FERROMAGNETIC TUNNEL JUNCTION STRUCTURE, AND MAGNETO-RESISTIVE ELEMENT AND SPINTRONICS DEVICE EACH USING SAME

• US 20120091548A1
• Filed: 04/15/2010
• Published: 04/19/2012
• Est. Priority Date: 04/16/2009
• Status: Active Grant

• Current Assignee: National Institute for Materials Science
• Original Assignee: National Institute for Materials Science
• Inventors: Hono, Kazuhiro, Sukegawa, Hiroaki, Inomata, Koichiro, Shan, Rong, Kodzuka, Masaya, Furubayashi, Takao, Wang, Wenhong
• Granted Patent: US 8,575,674 B2
• Time in Patent Office: Days
• US Class Current: 257/421
• 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: G01R 33/098 comprising tunnel junctions, e.g. tunnel magnetoresistance sensors
• CPC Class Codes: G11B 5/3906 Details related to the use of magnetic thin film layers or to their effects
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: H01F 10/1936 Half-metallic, e.g. epitaxial CrO2 or NiMnSb films
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H01F 41/307 insulating or semiconductive spacer
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

Disclosed is a ferromagnetic tunnel junction structure which is characterized by having a tunnel barrier layer that comprises a non-magnetic material having a spinel structure. The ferromagnetic tunnel junction structure is also characterized in that the non-magnetic material is substantially MgAl₂O₄. The ferromagnetic tunnel junction is also characterized in that at least one of the ferromagnetic layers comprises a Co-based full Heusler alloy having an L2₁ or B2 structure. The ferromagnetic tunnel junction structure is also characterized in that the Co-based full Heusler alloy comprises a substance represented by the following formula: Co₂FeAl_xSi_1-x (0≦x≦1). Also disclosed are a magnetoresistive element and a spintronics device, each of which utilizes the ferromagnetic tunnel junction structure and can achieve a high TMR value, that cannot be achieved by employing conventional tunnel barrier layers other than a MgO barrier.

Claims

1-6. -6. (canceled)

7. A metallic ferromagnetic tunnel junction structure comprising a structure having a tunnel barrier layer disposed between two ferromagnetic layers, wherein the ferromagnetic layers comprise a metal or a metal alloy, and the ferromagnetic layers are directly in contact with the upper and lower interfaces of the tunnel barrier layer, and in that the tunnel barrier layer is crystalline and an oxidation treatment product of a metal alloy thin film and is a non-magnetic material having a spinel structure.

8. The metallic ferromagnetic tunnel junction structure according to claim 7, wherein that the non-magnetic substance is MgAl₂O₄.

9. The metallic ferromagnetic tunnel junction structure according to claim 7, wherein at least one of the metallic ferromagnetic layers is a Co-based full Heusler alloy having an L2₁ or B2 structure.

10. The metallic ferromagnetic tunnel junction structure according to claim 8, wherein at least one of the metallic ferromagnetic layers is a Co-based full Heusler alloy having an L2₁ or B2 structure.

11. The metallic ferromagnetic tunnel junction structure according to claim 9, wherein the Co-based full Heusler alloy is Co₂FeAl_xSi_1-x (0≦

x≦

1).

12. The metallic ferromagnetic tunnel junction structure according to claim 10, wherein the Co-based full Heusler alloy is Co₂FeAl_xSi_1-x (0≦

x≦

1).

13. A magnetoresistive element using a metallic ferromagnetic tunnel junction structure comprising a structure having a tunnel barrier layer disposed between two metallic ferromagnetic layers, wherein that the metallic ferromagnetic tunnel junction structure is the metallic ferromagnetic tunnel junction structure according to claim 7.

14. A spintronics device using a metallic ferromagnetic tunnel junction structure comprising a structure having a tunnel barrier layer disposed between two metallic ferromagnetic layers, wherein the metallic ferromagnetic tunnel junction structure is the metallic ferromagnetic tunnel junction structure according to claim 7.

15. A method for producing the metallic ferromagnetic tunnel junction structure according to claim 7, wherein the method comprises forming at least a metallic ferromagnetic layer on a substrate and then, stacking a first pure metal thin film and a second pure metal thin film by sputtering and then subjecting the stacked films to plasma oxidation treatment, or sputtering an alloy of a first pure metal and a second pure metal and subjecting the sputtered alloy to plasma oxidation treatment, to form a tunnel barrier layer which is crystalline and a non-magnetic material having a spinel structure, and further forming a metallic ferromagnetic layer on the tunnel barrier layer.

16. The method for producing the metallic ferromagnetic tunnel junction structure according to claim 15, wherein the layer which is the MgAl₂O₄ is formed as the tunnel barrier layer.

17. The method for producing the metallic ferromagnetic tunnel junction structure according to claim 15, characterized in that at least one of the metallic ferromagnetic layers is formed as a layer which is a Co-based full Heusler alloy having an L2₁ or B2 structure.

18. The method for producing the metallic ferromagnetic tunnel junction structure according to claim 16, characterized in that at least one of the metallic ferromagnetic layers is formed as a layer which is a Co-based full Heusler alloy having an L2₁ or B2 structure.

19. The method for producing the metallic ferromagnetic tunnel junction structure according to claim 17, characterized in that the layer which is a Co-based full Heusler alloy is Co₂FeAl_xSi_1-x (0≦

x≦

1).

20. The method for producing the metallic ferromagnetic tunnel junction structure according to claim 18, characterized in that the layer which is a Co-based full Heusler alloy is Co₂FeAl_xSi_1-x (0≦

x≦

1).