PROPERTIES OF EPITAXIAL BA-HEXAFERRITE THIN-FILMS ON A-PLANE, R-PLANE, AND C-PLANE ORIENTED SAPPHIRE SUBSTRATES

Thin films of Ba-hexaferrite of the magnetoplumbite structure have bee n prepared on sapphire substrates of orientation (1120BAR), (1102BAR), and (0001BAR). Torque magnetometry indicates easy axes parallel, tilt ed off parallel, and perpendicular to the substrate for the A-, R-, an d C-plane substrates. X-ray diffraction shows that this is due to epit axy between the Ba-ferrite and sapphire. For each substrate orientatio n, the c axes of the Ba-hexaferrite and sapphire are parallel and the directions of close packing in the close-packed oxygen planes perpendi cular to the c axes are parallel. Torque measurements are consistent w ith the combined effects of crystal and shape anisotropy. These result s suggest that Ba-hexaferrite thin films with an easy axis at any angl e with respect to the substrate can be prepared by appropriate choice of the sapphire substrate orientation, which may be of interest for mi crowave and other applications.