Fabrication and magnetoresistance of tunnel junctions using half-metallic Fe3O4

Magnetite (Fe3O4) is believed to be half metal, providing 100% spin-polarized conduction electrons. The half-metallic nature of magnetic electrodes for tunneling junction devices is expected to induce a large magnetoresistance. We investigated the structural and chemical properties of interfaces in ferromagnet–insulator–ferromagnet (Fe3O4/MgO/Fe) tunnel junctions. Al/Ag/Fe3O4/MgO multilayers for magnetic tunnel junction have been fabricated on α-Al2O3 (001) and MgO (100) substrates by a molecular beam epitaxy system. The Fe3O4 quality was examined by reflection high-energy electron diffraction (RHEED), x-ray diffraction (XRD), superconducting quantum interference device magnetometry, atomic force microscopy (AFM), and in situ x-ray photoelectron spectroscopy. RHEED and XRD results showed that the epitaxial Fe3O4 layer with a smooth surface was successfully grown on substrates. The stoichiometric Fe3O4 was confirmed by Verway transition in temperature dependence of magnetization. AFM data showed relatively...