Magnetic multilayer strain gage
First Claim
1. In a strain gauge comprising magnetostrictive means having ferromagnetic material to which stress is applied causing angular displacement of magnetic moments therein away from an unstressed easy axis and means for measuring changes in electrical resistance of the magnetostrictive means in response to said angular displacement of the magnetic moments, the improvement residing in said ferromagnetic material being formed into a plurality of layers parallel to the easy axis and said magnetostrictive means further including, antiferromagnetic layers of conductive material between said layers of the ferromagnetic material and means applying a magnetic field to said layers for realigning the magnetic moments relative to the easy axis to increase the measured changes in the electrical resistance caused by the stress applied.
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Abstract
A strain gauge comprised of a magnetic multilayer assembly exhibiting spialve effect with individual ferromagnetic layers possessing magnetostrictive properties. A magnetic field source is used to bias the magnetic moments of the ferromagnetic layers in a given direction whereby stress applied causes previously antiferromagnetically coupled moments to be angularly realigned toward a ferromagnetic arrangement. Such realignment causes a corresponding resistance change of unexpectedly high magnitude thereby providing a highly sensitive strain gauge.
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Citations
10 Claims
- 1. In a strain gauge comprising magnetostrictive means having ferromagnetic material to which stress is applied causing angular displacement of magnetic moments therein away from an unstressed easy axis and means for measuring changes in electrical resistance of the magnetostrictive means in response to said angular displacement of the magnetic moments, the improvement residing in said ferromagnetic material being formed into a plurality of layers parallel to the easy axis and said magnetostrictive means further including, antiferromagnetic layers of conductive material between said layers of the ferromagnetic material and means applying a magnetic field to said layers for realigning the magnetic moments relative to the easy axis to increase the measured changes in the electrical resistance caused by the stress applied.
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