A study of orientation ratio in longitudinal magnetic thin-film media on plasma-treated textured substrates

The effects of plasma treatment of textured substrates on orientation ratio (OR) as well as in-plane Cr(200)/Co(11.0) preferred orientation (PO) and coercivity (Hc) in longitudinal magnetic recording media have been systematically investigated. OR is found to increase by ∼0.2–0.3 with enhanced PO and Hc for samples with slightly rf sputter etched substrates. Further Ar+ plasma dry etching (higher power/longer duration) leads to a slow decrease of OR to ≤1, then a worsened/vanishing PO and finally a drastic drop in Hc. The origin of OR is primarily attributed to stress effects (of most importance being the anisotropic stress induced preferential easy axis distribution), with anisotropic topography and PO as two necessary preconditions for OR >1. Ion beam bombardment induced chemical/structural modifications and residual stress in the substrate surface layer may play important roles in film growth/structures/properties and therefore in the mechanisms of the evolution of OR with plasma treatment.