A series of Ti1-xFexO2-δ (0 ≤ x ≤ 0.03) nanoparticles were synthesized by sol-gel route. The nanoparticles had a size distribution in the range of 15 to 40nm and were identified as the anatase TiO2 by X-ray diffraction and Raman analysis. X-ray diffraction, selected area electron diffraction, Raman and Mössbauer analysis ruled out the signature of Fe-cluster or any other oxides of Fe. The red-shifting of the band edge emission peak observed in UV-vis absorption studies further confirmed the doping of Fe ions in the TiO2 lattice. Raman studies revealed shifting and broadening in Eg(1) and Eg(3) modes with Fe doping. It was suggested that the activation of ferromagnetism with increasing Fe doping concentration was related to the oxygen vacancy defects. The presence of such defects was further confirmed by electron paramagnetic resonance measurements. The observed ferromagnetism was interpreted in terms of a bound magnetic polaron model.

Room-Temperature Ferromagnetism of Fe-Doped TiO2 Nanoparticles Driven by Oxygen Vacancy. Patel, S.K.S., Kurian, S., Gajbhiye, N.S.: Materials Research Bulletin, 2013, 48[2], 655-60