. That is, the saturated magnetization moments (MS) were enhanced by Ar+ bombardment. More detailed work was done to further explore the inherent mechanism. Ar+ sputtering was found to introduce additional O vacancies (VO) into the as deposited films (through X-ray photoelectron spectroscopy and Raman spectral analysis), which should make a certain contribution to the enhanced MS observed for Ar+ sputtered films. The experimental results provide direct evidence of VO enhanced ferromagnetism of insulating diluted magnetic oxides, and were consistent with the recently proposed F-center exchange coupling mechanism.

Direct Evidence of Oxygen Vacancy Mediated Ferromagnetism of Co Doped CeO2 Thin Films on Al2O3(0001) Substrates. Y.Q.Song, H.W.Zhang, Q.Y.Wen, L.Peng, J.Q.Xiao: Journal of Physics - Condensed Matter, 2008, 20[25], 255210 (5pp)