METHOD AND SYSTEM FOR PROVIDING A MAGNETIC ELEMENT AND MAGNETIC MEMORY BEING UNIDIRECTIONAL WRITING ENABLED

• US 20080310219A1
• Filed: 06/11/2008
• Published: 12/18/2008
• Est. Priority Date: 06/12/2007
• Status: Active Grant

• Current Assignee: Samsung Semiconductor Incorporated (Samsung Electronics Co. Ltd.)
• Original Assignee: Renesas Technology Corporation (Renesas Electronics Corporation), Grandis, Inc. (Samsung Electronics Co. Ltd.)
• Inventors: Chen, Eugene, Apalkov, Dmytro
• Granted Patent: US 7,800,942 B2
• Time in Patent Office: Days
• US Class Current: 365/173
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect

Abstract

A method and system for providing a magnetic element and memory utilizing the magnetic element are described. The magnetic element includes a reference layer, a nonferromagnetic spacer layer, and a free layer. The reference layer has a resettable magnetization that is set in a selected direction by a magnetic field generated externally to the reference layer. The reference layer is also magnetically thermally unstable at an operating temperature range and has K_uV/k_BT is less than fifty five. The spacer layer resides between the reference layer and the free layer. In addition, the magnetic element is configured to allow the free layer to be switched to each of a plurality of states when a write current is passed through the magnetic element.

Claims

1. A magnetic element comprising:

a reference layer having a resettable magnetization, the resettable magnetization being set in a selected direction by a magnetic field generated externally to the reference layer, the reference layer being magnetically thermally unstable at an operating temperature and have K_uV/k_BT less than fifty five;

a spacer layer, the spacer layer being nonferromagnetic; and

a free layer, the spacer layer residing between the reference layer and the free layer;

wherein the magnetic element is configured to allow the free layer to be switched to each of a plurality of states when a write current is passed through the magnetic element.

2. The magnetic element of claim 1 wherein at least one of the reference layer includes a superparamagnetic layer and the reference layer having a coercivity of not more than twenty Oe.

3. The magnetic element of claim 2 wherein the superparamagnetic layer has the coercivity of less than twenty Oe.

4. The magnetic element of claim 1 wherein the free layer is a synthetic free layer including at least a first ferromagnetic layer, a second ferromagnetic layer, and a nonmagnetic spacer layer between the first ferromagnetic layer and the second ferromagnetic layer.

5. The magnetic element of claim 1 wherein the spacer layer is an insulating barrier layer.

6. The magnetic element of claim 1 wherein the reference layer is a synthetic reference layer including at least a first magnetic layer, a second magnetic layer, and a nonmagnetic spacer layer between the first magnetic layer and the second magnetic layer, at least one of the first magnetic layer and the second magnetic layer being a superparamagnetic layer.

7. The magnetic element of claim 1 further comprising:

a bias layer adjacent to the free layer, the bias layer for stabilizing the free layer.

8. The magnetic element of claim 1 further comprising:

an additional spacer layer; and

an additional reference layer, the free layer residing between the spacer layer and the additional spacer layer, the additional spacer layer residing between the additional reference layer and the free layer.

9. The magnetic element of claim 8 wherein the additional reference layer has an additional resettable magnetization, the additional resettable magnetization being set in an additional selected direction by a magnetic field generated externally to the additional reference layer, the additional reference layer being magnetically thermally unstable and having an additional K_uV/k_BT less than fifty five.

10. The magnetic element of claim 9 wherein at least one of the additional reference layer includes a superparamagnetic layer and the additional reference layer has the additional resettable magnetization set in the selected layer by the magnetic field of not more than twenty Oersted.

11. The magnetic element of claim 9 wherein the additional selected direction is the same as the selected direction.

12. The magnetic element of claim 9 wherein the spacer layer has a first resistance area product, the additional spacer layer has a second resistance area product and wherein at least one of the first resistance area product is greater than the second resistance area product and the second resistance area product is greater than the first resistance area product.

13. The magnetic element of claim 1 wherein the free layer has a free layer damping constant and the reference layer has a reference layer damping constant greater than the free layer damping constant.

