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SLM Thin Film Magnetoresistive Sensor for Bubble Domains

IP.com Disclosure Number: IPCOM000087223D
Original Publication Date: 1976-Dec-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Cohen, MS: AUTHOR

Abstract

In bubble domain devices, it is common to fabricate bubble sensors from a bubble expander comprised of successive columns of chevrons of increasing length, together with a magnetoresistive sensor. The sense element is typically either a strip of NiFe that is considerably thinner than the NiFe of the chevrons (thin-film sensor) or a strip of NiFe having a serpentine form which interconnects the chevrons of a column and is of the same thickness as the chevrons (thick-film sensor).

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SLM Thin Film Magnetoresistive Sensor for Bubble Domains

In bubble domain devices, it is common to fabricate bubble sensors from a bubble expander comprised of successive columns of chevrons of increasing length, together with a magnetoresistive sensor. The sense element is typically either a strip of NiFe that is considerably thinner than the NiFe of the chevrons (thin-film sensor) or a strip of NiFe having a serpentine form which interconnects the chevrons of a column and is of the same thickness as the chevrons (thick-film sensor).

In order to provide a thin-film sensor element which provides greater output signal, a technique is described for making the thin-film sensor from a NiFe strip located between two chevron columns, where the sensor strip does not contact the chevrons. Single-level metallurgy is used to provide this sensor, which is advantageous over the straightforward substitution of a thick-film sense element positioned between chevron columns.

In the present thin-film sensor, an underlying NiFe element made of a thin film (about 300 angstroms thick) is associated with every thick film element. This thin film, termed a "shadow" film, is either in direct contact with the bubble domain film, or is a short distance away for maximum sensitivity of the sensor, where the sensor is a portion of the thin shadow film. The thick-film NiFe elements are used for normal bubble domain functions, such as propagation, and have the usual spacing from the bubble domain film.

The device is made by the conventional techniques of plating through a resist mask, except that prior to deposition of an oxide spacer, a thin layer of NiFe is deposited. This is illustrated in Fig. 1A, where the bubble film has a continuous thin-film layer of NiFe thereover. The oxide spacer is deposited over the thin shadow layer and the thick NiFe elements are provided in the usual manner. In this diagram, a "capping" layer is included on top of the thick NiFe layer for the purpose of p...