Exchange-coupled film, method for making exchange-coupled film, and magnetic sensing element including exchange-coupled film

• US 20050024793A1
• Filed: 07/21/2004
• Published: 02/03/2005
• Est. Priority Date: 07/29/2003
• Status: Active Grant

• Current Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Hasegawa, Naoya, Umetsu, Eiji, Nakabayashi, Ryou
• Granted Patent: US 7,365,948 B2
• Time in Patent Office: Days
• US Class Current: 360/324.110
• 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 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: G11B 5/3906 Details related to the use of magnetic thin film layers or to their effects
• CPC Class Codes: G11B 5/3932 Magnetic biasing films
• CPC Class Codes: H01F 10/30 characterised by the composition of the intermediate layers , e.g. seed, buffer, template, diffusion preventing, cap layers H01F10/06 and H01F10/32 take precedence
• 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 41/308 lift-off processes, e.g. ion milling, for trimming or patterning
• CPC Class Codes: H01F 41/325 applying a noble metal capping on a spin-exchange-coupled multilayer, e.g. spin filter deposition
• CPC Class Codes: Y10T 29/49021 Magnetic recording reproducing transducer [e.g., tape head, core, etc.]
• CPC Class Codes: Y10T 29/49032 Fabricating head structure or component thereof

Abstract

An exchange-coupled film includes a seed layer, an antiferromagnetic layer, and a ferromagnetic layer. The seed layer is formed at a thickness that is larger than the critical thickness, and the thickness of the seed layer is then decreased by etching so as to be smaller than or equal to the critical thickness. Thereby, a crystalline phase which extends through the seed layer from the upper surface to the lower surface can be formed, and/or the average size, in a direction parallel to the layer surface, of the crystal grains in the seed layer can be set to be larger than the thickness of the seed layer. Consequently, a large exchange coupling magnetic field Hex can be generated between the antiferromagnetic layer and the ferromagnetic layer.

Claims

1. An exchange-coupled film comprising a seed layer, an antiferromagnetic layer, and a ferromagnetic layer disposed in that order from the bottom, magnetization of the ferromagnetic layer being directed in a predetermined direction by an exchange coupling magnetic field generated at an interface between the antiferromagnetic layer and the ferromagnetic layer,

wherein the seed layer is a metal layer having a thickness that is smaller than or equal to a critical thickness and having a crystalline phase which extends through from an upper surface to a lower surface of the seed layer.

3. The exchange-coupled film according to claim 1, wherein a crystalline phase of the seed layer has a face-centered cubic structure and an equivalent crystal plane represented as {111} plane is preferentially oriented parallel to the interface.

4. The exchange-coupled film according to claim 1, wherein the seed layer comprises a NiCr alloy or a NiFeCr alloy.

6. The exchange-coupled film according to claim 4, wherein the Cr content in the NiCr alloy or the NiFeCr alloy is 40 to 60 atomic percent, and a thickness of the seed layer is larger than 0 Å

and smaller than or equal to 38 Å

.

7. The exchange-coupled film according to claim 4, wherein the Cr content in the NiCr alloy or the NiFeCr alloy is 35 to 60 atomic percent, and a thickness of the seed layer is larger than 0 Å

and smaller than or equal to 30 Å

.

10. The exchange-coupled film according to claim 6, wherein the thickness of the seed layer is 6 Å

or more.

11. The exchange-coupled film according to claim 10, wherein the thickness of the seed layer is 12 Å

or more.

12. A magnetic sensing element comprising a seed layer, an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic layer, and a free magnetic layer disposed in that order from the bottom, magnetization of the free magnetic layer being aligned in a direction substantially perpendicular to a magnetization direction of the pinned magnetic layer,

wherein the seed layer, the antiferromagnetic layer, and the pinned magnetic layer correspond to the exchange-coupled film according to claim 1.

13. A magnetic sensing element comprising a seed layer, an antiferromagnetic exchange bias layer, a free magnetic layer, a nonmagnetic layer, a pinned magnetic layer, and an antiferromagnetic layer disposed in that order from the bottom, the magnetization of the free magnetic layer being aligned in a direction substantially perpendicular to magnetization direction of the pinned magnetic layer,

wherein the seed layer, the exchange bias layer, and the free magnetic layer correspond to the exchange-coupled film according to claim 1.

14. A magnetic sensing element comprising a free magnetic layer, an upper nonmagnetic layer disposed on the free magnetic layer, a lower nonmagnetic layer disposed under the free magnetic layer, an upper pinned magnetic layer disposed on the upper nonmagnetic layer, a lower pinned magnetic layer disposed under the lower nonmagnetic layer, an upper antiferromagnetic layer disposed on the upper pinned magnetic layer, a lower antiferromagnetic layer disposed under the lower pinned magnetic layer, and a seed layer disposed under the lower antiferromagnetic layer, the magnetization of the free magnetic layer being aligned in a direction substantially perpendicular to a magnetization direction of the upper pinned magnetic layer and the lower pinned magnetic layer,

wherein the seed layer, the lower antiferromagnetic layer, and the lower pinned magnetic layer correspond to the exchange-coupled film according to claim 1.

15. A magnetic sensing element comprising a seed layer, an antiferromagnetic exchange bias layer, a magnetoresistive layer, a nonmagnetic layer, and a soft magnetic layer,

wherein the seed layer, the exchange bias layer, and the magnetoresistive layer correspond to the exchange-coupled film according to claim 1.

