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Stress Induced Anisotropy for Magnetoresistive Sensors

IP.com Disclosure Number: IPCOM000080133D
Original Publication Date: 1973-Jan-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Anderson, RA: AUTHOR [+5]

Abstract

Magnetoresistive sensor materials, Ni-Fe, Ni-Co, and the like, have become more in demand as detectors of magnetically stored information because they are not dependent on the rate of flux change.

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Stress Induced Anisotropy for Magnetoresistive Sensors

Magnetoresistive sensor materials, Ni-Fe, Ni-Co, and the like, have become more in demand as detectors of magnetically stored information because they are not dependent on the rate of flux change.

In many sensing applications, where the media produce relatively large sense fields, it is desirable that the magnetoresistive sensors possess large magnetic anisotropies. The achievement of a large anisotropy offers a convenient way of preventing the saturation of magnetoresistive sensors, without extreme reduction of its dimensions and, consequently simplifies the fabrication of the sensors and the detection of recorded information (lack of saturation gives rise to well-defined, unclipped pulses). A way has been found to create such large anisotropies by using stress induced anisotropy in the magnetoresistive material, namely, by depositing a magnetostrictive material on a substrate that has an anisotropic thermal coefficient of expansion.

It is known that noncubic materials such as quartz and sapphire, for example, exhibit anisotropic coefficients of thermal expansion when the material's C=axis lies in the plane of the substrate. The evaporation of a magnetoresistive film onto a quartz or sapphire single-crystal substrate at temperatures of the order of 250 degrees C, will induce an anisotropic stress in the film. If the films are also magnetostrictive, this induced stress will also cause magnetoelastic anisotropy. The magnitude and sign of this anisotropy are given by H(kappa sigma) = 2 kappa sigma over M, where kappa sigma = (3 over 2)) lambda sigma, M= saturation magnetization of the alloy, and sigma = YS, where Y is Young's modulus and S =...