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 6,496,338 B2
• Filed: 06/25/2001
• Issued: 12/17/2002
• Est. Priority Date: 10/07/1996
• Status: Expired due to Fees

• Current Assignee: TDK Corporation
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Hasegawa, Naoya, Saito, Masamichi, Makino, Akihiro
• Primary Examiner(s): OMETZ, DAVID LOUIS
• Application Number:
  US09/891,327
• Publication Number:
  US 20010050834A1
• Time in Patent Office: 540 Days
• Field of Search: 360/324.1, 360/324.11, 360/324.12, 360/327.3, 360/327.32
• 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 spin-valve magnetoresistive sensor comprising at least two ferromagnetic layers including a first and a second ferromagnetic layers. A first antiferromagnetic layer is layered adjacent to the first ferromagnetic layer for increasing the coercive force of the first ferromagnetic layer to pin the magnetization direction of the first ferromagnetic layer. A pair of second antiferromagnetic layers are respectively positioned adjacent to the longitudinal ends of the second ferromagnetic layer. Further, a pair of third ferromagnetic layers are respectively layered adjacent to said pair of second antiferromagnetic layers for inducing magnetic anisotropy to pin the magnetization direction of each third ferromagnetic layer in a direction perpendicular to the pinned magnetization direction of the first ferromagnetic layer, thereby imposing a longitudinal bias on the second ferromagnetic layer to stabilize magnetic domains therein in order to suppress Barkhausen noise. The magnetization direction of the second ferromagnetic layer remains free to rotate in accordance with the direction of an external magnetic field, thereby changing the electrical resistance of the sensor.

Claims

1. A spin-valve magnetoresistive sensor comprising:

(a) at least two ferromagnetic layers layered with a non-magnetic layer sandwiched therebetween, said at least two ferromagnetic layers including a first and a second ferromagnetic layers, said second ferromagnetic layer including a magnetic sensing region located midway along its longitudinal length, said magnetic sensing region being substantially equal in longitudinal length to a track width;

(b) a first antiferromagnetic layer layered adjacent to said first ferromagnetic layer for increasing the coercive force of said first ferromagnetic layer to pin the magnetization direction of said first ferromagnetic layer;

(c) a pair of second antiferromagnetic layers respectively layered adjacent to said second ferromagnetic layer on each longitudinal side of said magnetic sensing region for inducing magnetic anisotropy directly in said second ferromagnetic layer to pin the magnetization directions in said second ferromagnetic layer on each longitudinal side of said magnetic sensing region in a direction perpendicular to the pinned magnetization direction of said first ferromagnetic layer, thereby imposing a longitudinal bias on the magnetic sensing region to stabilize magnetic domains in said magnetic sensing region and orient the magnetization direction of said magnetic sensing region perpendicular to the pinned magnetization direction of said first ferromagnetic layer in the absence of any external magnetic field, whereas, in the presence of an external magnetic field, permitting the magnetization direction of said magnetic sensing region to freely rotate to the direction of said external magnetic field, wherein

(e) said first antiferromagnetic layer is made of α

-Fe₂O₃, and

(f) said pair of second antiferromagnetic layers are made of an X—

Mn system alloy having a disordered structure where said X is made of at least one metal selected from the group consisting of Pt, Pd, Ir, Ru or Rh.

2. A spin-valve magnetoresistive sensor according to claim 1, wherein the coercive force of said first ferromagnetic layer increased by said first antiferromagnetic layer is larger than a unidirectional exchange bias magnetic field induced in said first ferromagnetic layer by said first antiferromagnetic layer.

3. A spin-valve magnetoresistive sensor according to claim 1, wherein X is contained in the alloy at:

10 to 45 atomic % when X is Ru;

10 to 40 atomic % when X is Rh;

10 to 40 atomic % when X is Ir;

10 to 25 atomic % when X is Pd; and

10 to 25 atomic % when X is Pt.

4. A spin-valve magnetoresistive sensor according to claim 1, wherein said at least two ferromagnetic layers are made of at least one material selected from the group consisting of a NiFe alloy, a CoFe alloy, a NiCo alloy, Co, and a NiFeCo alloy.

5. A spin-valve magnetoresistive sensor according to claim 1, wherein said second ferromagnetic layer comprises a Co layer arranged between said second ferromagnetic layer and said non-magnetic layer, and a NiFe alloy layer arranged on the surface of said second ferromagnetic layer opposite to the surface to which said Co layer is arranged.

6. A spin-valve magnetoresistive sensor according to claim 1, wherein said at least two ferromagnetic layers comprise a Co layer arranged between said non-magnetic layer and each of said at least two ferromagnetic layers.