Sperry Rand Corporation

Roger Edward Lund

Marlin M Hanson

Ernest J Torok

Stanley J Lins

John M Gorres

William J Simon

A method of and an apparatus for improving the selective positioning of single wall domains or bubble domains in a bubble domain memory system is disclosed. The method includes the use of slotted intersecting digit and word drive lines that form memory areas, each memory area being defined by the inside opposing edges of the slotted drive lines at each intersection. Each memory area has four quadrants, three of which are effectively optically blocked by an opaque shield--a bubble domain in the one unblocked quadrant provides the desired Faraday rotation of a plane polarized coherent light beam to generate a beamlet that is optically detected as a binary digital signal. The slotted drive lines are formed below the surface of the bubble domain supporting layer whereby the so-provided magneto static barriers prevent bubble domain sticking in a selected one quadrant of the four quadrants of the memory area and prevent bubble domain escape from the memory area itself.

Method of improving the operation of a single wall domain memory system

Defining the structuring of bubble domains in the magnetizable layer of a bubble domain memory plane is determined by modification of the magnetic characteristics of the magnetizable layer in the confinement area. The memory plane is comprised of a non-magnetic Gadolinium Gallium Garnet (GGG) layer which is a supporting substrate upon which is formed by the liquid phase epitaxy (LPE) method a magnetizable layer in which bubble domains are capable of being generated, sustained and moved about. Formed upon the bubble domain supporting magnetizable layer is a matrix array of conductive drive lines, the intersections of which define respective memory areas. In each memory area the position of the bubble domain in the magnetizable layer is determined by modifying the magnetic characteristics of the magnetizable layer in a confinement area as by an ion milling process. The ion milled confinement area along the line of the thickness gradient generates a perpendicular field H.sub.P that tends to prevent the bubble domain from escaping from the so-defined confinement area. The perpendicular field H.sub.P component that is generated by the thickness gradient produces a sharp potential minimum at the edge of the ion milled region. This potential minimum draws the bubble domain toward the edge of the thickness gradient whereby the bubble domain size may be expanded to fill the confinement area. Additionally, the confinement area may consist of a plurality of interconnected lobes each of which defines a given bubble position, each of which bubble positions may be utilized to define a memory position that may be utilized in an optical page composer of an optical data processing system.

Structuring of bubble domains in a bubble domain memory plane

Defining the structuring of bubble domains in a magnetizable layer of a bubble domain memory plane is determined by modifying the magnetic characteristics of the magnetizable layer in the confinement area. The bubble domain memory plane is comprised of a non-magnetic Gadolinium Gallium Garnet (GGG) layer which is a supporting layer upon which is formed by the liquid phase epitaxy (LPE) method a plurality of magnetizable layers in each of which a bubble domain is capable of being generated and sustained. Upon the memory plane are formed, as by any of many well-known deposition techniques, a matrix array of a parallel set of horizontally oriented X drive lines and an orthogonally oriented parallel set of Y drive lines. Each X drive line, Y drive line intersection of the matrix array defines a memory area having four quadrants. In only one of the four quadrants is there provided a bubble domain supporting magnetizable layer, all other areas of the memory plane having no magnetizable layer or a magnetizable layer of an insufficient thickness to support bubble domains therein. Accordingly, in only one of the four quadrants of each of the memory areas is there a magnetizable layer of sufficient thickness to support a bubble domain thereat.

Bubble domain structuring in bubble domain memory plane

Disclosed is an apparatus for and a method of propagating bubble domains along fixed guidance channel forming stripe domains by capturing them in moveable stripe domains and then moving the capturing moveable stripe domains. The memory plane comprises a non-magnetic Gadolinium Gallium Garnet (GGG) layer which is a supporting substrate upon which are successively formed by the liquid phase epitaxy (LPE) method: a first stripe domain layer, a first non-magnetic spacer layer; a bubble domain layer; a second non-magnetic spacer layer; a second stripe domain layer; and a third non-magnetic spacer layer upon which is formed the necessary propagation circuitry. The method of propagating the bubble domains involves forming fixed guidance channel forming stripe domains in the first stripe domain layer, orienting moveable stripe domains in the second stripe domain layer in a direction orthogonal to the direction of the fixed guidance channels, establishing bubble domains in the bubble domain layer at selected ones of each fixed guidance channel, moveable stripe domain intersection and finally oscillating the moveable stripe domains in a direction parallel to the fixed guidance channels by a time-varying, i.e., temporally changing, localized bias field gradient. A moveable stripe domain in a first position under a bias field gradient producing strip line captures a bubble domain, slowly moves the bubble domain a predetermined propagation direction under the strip line and along its associated fixed guidance channel into a second position under the strip line and then subsequently quickly moves back to its first position under the strip line allowing the bubble domain to escape therefrom leaving the propagated, escaped bubble domain in the second position under the strip line to be captured by a next adjacent downstream moveable stripe domain. Successive capture, propagate, escape operations propagate all the bubble domains along each capturing moveable stripe domain, in parallel, in the downstream propagation direction through the memory plane.

Bubble domain propagation using oscillating stripe domains

A method of and an apparatus for improving the selective positioning of single wall domains or bubbles in a memory system is disclosed. The method includes the use of slotted intersecting digit and word lines that are coated with a magnetic material of relatively high retentivity.

A method of operating and an apparatus comprising a very compact, bit-organized nondestructive readout (NDRO) random-access magnetic memory system is disclosed. The memory system is directed toward an improvement of the memory system of the D. S. Lo, et al., U.S. Pat. No. 3,550,101 and includes a continuous oligatomic ferromagnetic film (a film that is too thin to permit either Bloch walls or cross-tie walls, but does permit Neel walls) that has the property of uniaxial anisotropy which property provides an easy axis in the plane of the film along which the film's remanent magnetization may be aligned in either of two opposed information states and a hard axis in the plane of the film that is perpendicular to the easy axis. The film is initially saturated in a first direction along the easy axis while provided in the plane of the film are static, alternating-directioned parallel and antiparallel bias fields: parallel to the first direction in the vicinity of the memory areas as defined by the intersections of superposed, orthogonal word lines and sense-digit lines and antiparallel to the first direction in the areas between the memory areas. The bias field converts the magnetic domain of the D. S. Lo, et al., patent into a field stabilized domain, analogous to a bubble domain, in which the bias field and the demagnetizing field of the field stabilized domain stabilize the field stabilized domain against disturbing magnetic fields.

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Woodbury, MN, United States of America

Roger Edward Lund