Spin-transfer multilayer stack containing magnetic layers with resettable magnetization

• US 20040130936A1
• Filed: 01/07/2003
• Published: 07/08/2004
• Est. Priority Date: 01/07/2003
• Status: Active Grant

• Current Assignee: Samsung Semiconductor Incorporated (Samsung Electronics Co. Ltd.)
• Original Assignee: Grandis, Inc. (Samsung Electronics Co. Ltd.)
• Inventors: Nguyen, Paul P., Huai, Yiming
• Granted Patent: US 7,190,611 B2
• Time in Patent Office: Days
• US Class Current: 365/158
• CPC Class Codes: G11C 11/15 using multiple magnetic layers G11C11/155 takes precedence
• CPC Class Codes: G11C 11/5607 using magnetic storage elements

Abstract

A magnetic element for a high-density memory array includes a resettable layer and a storage layer. The resettable layer has a magnetization that is set in a selected direction by at least one externally generated magnetic field. The storage layer has at least one magnetic easy axis and a magnetization that changes direction based on the spin-transfer effect when a write current passes through the magnetic element. An alternative embodiment of the magnetic element includes an additional multilayer structure formed from a tunneling barrier layer, a pinned magnetic layer and an antiferromagnetic layer that pins the magnetization of the pinned layer in a predetermined direction. Another alternative embodiment of the magnetic element includes an additional multilayer structure that is formed from a tunneling barrier layer and a second resettable layer having a magnetic moment that is different from the magnetic moment of the resettable layer of the basic embodiment.

Claims

1. A magnetic element, comprising:

a resettable layer having a first magnetization that is set in a selected direction by at least one magnetic field, each magnetic field being generated externally to the resettable layer;

a storage layer having at least one magnetic easy axis and having a second magnetization that changes direction based on a spin-transfer effect when a write current passes through the magnetic element; and

a spacing layer formed between the resettable layer and the storage layer.

2. The magnetic element according to claim 1, wherein at least a portion of the storage layer is formed from one of a ferromagnetic material, a ferrimagnetic material, a sperimagnetic material, and a half-metallic material.

3. The magnetic element according to claim 1, wherein the storage layer is formed from a synthetic antiferromagnet.

4. The magnetic element according to claim 1, wherein the write current passes through the magnetic element only in a forward-bias switching mode direction.

5. The magnetic element according to claim 1, wherein the storage layer has at least one magnetic shape anisotropy.

6. The magnetic element according to claim 1, wherein the storage layer has a first shape and the resettable layer has a second shape that is different from the first shape.

7. The magnetic element according to claim 6, wherein the storage layer has a shape that induces at least one magnetic shape anisotropy and the resettable layer has a magnetically isotropic shape.

8. The magnetic element according to claim 1, wherein at least a portion of the resettable layer is formed from one of a ferromagnetic material, a ferrimagnetic material, a sperimagnetic material, and a half-metallic material.

9. The magnetic element according to claim 1, wherein the resettable layer is formed to have a magnetization that is set in a desired direction using an external magnetic field that is less than about 20 Oe.

10. The magnetic element according to claim 1, wherein the resettable layer is formed from a synthetic antiferromagnet.

11. The magnetic element according to claim 1, wherein the spacing layer is a tunneling barrier layer.

12. The magnetic element according to claim 11, further comprising a layer of high spin-polarization material formed between the resettable layer and the tunneling barrier layer.

13. The magnetic element according to claim 1, wherein the spacing layer is a conductive spacer layer.

14. The magnetic element according to claim 13, further comprising a layer of high spin-polarization material formed between the resettable layer and the conductive spacer layer.

15. The magnetic element according to claim 1, further comprising an electrical uni-directional element connected in electrical series with the storage layer and the resettable layer.

16. The magnetic element according to claim 1, wherein the storage layer has a first side and a second side, the first side of the storage layer being closer to the resettable layer than the second side of the storage layer, and

the magnetic element further comprising a multilayer structure formed on the second side of the storage layer.

17. The magnetic element according to claim 16, further comprising an electrical unidirectional element connected in electrical series with the storage layer and the multilayer structure.

