Development of Co_1+xFe_2-xO₄ (x=0-0.5) thin films on SiO₂ glass by the sol-gel method and the study of the effect of composition on their magnetic properties

Spinel-type Co_1+xFe_2-xO₄ (x=0-0.5) thin films (∼450 nm thickness) on SiO₂ glass substrate were prepared by the sol-gel method using spinning technique (2000 rpm) from the aqueous solution of FeCl₃.6H₂O and CoCl₂.6H ₂O. All the films were heat treated at different temperatures ranging from 700 to 1100°C. The films were structurally characterized by using the X-ray diffraction technique (XRD), and the morphology was studied by field emission scanning electron microscope (FESEM). The effects of temperature and the composition ([Co²⁺]/ [Fe³⁺] ratio) on the formation of Co_1+xFe_2-xO₄ thin films were also studied. The films obtained at relatively low temperature showed mixed phases of α-Fe₂O₃, CoO, along with CoFe₂O ₄, while the formation of the CoFe₂O₄ phase increases with increasing temperature. Furthermore, the composition of the solution in terms of [Co²⁺]/[Fe³⁺] plays a great role on the formation and magnetic properties of the films. The magnetic properties of the films, studied using vibrating sample magnetometer (VSM), showed relatively small saturation magnetization, and coercivity was observed to be low as compared with that of other reports. Saturation magnetization also increases with increasing heat treatment temperature.