Magnetic field sensor

• US 20040165319A1
• Filed: 02/20/2003
• Published: 08/26/2004
• Est. Priority Date: 02/20/2003
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Wan, Hong, Withanawasam, Lakshman S.
• Granted Patent: US 7,016,163 B2
• Time in Patent Office: Days
• US Class Current: 360/324.1
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G11B 2005/0008 Magnetic conditionning of heads, e.g. biasing

Abstract

A spin valve GMR sensor configured in a bridge configuration is provided. The bridge includes two spin valve element pairs. The spin valve elements include a free layer, a space layer, a pinning layer, and a bias layer. The bias layer includes a first bias layer and a second bias layer. The first and second spin valve element pairs are formed on separate metal layers and a current pulse is applied to the metal layers, which sets the direction of magnetization in the pinning layer of the first pair of spin valve elements to be antiparallel to the direction of magnetization in the pinning layer of the second pair of spin valve elements. The same effect can be accomplished by making the pinning layer substantially thicker than the second bias layer in the first spin valve element pair and the pinning layer is substantially thinner than the second bias layer in the second spin valve element pair and applying a magnetic field to the first and the second spin valve element pairs.

Claims

1. A spin valve giant magnetoresistive sensor in a bridge configuration, comprising in combination:

a first pair of spin valve elements electrically coupled to a first metal layer; and

a second pair of spin valve elements electrically coupled to a second metal layer, wherein a current pulse applied to the first metal layer and the second metal layer sets a direction of magnetization in the first pair of spin valve elements and the second pair of spin valve elements.

2. The sensor of claim 1, further comprising:

a first dielectric layer located substantially between the first pair of spin valve elements and the first metal layer; and

a second dielectric layer located substantially between the second pair of spin valve elements and the second metal layer.

3. The sensor of claim 1, wherein the first metal layer and the second metal layer are connected to electrodes.

4. The sensor of claim 3, wherein the current pulse is applied to the electrodes connected to the first metal layer and the second metal layer.

5. The sensor of claim 1, wherein the current pulse is applied substantially after fabricating the sensor.

6. The sensor of claim 1, wherein the current pulse is applied for approximately 1 microsecond and has a peak greater than 100 milliamperes.

7. The sensor of claim 1, wherein the current pulse generates a first magnetic field in the first pair of spin valve elements and a second magnetic field in the second pair of spin valve elements.

8. The sensor of claim 7, wherein the first magnetic field is in a direction substantially opposite to that of the second magnetic field.

9. The sensor of claim 7, wherein the first magnetic field and the second magnetic field set a direction of magnetization in a pinning layer of the first spin valve element pair to be substantially antiparallel to a direction of magnetization in a pinning layer of the second spin valve element pair.

10. A method of fabricating a spin valve giant magnetoresistive sensor in a Wheatstone bridge configuration, comprising in combination:

depositing at least one metal layer;

depositing spin valve element layers to form spin valve elements;

depositing dielectric layers substantially between the at least one metal layer and the spin valve elements; and

applying a current pulse to the at least one metal layer.

11. The method of claim 10, wherein a separate metal layer is deposited for each spin valve element.

12. The method of claim 10, wherein a separate metal layer is deposited for each spin valve element pair.

13. The method of claim 10, wherein the spin valve element layers include a free layer, a space layer, a pinning layer, and a bias layer.

14. The method of claim 10, wherein the current pulse is applied after forming the spin valve elements.

15. The method of claim 10, wherein the current pulse sets a direction of magnetization in the spin valve elements.

16. The method of claim 10, wherein the current pulse is applied for approximately 1 microsecond and has a peak greater than 100 milliamperes.

17. The method of claim 10, wherein the current pulse generates a first magnetic field in a first pair of spin valve elements and a second magnetic field in a second pair of spin valve elements.

18. The method of claim 17, wherein the first magnetic field is in a direction substantially opposite to that of the second magnetic field.

19. The method of claim 17, wherein the first magnetic field and the second magnetic field set a direction of magnetization in a pinning layer of the first spin valve element pair to be substantially antiparallel to a direction of magnetization in a pinning layer of the second spin valve element pair.

