Permalloy Rail-Cylindrical Magnetic Domain Systems

Abstract

Recently proposed bubble‐memory designs employing Permalloy rails are examined to determine an optimization of their geometries. This is done by determining the interaction force of Permalloy films with cylindrical domains. The appropriate rail geometry is shown to yield a bistable condition for the bubbles; that is, the reading of a one or zero is insured by the fact that the bubbles will not ride directly underneath the rail but only on one side of the rail. Calculations of the forces between bubbles and various geometric shapes (squares, circles, etc.) are also given. The results enable a determination of the geometric shape required to propagate bubbles along the rails with the least expense of energy when a single‐phase drive circuit is used. General design considerations resulting from the mutual repulsive force between bubbles and the effects of demagnetizing fields are included in the above analyses.