Magnetic Tunnel Junctions Including Crystalline and Amorphous Tunnel Barrier Materials

• US 20080291584A1
• Filed: 06/25/2008
• Published: 11/27/2008
• Est. Priority Date: 04/04/2005
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Parkin, Stuart Stephen Papworth
• Granted Patent: US 7,570,463 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: G01R 33/06 using galvano-magnetic 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 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: H10N 50/10 Magnetoresistive devices

Abstract

Magnetic tunnel junctions are disclosed that include ferromagnetic (or ferrimagnetic) materials and a bilayer tunnel barrier structure. The bilayer includes a crystalline material, such as MgO or Mg—ZnO, and Al₂O₃, which may be amorphous. If MgO is used, then it is preferably (100) oriented. The magnetic tunnel junctions so formed enjoy high tunneling magnetoresistance, e.g., greater than 100% at room temperature.

Claims

1. A device, comprising:

a tunnel barrier structure that includes a crystalline MgO tunnel barrier in proximity with an Al₂O₃ tunnel barrier; and

first and second magnetic materials on different sides of the tunnel barrier structure, wherein;

i) the first magnetic material, the MgO tunnel barrier, the Al₂O₃ tunnel barrier, and the second magnetic material are in proximity with each other, thereby enabling spin-polarized current to pass from the first magnetic material, through the tunnel barriers, and into the second magnetic material; and

ii) the first and second magnetic materials are selected from the group of materials consisting of ferromagnetic materials and ferrimagnetic materials.

2. The device of claim 1, wherein the thickness of the Al₂O₃ tunnel barrier is less than 30 angstroms.

3. The device of claim 1, wherein the thickness of the Al₂O₃ tunnel barrier is between 2 and 20 angstroms.

4. The device of claim 1, wherein the thickness of the MgO tunnel barrier is less than 50 angstroms.

5. The device of claim 1, wherein the thickness of the MgO tunnel barrier is between 3 and 20 angstroms.

6. The device of claim 1, wherein the tunnel barriers and the magnetic materials form a magnetic tunnel junction having a tunneling magnetoresistance of at least 50% at room temperature.

7. The device of claim 1, wherein the tunnel barriers and the magnetic materials form a magnetic tunnel junction having a tunneling magnetoresistance of at least 100% at room temperature.

8. The device of claim 1, wherein the Al₂O₃ tunnel barrier is substantially amorphous.

9. The device of claim 1, wherein the Al₂O₃ tunnel barrier is sufficiently thick that a surface of the MgO tunnel barrier is substantially covered by the Al₂O₃ tunnel barrier.

10. The device of claim 1, wherein the MgO tunnel barrier is (100) oriented.

11. The device of claim 1, wherein the MgO tunnel barrier is (111) oriented.

12. The device of claim 1, wherein the tunnel barrier structure includes at least two MgO tunnel barriers, and the Al₂O₃ tunnel barrier is sandwiched between two MgO tunnel barriers.

13. A device, comprising:

a tunnel barrier structure that includes a crystalline tunnel barrier in proximity with an amorphous tunnel barrier, wherein the crystalline tunnel barrier and the amorphous tunnel barrier have different chemical compositions;

a first layer of magnetic material; and

a second layer of magnetic material, wherein;

i) the first magnetic layer, the tunnel barrier structure, and the second magnetic layer are in proximity with each other, thereby enabling spin-polarized current to pass from the first magnetic material, through the tunnel barrier structure, and into the second magnetic material; and

ii) the magnetic materials of the first and second layers are selected from the group of materials consisting of ferromagnetic materials and ferrimagnetic materials.

14. The device of claim 13, wherein the crystalline tunnel barrier includes a (100) oriented MgO tunnel barrier.

15. The device of claim 13, wherein the crystalline tunnel barrier includes a (111) oriented MgO tunnel barrier.

16. The device of claim 13, wherein the crystalline tunnel barrier includes a Mg—

ZnO tunnel barrier.

17. The device of claim 13, wherein the amorphous tunnel barrier includes an Al₂O₃ tunnel barrier.

18. A magnetic tunnel junction, comprising:

a first layer of magnetic material selected from the group of materials consisting of ferromagnetic materials and ferrimagnetic materials;

a second layer of magnetic material selected from the group of materials consisting of ferromagnetic materials and ferrimagnetic materials; and

a bilayer of respective tunnel barriers, the bilayer being sandwiched between the first and second magnetic layers, so that the first layer, the bilayer, and the second layer form a magnetic tunnel junction, wherein;

the bilayer includes i) a layer of amorphous Al₂O₃ that forms a first tunnel barrier and ii) a layer of crystalline material that forms a second tunnel barrier, the crystalline material including at least one of MgO and Mg—

ZnO.

19. The magnetic tunnel junction of claim 18, wherein the thickness of the Al₂O₃ layer is less than 30 angstroms.

20. The magnetic tunnel junction of claim 18, wherein the bilayer includes a MgO tunnel barrier having a thickness of less than 50 angstroms.

21. The magnetic tunnel junction of claim 18, wherein the bilayer includes a MgO tunnel barrier having a thickness of between 3 and 20 angstroms.

22. The magnetic tunnel junction of claim 18, wherein the tunnel barriers and the magnetic layers form a magnetic tunnel junction having a tunneling magnetoresistance of at least 50% at room temperature.

23. The magnetic tunnel junction of claim 18, wherein the tunnel barriers and the magnetic layers form a magnetic tunnel junction having a tunneling magnetoresistance of at least 100% at room temperature.

24. The magnetic tunnel junction of claim 18, wherein the bilayer includes a (100) oriented MgO tunnel barrier.

25. The magnetic tunnel junction of claim 18, wherein the bilayer includes a (111) oriented MgO tunnel barrier.