Tunnel magnetoresistive element

• US 20040144995A1
• Filed: 11/26/2003
• Published: 07/29/2004
• Est. Priority Date: 05/31/2001
• Status: Active Grant

• Current Assignee: National Institute of Advanced Industrial Science and Technology (Government of Japan), Japan Science And Technology Agency
• Original Assignee: National Institute of Advanced Industrial Science and Technology (Government of Japan), Japan Science And Technology Agency
• Inventors: Suzuki, Yoshishige, Nagahama, Taro, Yuasa, Shinji
• Granted Patent: US 7,220,498 B2
• Time in Patent Office: Days
• US Class Current: 257/200
• 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: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G01R 33/098 comprising tunnel junctions, e.g. tunnel magnetoresistance sensors
• 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: H01F 10/3231 via a non-magnetic spacer
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H10B 61/00 Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: Y10T 428/1114 having tunnel junction effect
• CPC Class Codes: Y10T 428/1143 with defined structural feature
• CPC Class Codes: Y10T 428/1157 Substrate composition
• CPC Class Codes: Y10T 428/1193 with interlaminar component [e.g., adhesion layer, etc.]

Abstract

By varying only the thickness of a known material having superior magnetic characteristics to increase spin polarization without changing the chemical composition, a tunnel magnetoresistive element capable of producing a larger magnetoresistive effect is provided.

The tunnel magnetoresistive element includes an underlayer (nonmagnetic or antiferromagnetic metal film) (1); an ultrathin ferromagnetic layer (2) disposed on the underlayer (1); an insulating layer (3) disposed on the ultrathin ferromagnetic layer (2); and a ferromagnetic electrode (4) disposed on the insulating layer (3).

Claims

1. A tunnel magnetoresistive element comprising:

(a) an underlayer;

(b) an ultrathin ferromagnetic layer disposed on the underlayer;

(c) an insulating layer disposed on the ultrathin ferromagnetic layer; and

(d) a ferromagnetic electrode disposed on the insulating layer.

2. A tunnel magnetoresistive element according to claim 1, wherein the thickness of the ultrathin ferromagnetic layer is on the order of atomic layers.

3. A tunnel magnetoresistive element according to claim 2, wherein the thickness of the ultrathin ferromagnetic layer is in the range of 1 to 15 atomic layers.

4. A tunnel magnetoresistive element according to claim 1, wherein the underlayer comprises a nonmagnetic or antiferromagnetic metal film.

5. A tunnel magnetoresistive element according to claim 1, wherein the underlayer is a nonmagnetic or antiferromagnetic metal film formed on a ferromagnetic exchange coupling film.

6. A tunnel magnetoresistive element according to claim 4, wherein the nonmagnetic or antiferromagnetic metal film comprises Au, Ag, Cu, Cr, V, Nb, Mo, Ta, W, Al, Pt, Ir, Rh, Ru, Pd, Os, or Mn.

7. A tunnel magnetoresistive element according to claim 6, wherein the nonmagnetic metal film is formed from a single crystal, thereby enhancing thickness controllability.

8. A tunnel magnetoresistive element according to claim 7, wherein the crystal orientation of the nonmagnetic metal film is set in the direction of (100)±

10°

, (111)±

10°

, (110)±

10°

, or (112)±

10°

of a cubic system, and thereby evenness is increased.

9. A tunnel magnetoresistive element having a structure in which a nonmagnetic single-crystal metal or nonmagnetic highly-oriented-polycrystalline interlayer lies between a barrier layer and a ferromagnetic electrode.

10. A tunnel magnetoresistive element according to claim 9, wherein the interlayer comprises Cu, Au, Ag, Cr, or an alloy thereof.

11. A tunnel magnetoresistive element according to claim 9, wherein the thickness of the interlayer is controlled.

12. A tunnel magnetoresistive element according to claim 9, wherein bias voltage applied to the interlayer is controlled.

13. A tunnel magnetoresistive element according to claim 9, wherein the crystal orientation of the nonmagnetic single-crystal metal layer is set in the direction of (100)±

10°

, (111)±

10°

, (110)±

10°

, or (112)±

10°

of a cubic system, thereby increasing electron conductivity and evenness.

14. A tunnel magnetoresistive element according to claim 9, disposed so as to be connected to intersections of word lines and bit lines of a matrix-type magnetic random access memory.

15. A tunnel magnetoresistive element having a double underlayer including an amorphous MgO layer and a (001)-highly-oriented MgO layer.

16. A tunnel magnetoresistive element according to claim 15, wherein the thickness of the amorphous MgO layer is set in the range of 3 to 10 nm and the thickness of the (001)-highly-oriented MgO layer is set in the range of 3 to 10 nm, and thereby surface roughness is reduced.

17. A tunnel magnetoresistive element according to claim 15, wherein, by using the underlayer, roughness of a ferromagnetic layer is reduced and magnetostatic coupling between ferromagnetic layers is reduced.

18. A tunnel magnetoresistive element according to claim 15, wherein, by using the underlayer, roughness of an ultrathin ferromagnetic electrode layer with a thickness of 15 atomic layers or less is reduced and the magnetoresistive effect is increased.

19. A tunnel magnetoresistive element according to claim 15, wherein a flat nonmagnetic layer with a thickness of 20 atomic layers or less is disposed between a barrier layer and a ferromagnetic electrode layer, with the underlayer lying, and, thus the bias dependence of magnetoresistive effect is controlled.

20. A tunnel magnetoresistive element according to claim 15, wherein, by using the underlayer so that a ferromagnetic electrode layer is oriented in the (001) direction of a body-centered cubic lattice, a face-centered cubic lattice, or a tetragonal lattice and using a (001)-highly-oriented MgO layer as a barrier layer, a large magnetoresistive effect is produced.

21. A tunnel magnetoresistive element according to claim 15, wherein a (001)-oriented layer formed by combining Au, Ag, Cu, Al, Pt, Ir, Pd, Mo, W, Ta, Cr, Ru, Rh, Mn, Fe, Co, and Ni is disposed between the underlayer and the magnetoresistive element, and thereby evenness is improved and electrode resistance is reduced.