yEpitaxial magnetite (Fe3O4) thin films were deposited on (001) SrTiO3 substrates by molecular beam epitaxy using molecular oxygen and characterized by transmission electron microscopy and magneto-optic Kerr effect measurements. The films are epitaxial with (001)f parallel to(001)s and [110]f parallel to[110]s and the film/substrate interface is nearly atomically abrupt. Misfit dislocations and twins are present in the film due to the large mismatch between the film and substrate. Antiphase boundaries were also observed. The values for the coercive field of the epitaxial film are nearly the same as those of bulk magnetite. (C) 2007 American Vacuum Society.