Raman studies of Ti1-xFexO2 nano-particles

Ti_1-xFe_xO₂ (x=0.00-0.13) nano-particles were prepared by hydrolysis method and characterized by SEM, , TEM, XRD, and magnetization measurements (VSM). We investigated the effects of Fe doping on the structure of the Ti_1-xFe_xO₂ system by Raman scattering studies. SEM, TEM and XRD measurements show that the particle size of the powder is in nano-scale, and that the magnetic Fe impurities substitute for the Ti sites in the anatase TiO₂ phase. All the samples with x>0 were found to be superparamagnetic at room temperature. Raman spectra show no iron-oxide peak at around 610 cm^-1, strongly supporting that the Fe atoms go into the Ti-site in TiO₂ of nano-particles. However, for the ceramic samples, one additional Raman peaks at around 610 cm^-1 are observed. This may be related to the clusters or disorders created by mixture of various valence state of Fe ions. This may explain the existence if ferromagnetism in the ceramic Ti_1-xFe_xO₂ system, but none in the Ti_1-xFe_xO₂ nano-particles.