14. A magnetic memory comprising:

a plurality of magnetic storage cells, each of the plurality of magnetic storage cells including at least one magnetic element, each of the at least one magnetic element include a reference layer, a spacer layer, and a free layer, the reference layer having a resettable magnetization, the resettable magnetization being set in a selected direction by a magnetic field generated externally to the reference layer, the reference layer being magnetically thermally unstable at an operating temperature and have a K_uV/k_BT less than fifty five, the spacer layer being nonferromagnetic, the spacer layer residing between the reference layer and the free layer, the magnetic element being configured to allow the free layer to be switched to each of a plurality of states when a write current is passed through the magnetic element.

a plurality of word lines coupled with the plurality of magnetic storage cells; and

a plurality of bit lines coupled with the plurality of storage cells.

15. The magnetic memory of claim 14 wherein at least one of the reference layer includes a superparamagnetic layer and the reference layer has a coercivity of not more than twenty Oe.

16. The magnetic memory of claim 14 wherein the reference layer is a synthetic reference layer including at least a first magnetic layer, a second magnetic layer, and a nonmagnetic spacer layer between the first magnetic layer and the second magnetic layer, at least one of the first magnetic layer and the second magnetic layer being a superparamagnetic layer.

17. The magnetic memory of claim 14 wherein the at least one magnetic element further includes:

an additional spacer layer; and

an additional reference layer, the free layer residing between the spacer layer and the additional spacer layer, the additional spacer layer residing between the additional reference layer and the free layer.

18. The magnetic memory of claim 17 wherein the additional reference layer has an additional resettable magnetization, the additional resettable magnetization being set in an additional selected direction by the magnetic field generated externally to the additional reference layer, the additional reference layer being magnetically thermally unstable at memory operating temperature range (K_uV/k_BT is less than fifty five).

19. The magnetic memory of claim 18 wherein at least one of the additional reference layer being an additional superparamagnetic layer and the additional reference layer having a coercivity of not more than twenty Oersted.

20. The magnetic memory of claim 18 wherein the spacer layer has a first resistance area product, the additional spacer layer has a second resistance area product and wherein at least one of the first resistance area product is greater than the second resistance area product and the second resistance area product is greater than the first resistance area product.

21. The magnetic memory of claim 15 wherein each of the plurality of magnetic storage cells further includes:

at least one transistor coupled to the magnetic element.

22. The magnetic memory of claim 21 wherein the at least one transistor is a single transistor.

23. The magnetic memory of claim 21 wherein the at least one transistors is at least two transistors.

24. The magnetic memory of claim 14 wherein the plurality of bit lines are configured to provide the magnetic field for setting the resettable magnetization.

25. The magnetic memory of claim 14 further comprising:

a plurality of write lines configured to generate the magnetic field for setting the resettable magnetization.

26. The magnetic memory of claim 14 wherein the free layer has a free layer damping constant and the reference layer has a reference layer damping constant greater than the free layer damping constant.

27. A method for using a magnetic memory, the magnetic memory including a plurality of storage cells, a plurality of bit lines coupled to the plurality of storage cells, and a plurality of word lines coupled to the plurality of storage cells, each of the plurality of storage cells including at least one magnetic element, the method comprising:

If a portion of the plurality of storage cells is to be written, generating a magnetic field, each of the at least one magnetic element include a reference layer, a spacer layer, and a free layer, the magnetic field being generated externally to the reference layer, the reference layer having a resettable magnetization, the resettable magnetization being set in a selected direction of a plurality of directions by the magnetic field, the reference layer including a layer that is magnetically thermally unstable and having K_uV/k_BT is less than fifty five at an operating temperature, the layer being at least one of a superparamagnetic layer and having a low coercivity layer having a coercivity of not more than twenty Oe, the spacer layer being nonferromagnetic and residing between the reference layer and the free layer, the magnetic element being configured to allow the free layer to be switched to each of a plurality of states when a write current is passed through the magnetic element;

providing a unidirectional write current through the at least one magnetic element of the portion of the plurality of magnetic storage cells If the portion of the plurality of storage cells is to be written, a state of the at least one magnetic element being determined by the unidirectional write current and the resettable magnetization;

if the portion of the plurality of magnetic storage cells is to be read, generating a read magnetic field externally to the reference layer for the portion of the plurality of magnetic storage cells, the read magnetic field having a particular direction independent of the state of the at least one magnetic element; and

providing a read current less than the write current through the at least one magnetic element of the portion of the plurality of magnetic storage cells If the portion of the plurality of storage cells is to be read.