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Contiguous Bubble Domain Propagation Structures

IP.com Disclosure Number: IPCOM000085137D
Original Publication Date: 1976-Feb-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Cohen, MS: AUTHOR

Abstract

An advantageous high-density bubble structure is represented by a gapless structure whose finest detail is considerably larger than the bubble diameter. The limitations of the lithography process and the subsequent fabrication steps are mitigated in this type of structure, thus permitting very high densities. An example of such a structure is the contiguous disk structure (Fig. 1) in which the bubble propagates around the periphery of the figure.

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Contiguous Bubble Domain Propagation Structures

An advantageous high-density bubble structure is represented by a gapless structure whose finest detail is considerably larger than the bubble diameter. The limitations of the lithography process and the subsequent fabrication steps are mitigated in this type of structure, thus permitting very high densities. An example of such a structure is the contiguous disk structure (Fig. 1) in which the bubble propagates around the periphery of the figure.

During the "favorable" part of the rotation period of the in-plane field, the bubble traverses the curved portion of the disks, from cusp to cusp; however, during the "unfavorable" portion of the period means must be provided to hold the bubble in the vicinity of the cusp so that the bubble does not leave its track.

Several mechanisms have been suggested for providing this binding force, but certain difficulties have been encountered either in proper exploitation of the physical principles involved, or in the fabrication. Two possible binding mechanisms are used here which allow a relatively simple fabrication technique.

The mechanisms are: (1) decrease of wall energy of a bubble at the edge of a piece of bubble material, and (2) decrease of magnetostatic energy by NiFe under a bubble. Mechanism (1) is effective simply because no wall is necessary at the "void" side of a bubble at an edge. Mechanism (2) is explained by the improved flux closure offered by such a structure.

The fabrication of a device where both mechanisms are acting is shown in Fig. 2, which is a cross-sectional elevation taken along direction 2-2 of Fig. 1. Here a "holey" substrate is employed. Thus, for example, the inside of the structure in Fig. 1 would be a hole in the substrate (that is, a hole down to a base supporting layer). A practical method of obtaining such a holey substrate is to develop a hole in a photo- or electron- resist layer, suitably harden the layer, and then deposit the overlying films directly on the resist.

In Fig. 2 the amorphous bubble film, the spacer layer 10, and the NiFe film 12 are sequentially deposited. The presence of the void makes possible the first mechanism of wall energy as a bubble-binding mechanism. If, however, the relative thicknesses of the resist and the multiple layers are chosen correctly, the NiFe film 12 in the hole will be in proximity to the bottom of the amorphous film, thus permitting mechanism (2) to act on a bubble in the vicinity of the edge.

Holes may be made in other suitable substrates, not directly in resist, if desired. For example, su...