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The thin films of CoFe2O4 spinel ferrite were prepared on the substrates of monocrystalline silicon(100) at low temperature by means of a developed citrate processing.Structural properties and surface morphology of deposited films were examined using an X-ray diffractometer (XRD) and a field emission scanning electron microscope (FESEM). XRD patterns of all deposited films consisted of a single phase of cobalt ferrite and they did not have any preferred orientation. FESEM micrographs of CoFe2O4 films showed that the film calcined at 400℃ had a surface morphology different from the ones at 700℃ and 800℃. The surface morphology of the samples was very different with various alcined temperatures. Magnetic properties measured at room temperature showed that the films did not have any magnetically preferred orientation. The maximum values of the coercivities measured at perpendicular and in-plane directions were 3.873 and 2.70 kOe, respectively.

The Ba0.8Sr0.2TiO3/CoFe2O4 layered heterostructure film was grown on Pt/TiO2/SiO2/Si substrate by radio frequency-magnetron sputtering. X-ray diffraction shows that the heterostructure film is composed of perovskite Ba0.8Sr0.2TiO3 phase and spinel CoFe2O4 phase. The microstructures of the heterostructure film were observed by field-emission scanning electron microscope (FESEM), showing good surface morphology and clear interfaces among the Ba0.8Sr0.2TiO3 film and CoFe2O4 film and substrate. The heterostructure film simultaneously diplays distinct ferroelectricity and ferromagnetism. Moreover, an obvious direct magnetoelectric coupling effect is observed in the heterostructure film with a maximum magnetoelectric voltage coefficient of 9.4 mV/cm Oe.