Spin-valve magnetoresistive sensor including a first antiferromagnetic layer for increasing a coercive force and a second antiferromagnetic layer for imposing a longitudinal bias

• US 20010050834A1
• Filed: 06/25/2001
• Published: 12/13/2001
• Est. Priority Date: 10/07/1996
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Hasegawa, Naoya, Saito, Masamichi, Makino, Akihiro
• Granted Patent: US 6,496,338 B2
• Time in Patent Office: Days
• US Class Current: 360/324.12
• 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 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• 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 5/012 Recording on, or reproducing or erasing from, magnetic disks G11B17/00, G11B19/00 take precedence
• CPC Class Codes: G11B 5/3163 Fabrication methods or processes specially adapted for a particular head structure, e.g. using base layers for electroplating, using functional layers for masking, using energy or particle beams for shaping the structure or modifying the properties of the basic layers
• 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 5/3929 Disposition of magnetic thin films not used for directly coupling magnetic flux from the track to the MR film or for shielding
• CPC Class Codes: G11B 5/3967 Composite structural arrangements of transducers, e.g. inductive write and magnetoresistive read G11B5/3906 takes precedence
• CPC Class Codes: H01F 10/3268 the exchange coupling being asymmetric, e.g. by use of additional pinning, by using antiferromagnetic or ferromagnetic coupling interface, i.e. so-called spin-valve [SV] structure, e.g. NiFe/Cu/NiFe/FeMn
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

The present invention provides a magnetoresistive sensor having at least two ferromagnetic layers provided with a non-magnetic layer therebetween; a coercive force increasing layer consisting of an antiferromagnetic material and provided adjacent to one of the ferromagnetic layers, for increasing the coercive force thereof to pin magnetization reversal, the other ferromagnetic layer having free magnetization reversal; and an antiferromagnetic layer provided to adjacent to the other ferromagnetic layer having free magnetization reversal, for applying a longitudinal bias to the other ferromagnetic layer to induce magnetic anisotropy therein due to an unidirectional exchange bias magnetic field to stabilize a magnetic domain.

Claims

1. A magnetoresistive sensor comprising:

at least two ferromagnetic layers provided with a non-magnetic layer therebetween;

a coercive force increasing layer comprising a first antiferromagnetic material and provided adjacent to one of the ferromagnetic layers, for increasing the coercive force of the ferromagnetic layer to pin magnetization reversal thereof, the other ferromagnetic layer having free magnetization reversal; and

an antiferromagnetic layer comprising a second antiferromagnetic material and provided adjacent to the other ferromagnetic layer having free magnetization reversal, for applying a longitudinal bias to the ferromagnetic layer to induce magnetic anisotropy by an unidirectional exchange bias magnetic field to stabilize a magnetic domain;

wherein the magnetization direction of the ferromagnetic layer having pinned magnetization reversal crosses at substantially right angles the magnetization direction of the other ferromagnetic layer having free magnetization reversal without an external magnetic field.

2. A magnetoresistive sensor according to

claim 1

, wherein the coercive force increasing layer comprises α

-Fe₂O₃, and the coercive force of the ferromagnetic layer having magnetization reversal pinned by the coercive force increasing layer is larger than the unidirectional exchange bias magnetic field induced in the ferromagnetic layer by the coercive force increasing layer.

3. A magnetoresistive sensor according to

claim 1

, wherein the second antiferromagnetic layer for applying the longitudinal bias is formed on either side of the magnetic sensing region of the other ferromagnetic layer having free magnetization reversal with a space therebetween, which equals to a predetermined track width corresponding to the width of the magnetic sensing region, so as to be adjacent to the other ferromagnetic layer.

4. A magnetoresistive sensor according to

claim 1

, wherein the other ferromagnetic layer having free magnetization reversal is formed with the width of the magnetic sensing region corresponding to the track width, and a laminate of an antiferromagnetic layer and another ferromagnetic layer laminated on the antiferromagnetic layer is formed on either side of the other ferromagnetic layer having free magnetization reversal to apply the longitudinal bias to the ferromagnetic layer.

5. A magnetoresistive sensor according to

claim 1

, wherein the second antiferromagnetic layer for applying the longitudinal bias comprises an X—

Mn (wherein X indicates at least one of Pt, Pd, Ir, Ru and Rh) system alloy thin film.

6. A magnetoresistive sensor according to

claim 2

, wherein the second antiferromagnetic layer for applying the longitudinal bias is disposed on either side of the magnetic sensing region of the other ferromagnetic layer having free magnetization reversal with a space therebetween which equals to a predetermined track width corresponding to the width of the magnetic sensing region, so as to be adjacent to the other ferromagnetic layer.

7. A magnetoresistive sensor according to

claim 2

, wherein the other ferromagnetic layer having free magnetization reversal is formed with the width of the magnetic sensing region corresponding to the track width, and a laminate of an antiferromagnetic layer and another ferromagnetic layer laminated on the antiferromagnetic layer is formed on either side of the other ferromagnetic layer having free magnetization reversal to apply the longitudinal bias to the other ferromagnetic layer.

8. A magnetoresistive sensor according to

claim 2

, wherein the antiferromagnetic layer for applying the longitudinal bias comprises an X—

Mn (wherein X indicates at least one of Pt, Pd, Ir, Ru and Rh) system alloy thin film.

9. A magnetoresistive sensor according to

claim 3

, wherein the antiferromagnetic layer for applying the longitudinal bias comprises an X—

Mn (wherein X indicates at least one of Pt, Pd, Ir, Ru and Rh) system alloy thin film.

10. A magnetoresistive sensor according to

claim 4

, wherein the ferromagnetic layer laminated on the second antiferromagnetic layer for applying the longitudinal bias comprises an amorphous thin film.

