# US 4,588,653 A · Magnetic memory disk

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- Number: US 4,588,653 A
- Document ID: US4588653A
- Status: Granted
- Kind: A
- Application number: 06/619,475
- Filed: 1984-06-11
- Granted: 1986-05-13
- Earliest claimed: 1983-08-29
- Assignees: Dynamic Disk, Inc.
- Inventors: Daniel X. Wray
- Web page: https://patentgrep.com/patent/US4588653A

## CPC

- G11B 5/858: Producing a magnetic layer by electro-plating or electroless plating
- C25D 5/02: Electroplating of selected surface areas
- C25D 5/022: {using masking means}
- C25D 7/001: {Magnets}
- C25D 17/008: {Current shielding devices}
- Y10S 428/928: Magnetic property
- Y10T 428/12389: having variation in thickness
- Y10T 428/12458: having composition, density, or hardness gradient
- Y10T 428/12736: Al-base component
- Y10T 428/12792: Zn-base component
- Y10T 428/12861: Group VIII or IB metal-base component
- Y10T 428/12944: Ni-base component
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## 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.

## Claims

### Claim 1

A magnetic memory disk, comprising:
a disk-shaped substrate;
an electroplated base layer over a surface of the disk; and
an electroplated magnetic layer formed on the base layer, said magnetic layer comprising an alloy of at least two metals varying in relative concentrations in the alloy in a controlled fashion radially along the disk and providing a controlled varying value of coercivity in the radial direction of the disk.

### Claim 2 (depends on 1)

A magnetic memory disk according to claim 1 wherein the alloy includes cobalt and nickel.

### Claim 3 (depends on 1)

A disk according to claim 1 wherein the magnetic layer has a predetermined thickness which varies in a controlled fashion in the radial direction to provide predetermined remanence characteristics which vary along the radius of the disk.

### Claim 4 (depends on 1)

A disk according to claim 1, wherein the substrate is aluminum and including a zinc layer formed on the surface of the substrate, wherein said base layer is formed on the surface of the zinc layer.

### Claim 5

A magnetic memory disk, comprising:
a disk-shaped substrate;
an electroplated base layer formed over a surface of the substrate; and
an electroplated magnetic layer formed on the base layer, said magnetic layer having a controlled varying thickness in the radial direction to provide predetermined magnetic response characteristics, said magnetic layer being comprised of an alloy of at least two metals, wherein the relative concentration of the metals varies in a controlled fashion in the radial direction to provide predetermined coercivity characteristics.

### Claim 6 (depends on 5)

A memory disk according to claim 5 wherein the magnetic layer includes cobalt and nickel.

### Claim 7 (depends on 5)

A memory disk according to claim 5 wherein the magnetic layer includes cobalt, nickel and phosphorus.

### Claim 8 (depends on 5)

A disk according to claim 5, wherein the substrate is aluminum and including a zinc layer formed on the surface of the substrate, wherein said base layer is formed on the surface of the zinc layer.