Magnetic memory device and method

• US 20040008537A1
• Filed: 07/15/2002
• Published: 01/15/2004
• Est. Priority Date: 07/15/2002
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Tran, Lung the, Sharma, Manish
• Granted Patent: US 6,850,433 B2
• Time in Patent Office: Days
• US Class Current: 365/173
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H01F 10/3277 by use of artificial ferrimagnets [AFI] only

Abstract

The present invention is a magnetic memory device and method. In one embodiment a present invention magnetic memory device includes a synthetic ferrimagnetic data, a soft reference layer and a tunneling layer. The synthetic ferrimagnetic data layer has a magnetic moment directable to a first orientation and a second orientation. The soft reference layer has a lower coercivity than the synthetic ferrimagnetic data layer. The tunneling layer has electrical resistance qualities which are influenced by magnetic moment orientations of the synthetic ferrimagnetic data layer and the soft reference layer.

Claims

1. A magnetic memory device comprising:

a synthetic ferrimagnetic data layer having a magnetic moment directable to a first orientation and a second orientation;

a soft reference layer with a lower coercivity than said synthetic ferrimagnetic data layer; and

a tunneling layer having electrical resistance qualities which are influenced by magnetic moment orientations of said synthetic ferrimagnetic data layer and said soft reference layer.

2. A magnetic memory device of claim 1, where in said soft reference layer includes ferromagnetic material.

3. A magnetic memory device of claim 1, wherein said soft reference layer is a soft synthetic ferrimagnetic reference layer.

4. A magnetic memory device of claim 3, wherein said synthetic ferrimagnetic data layer and said soft synthetic ferrimagnetic reference layer each include:

a first sub-layer having a magnetic moment orientation rotatable to either said first or said second orientations;

a second sub-layer having a magnetic moment orientation that is maintained substantially opposite of said first sub-layer; and

a spacer sub-layer that magnetically couples said first layer sub-layer and said second sub-layer.

5. A magnetic memory device of claim 4, wherein said soft synthetic ferrimagnetic reference layer has a net coercivity that is substantially zero.

6. A magnetic memory device of claim 4, wherein said data synthetic ferrimagnetic layer has a net coercivity that is substantially greater than said soft synthetic ferrimagnetic reference layer.

7. A magnetic memory device of claim 4, wherein said first sub-layer and said second sub-layer have different configurations in said synthetic ferrimagnetic data layer and said soft synthetic ferrimagnetic reference layer.

8. A magnetic memory device of claim 1, wherein said synthetic ferrimagnetic data layer and said soft reference layer are cladded.

9. A magnetic memory device of claim 1, wherein said first and second magnetic orientations are induced by an applied magnetic field.

10. A magnetic memory device of claim 9, wherein the intensity of said applied magnetic field is on the order of less than a few thousand amperes/meter.

11. A magnetic memory method comprising:

establishing a particular magnetic moment orientation in a synthetic ferrimagnetic data layer;

applying a relatively small magnetic field to a soft reference layer, wherein said relatively small magnetic field causes said second magnetic layer to have a predetermined magnetic moment orientation without changing the magnetic orientation of said first magnetic layer; and

measuring a resistance between said synthetic ferrimagnetic data layer and said soft reference layer to determine the magnetic orientation of said first magnetic layer.

12. A magnetic memory method of claim 11, further comprising exposing said data layer to a magnetic field that creates a magnetic orientation in said data layer.

13. A magnetic memory method of claim 11, wherein applying said magnetic field causes said magnetic orientation in a first sub-layer of said soft reference layer to be either substantially parallel or substantially anti-parallel to said magnetic orientation in said data layer.

14. A magnetic memory method of claim 13, wherein said magnetic field is applied in a direction that is substantially parallel to the easy axis of a first sub-layer of said soft reference layer.

15. A magnetic memory method of claim 13, wherein said magnetic field is applied asymmetrically in a region of said first and second sub-layers, and said magnetic orientation of said first layer is forced to a known position.

16. A magnetic memory method of claim 13, further comprising passing a current in the vicinity of said soft reference layer and said data layer.

17. The magnetic memory method of claim 13, further comprising applying a voltage differential between said synthetic ferrimagnetic data layer and said soft reference layer.

18. A magnetic memory device comprising:

a synthetic ferrimagnetic sense layer operable for magnetization in either of two discernable states;

a soft reference layer that changes magnetization orientation easier than said synthetic ferrimagnetic data layer; and

a resistance layer that resists electrical current, wherein resistance to said electrical current changes depending upon the relative direction of said first orientation and said second orientation.

19. A magnetic memory device of claim 18, wherein said soft reference layer is a soft synthetic ferrimagnetic reference layer.

20. A magnetic memory device of claim 19, wherein said synthetic ferrimagnetic data layer and said soft synthetic ferrimagnetic reference layer each comprise:

a first sub-layer controllable to either of two magnetic vector orientations;

a second sub-layer that maintains a magnetic vector orientation substantially opposite to a magnetic vector orientation of said first sub-layer of magnetic material; and

a spacer sub-layer that magnetically couples said first sub-layer and said second sub-layer.

21. A magnetic memory device of claim 20, wherein said first sub-layer of magnetic material and said second sub-layer of magnetic material have a combined coercivity that is relatively small compared to the coercivity of said sense layer.

22. A magnetic memory device of claim 21, wherein said first sub-layer of magnetic material and said second sub-layer of magnetic material have a combined coercivity that is relatively large compared to the coercivity of said soft reference layer.

23. A magnetic memory system comprising:

an array of magnetic storage cells, wherein said storage cells include a synthetic ferrimagnetic data layer and a soft reference layer;

a plurality of first electrically conductive elements extending along said array in a first direction, said plurality of first electrically conductive elements magnetically coupled to said storage cells; and

a plurality of second electrically conductive elements extending along said array in a second direction, said plurality of second electrically conductive elements magnetically coupled to said storage cells.

24. The magnetic memory system of claim 23, further comprising a plurality of third electrically conductive elements extending in said second direction, said second and third electrically conductive elements being separated by an electrical insulator.

25. The magnetic memory system of claim 23, further comprising a circuit for applying a current to selected elements of said plurality of first electrical conductive elements and said plurality of second electrical conductive elements.

26. The magnetic memory system of claim 23, further comprising a circuit for applying a voltage between a selected element of said first electrically conductive elements and a selected element of said second electrically conductive elements.

27. The magnetic memory system of claim 27, further comprising a circuit for measuring current through said selected elements of said first and second electrically conductive elements to measure resistance to said current.

28. A magnetic memory device comprising:

a means for establishing a first magnetic moment orientation, wherein said first magnetic orientation is the sum effect of multiple magnetic moments in sub-layers;

a means for establishing a second magnetic moment orientation that is softer than said first magnetic moment orientation; and

a means for resisting a current flow, wherein resistance to said current flow is altered according to the direction of said magnetic moment orientations.

29. The magnetic memory device of claim 28 wherein said first magnetic moment orientation is associated with the logical value of an information bit.

30. The magnetic memory device of claim 28 wherein said second magnetic moment orientation is a predetermined reference direction.

31. The magnetic memory device of claim 28 wherein said means for resisting a current flow includes a means for establishing a magneto-resistive tunnel.