11. A magnetoresistive sensor according to

claim 4

, wherein the antiferromagnetic layer for applying the longitudinal bias comprises an X—

Mn (wherein X indicates at least one of Pt, Pd, Ir, Ru and Rh) system alloy thin film.

12. A magnetoresistive sensor according to

claim 6

, wherein the antiferromagnetic layer for applying the longitudinal bias comprises an X—

Mn (wherein X indicates at least one of Pt, Pd, Ir, Ru and Rh) system alloy thin film.

13. A magnetoresistive sensor according to

claim 7

, wherein the ferromagnetic layer laminated on the second antiferromagnetic layer for applying the longitudinal bias comprises an amorphous thin film.

14. A magnetoresistive sensor according to

claim 7

, wherein the antiferromagnetic layer for applying the longitudinal bias comprises an X—

Mn (wherein X indicates at least one of Pt, Pd, Ir, Ru and Rh) system alloy thin film.

15. A magnetoresistive sensor according to

claim 10

, wherein the antiferromagetic layer for applying the longitudinal bias comprises an X—

Mn (wherein X indicates at least one of Pt, Pd, Ir, Ru and Rh) system alloy thin film.

16. A magnetoresistive sensor according to

claim 13

, wherein the antiferromagnetic layer for applying the longitudinal bias comprises an X—

Mn (wherein X indicates at least one of Pt, Pd, Ir, Ru and Rh) system alloy thin film.

17. A method of manufacturing a magnetoresistive sensor comprising:

providing at least two ferromagnetic layers with a non-magnetic layer therebetween;

providing a coercive force increasing layer comprising a first antiferromagnetic material adjacent to one of the ferromagnetic layers, for increasing the coercive force of the ferromagnetic layer to pin the magnetization reversal thereof, the other ferromagnetic layer having free magnetization reversal; and

providing an antiferromagnetic layer comprising a second antiferromagnetic material adjacent to the other ferromagnetic layer having free magnetization reversal, for applying a longitudinal bias to the other ferromagnetic layer to induce magnetic anisotropy due to a unidirectional exchange bias magnetic field to stabilize a magnetic domain;

wherein the magnetization direction of the ferromagnetic layer having pinned magnetization reversal crosses at substantially right angles the magnetization direction of the ferromagnetic layer having free magnetization reversal without an external magnetic field, the second antiferromagnetic layer for applying the longitudinal bias is formed on either side of the magnetic sensing region of the ferromagnetic layer having free magnetization reversal with a space therebetween, which equals to a predetermined track width corresponding to the width of the magnetic sensing region, so as to be adjacent to the ferromagnetic layer, the unidirectional magnetic anisotropy induced in the other ferromagnetic layer having free magnetization reversal and provided adjacent to the second antiferromagnetic layer for applying the longitudinal bias is produced by forming the other ferromagnetic layer while applying a magnetic field thereto or performing heat treatment in a magnetic field after formation of the other ferromagnetic layer, and the magnetization direction of the ferromagnetic layer having pinned magnetization reversal and adjacent to the coercive force increasing layer is determined in a permanent magnetization step after a step for determining the direction of the magnetic anisotropy of the other ferromagnetic layer having free magnetization reversal.

18. A method of manufacturing a magnetoresistive sensor according to

claim 17

wherein the coercive force increasing layer comprises α

-Fe₂O₃, and the coercive force of the ferromagnetic layer having pinned magnetization reversal is larger than the unidirectional exchange bias magnetic field induced in the ferromagnetic layer by the coercive force increasing layer.

19. A method of manufacturing a magnetoresistive sensor comprising:

providing at least two ferromagnetic layers with a non-magnetic layer therebetween;

providing a coercive force increasing layer comprising a first antiferromagnetic material adjacent to one of the ferromagnetic layers, for increasing the coercive force of the ferromagnetic layer to pin magnetization reversal thereof, the other ferromagnetic layer having free magnetization reversal; and

providing an antiferromagnetic layer comprising a second antiferromagnetic material adjacent to the other ferromagnetic layer having free magnetization reversal, for applying a longitudinal bias thereto to induce magnetic anisotropy due to a unidirectional exchange bias magnetic field to stabilize a magnetic domain;

wherein the magnetization direction of the ferromagnetic layer having pinned magnetization reversal crosses at substantially right angles the magnetization direction of the ferromagnetic layer having free magnetization reversal without an external magnetic field, the ferromagnetic layer having free magnetization reversal is formed with the width of a magnetic sensing region corresponding to a track width, a laminate of an antiferromagnetic layer and another ferromagnetic layer laminated thereon is formed on either side of the ferromagnetic layer having free magnetization reversal to apply a longitudinal bias to the ferromagnetic layer having free magnetization reversal, the unidirectional magnetic anisotropy induced in the ferromagnetic layer which is provided to form each of the laminates adjacent to the second antiferromagnetic layer for applying the longitudinal bias is produced by forming the ferromagnetic layer while applying a magnetic field or performing heat treatment in a magnetic field after formation of the ferromagnetic layer, and the magnetization direction of the ferromagnetic layer having pinned magnetization reversal and adjacent to the coercive force increasing layer is determined by a permanent magnetization step after a step for determining the magnetic anisotropy of the ferromagnetic layer of each laminate.

20. A method of manufacturing a magnetoresistive sensor according to

claim 19

wherein the coercive force increasing layer comprises α

-Fe₂O₃, and the coercive force of the ferromagnetic layer having pinned magnetization reversal is larger than the unidirectional exchange bias magnetic field induced in the ferromagnetic layer by the coercive force increasing layer.