18. The magnetic element according to claim 16, wherein the multilayer structure includes:

a second spacing layer formed adjacent to the storage layer;

a pinned magnetic layer having a third magnetization; and

an antiferromagnetic layer.

19. The magnetic element according to claim 18, wherein the second spacing layer is a tunneling barrier.

20. The magnetic element according to claim 18, wherein the second spacing layer is a conductive spacer layer.

21. The magnetic element according to claim 18, wherein the pinned magnetic layer is a synthetic antiferromagnet.

22. The magnetic element according to claim 16, wherein the multilayer structure includes:

a tunneling barrier layer formed adjacent to the storage layer; and

a second resettable layer having a third magnetization, the second resettable layer having a magnetic moment that is different from a magnetic moment of the resettable layer having the first magnetization.

23. The magnetic element according to claim 22, wherein the second resettable layer has a magnetically isotropic shape.

24. The magnetic element according to claim 22, wherein the second resettable layer is formed to have a magnetization that is set in a desired direction using an external magnetic field that is less than about 20 Oe.

25. The magnetic element according to claim 22, wherein the second resettable layer is a synthetic antiferromagnet.

26. The magnetic element according to claim 22, wherein the first magnetization of the resettable layer and the third magnetization of the second resettable layer are set in a selected direction by at least one magnetic field, each magnetic field being generated by a current that is external to the magnetic element.

27. A magnetic memory having a plurality of magnetic cells, at least one magnetic cell including a magnetic element comprising:

a resettable layer having a first magnetization that is set in a selected direction by at least one magnetic field, each magnetic field being generated externally to the resettable layer;

a storage layer having at least one magnetic easy axis and having a second magnetization that changes direction based on a spin-transfer effect when a write current passes through the magnetic element; and

a spacing layer formed between the resettable layer and the storage layer.

28. The magnetic memory according to claim 27, wherein at least a portion of the storage layer is formed from one of a ferromagnetic material, a ferrimagnetic material, a sperimagnetic material, and a half-metallic material.

29. The magnetic memory according to claim 27, wherein the storage layer is formed from a synthetic antiferromagnet.

30. The magnetic memory according to claim 27, wherein the write current passes through the magnetic element in only a forward-bias switching mode direction.

31. The magnetic memory according to claim 27, wherein the storage layer has at least one magnetic shape anisotropy.

32. The magnetic memory according to claim 27, wherein the storage layer has a first shape and the resettable layer has a second shape that is different from the first shape.

33. The magnetic memory according to claim 32, wherein the storage layer has a shape that induces at least one magnetic shape anisotropy and the resettable layer has a magnetically isotropic shape.

34. The magnetic memory according to claim 27, wherein at least a portion of the resettable layer is formed from one of a ferromagnetic material, a ferrimagnetic material, a sperimagnetic material, and a half-metallic material.

35. The magnetic memory according to claim 27, wherein the resettable layer is formed from a magnetic material having a magnetization that is set in a desired direction using an external magnetic field that is less than about 20 Oe.

36. The magnetic memory according to claim 27, wherein the resettable layer is formed from a synthetic antiferromagnet.

37. The magnetic memory according to claim 27, wherein the spacing layer is a tunneling barrier.

38. The magnetic memory according to claim 37, further comprising a layer of high spin-polarization material formed between the resettable layer and the tunneling barrier layer.

39. The magnetic memory according to claim 37, wherein the spacing layer is a conductive spacer layer.

40. The magnetic memory according to claim 39, further comprising a layer of high spin-polarization material formed between the resettable layer and the conductive spacer layer.

41. The magnetic memory according to claim 27, further comprising an electrical uni-directional element connected in electrical series with the storage layer and the resettable layer.

42. The magnetic memory according to claim 27, wherein the storage layer has a first side and a second side, the first side of the storage layer being closer to the resettable layer than the second side of the storage layer, and

the magnetic element further comprising a multilayer structure formed on the second side of the storage layer.

43. The magnetic memory according to claim 42, further comprising an electrical uni-directional element connected in electrical series with the storage layer and the multilayer structure.

44. The magnetic memory according to claim 42, wherein the multilayer structure includes:

a second spacing layer formed adjacent to the storage layer,

a pinned magnetic layer having a third magnetization; and

an antiferromagnetic layer that pins the third magnetization in a predetermined direction.

