Structure and magnetic characterizations of cobalt ferrite films prepared by spray pyrolysis

Cobalt ferrite films were prepared by spray pyrolysis with post-annealing. For the as-deposited film, the differential scanning calorimetry measurement shows a crystallization peak at around 375 °C during the isochronal heating at 20 °C/min, and the X-ray diffraction pattern shows its amorphous-like characteristic. The isothermal post-annealings were performed for 2 h at various temperatures from 400 to 700 °C, leading to the crystallization of films, forming the spinel structure. The cross-sectional analysis with scanning electron microscopy shows that the film's thickness keeps almost constant after annealing, and the layered granular structure appears when the annealing temperature is high. The magnetic hysteresis loops of as-deposited and annealed films show that both the saturation magnetization and coercivity increase with the annealing temperature, due to the crystallization of CoFe2O4 phase.