Magnetic tunnel barriers and associated magnetic tunnel junctions with high tunneling magnetoresistance

• US 20060012926A1
• Filed: 07/15/2004
• Published: 01/19/2006
• Est. Priority Date: 07/15/2004
• Status: Active Application

• Current Assignee: Stuart Stephen Papworth Parkin
• Original Assignee: Stuart Stephen Papworth Parkin
• Inventors: Parkin, Stuart Stephen Papworth
• Application Number:
  US10/891,363
• Publication Number:
  US 20060012926A1
• Time in Patent Office: Days
• US Class Current: 360/324.200
• CPC Class Codes: G11B 5/39 using magneto-resistive devices or effects
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices

Abstract

Magnetic tunneling devices are formed from a first body centered cubic (bcc) magnetic layer and a second bcc magnetic layer. At least one spacer layer of bcc material between these magnetic layers exchange couples the first and second bcc magnetic layers. A tunnel barrier in proximity with the second magnetic layer permits spin-polarized current to pass between the tunnel barrier and the second layer; the tunnel barrier may be either MgO and Mg—ZnO. The first magnetic layer, the spacer layer, the second magnetic layer, and the tunnel barrier are all preferably (100) oriented. The MgO and Mg—ZnO tunnel barriers are prepared by first depositing a metallic layer on the second magnetic layer (e.g., a Mg layer), thereby substantially reducing the oxygen content in this magnetic layer, which improves the performance of the tunnel barriers.

Claims

1. A magnetic tunneling device, comprising:

a first body centered cubic (bcc) magnetic layer and a second bcc magnetic layer, wherein the first and second magnetic layers include material selected from the group consisting of ferromagnetic materials and ferrimagnetic materials;

at least one spacer layer of bcc material between the magnetic layers, wherein the spacer layer exchange couples the first and second bcc magnetic layers; and

a tunnel barrier in proximity with the second magnetic layer to permit spin-polarized current to pass between the tunnel barrier and the second layer, wherein the tunnel barrier is selected from the group consisting of MgO and Mg—

ZnO tunnel barriers.

2. The device of claim 1, wherein each of the first magnetic layer, the spacer layer, the second magnetic layer, and the tunnel barrier are (100) oriented.

3. The device of claim 2, wherein each of the first magnetic layer, the spacer layer, the second magnetic layer, and the tunnel barrier are polycrystalline.

4. The device of claim 3, wherein each of the first magnetic layer, the spacer layer, the second magnetic layer, and the tunnel barrier include polycrystalline grains whose lateral extent is in the range of 100 to 500 angstroms.

5. The device of claim 3, wherein the tunnel barrier is a MgO tunnel barrier.

6. The device of claim 5, wherein the MgO tunnel barrier has a thickness of between 3 and 20 angstroms.

7. The device of claim 3, wherein the tunnel barrier is a Mg—

ZnO tunnel barrier.

8. The device of claim 7, wherein the Mg—

ZnO tunnel barrier has a thickness of between 3 and 50 angstroms.

9. The device of claim 3, wherein the second magnetic layer is substantially free of oxide.

10. The device of claim 3, wherein the spacer layer includes Cr.

11. The device of claim 10, wherein the spacer layer is at least 50 atomic % Cr.

12. The device of claim 10, wherein the spacer layer is at least 70 atomic % Cr.

13. The device of claim 10, wherein the spacer layer includes a non-ferromagnetic, non-ferrimagnetic alloy of Cr and at least one element selected from the group consisting of V, W, and Fe.

14. The device of claim 10, wherein the spacer layer includes an alloy of Cr and Mo.

15. The device of claim 14, wherein the Mo content of the alloy is between 10 and 50 atomic %.

16. The device of claim 14, wherein the thickness of the spacer layer is between 10 and 20 angstroms.

17. The device of claim 10, wherein the spacer layer includes an alloy of Cr and Nb.

18. The device of claim 17, wherein the Nb content of the alloy is between 10 and 50 atomic %.

19. The device of claim 1, wherein the thickness of the spacer layer is between 10 and 20 angstroms.

20. The device of claim 10, wherein the spacer layer has a thickness of between 3 and 30 angstroms.

21. The device of claim 3, wherein each of the first magnetic layer and the second magnetic layer includes an alloy of Co and Fe.

