TMR sensor
First Claim
1. A sensor for measuring mechanical changes in length, comprising a sandwich system with two flat and superposed electrodes separated by a tunnel barrier, an electric current being set up between the electrodes and through the tunnel barrier,whereina first one of the electrodes includes a highly magnetostrictive layer responding to elongation, having signal contributions due to anisotropies caused by mechanical tension being larger than those due to intrinsic anisotropies, and providing relative changes in system resistance Δ
- R/R of more than 10% upon elongation at room temperature; and
the highly magnetostrictive layer includes an alloy containing CoFe.
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Accused Products
Abstract
A sensor for measuring mechanical changes in length, in particular a compressive and/or tensile stress sensor, includes a sandwich system with two flat and superposed electrodes separated from each other by a tunnel element (tunnel barrier), in particular an oxide barrier, a current being set up between the electrodes and through the tunnel barrier, one electrode consisting of a magnetostrictive layer 3 which responds to elongation, and wherein the contributions of the anisotropies caused by mechanical tension are larger than those from the intrinsic anisotropies, relative changes in system resistance ΔR/R larger than 10% at room temperature being attained during elongation.
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Citations
26 Claims
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1. A sensor for measuring mechanical changes in length, comprising a sandwich system with two flat and superposed electrodes separated by a tunnel barrier, an electric current being set up between the electrodes and through the tunnel barrier,
wherein a first one of the electrodes includes a highly magnetostrictive layer responding to elongation, having signal contributions due to anisotropies caused by mechanical tension being larger than those due to intrinsic anisotropies, and providing relative changes in system resistance Δ - R/R of more than 10% upon elongation at room temperature; and
the highly magnetostrictive layer includes an alloy containing CoFe. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
- R/R of more than 10% upon elongation at room temperature; and
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15. A sensor for measuring mechanical changes in length, comprising a multilayer structure comprising a plurality of layers stacked one upon another in a thickness direction of said structure;
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said layers comprising upper and lower layers which are electrodes and an intermediate layer sandwiched between said upper and lower layers; said intermediate layer being a tunnel barrier which exhibits the tunnel magneto-resistance (TMR) effect, and defines, together with said electrodes, a tunnel current path tat extends from the upper layer, through an entire thickness of the intermediate layer and to the lower layer; and wherein said upper layer includes a highly magnetostrictive material that responds to stress applied thereto; and the highly magnetostrictive layer includes a CoFe alloy. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 25, 26)
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23. A sensor for measuring mechanical changes in length, comprising a multilayer structure comprising a plurality of layers stacked one upon another in a thickness direction of said structure;
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said layers comprising upper and lower layers which are electrodes and an intermediate layer sandwiched between said upper and lower layers; said intermediate layer being a tunnel barrier which exhibits the tunnel magneto-resistance (TMR) effect, and defines, together with said electrodes, a tunnel current path that extends from the upper layer, through an entire thickness of the intermediate layer and to the lower layer; and wherein said upper layer includes a highly magnetostrictive material that responds to stress applied thereto; and said lower layer is a reference layer having low magnetostriction or a magnetostriction sign opposite to that of the highly magnetostrictive material of said upper layer.
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24. A method of measuring physical changes in length, said method comprising
providing a multilayer structure comprising a plurality of layers stacked one upon another in a thickness direction of said structure; -
wherein said layers comprise upper and lower layers which are electrodes and an intermediate layer sandwiched between said upper and lower layers; said intermediate layer is a tunnel barrier which exhibits the tunnel magneto-resistance (TMR) effect, and defines, together with said electrodes, a tunnel current path that extends from the upper layer, through an entire thickness of the intermediate layer and to the lower layer; and said upper layer includes a highly magnetostrictive material that responds to stress applied thereto, and the highly magnetostrictive layer includes a CoFe alloy; applying stress to said highly magnetostrictive material of said upper layer to cause a change in a physical dimension of said material of said upper highly magnetostrictive layer; measuring a current flowing in said current path when said stress is applied to said highly magnetostrictive material of said upper layer; and based on the measured current, outputting a signal indicative of said change in the physical dimension of said material of said upper highly magnetostrictive layer.
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Specification