William D Simon

US Patent:

39640345, Jun 15, 1976

Filed:

Jul 1, 1974

Appl. No.:

5/484833

Inventors:

Ernest J. Torok - St. Paul MN
Roger E. Lund - Cottage Grove MN
William J. Simon - Shakopee MN

Assignee:

Sperry Rand Corporation - New York NY

International Classification:

G11C 1114

US Classification:

340174TF

Abstract:

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.