Abstract: A magnetic memory disk which has controlled magnetic characteristics in the radial direction is provided by controlling the thickness and composition of the magnetic layer which is formed on the disk. The thickness of the layer may be varied in the radial direction to control the remanence of the disk and the composition of the magnetic layer varied to control the coercivity of the disk. The magnetic layer is formed by an electroplating operation employing one or more rotating apertured masks in an electrolyte solution between an anode and a disk (cathode) which is to be plated. The thickness of the plated layer is determined by the configuration of the apertures in the mask, and the relative composition of the layer is determined by the variation and distance of the mask to the disk in the radial direction. Thickness characteristics of layers other than the magnetic layer may also be precisely controlled in the radial direction to achieve desired characteristics.

Abstract: A process and apparatus for producing magnetic memory disks, and the like, of the type in which a thin layer of fine grain nickel/phosphorous paramagnetic material is first deposited on a large grain electrically conductive substrate, and a main magnetic layer is then electroplated over the nickel/phosphorous paramagnetic layer. In the practice of the method of the invention, the paramagnetic layer is electroplated onto the substrate through one or more openings in one or more rotating masks to provide directly a smooth fine grain layer of uniform density and thickness so as to obviate any necessity for time consuming and expensive polishing and burnishing operations of the paramagnetic film prior to the electroplating thereon of the main magnetic film; and the magnetic layer is also electroplated onto the paramagnetic layer through openings in one or more masks to provide a magnetic layer of controlled thickness for uniform magnetic response over the entire surface of the disk.