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Coupled Film Magnetoresistive Detector for Use with Submicron Size Bubble Domains

IP.com Disclosure Number: IPCOM000078912D
Original Publication Date: 1973-Apr-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Almasi, GS: AUTHOR [+4]

Abstract

Detection of magnetic bubble domains, using a magnetoresistive effect, depends upon the magnetoresistive (MR) element being able to assume two predictable states. These states are with the magnetization parallel and perpendicular to the bias current flowing in the detector. Normally, the crystalline anisotropy of a uniaxial film and the field from the bubble (Hb) are the forces used, with the bubble field being equal to or greater than the anisotropy field. However, small bubbles require small detectors and shape anisotropy (Hd) becomes larger than crystalline anisotropy. The smaller the ratio of Hb/Hd, the less the magnetization of the detector is rotated with the net result being a smaller sense signal.

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Coupled Film Magnetoresistive Detector for Use with Submicron Size Bubble Domains

Detection of magnetic bubble domains, using a magnetoresistive effect, depends upon the magnetoresistive (MR) element being able to assume two predictable states. These states are with the magnetization parallel and perpendicular to the bias current flowing in the detector. Normally, the crystalline anisotropy of a uniaxial film and the field from the bubble (Hb) are the forces used, with the bubble field being equal to or greater than the anisotropy field. However, small bubbles require small detectors and shape anisotropy (Hd) becomes larger than crystalline anisotropy. The smaller the ratio of Hb/Hd, the less the magnetization of the detector is rotated with the net result being a smaller sense signal.

What is proposed is the use of a coupled film to reduce or eliminate demagnetization effects in an MR detector. Illustrated is a top view of a closed- flux MR detector. Fig. 1 depicts the detector in the absence of a bubble, while Fig. 2 depicts the detector in the presence of a bubble. A bias current 1b is shown as flowing through a conductor of high-resistivity material, utilized to break up exchange coupling. For ease of presentation, a side view of the MR detector is shown in Fig. 3 which also depicts the state of the detector in the absence of a bubble. In Figs. 1 and 3, the magnetization of the detector is seen to be coupled, in that the magnetization of a first permalloy lay...