Oxygen pressure-tuned epitaxy and magnetic properties of magnetite thin films

Quasi-two-dimensional magnetite epitaxial thin films have been synthesized by pulsed laser deposition technique at various oxygen pressures. The saturation magnetizations of the magnetite films were found to decrease from 425 emu/cm3, which is close to the bulk value, to 175 emu/cm3 as the growth atmospheres varying from high vacuum (∼1 × 10−8 mbar) to oxygen pressure of 1 × 10−3 mbar. The ratio of the Fe3+ to Fe2+ increases from 2 to 2.7 as oxygen pressure increasing shown by XPS fitting, which weakens the net magnetic moment generated by Fe2+ at octahedral sites as the spins of the Fe3+ ions at octahedral and tetrahedral sites are aligned in antiparallel. The results offer direct experimental evidence of the influence to the Fe3+/Fe2+ ratio and the magnetic moment in magnetite epitaxy films by oxygen pressure, which is significant for spintronic applications.