45. The magnetic memory according to claim 44, wherein the second spacing layer is a tunneling barrier.

46. The magnetic memory according to claim 44, wherein the second spacing layer is a conductive spacer layer.

47. The magnetic memory according to claim 44, wherein the pinned magnetic layer is a synthetic antiferromagnet.

48. The magnetic memory according to claim 42, wherein the multilayer structure includes:

a tunneling barrier layer formed adjacent to the storage layer; and

a second resettable layer having a third magnetization, the second resettable layer having a magnetic moment that is different from a magnetic moment of the resettable layer having the first magnetization.

49. The magnetic memory according to claim 48, wherein the second resettable layer has a magnetically isotropic shape.

50. The magnetic memory according to claim 48, wherein the second resettable layer is formed from a magnetic material having a magnetization that is set in a desired direction using an external magnetic field that is less than about 20 Oe.

51. The magnetic memory according to claim 48, wherein the second resettable layer is a synthetic antiferromagnet.

52. The magnetic memory according to claim 48, wherein the first magnetization of the resettable layer and the third magnetization of the second resettable layer are set in the selected direction by at least one magnetic field, each magnetic field being generated a current that is external to the magnetic element.

53. A method for forming a magnetic element, the method comprising steps of:

forming a resettable layer having a first magnetization that is set in a selected direction by at least one magnetic field, each magnetic field being generated externally to the resettable layer;

forming a storage layer having at least one magnetic easy axis and having a second magnetization that changes direction based on a spin-transfer effect when a write current passes through the magnetic element; and

forming a spacing layer between the resettable layer and the storage layer.

54. The method according to claim 53, further comprising a step of forming an electrical uni-directional element in electrical series with the storage layer and the multilayer structure.

55. The method according to claim 53, wherein the storage layer has a first side and a second side, the first side of the storage layer being closer to the resettable layer than the second side of the storage layer,

the method further comprising a step of forming a multilayer structure on the second side of the storage layer.

56. The method according to claim 55, wherein the step of forming the multilayer structure includes steps of

forming a second spacing layer adjacent to the storage layer,

forming a pinned magnetic layer having the third magnetization;

and

forming an antiferromagnetic layer that pins the third magnetization in a predetermined direction.

57. The method according to claim 56, wherein the second spacing layer is a tunneling barrier layer.

58. The method according to claim 56, wherein the second spacing layer is a conductive spacer layer.

59. The method according to claim 55, wherein the step of forming the multilayer structure includes a step of forming a second resettable layer having a third magnetization, the second resettable layer having a magnetic moment that is different from a magnetic moment of the resettable layer having the first magnetization.

60. The method according to claim 53, wherein the storage layer is formed to have at least one magnetic shape anisotropy.

61. The method according to claim 53, wherein the storage layer is formed to have more than one easy magnetic axis.

62. The method according to claim 53, wherein the storage layer is formed to have a first shape and the resettable layer is formed to have a second shape that is different firom the first shape.

63. The method according to claim 53, wherein the storage layer is formed to have a shape that induces at least one magnetic shape anisotropy and the resettable layer is formed to have a magnetically isotropic shape.

64. A method for writing information to a magnetic element, the magnetic element including a resettable layer having a first magnetization that is set in a selected direction by at least one magnetic field, each magnetic field being generated by a current flowing externally to the magnetic element, a storage layer having at least one magnetic easy axis and having a second magnetization that changes direction based on a spin-transfer effect when a write current passes through the magnetic element, and a spacing layer formed between the resettable layer and the storage layer, the method comprising steps of:

setting the first magnetization of the resettable layer in the selected direction by generating the external magnetic field; and

changing a direction of the second magnetization of the storage layer by passing a write current through the magnetic element, the write current having a magnitude that is greater than or equal to a magnitude of a current that switches the magnetization of the storage layer.

65. The method according to claim 64, wherein the spacing layer is a tunneling barrier layer.

66. The method according to claim 64, wherein the spacing layer is a conductive spacer layer.

67. The method according to claim 64, wherein the step of setting the first magnetization of the resettable layer includes a step of passing a setting current through a conductive line that is in proximity to the resettable layer for generating the external magnetic field.

