Design of Bubble Device Elements Employing Ion-Implanted Propagation Patterns

Recently, multiple implantation conditions,1 single epitaxial layer composition,2,3 and propagation pattern designs4 have been demonstrated that should permit the fabrication of major-minor loop-organized bubble memory devices based on the use of ion-implanted propagation patterns (I2P2's).5 The use of I2P2's at 8-/tm period is expected to permit at least a factor of two increase in the minimum feature size, relative to Permalloy propagation patterns (3P's) of the same period, while reducing the coil power by a factor of two or more. The device components are not yet developed, however. Some early investigations of propagation 5 and of other components 6,7 have been reported, and a more complete account 8 of nucleate generator design has been given. In this paper, descriptions are given of components which provide insight into the design of large circuits based on ionimplanted propagation. Experimental 8-jum period magnetic bubble devices have been made on YSmLuCaGe-IG films, as indicated schematically in Fig. 1. The damaged layer has a stronger overall in-plane preference when a combination of three implantations is used to produce a more uniform damage profile, and a thicker layer with planar magnetization. Because of this stronger preference, single epitaxial garnet films can be used 230 THE BELL SYSTEM TECHNICAL JOURNAL, FEBRUARY 1980