Effect of Co2+ ions on the microstructure and magnetic properties of nanocrystalline CoxFe3−xO4 films

CoxFe3−xO4 nanocrystalline films (x=0.2-0.8) on SiO2 substrates were prepared by a sol-gel method. The microstructural and magnetic properties of samples were measured by an X-ray diffractometer (XRD) and a vibrating sample magnetometer (VSM), respectively. Atomic force microscopy (AFM) was used to investigate the surface image of the sample. The measurement results of XRD at room temperature show that the pure spinel structure of the film could be obtained at x=0.8. The magnetic measurements reveal the magnetic properties of the samples depend strongly on Co2+ ions content, and the optimal parameters of the saturation magnetization and coercivity in CoxFe3−xO4films are obtained at x=0.8. Here the coercivity reaches 1.954 kOe. The average grain sizes of the film are less than 30 nm obtained from the microscopy images. The situ measurement at high temperatures of range from 293 to 773 K shows that the microstructures of Co0.8Fe2.2O4 film have good thermal stabilization.