Preparation and magnetic properties of epitaxial barium ferrite thin films on sapphire with in-plane, uniaxial anisotropy

For the first time, epitaxial barium-ferrite thin films, predominantly of the magnetoplumbite structure, with an easy axis of magnetization in-plane have been prepared on single-crystal sapphire substrates by reactive sputtering and post-deposition annealing. Lattice images by high resolution transmission electron microscopy reveal the probable origin of the magnetic anisotropy to be epitaxy between the Ba-ferrite and sapphire, causing the c-axis of the Ba-ferrite to lie nearly in-plane. Coercivities of more than 9 kOe have been achieved in the easy-axis direction in Al substituted films with magnetization reduced to approximately 25% of the value for unsubstituted films.