68. The method according to claim 64, wherein the step of setting the first magnetization of the resettable layer includes a step of generating a plurality of external magnetic fields.

69. The method according to claim 68, wherein the step of generating the plurality of external magnetic fields includes a step of passing a setting current through a conductive line corresponding to each magnetic field, each conductive line being in proximity to the resettable layer.

70. The method according to claim 64, wherein the storage layer of the magnetic element has a first side and a second side, the first side of the storage layer being closer to the resettable layer than the second side of the storage layer, and

wherein the magnetic element further includes a multilayer structure formed on the second side of the storage layer.

71. The method according to claim 70, wherein the multilayer structure includes a second spacing layer formed adjacent to the storage layer, a pinned magnetic layer having a third magnetization, and an antiferromagnetic layer that pins the third magnetization in a predetermined direction.

72. The method according to claim 71, wherein the second spacing layer is a tunneling barrier.

73. The method according to claim 71, wherein the second spacing layer is a conductive spacer layer.

74. The method according to claim 70, wherein the multilayer structure includes a tunneling barrier layer formed adjacent to the storage layer, and a second resettable layer having a third magnetization and a magnetic moment that is different from a magnetic moment of the resettable layer having the first magnetization.

75. A method for reading a magnetic element, the magnetic element including at least one resettable layer, each resettable layer having a magnetization that is set in a selected direction by at least one magnetic field, each magnetic field being generated by a current flowing externally to the magnetic element, and a storage layer having at least one magnetic easy axis and having a second magnetization that changes direction based on a spin-transfer effect when a write current is passed through the magnetic element, the method comprising steps of:

setting the magnetization of each resettable layer in a first selected direction by generating at least one external magnetic field;

passing a first current through the magnetic element while the magnetization of each resettable layer is set in the first selected direction;

setting the magnetization of each resettable layer in a second selected direction by generating at least one external magnetic field, the second selected direction being opposite the first selected direction;

passing a second current through the magnetic element while the magnetization of each resettable layer is set in the second selected direction;

detecting a voltage across the magnetic element when each respective read current is passed through the magnetic element; and

determining an information value stored in the magnetic cell based on the detected voltages.

76. The method according to claim 75, wherein the step of determining the stored information value of the magnetic element includes a step of comparing the detected voltage to a voltage from a reference magnetic cell.

77. The method according to claim 75, wherein the magnetic element further includes a tunneling barrier layer formed adjacent to the storage layer, and a second resettable layer having a third magnetization, the second resettable layer having a magnetic moment that is different from a magnetic moment of the resettable layer having the first magnetization.

78. A method for reading a magnetic element, the magnetic element including a resettable layer having a first magnetization that is set in a selected direction by at least one magnetic field, each magnetic field being generated by a current flowing externally to the magnetic element, a storage layer having at least one magnetic easy axis and having a second magnetization that changes direction based on a spin-transfer effect when a write current passes through the magnetic element, a pinned magnetic layer having a third magnetization, an antiferromagnetic layer that pins the third magnetization in a predetermined direction, and a tunneling barrier layer between storage layer and the pinned layer, the method comprising steps of:

passing a first read current through the magnetic element, the first read current having a magnitude that is less than a magnitude of a current that switches the magnetization of the storage layer;

detecting a first voltage across the magnetic element when the first read current is passed through the magnetic element;

setting the first magnetization of the resettable layer in the selected direction by generating at least one external magnetic field;

passing a write current through the magnetic element, the write current having a magnitude that is greater than or equal to the magnitude of the current that switches the magnetization of the storage layer;

passing a second read current through the magnetic element, the second read current having a magnitude that is less than the magnitude of the current that switches the magnetization of the storage layer;

detecting a second voltage across the magnetic element when the second read current is passed through the magnetic element;

determining an information value stored in the magnetic cell by comparing the first and second detected voltages.

79. The method according to claim 78, further comprising a step of writing the determined information value back into the magnetic element after the information value has been determined.

80. The method according to claim 78, wherein the step of determining the stored information value of the magnetic element includes a step of comparing the detected voltage to a voltage from a reference magnetic cell.