16. A magnetic sensing element comprising a pinned magnetic layer, a free magnetic layer, and a nonmagnetic layer interposed between the pinned magnetic layer and the free magnetic layer,

wherein the pinned magnetic layer comprises a plurality of magnetic sublayers, two adjacent magnetic sublayers being separated by a nonmagnetic intermediate sublayer, the plurality of magnetic sublayers including a first magnetic sublayer located farthest from the nonmagnetic layer, and the first magnetic sublayer is in contact with a nonmagnetic metal layer comprising a PtMn alloy or an X—

MN alloy, wherein X is at least one element selected from the group consisting of Pt, Pd, Ir, Rh, Ru, Os, Ni, and Fe;

wherein crystals in the nonmagnetic metal layer and crystals in the first magnetic sublayer are epitaxial or heteroepitaxial;

wherein an end face of the pinned magnetic layer facing a recording medium is exposed; and

wherein the nonmagnetic metal layer is disposed on the seed layer according to claim 1.

2. An exchange-coupled film comprising a seed layer, an antiferromagnetic layer, and a ferromagnetic layer disposed in that order from the bottom, the magnetization of the ferromagnetic layer being directed in a predetermined direction by an exchange coupling magnetic field generated at an interface between the antiferromagnetic layer and the ferromagnetic layer,

wherein the seed layer is a metal layer having a thickness that is smaller than or equal to a critical thickness and having a crystalline phase, and an average size, in a direction parallel to the layer surface, of the crystal grains in the seed layer is larger than a thickness of the seed layer.

5. An exchange-coupled film comprising a seed layer, an antiferromagnetic layer, and a ferromagnetic layer disposed in that order from the bottom, the magnetization of the ferromagnetic layer being directed in a predetermined direction by an exchange coupling magnetic field generated at an interface between the antiferromagnetic layer and the ferromagnetic layer,

wherein the seed layer comprises a NiCr alloy or a NiFeCr alloy, the Cr content in the NiCr alloy or the NiFeCr alloy being 35 to 60 atomic percent;

and

wherein a thickness of the seed layer is smaller than or equal to a critical thickness.

8. The exchange-coupled film according to claim 5, wherein the Cr content in the NiCr alloy or the NiFeCr alloy is 50 atomic percent or less.

9. The exchange-coupled film according to claim 5, wherein in the NiFeCr alloy, the Fe/Ni atomic ratio is greater than 0/100 and less than or equal to 30/70.

17. A method for making an exchange-coupled film comprising the steps of:

(a) forming a seed layer at a thickness that is larger than a critical thickness so that a crystalline phase extends through from a upper surface to a lower surface of the seed layer;

(b) etching the upper surface of the seed layer so that the thickness of the seed layer is smaller than or equal to the critical thickness; and

(c) depositing an antiferromagnetic layer and a ferromagnetic layer on the seed layer.

19. The method for making the exchange-coupled film according to claim 17, wherein in said step (a), the seed layer is formed with a metal material which has a face-centered cubic structure and a crystalline phase in which the equivalent crystal plane represented as {111} plane is preferentially oriented parallel to an interface between the antiferromagnetic layer and the ferromagnetic layer.

20. The method for making the exchange-coupled film according to claim 17, wherein the seed layer is formed with a NiCr alloy or a NiFeCr alloy.

22. The method for making the exchange-coupled film according to claim 20, wherein the Cr content in the NiCr alloy or the NiFeCr alloy is 40 to 60 atomic percent, and in said step (b), the seed layer is etched so that the thickness of the seed layer is larger than 0 Å

and smaller than or equal to 38 Å

.

23. The method for making the exchange-coupled film according to claim 20, wherein the Cr content in the NiCr alloy or the NiFeCr alloy is 35 to 60 atomic percent, and in said step (b), the seed layer is etched so that the thickness of the seed layer is larger than 0 Å

and smaller than or equal to 30 Å

.

25. The method for making the exchange-coupled film according to claim 22, wherein in the NiFeCr alloy, the Fe/Ni atomic ratio is greater than 0/100 and less than or equal to 30/70.

26. The method for making the exchange-coupled film according to claim 22, wherein in said step (b), the thickness of the seed layer is set at 6 Å

or more.

27. The method for making the exchange-coupled film according to claim 26, wherein in said step (b), the thickness of the seed layer is set at 12 Å

or more.

18. A method for making an exchange-coupled film comprising the steps of:

(d) forming a seed layer with a crystalline phase at a thickness that is larger than a critical thickness;

(e) etching a surface of the seed layer so that the thickness of the seed layer is smaller than or equal to the critical thickness and so that an average size, in a direction parallel to the layer surface, of the crystal grains in the seed layer is larger than the thickness of the seed layer; and

(f) depositing an antiferromagnetic layer and a ferromagnetic layer on the seed layer.

21. A method for making an exchange-coupled film comprising the steps of:

(g) forming a seed layer at a thickness that is larger than a critical thickness with a NiCr alloy or a NiFeCr alloy having a Cr content of 35 to 60 atomic percent;

(h) etching a surface of the seed layer so that the thickness of the seed layer is smaller than or equal to the critical thickness; and

(i) depositing an antiferromagnetic layer and a ferromagnetic layer on the seed layer.

24. The method for making the exchange-coupled film according to claim 21, wherein the Cr content in the NiCr alloy or the NiFeCr alloy is 50 atomic percent or less.

28. A method for making an exchange-coupled film comprising the steps of:

(a) forming a seed layer at a thickness that is larger than a critical thickness so that a crystalline phase extends through from an upper surface to a lower surface of the seed layer;

(b) etching the upper surface of the seed layer so that the thickness of the seed layer is smaller than or equal to the critical thickness; and

(j) depositing a ferromagnetic layer on the seed layer.