We have studied the correlation between film structure and the azimuthal dependence of the magnetization reversal in (001) and (111) epitaxial Ni films grown on MgO substrates using two different deposition techniques: molecular beam epitaxy (MBE) and dc magnetron sputtering. The films were grown and in situ annealed under identical conditions. The magnetization reversal was investigated using MOKE. The coercive field in the sputtered (001) Ni films exhibits fourfold azimuthal symmetry as expected for crystalline films of good epitaxial quality, while MBE (001) Ni grown films exhibit an additional uniaxial symmetry superimposed to the fourfold symmetry. We performed high-resolution XRD studies as well as cross sectional TEM studies in order to establish similarities and differences in the structure of the films. Both types of films exhibit epitaxial growth and very good crystalline quality with no indication of strain. The main difference between the films is the different magnetic anisotropy. We postulate that this difference may be due to different interfacial structure and/or morphology due to the possible formation of a NiO interfacial layer only present or highly ordered in the MBE grown films. Polarized neutron reflectivity measurements performed on some of the films are correlated with the interfacial structure and magnetic anisotropy. 0 2004 American Vacuum Society.