Use of multi-layer thin films as stress sensors
First Claim
1. A method of sensing pressure in which applied pressure causes a change in the magnetization vectors of ferromagnetic layers within the device and a corresponding change in resistance that can be sensed upon application of an externally supplied voltage comprising the steps of:
- providing a sensing device with a sensor including plurality of layers, the plurality of layers comprising a non magnetic insulating barrier layer disposed between at least two ferromagnetic layers which are in an initial state such that their magnetization vectors are stable with respect to each other, and at least one of the ferromagnetic layers having non-zero magnetostriction; and
sensing the resistance in the plurality of layers upon application of pressure while the externally supplied voltage is applied, the applied pressure causing the magnetization vector of at least one of the ferromagnetic layers to rotate from the initial state through the property of magnetostriction and thereby changing the resistance to a tunneling current produced by the applied voltage that flows in a direction orthogonal to a plane of the plurality of layers.
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Abstract
The present invention provides a pressure sensing device that includes at least one TMR sensor, and preferably an array of TMR sensors, with each TMR sensor having an insulating spacer layer interposed between a pinned and a free ferromagnetic layer. In an unbiased state, the magnetization vector of each of the ferromagnetic layers is preferably parallel to each other. Upon application of a small voltage, the magnetization vectors remain unchanged. Upon application of stress, the magnetization vector of the free magnetic layer 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
85 Claims
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1. A method of sensing pressure in which applied pressure causes a change in the magnetization vectors of ferromagnetic layers within the device and a corresponding change in resistance that can be sensed upon application of an externally supplied voltage comprising the steps of:
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providing a sensing device with a sensor including plurality of layers, the plurality of layers comprising a non magnetic insulating barrier layer disposed between at least two ferromagnetic layers which are in an initial state such that their magnetization vectors are stable with respect to each other, and at least one of the ferromagnetic layers having non-zero magnetostriction; and sensing the resistance in the plurality of layers upon application of pressure while the externally supplied voltage is applied, the applied pressure causing the magnetization vector of at least one of the ferromagnetic layers to rotate from the initial state through the property of magnetostriction and thereby changing the resistance to a tunneling current produced by the applied voltage that flows in a direction orthogonal to a plane of the plurality of layers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A sensor apparatus that is capable of sensing an applied pressure using an externally supplied current comprising:
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a sensing device with at least one sensor including a plurality of layers, the plurality of layers comprising a non magnetic insulating barrier layer disposed between two ferromagnetic layers, and at least one of the ferromagnetic layers having non-zero magnetostriction, wherein the applied pressure will cause a change in the magnetization vector of the at least one ferromagnetic layer having non-zero magnetostriction, which can be sensed as a change in resistance to a tunneling current that develops in a direction orthogonal to a plane of the plurality of layers upon the application of the externally supplied voltage also applied in the direction orthogonal to the plane of the layers. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)
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53. A method of sensing pressure using an externally supplied voltage in which applied pressure causes a change in the magnetization vectors of ferromagnetic layers within the device and a corresponding change in resistance comprising the steps of:
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providing a sensing device with a sensor including plurality of layers, the plurality of layers comprising a non magnetic insulating layer disposed between the free ferromagnetic layer and a pinned ferromagnetic layer, and an anti-ferromagnetic layer disposed over the pinned ferromagnetic layer, the non magnetic insulating layer providing ferromagnetic coupling of the free and the pinned ferromagnetic layers in an initial state such that magnetization vectors of the free and pinned ferromagnetic layers are substantially parallel to each other; and sensing the resistance in the plurality of layers upon application of pressure while the externally supplied voltage is being applied in a direction orthogonal to a plane of the layers, the applied pressure causing the magnetization vector of the free ferromagnetic layer to change from the initial state, and thereby result in a change in resistance to a tunneling current produced by the applied voltage and that flows orthogonal to the plane of the plurality of layers. - View Dependent Claims (54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64)
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65. An apparatus for sensing applied pressure upon application of an externally supplied voltage comprising:
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a sensor including; an antiferromagnetic pinning layer; a pinned ferromagnetic layer that is pinned by the antiferromagnetic layer; a free ferromagnetic layer with non-zero magnetostriction; and a non magnetic insulating barrier layer disposed between the free and pinned ferromagnetic layers, wherein, in an initial state, a net magnetization vector of each of the free and pinned ferromagnetic layers are stable with respect to each other, and wherein applied pressure causes a change in the magnetization vector of one the free ferromagnetic layer through the property of magnetostriction and a corresponding change in resistance, such that the resistance can then be sensed by application of the externally supplied voltage in a direction orthogonal to the plane of the plurality of the layers. - View Dependent Claims (66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85)
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Specification