Abstract
The performance of spintronic devices depends critically on the ability to control the properties of high spin-polarization materials such as magnetite (Fe3O4) in thin films. In this work, the effect of oxygen pressure on the transport and magnetic properties of Fe3O4 thin films was extensively investigated. The 20 nm Fe3O4 films were grown on MgO (001) substrates using molecular beam epitaxy under different oxygen pressure. The quality of epitaxial Fe3O4 thin films was judged by observation of the Verwey transition and corroborated by x-ray photoemission spectroscopy (XPS). In particular, the resistivity measurements showed the Verwey transition to be as sharp as bulk magnetite, which has not been seen in previous studies for film thicknesses less than 30 nm. Therefore, this work provides insight for the growth of ultrathin magnetite films with high crystal quality and sharp Verwey transition. Furthermore, the magnitude of the magnetization change at the Verwey transition was observed to be sensitive to the oxygen pressure during film growth. These results are consistent with the XPS measurements and indicate a relative narrow range of optimal oxygen pressure for the formation of high quality thin magnetite films with electronic and magnetic properties close to bulk Fe3O4.