Preparation of sputtered Fe₃O₄ thin film

Fe₃O₄, as a half-metallic ferrimagnetic material, is believed to be one of the most promising materials in spin transport for spintronics. However, fabricating stoichiometric Fe₃O₄ film is still challenging because the oxidation is hard to control for various preparing methods. In this paper, series of Fe₃O₄ thin films on Si (100) substrates are grown by sputtering from a Fe₃O₄ target without oxygen atmosphere at different growth temperature and then extra heat treatment in high vacuum. By combining X-ray diffractometer (XRD), Raman spectrum, X-ray photoelectron spectroscopy and X-ray magnetic circular dichroism, VSM analysis, we see that the structure and magnetic moment of Fe₃O₄ film are not only related with growth temperature during sputtering, but also refer to the temperature of post-heat treatments. When the growth temperature is lower than 300 °C, the film does not show any XRD diffraction peaks. When the growth temperature increases from 300 to 500 °C, the film shows the (111) texture of Fe₃O₄ film clearly. However, the other XRD diffraction peaks are observed after post-heat treatment. The saturation magnetization increases with growth temperature and the largest saturation magnetization is 473 emu/cm³ for growth temperature of 450 °C and extra heat treatment, which is close to bulk Fe₃O₄. Our results suggest that a selectable method can be used to fabricate high magnetic moment of Fe₃O₄ thin film.