Sensor device having a magnetostrictive force sensor

• US 20040216534A1
• Filed: 04/29/2004
• Published: 11/04/2004
• Est. Priority Date: 04/29/2003
• Status: Active Grant

• Current Assignee: Stiftung Caesar
• Original Assignee: Stiftung Caesar
• Inventors: Lohndorf, Markus, Wecker, Joachim, Ludwig, Alfred, Ruhrig, Manfred, Quandt, Eckhardt
• Granted Patent: US 6,988,414 B2
• Time in Patent Office: Days
• US Class Current: 73/862.626
• CPC Class Codes: G01L 1/125 by using magnetostrictive means magnetostrictive sensors H10N35/101

Abstract

A sensor device having a magnetostrictive force sensor is provided. To detect a force, the sensor device contains a TMR force sensor element having a magnetic detection layer of material having a magnetostriction coefficient λ≧|5·10⁻⁶|, a magnetically harder reference layer, and a tunnel barrier disposed between these layers. Established in the detection layer is a starting magnetization that relative to the magnetization of the reference layer, which is directed in the direction of force, forms an angle of other than 0° and thus is rotated out of its starting position under the effect of the force.

Claims

1. A sensor device for detecting a force that acts in a prescribed direction of force, comprising:

a tunnel-magnetoresistive sensor element, as a force sensor element, which is provided with a thin layer system comprising;

a detection layer of magnetic material having a magnetostriction coefficient λ

, where λ

≧

|5.10<sup>−

6</sup>|;

a comparatively magnetically harder reference layer or a corresponding reference layer system;

an intermediate layer of insulating material, as a tunnel barrier, disposed between said detection layer and said reference layer or layer system; and

electrical connections on said reference layer or reference layer system and on said detection layer, wherein in said detection layer a starting magnetization is established that relative to a magnetization of said reference layer or reference layer system, which is directed at least approximately in the direction of force, forms an angle of other than 0°

, so that said starting magnetization of said detection layer is rotated out of a starting position under the effect of the force.

2. A sensor device according to claim 1, wherein said detection layer is made of a magnetic material having a magnetostriction coefficient λ

, where λ

≧

|5.10<sup>−

5|.</sup>

3. A sensor device according to claim 1, wherein said angle has a value of at least approximately 90°

.

4. A sensor device according to claim 1, wherein said angle has a value of less than 90°

.

5. A sensor device according to claim 4, wherein said angle has a value between 75°

and 15°

.

6. A sensor device according to claim 5, wherein said angle has a value of at least approximately 45°

.

7. A sensor device according to claim 1, wherein said thin layer system of said tunnel-magnetostrictive sensor element, on both sides of said reference layer or reference layer system, has a respective detection layer wherein said detection layers are spaced apart by a tunnel barrier layer.

8. A sensor device according to claim 7, which includes a reference layer system having two magnetic layers and a non-magnetic intermediate layer disposed between said two magnetic layers, wherein magnetizations in said magnetic layers are oriented anti-parallel to one another.

9. A sensor device according to claim 1, including a plurality of tunnel-magnetostrictive sensor elements in a bridge connection.

10. A sensor device according to claim 1, wherein said detection layer has a multi-domain condition.

11. A sensor device according to claim 1, wherein said detection layer has an at least approximately single-domain condition.

12. A sensor device according to claim 11, including a ferromagnetic (Né

el) coupling of said detection layer to said reference layer or reference layer system.

13. A sensor device according to claim 1, including a magnetic pre-tensioning of said detection layer.

14. A sensor device according to claim 1, which includes at least one detection layer that contains at least one of the group consisting of cobalt, iron and nickel.

15. A sensor device according to claim 14, wherein the material of said detection layer has an amorphous structure.