Abstract: A thin-film medium formed on a low-friction glass substrate. The substrate is micro-roughened by plasma etching, under conditions which produce a desired surface density of zero crossings and depth of microscopic surface irregularities.

Abstract: A high-density thin-film magnetic disc and method of producing the disc. In forming the disc, chromium is sputtered onto a smooth-surfaced, non-metallic substrate, such as a glass substrate, first at room temperature, to form a substratum with a random structure, then at a high temperature, to form a chromium underlayer with anisotropic crystal orientation. A cobalt-based alloy is sputtered onto the underlayer to form the thin film magnetic layer. The disc has high coercivity, low bit shift, and can be operated at a flying height of between 2-4 .mu.inches.