Abstract: A magnetic thin-film disc having a magnetic thin film formed of a lower and upper sublayers. The two sublayers are characterized by lower coercivity, smaller grains, and more isolated grains in the lower sublayer, and higher coercivity, and larger grains in the upper sublayer. In one embodiment, the sublayers are characterized by an increasing magnetic remanence on progressing from the outer to the inner diameter of the disc. Also disclosed are sputtering methods for producing the disc.

Abstract: The method and apparatus of this invention are to sort disks into predetermined ranks depending on their thickness. The disks are conveyed stepwise in each supply cassette at equal intervals, and partly pushed to measure their thickness. They are transferred from the supply cassette to a receiving cassette of the corresponding thickness rank.

Abstract: A thin film magnetic disc having a carbon overcoat which is characterized by (a) a thickness of less than about 500 .ANG. and (b) surface nitrogen atoms having a nitrogen (1s) electron principle binding energy, as determined by electron spectroscopy for chemical analysis (ESCA), of about 399.4 eV. The nitrogen atoms enhance lubricant adhesion to the overcoat. In a preferred embodiment, the overcoat is formed by sputtering under an argon/hydrocarbon/nitrogen gas atmosphere to produce long resistance-to-erosion times, and high lubricity properties.

Abstract: A method for texturing a disc substrate, and a particle slurry for use in the method. The slurry includes two populations of different-size particles, preferably one population containing particles in a 3 micron size range, and a second population containing particles in a 1 micron size range. The particles, when used to abrade the surface of a disc, create a surface texture characterized by a low peak/peak-to-valley ratio.

Abstract: A target assembly is provided having a circular flat target with an inner ring and an outer ring extending from the sputtering surface. A ferromagnetic outer pole member surrounds the target and the outer ring. A ferromagnetic inner pole member is surrounded by the target and the inner ring. A ferromagnetic backing member is positioned against the base surface of the target and has an outer portion positioned against the outer pole member, and an inner portion positioned against the inner pole member. These are positioned relative to the source of the magnetic field for conducting flux in a first path through the outer portion and the outer pole member, across the sputtering surface between the outer and inner rings, and through the inner pole member and inner portion. The backing member further includes a shunt portion intermediate between and magnetically spaced from the inner and outer portions.

Abstract: Method and apparatus for texturing a substrate for use in a magnetic recording disc. A texturing pad used in the invention has inner and outer coaxial regions, with the outer region being more compressible. When the pad and a substrate are rotated about parallel, offset axes, and pressed against one another in the presence of a particle slurry, the inner, less compressible region of the pad produces a deeper-groove texturing on an inner annular surface region of the disc.

Abstract: A method of forming an isotropic texture having a selected summit density and surface roughness in a selected inner-diameter annular zone of a thin-film medium substrate having a polished metal coating on the substrate. The zone is selectively exposed to a chemical etchant, under etchant strength, temperature, and exposure time, until the selected summit density and roughness are achieved. In a preferred embodiment, the etching conditions are selected to produce a summit density between about 500-20,000/mm.sup.2, and an arithmetic mean roughness value between about 20-70 .ANG. in the inner zone, and a substantially reduced roughness value in an annular, isotropically textured outer-diameter zone of the coating. A thin-film medium formed on the substrate is suitable for near-contact recording.

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 method of evaluating the start/stop lifetime of a thin-film magnetic medium having an overcoat formed by sputtering a carbon-containing overcoat on a magnetic-film substrate. Resistance to erosion of the medium is evaluated by the time required to wear away the overcoat during a high-speed abrasion treatment. Lubricity is measured either in terms of the coefficient of friction of the disc, or in terms or surface hydrophobicity, as gauged by one of a number of measurable surface properties. The method allows for rapid assessment of disc wear properties, and can be used to optimize sputtering conditions required to achieve selected hardness and lubricity properties in a disc overcoat.

Abstract: A high-coercivity thin-film magnetic recording medium, and method of producing the medium, is disclosed. The medium has a sputtered chromium underlayer, preferably about 300-1,000 .ANG. thick, and a sputtered magnetic layer, preferably about 200-800 .ANG. thick, composed of an alloy containing between 70-80% cobalt, 10-20% chromium, 3-20% platinum, and 2-10% tantalum, formed on the chromium underlayer. The medium is characterized by high coercivity, resolution, amplitude and loop squareness value, and low bit shift.

Abstract: A high-coercivity thin-film magnetic recording medium, and method of producing the medium, is disclosed. The medium has a sputtered chromium underlayer, preferably about 300-1,000 .ANG. thick, and a sputtered magnetic layer, preferably about 200-800 .ANG. thick, composed of an alloy containing between 70-80% cobalt, 10-20% chromium, 3-20% platinum, and 2-10% tantalum, formed on the chromium underlayer. The medium is characterized by high coercivity, resolution, amplitude and loop squareness value, and low bit shift.

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.

Abstract: Method and apparatus for treating the surface of a magnetic disc to remove surface asperities and loosely bound material. The disc is alternatively treated by contact with a pair of moving belt-like tapes, a pair of flying heads, and second contact with the belt-like tape, with the disc carried at a fixed position for rotation in a vertical plane throughout, but rotated at a higher speed during the intermediate flying waffling step. The first and/or second tape-treatment steps can be used to apply a lubricant film to the disc surface.

Abstract: A high-coercivity thin-film magnetic recording medium, and method of producing the medium, is disclosed. The medium has a sputtered chromium underlayer, preferably about 600-1,000 .ANG. thick, and a sputtered magnetic layer, preferably about 200-800 .ANG. thick, composed of an alloy containing between 70-80% cobalt, 10-20% chromium, 8-20% platinum, and 2-10% tantalum, formed on the chromium underlayer. The medium is characterized by high coercivity, resolution, amplitude and loop squareness value, and low bit shift.