Strain mediated asymmetric response of the cation distribution on epitaxial CoFe ₂ O ₄ films

The asymmetric response of the cation distribution on [0 0 1] oriented CoFe ₂ O ₄ films were examined. Depending on the deposition temperature and substrates (MgO(0 0 1) or SrTiO ₃ (0 0 1)), the films exhibited a range of compressive or tensile strain states along the out-of-plane. With increases in deposition temperature, the initial compressive (tensile) strain for the films grown on MgO(0 0 1) (SrTiO ₃ (0 0 1)) was reduced. Furthermore, the out-of-plane (in-plane) magnetic anisotropy of the film grown on MgO(0 0 1) (SrTiO ₃ (0 0 1)) decreased with increasing deposition temperature. The uniaxial magnetic anisotropy energy calculation based on the magnetic anisotropy (crystalline and shape) and strain of films confirmed that the strain reduction with increasing deposition temperature is the main source of the uniaxial magnetic anisotropy reduction, regardless of the sign of the strain. X-ray photoelectron spectroscopy explained the saturation magnetization variation by the cation distribution depending on the strain state. Furthermore, the calculated magnetic moment based on the cation distribution were well matched for the high crystalline films.