The finite size effect on the transport and magnetic properties of epitaxial Fe3O4 thin films

Magnetite (Fe3O4) has great potential for use in the new field of spintronics due to its interesting physical properties, e.g., half-metallic ferromagnetic nature and metal-insulator transition (Verwey transition). Therefore, a basic understanding of these properties is essential for applications in spintronics devices, especially as the film thickness is reduced. In this work, the transport and magnetic properties of stoichiometric ultrathin epitaxial Fe3O4 films have been investigated. The Fe3O4 films were grown on MgO (001) substrates using molecular beam epitaxy under optimal growth conditions. Low energy electron diffraction and X-ray photoemission spectroscopy confirmed that the films are single phase Fe3O4 . The Verwey transition has been investigated using both transport and magnetization measurements. The magnetization measurements show a sharp Verwey transition in all of these films, which indicates that the films have properties comparable to the bulk. Furthermore, the magnetization measurements at room temperature show that the ultrathin films with thickness t < 20 nm are ferromagnetic with magnetization values greater than those for bulk magnetite. Such enhanced magnetization in ultrathin Fe3O4 films is very promising for spin injection and other applications.