Anisotropy in Epitaxial Fe3O4 and NiFe2O4 Thin Films

Abstract
Fe3O4 and NiFe2O4 films were deposited on and MgO substrates by dc magnetron reactive sputtering. X-ray diffraction studies indicate epitaxial films under an inplane tensile stress. Magnetization studies show that the moments of the films are unsaturated in 70 kOe applied fields and they approach bulk values only in extrapolation. Conversion electron Mössbauer spectroscopy (CEMS) studies indicate bulk parameters for the Fe3O4 films, but show deviations from bulk properties for NiFe2O4 films. CEMS studies further indicate a random moment distribution for all films which is an unexpected property. In-plane torque curves are discussed in terms of single crystal behavior. The effect of the inplane tensile stress is also indicated in the torque curves.