22. The device of claim 21, wherein the Fe content of the alloy is between 15 and 60 atomic %.

23. The device of claim 1, further comprising a free magnetic layer in proximity with the tunnel barrier, the device thereby forming a magnetic tunnel junction, wherein the free magnetic layer is selected from the group consisting of ferromagnetic magnetic materials and ferrimagnetic materials.

24. The device of claim 23, the free layer comprising:

two additional bcc magnetic layers including material selected from the group consisting of ferromagnetic materials and ferrimagnetic materials; and

at least one additional spacer layer of bcc material between said two additional bcc magnetic layers, wherein the additional spacer layer exchange couples said two additional bcc magnetic layers.

25. The device of claim 23, further comprising an additional layer in proximity with the first magnetic layer that forms an exchange bias with the first magnetic layer, the additional layer including at least one anti-ferromagnetic material.

26. The device of claim 23, wherein the tunneling magnetoresistance of the junction is at least 50% at room temperature.

27. The device of claim 23, wherein the tunneling magnetoresistance of the junction is at least 70% at room temperature.

28. The device of claim 23, wherein the tunneling magnetoresistance of the junction is at least 100% at room temperature.

29. The device of claim 1, wherein the spacer layer exchange couples the magnetic layers so that their magnetic moments are anti-parallel.

30. The device of claim 1, wherein the spacer layer exchange couples the magnetic layers so that their magnetic moments are parallel.

31. The device of claim 1, wherein the tunnel barrier is in contact with the second magnetic layer.

41. The device of claim 3.2, wherein the spacer layer is at least 50 atomic % Cr.

32. A magnetic tunnel junction device, comprising:

a first (100) oriented, body centered cubic (bcc) magnetic layer and a second (100) oriented, bcc magnetic layer, wherein the first and second magnetic layers include material selected from the group consisting of ferromagnetic materials and ferrimagnetic materials;

at least one spacer layer of (100) oriented bcc material between the magnetic layers, wherein the spacer layer exchange couples the first and second bcc magnetic layers, the spacer layer including Cr;

a (100) oriented tunnel barrier in proximity with the second magnetic layer, wherein the tunnel barrier is selected from the group consisting of MgO and Mg—

ZnO tunnel barriers; and

a free magnetic layer in proximity with the tunnel barrier, wherein the free magnetic layer includes magnetic material selected from the group consisting of ferromagnetic magnetic materials and ferrimagnetic materials, wherein the free magnetic layer, the first and second magnetic layers, the spacer layer, and the tunnel barrier form a magnetic tunnel junction that has a tunneling magnetoresistance of at least 50% at room temperature.

33. The device of claim 32, wherein each of the first magnetic layer, the spacer layer, the second magnetic layer, and the tunnel barrier are polycrystalline.

34. The device of claim 33, wherein each of the first magnetic layer, the spacer layer, the second magnetic layer, and the tunnel barrier include polycrystalline grains whose lateral extent is in the range of 100 to 500 angstroms.

35. The device of claim 32, further comprising an additional layer in proximity with the first magnetic layer that forms an exchange bias with the first magnetic layer, the additional layer including at least one anti-ferromagnetic material.

36. The device of claim 32, wherein the tunnel barrier is a MgO tunnel barrier.

37. The device of claim 36, wherein the MgO tunnel barrier has a thickness of between 3 and 20 angstroms.

38. The device of claim 32, wherein the tunnel barrier is a Mg—

ZnO tunnel barrier.

39. The device of claim 38, wherein the Mg—

ZnO tunnel barrier has a thickness of between 3 and 50 angstroms.

40. The device of claim 32, wherein the second magnetic layer is substantially free of oxide.

42. The device of claim 32, wherein the spacer layer is at least 70 atomic % Cr.

43. The device of claim 32, wherein the spacer layer includes a non-ferromagnetic, non-ferrimagnetic alloy of Cr and at least one element selected from the group consisting of V, W, and Fe.

