Use of multi-layer thin films as stress sensors
First Claim
1. An apparatus for sensing pressure comprising:
- a sensor including;
first and second free ferromagnetic layers; and
a non magnetic conducting layer disposed between the first and second free ferromagnetic layers, the non magnetic conducting layer providing ferromagnetic coupling of the first and second free ferromagnetic layers in an initial state such that magnetization vectors of the first and second free ferromagnetic layers are substantially parallel to each other, wherein applied pressure causes a change in the magnetization vectors of the first and second ferromagnetic layers through the property of non-zero magnetostriction and a corresponding change in resistance of the first and second ferromagnetic layers.
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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
24 Claims
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1. An apparatus for sensing pressure comprising:
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a sensor including;
first and second free ferromagnetic layers; and
a non magnetic conducting layer disposed between the first and second free ferromagnetic layers, the non magnetic conducting layer providing ferromagnetic coupling of the first and second free ferromagnetic layers in an initial state such that magnetization vectors of the first and second free ferromagnetic layers are substantially parallel to each other, wherein applied pressure causes a change in the magnetization vectors of the first and second ferromagnetic layers through the property of non-zero magnetostriction and a corresponding change in resistance of the first and second ferromagnetic layers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification