A study was made of the structural, chemical and magnetic properties of non-doped ceria thin films electrodeposited on silicon substrates. Experimental results confirmed that the observed room temperature ferromagnetism was driven by both cerium and oxygen vacancies. Ceria films which contained vacancy concentrations which were well above the percolation limit were investigated. Irradiation experiments with neon ions were employed to generate highly oxygen defective CeO2-δ structures. X-ray photoelectron spectroscopy and X-ray absorption near-edge structure spectroscopy were used to estimate the concentration of Ce3 + sites in the films, which could reach up to 50% of Ce3 + replacing Ce4 + , compared to a stoichiometric CeO2 structure. Despite the increment of structural disorder, it was observed that the saturation magnetization increased continuously with Ce3 + concentration. The experiments demonstrated that the ferromagnetism observed in ceria thin films, highly disordered and oxygen-deficient, preserving the fluorite-type structure only in a nanometer scale, remained intrinsically stable at room temperature.

Ferromagnetism Induced by Oxygen and Cerium Vacancies Above the Percolation Limit in CeO2. V.Fernandes, P.Schio, A.J.A.de Oliveira, W.A.Ortiz, P.Fichtner, L.Amaral, I.L.Graff, J.Varalda, N.Mattoso, W.H.Schreiner, D.H.Mosca: Journal of Physics - Condensed Matter, 2010, 22[21], 216004