Coupled ferromagnetic systems having modified interfaces

• US 20040257717A1
• Filed: 06/18/2003
• Published: 12/23/2004
• Est. Priority Date: 06/18/2003
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Hewlett-Packard Development Co. (HP Inc.)
• Inventors: Sharma, Manish, Nickel, Janice H.
• Granted Patent: US 7,054,119 B2
• Time in Patent Office: Days
• US Class Current: 360/324.2
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: G11B 2005/3996 large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices
• CPC Class Codes: G11B 5/3903 using magnetic thin film layers or their effects, the films being part of integrated structures
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11C 11/15 using multiple magnetic layers G11C11/155 takes precedence
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H01F 10/3263 the exchange coupling being symmetric, e.g. for dual spin valve, e.g. NiO/Co/Cu/Co/Cu/Co/NiO
• CPC Class Codes: H01F 10/3272 by use of anti-parallel coupled [APC] ferromagnetic layers, e.g. artificial ferrimagnets [AFI], artificial [AAF] or synthetic [SAF] anti-ferromagnets
• CPC Class Codes: H01F 41/303 with exchange coupling adjustment of magnetic film pairs, e.g. interface modifications by reduction, oxidation
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: Y10T 29/49034 Treating to affect magnetic properties

Abstract

A coupled ferromagnetic structure includes a first ferromagnetic layer, a spacer layer on a first surface of the first ferromagnetic layer, and a second ferromagnetic layer on the spacer layer. Interlayer exchange coupling occurs between the first and second ferromagnetic layers. The coupling may be ferromagnetic or antiferromagnetic. Morphology of the first surface is modified to tailor the interlayer exchange coupling. The structure may form a part of a magnetoresistive device such as a magnetic tunnel junction.

Claims

1. A coupled ferromagnetic structure comprising:

a first ferromagnetic layer;

a spacer layer on a first surface of the first ferromagnetic layer; and

a second ferromagnetic layer on the spacer layer, interlayer exchange coupling occurring between the first and second ferromagnetic layers;

morphology of the first surface modified to tailor the interlayer exchange coupling;

the interlayer exchange coupling being one of ferromagnetic and antiferromagnetic.

2. The structure of claim 1, wherein the interlayer exchange coupling is ferromagnetic, whereby the ferromagnetic and spacer layers form an artificial ferromagnet.

3. The structure of claim 1, wherein the interlayer exchange coupling is antiferromagnetic, wherein the ferromagnetic and spacer layers form an artificial antiferromagnet.

4. The structure of claim 1, further comprising an amorphous layer, the first ferromagnetic layer directly on the amorphous layer.

5. The device of claim 4, wherein the amorphous layer is an insulating tunnel barrier.

6. The structure of claim 1, wherein the morphology of the first surface is modified to increase the interlayer exchange coupling.

7. The structure of claim 1, wherein the morphology of the first surface is modified by redepositing material on the first surface to fill in grain boundaries.

8. The structure of claim 1, wherein the morphology of the first surface is modified by modifying roughness of the first surface.

9. A magnetoresistive device including at least one structure of claim 1.

10. The device of claim 9, wherein at least one structure forms a reference layer.

11. The device of claim 9, wherein at least one structure forms a free layer.

12. A magnetic tunnel junction including the structure of claim 1.

13. A memory cell of a data storage device, the memory cell including the magnetic tunnel junction of claim 12.

14. A data storage device including an array of memory cells, each memory cell including at least one magnetic tunnel junction of claim 12.

15. A read head for a hard disk drive, the read head including the magnetic tunnel junction of claim 12.

16. A hard disk drive including at least one read head, each read head including the magnetic tunnel junction of claim 12.

17. A magnetoresistive device comprising:

a free ferromagnetic layer;

a first spacer layer on the free ferromagnetic layer, the first spacer layer made of an amorphous material; and

a coupled ferromagnetic structure on the spacer layer, the structure including a first ferromagnetic layer on the first spacer layer;

a second spacer layer on the first ferromagnetic layer, and a second ferromagnetic layer on the second spacer layer, interlayer exchange coupling between the first and second ferromagnetic layers being antiferromagnetic, the first ferromagnetic layer and the second spacer layer forming an interface, morphology of the interface having been modified to increase the interlayer exchange coupling.

18. The device of claim 17, wherein the first spacer layer is an insulating tunnel barrier.

19. The device of claim 18, further comprising an AF pinning layer on the coupled ferromagnetic structure;

wherein the device is a top-pinned magnetic tunnel junction.

20. The device of claim 18, further comprising a second insulating tunnel barrier on the coupled ferromagnetic structure;

and a second free layer on the second barrier;

wherein the device is a dual-junction magnetic tunnel junction.

21. A magnetic random access memory device including an array of memory cells, each memory cell including the device of claim 17.

22. A memory cell of a data storage device, the memory cell including the device of claim 17.

23. A hard disk drive including at least one read head, each read head including the device of claim 17.

24. A read head for a hard disk drive, the read head including the device of claim 17.

25. A method of adjusting interlayer exchange coupling between two ferromagnetic layers having a non-magnetic spacer layer therebetween, the interlayer exchange coupling being either ferromagnetic or antiferromagnetic, the method comprising adjusting roughness of at least one interface between the spacer layer and the ferromagnetic layers.

26. The method of claim 25, wherein the roughness is adjusted by ion etching.

27. A method of forming a coupled ferromagnetic structure, the method comprising:

depositing a first ferromagnetic layer;

modifying morphology of an exposed surface of the first layer;

depositing a spacer layer on the first layer; and

depositing a second ferromagnetic layer on the metal spacer layer.

28. The method of claim 27, further comprising modifying morphology of an exposed surface of the spacer layer before depositing the second ferromagnetic layer.

29. The method of claim 27, wherein the morphology is modified to increase interlayer exchange coupling between the first and second ferromagnetic layers.

30. The method of claim 27, wherein the morphology is modified by modifying roughness of the exposed surface.

31. The method of claim 27, wherein the morphology is modified by filling in grain boundaries on the exposed surface.

32. The method of claim 27, wherein the morphology is modified by ion etching.

33. The method of claim 32, wherein the morphology is modified in a controlled manner by adjusting time and energy of the ion etching.

34. The method of claim 27, further comprising forming the first ferromagnetic layer on an amorphous layer.