The surface and interface structure as well as the electronic properties of thin epitaxial ${\mathrm{Fe}}_3{\mathrm{O}}_4\mathrm{}\left(111\right)\mathrm{}$ films prepared by in situ oxidation of thin Fe(110) films grown on ${\mathrm{Al}}_2{\mathrm{O}}_3\left(112\mathrm{}¯0\right)$ substrates using a Mo(110) buffer layer were investigated by low-energy electron diffraction (LEED), scanning tunneling microscopy (STM), transmission electron microscopy (TEM), and spin-polarized angle-resolved photoemission spectroscopy (SPARPES). The annealing of Fe(110) films at 700 °C in an ${\mathrm{O}}_2$ atmosphere leads to the formation of epitaxial ${\mathrm{Fe}}_3{\mathrm{O}}_4\mathrm{}\left(111\right)\mathrm{}$ films. Atomically resolved STM images of the ${\mathrm{Fe}}_3{\mathrm{O}}_4\mathrm{}\left(111\right)\mathrm{}$ surface show a hexagonal symmetry with 6 Å periodicity. Well-controlled interface properties at the ${\mathrm{Fe}}_3{\mathrm{O}}_4\mathrm{}\left(111\right)/\mathrm{Fe}\mathrm{}\left(110\right)\mathrm{}$ and Fe(110)/Mo(110) interfaces were confirmed by TEM. A high spin polarization value of about $-(60\mathrm{}\pm 5)\%$ was found near the Fermi energy $E_F$ at room temperature by means of SPARPES with a photon energy of $h\nu =21.2\mathrm{}\mathrm{eV}.$ The electronic structure and spin polarization are compared to the corresponding values recently found on epitaxial ${\mathrm{Fe}}_3{\mathrm{O}}_4\mathrm{}\left(111\right)\mathrm{}$ films grown on W(110) single-crystal substrates.

• Received 29 January 2003

DOI:https://doi.org/10.1103/PhysRevB.68.045414