Magnetic and optical properties of rf-sputtered zinc ferrite thin films

Zn-ferrite (ZnFe2O4) thin films were deposited by rf-magnetron sputtering on glass substrates at room temperature (RT) in pure oxygen environment. The as-deposited films were investigated by x-ray diffraction to show that single phase nanocrystalline spinel patterns belong to zinc ferrite. The magnetization shows ferrimagnetic behavior, and it strongly depends on oxygen working pressure. The maximum magnetization of 230 emu/cm3 (42 emu/g) at RT is obtained for the film deposited at 27 mTorr of oxygen pressure. The oxygen vacancy concentration and random distribution of Zn2+ and Fe3+ on both tetrahedral and octahedral sites are the possible reasons of high magnetization due to rapid cooling of sputtered vapors to form solid state film. The optical properties of the films show 85% transparency above 550 nm wavelength. The estimated values of direct and indirect band gaps are 2.5 and 1.9 eV, respectively.