Obliquely evaporated iron-cobalt and iron-cobalt-chromium thin film recording media

Thin films of Fe-Co and Fe-Co-Cr were deposited onto a variety of substrates by e-beam evaporation at an oblique angle of incidence of 60 degrees to the substrate normal. Deposition at this angle results in the formation of an easy axis in the plane of the magnetic films, oriented perpendicular to the plane of vapor incidence. Electron microscopy reveals the anisotropy to be due to the formation of parallel crystallite chains, which are, on the average, aligned transverse to the plane of the vapor beam. The lateral dimensions and the extent of alignment of these chains depend mainly on the substrate microtopography, so that with increasing surface roughness the alignment decreases, thereby leading to a decrease of the squareness value S and the in-plane anisotropy Mr(easy)/Mr(hard). The film coercivity, too, is to some degree determined by such aligned crystallite chains. However, Hc in general increases with increasing substrate microtopography and with decreasing film thickness.