Raman Studies of ${\rm Ti}_{\bm{ 1-x}} {\rm Fe}_{\bm x} {\rm O}_{\bm 2}$ Nanoparticles

Ti
_1-x
Fe
_x
O
₂
(x = 0.00-0.13) nanoparticle samples were prepared by hydrolysis method. We investigated the effects of Fe doping on the structural and magnetic properties of the Ti
_1-x
Fe
_x
O
₂
nanoparticle system. Scanning electron microscopy and X-ray diffraction measurements confirm that the particle size of the powder is in nanoscale, and that the magnetic Fe impurities substitute for the Ti sites in the anatase TiO
₂
phase. All the samples with x > 0 were found to be super-paramagnetic at room temperature by magnetization measurements. Raman spectra also strongly support that the Fe atoms go into the Ti-site in theTiO
₂
structure. For comparison, ceramic Ti
_1-x
Fe
_x
O
₂
samples were also prepared by usual ceramic method. Ferromagnetism was observed only in the ceramic Ti
_1-x
Fe
_x
O
₂
system. Additional Raman peak at around 610 cm
^-1
is observed only in the ceramic samples. This may be related to the clusters created by mixture of various valence state of Fe, which probably would be the cause for ferromagnetism observed in the ceramic Ti
_1-x
Fe
_x
O
₂
system.