Epitaxial magnetite (Fe3O4) thin films were deposited by molecular beam epitaxy using molecular oxygen as the oxidant. Films deposited on (001) SrTiO3, (001) MgO, and (001) BaTiO3 Surfaces are epitaxial with the film (001) parallel to the substrate (001) and the film < 100 > parallel to the substrate (100). X-ray magnetic circular dichroism was used to determine the relative Fe2+/Fe3+ stoichiometry of the magnetite films, which was nearly independent of oxygen partial pressure over the range studied. All films show no in-plane magnetic anisotropy. Coercive fields ranged from 0.019 to 0.039 T and depended on film roughness. (c) 2007 American Vacuum Society.