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Magnetic Thin-Film Sense Head With Stress-Induced Anisotropy for Avoiding Instabilities

IP.com Disclosure Number: IPCOM000062501D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Max, E: AUTHOR [+2]

Abstract

For avoiding magnetic instabilities, as may occur in thin-film heads, controlled mechanical stress is produced in a sense material with low negative magnetostriction. The combination of negative magnetostriction and mechanical stress produces a controlled magnetic anisotropy which avoids magnetic instabilities. Instabilities may be reduced by using low negative magnetostriction material as was found by experiment and as is described in U.S. Patent 4,242,710. The basic concept of the solution described in this article is that a specific controlled magnetic anisotropy, eliminating instability effects, may be generated by suitable measures in magnetostrictive permalloy. Magnetostriction in permalloy may be controlled through the composition.

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Magnetic Thin-Film Sense Head With Stress-Induced Anisotropy for Avoiding Instabilities

For avoiding magnetic instabilities, as may occur in thin-film heads, controlled mechanical stress is produced in a sense material with low negative magnetostriction. The combination of negative magnetostriction and mechanical stress produces a controlled magnetic anisotropy which avoids magnetic instabilities. Instabilities may be reduced by using low negative magnetostriction material as was found by experiment and as is described in U.S. Patent 4,242,710. The basic concept of the solution described in this article is that a specific controlled magnetic anisotropy, eliminating instability effects, may be generated by suitable measures in magnetostrictive permalloy. Magnetostriction in permalloy may be controlled through the composition. The following relations apply:

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A free magnetostrictive film MF expands and/or is compressed under the influence of a magnetic field H (Fig. 1). Positive magnetostriction (g > 0) expands and negative magnetostriction compresses the film in the direction of the applied magnetic field H. For g > 0 (Fig. 1A), a magnetic anisotropy is induced for expanding and compressing the film in the x and the y direction, respectively. The anisotropy is such that magnetization M occurs in the x direction. This holds with opposite signs for g < 0 (Fig. 1B). If a magnetostrictive film MF is deposited on a substrate S, the deformation may be transferred to the film by expanding or compressing substrate S. This is accomplished by the following measures. During deposition of permalloy film MF, substrate S is suitably expanded or compressed. If substrate S is unstressed after deposition of the film, the permalloy...