44. The device of claim 32, wherein the spacer layer includes an alloy of Cr and Mo.

45. The device of claim 44, wherein the Mo content of the alloy is between 10 and 50 atomic %.

46. The device of claim 32, wherein the spacer layer includes an alloy of Cr and Nb.

47. The device of claim 46, wherein the Nb content of the alloy is between 10 and 50 atomic %.

48. The device of claim 32, wherein the spacer layer has a thickness of between 3 and 30 angstroms.

49. The device of claim 32, wherein each of the first magnetic layer and the second magnetic layer includes an alloy of Co and Fe.

50. The device of claim 49, wherein the Fe content of the alloy is between 15 and 60 atomic %.

51. The device of claim 32, wherein the tunnel barrier is a MgO tunnel barrier, and the tunneling magnetoresistance of the junction is at least 100% at room temperature.

52. A method, comprising:

forming a tunnel barrier over a first body centered cubic (bcc) magnetic layer; and

forming a second bcc magnetic layer over the tunnel barrier, in which the first bcc magnetic layer, the tunnel barrier, and the second bcc magnetic layer constitute a magnetic tunnel junction, wherein;

at least one of the first and second bcc magnetic layers includes two bcc magnetic layers separated by a bcc spacer layer that exchange couples said two bcc magnetic layers.

53. The method of claim 52, said forming the tunnel barrier comprising:

depositing Mg onto a surface to form a Mg layer thereon, wherein the surface is selected to be substantially free of oxide; and

directing additional Mg, in the presence of oxygen, towards the Mg layer to form a MgO tunnel barrier in contact with the surface, the oxygen reacting with the additional Mg and the Mg layer.

54. The method of claim 53, wherein the Mg layer has a thickness of between 3 and 20 angstroms.

55. The method of claim 53, wherein the MgO tunnel barrier is annealed at a temperature selected to yield a tunneling magnetoresistance of greater than 70% at room temperature.

56. The method of claim 53, wherein the MgO tunnel barrier is annealed at a temperature selected to yield a tunneling magnetoresistance of greater than 100% at room temperature.

57. The method of claim 52, said forming the tunnel barrier comprising:

depositing a metal layer onto a surface selected to be substantially free of oxide;

directing additional metal towards the metal layer, in the presence of oxygen, to form a magnesium-zinc oxide tunnel barrier in contact with the surface, the oxygen reacting with the additional metal and the metal layer, wherein;

at least one of the metal layer and the additional metal includes Zn, and at least one of the metal layer and the additional metal includes Mg.

58. The method of claim 57, wherein the Mg—

ZnO tunnel barrier has a thickness of between 3 and 50 angstroms.

59. The method of claim 57, wherein the Mg—

ZnO tunnel barrier is annealed at a temperature selected to yield a tunneling magnetoresistance of greater than 50% at room temperature.

60. The method of claim 52, wherein the tunnel barrier, the first bcc magnetic layer, and the second bcc magnetic layer are each (100) oriented to improve the performance of the tunnel element.

61. The method of claim 52, wherein each of the tunnel barrier, the first bcc magnetic layer, and the second bcc magnetic layer is polycrystalline.

62. The method of claim 52, wherein each of the tunnel barrier, the first bcc magnetic layer, and the second bcc magnetic layer includes polycrystalline grains whose lateral extent is in the range of 100 to 500 angstroms.

63. The method of claim 52, wherein the first bcc magnetic layer and the second bcc magnetic layer each include two bcc magnetic layers that are exchange coupled by a bcc spacer layer.

64. The method of claim 52, wherein the spacer layer includes Cr.

65. The method of claim 64, wherein the spacer layer is at least 50 atomic % Cr.

66. The method of claim 64, wherein the spacer layer is at least 70 atomic % Cr.

67. The method of claim 64, wherein the spacer layer includes a single-phase, non-ferromagnetic, non-ferrimagnetic alloy of Cr and at least one element selected from the group consisting of V, Nb, Mo, W, and Fe.

68. The method of claim 67, wherein the concentration of said at least one element is selected to lattice match the spacer layer with the bcc magnetic layers.

69. The method of claim 52, further comprising annealing the tunnel barrier to improve its performance.

70. The method of claim 69, wherein the tunnel barrier is annealed at a temperature in the range of 300°

C. to 400°

C.

71. The method of claim 69, wherein the tunnel barrier is annealed at a temperature greater than 300°

C.

72. The method of claim 69, wherein the tunnel barrier is annealed at a temperature greater than 340°

C.