Structural and magnetic study of undoped and cobalt doped TiO₂ nanoparticles

The present study investigates the influence of cobalt doping on the structural and magnetic properties of TiO₂ nanoparticles prepared by a simple wet chemical method. The single phase anatase structure of Co-doped TiO₂ nanoparticles was confirmed by X-ray powder diffraction. A morphological study using scanning electron microscopy and transmission electron microscopy indicates the formation of TiO₂ nanoparticles of sizes 6-10 nm. The high resolution TEM image shows clear lattice fringes indicating the highly crystalline nature of the nanoparticles which was further analysed by selected area electron diffraction pattern which indicates a polycrystalline nature of anatase TiO₂. The shifting and broadening of the most intense E_g (1) mode in micro-Raman study of Co-doped TiO₂ nanoparticles and XPS spectra indicate the incorporation of Co in TiO₂. Magnetic measurement shows ferromagnetic behavior at room temperature in undoped TiO₂ which has originated due to the presence of oxygen vacancies which are intrinsic in nature. But the M-H curve of Co-doped TiO₂ shows the coexistence of ferromagnetic and paramagnetic phases with enhanced magnetization. The enhancement in magnetization has arisen due to Co doping and the paramagnetism may be due to the presence of some undetected clusters of oxides of cobalt.