20. A spin valve giant magnetoresistive sensor in a bridge configuration, comprising in combination:

a first pair of spin valve elements in which each spin valve element contains at least a free layer, a space layer, a pinning layer and a bias layer, wherein the bias layer includes a first bias layer and a second bias layer, wherein the first bias layer is located substantially between the pinning layer and the second bias layer, and wherein the pinning layer is substantially thicker than the second bias layer; and

a second pair of spin valve elements in which each spin valve element contains at least a free layer, a space layer, a pinning layer and a bias layer, wherein the bias layer includes a first bias layer and a second bias layer, wherein the first bias layer is located substantially between the pinning layer and the second bias layer, wherein the pinning layer is substantially thinner than the second bias layer, and wherein a direction of magnetization in the pinning layer of the first pair of spin valve elements is antiparallel to a direction of magnetization in the pinning layer of the second pair of spin valve elements.

21. The sensor of claim 20, wherein the first spin valve element pair is formed on a substrate.

22. The sensor of claim 20, wherein a dielectric layer is deposited substantially around a top and two sides of the first spin valve element pair.

23. The sensor of claim 20, wherein the second spin valve element pair is formed on a dielectric layer located substantially adjacent to the first spin valve element pair.

24. The sensor of claim 20, wherein the pinning layer and the second bias layer are composed of cobalt.

25. The sensor of claim 20, wherein the first bias layer is composed of ruthenium.

26. The sensor of claim 20, wherein the first bias layer is operable to couple the pinning layer and the second bias layer.

27. The sensor of claim 20, wherein a magnetic field is applied to the first spin valve element pair and the second spin valve element pair.

28. The sensor of claim 27, wherein the magnetic field is greater than 10 Gauss.

29. The sensor of claim 27, wherein the magnetic field is operable to set a direction of magnetization in the pinning layer of the first pair of spin valve elements and the second bias layer of the second pair of spin valve elements in a direction of the magnetic field.

30. The sensor of claim 27, wherein the magnetic field is operable to set a direction of magnetization in the pinning layer of the second pair of spin valve elements and the second bias layer of the first pair of spin valve elements in a direction substantially opposite to that of the magnetic field.

31. The sensor of claim 27, wherein the magnetic field is operable to set a direction of magnetization in the pinning layer of the first pair of spin valve elements to be substantially antiparallel to a direction of magnetization in the pinning layer of the second pair of spin valve elements.

32. A method of fabricating a spin valve GMR sensor in a bridge configuration, comprising in combination:

forming a first spin valve element pair in which each spin valve element contains at least a free layer, a space layer, a pinning layer and a bias layer, wherein the bias layer includes a first bias layer and a second bias layer, wherein the first bias layer is located substantially between the pinning layer and the second bias layer, and wherein the pinning layer is substantially thicker than the second bias layer;

forming a second spin valve element pair in which each spin valve element contains at least a free layer, a space layer, a pinning layer and a bias layer, wherein the bias layer includes a first bias layer and a second bias layer, wherein the first bias layer is located substantially between the pinning layer and the second bias layer, and wherein the pinning layer is substantially thinner than the second bias layer; and

applying a magnetic field to the first spin valve element pair and the second spin valve element pair, thereby setting a direction of magnetization in the pinning layer of the first pair of spin valve elements that is substantially antiparallel to a direction of magnetization in the pinning layer of the second pair of spin valve elements.

33. The method of claim 32, wherein the pinning layer and the second bias layer are composed of cobalt.

34. The method of claim 32, wherein the first bias layer is composed of ruthenium.

35. The method of claim 32, wherein the first bias layer is operable to couple the pinning layer and the second bias layer.

36. The method of claim 32, wherein the magnetic field is greater than 10 Gauss.

37. The method of claim 32, wherein the magnetic field is operable to set a direction of magnetization in the pinning layer of the first pair of spin valve elements and the second bias layer of the second pair of spin valve elements in a direction of the magnetic field.

38. The method of claim 32, wherein the magnetic field is operable to set a direction of magnetization in the pinning layer of the second pair of spin valve elements and the second bias layer of the first pair of spin valve elements in a direction substantially opposite to that of the magnetic field.