Magnetic and crystallographic properties of molecular beam epitaxially grown Fe3O4/NiO superlattices and Fe3O4 filmsWe have grown epitaxial NiO ͕111͖ films of thicknesses ranging from 60 to 1200 Å, deposited 45 Å NiFe films on these NiO substrates, and made measurements of exchange field and coercivity, of the effective uniaxial anisotropy, of rotational hysteresis, and of the training effect on these films. We find that the large coercive fields, ϳ500 Oe, observed in these epitaxial systems can be understood using a model in which the magnetization reversal process is by rotation, with the coercive field determined by the effective uniaxial anisotropy of the system. This effective anisotropy is in turn determined by the anisotropy of the NiO and depends on NiO thickness.