Use of multi-layer thin films as stress sensor
First Claim
1. A method of sensing pressure in which applied pressure causes a change in magnetization vectors of ferromagnetic layers and a corresponding change in resistance comprising the steps of:
- providing a sensing device with a sensor including a plurality of layers, the plurality of layers comprising a non magnetic conducting layer disposed between at least two ferromagnetic layers, at least one of the ferromagnetic layers having a non-zero magnetostriction;
biasing at least one of the two ferromagnetic layers with an externally supplied current such that the magnetization vectors of each ferromagnetic layer in a biased state are changed from an initial state; and
sensing a resistance in the plurality of layers upon application of pressure while the externally supplied current is being applied, the applied pressure causing the magnetization vectors of at least one of the ferromagnetic layers to change from the biased state, and thereby result in a change in resistance.
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Abstract
The present invention provides a pressure sensing device that includes at least one GMR sensor, and preferably an array of GMR sensors, with each GMR sensor having a conducting spacer layer interposed between two ferromagnetic layers. In an unbiased state, the magnetization vector of each of the ferromagnetic layers is preferably parallel to each other. Upon application of a current, however, the magnetization vector of each ferromagnetic layer is changed, preferably to an antiparallel position, in which state the sensor is used to then sense stress applied thereto. Upon application of stress, the magnetization vectors of both free magnetic layers will rotate, thus causing a corresponding and proportionally related change in the resistance of the sensor. This change in resistance can be sensed and used to calculate the stress applied thereto.
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Citations
19 Claims
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1. A method of sensing pressure in which applied pressure causes a change in magnetization vectors of ferromagnetic layers and a corresponding change in resistance comprising the steps of:
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providing a sensing device with a sensor including a plurality of layers, the plurality of layers comprising a non magnetic conducting layer disposed between at least two ferromagnetic layers, at least one of the ferromagnetic layers having a non-zero magnetostriction;
biasing at least one of the two ferromagnetic layers with an externally supplied current such that the magnetization vectors of each ferromagnetic layer in a biased state are changed from an initial state; and
sensing a resistance in the plurality of layers upon application of pressure while the externally supplied current is being applied, the applied pressure causing the magnetization vectors of at least one of the ferromagnetic layers to change from the biased state, and thereby result in a change in resistance. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification