Preparation and magnetic properties of the CoFe₂O₄ thin films on Si substrate by sol-gel technique

A stable precursor for CoFe₂O₄ thin film was prepared by sol-gel technique from the aqueous solution of FeCl₃•6H ₂O and CoCl₂•6H₂O. Sol was deposited on a naturally oxidized silicon-substrate by spinning technique (2000 rpm) and heat treated at different temperatures ranging from 700 to 1100°C. Thickness of the films was controlled in the range of 400-500 nm and all the films were characterized by using XRD and SEM. The effects of temperature and the composition on the formation of CoFe₂O₄ thin film were also studied. Films obtained at relatively lower temperature showed multi-phases of α-Fe₂O₃, CoFe₂O₄ and CoO while the formation of CoFe₂O₄ phase increases with increasing temperature. Furthermore, the composition of the solution in mol% has great role on the formation of CoFe₂O₄ films and the film containing 50 mol% of Co²⁺ exhibited CoFe₂O₄ mono-phase. Surface morphology of the films was studied by scanning electron microscope (SEM). Magnetic properties of the films, studied by using vibrating sample magnetometer (VSM), showed relatively high saturation magnetization (8.04-22.21 kWb/m²) as well as high coercivity (44.59-63.30 kA/m). Saturation magnetization also increases with increasing heat treatment temperature.