Magnetoresistive sensor, magnetic head and magnetic disk apparatus

• US 6,636,391 B2
• Filed: 03/20/2001
• Issued: 10/21/2003
• Est. Priority Date: 04/06/2000
• Status: Expired due to Term

• Current Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Hitachi, Ltd.
• Inventors: Arai, Reiko, Watanabe, Katsuro, Kawato, Yoshiaki
• Primary Examiner(s): Watko, Julie Anne
• Application Number:
  US09/811,482
• Publication Number:
  US 20010040777A1
• Time in Patent Office: 945 Days
• Field of Search: 360/324.12, 360/321, 360/324.1, 360/324.2, 360/313, 360/110, 360/324
• US Class Current: 360/321
• 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 5/3156 providing interaction by induced or exchange coupling
• 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 5/3919 the guide being interposed in the flux path
• 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

Abstract

A magnetoresistive sensor employing a magnetoresistive sensor film of a GMR film or a TMR film and a magnetic flux guide to ensure high sensitivity and high stability. Magnetization of a magnetic flux guide and a first ferromagnetic layer, which is a free layer of a GMR sensor film or a TMR sensor film, are made to antiferromagnetically couple to each other via a nonmagnetic intermediate layer 21. Since net magnetic moment has become small in the area in which the magnetoresistive sensor film is arranged, and an angle of magnetization of the ferromagnetic layer rotated by magnetic field which has been guided by the magnetic flux guide enlarges, high sensitivity can be obtained. When a longitudinal biasing layer is provide for the magnetic flux guide, longitudinal biasing magnetic field is applied to the ferromagnetic layer as well which is antiferromagnetically coupled to the magnetic flux guide, thus being able to suppress Barkhausen noise of both the magnetic flux guide and the ferromagnetic layer.

Claims

1. A magnetoresistive sensor comprising:

a magnetoresistive sensor film having a ferromagnetic layer whose magnetization rotates in response to magnitude of an applied magnetic field;

a pair of electrodes for flowing a signal sensing current to said magnetoresistive sensor film; and

a magnetic flux guide for guiding a leakage flux from a magnetic recording medium to said magnetoresistive sensor film,

wherein said ferromagnetic layer of said magnetoresistive sensor film whose magnetization rotates in response to magnitude of the applied magnetic field is antiferromagnetically coupled to said magnetic flux guide.

2. The magnetoresistive sensor according to claim 1, wherein said ferromagnetic layer of said magnetoresistive sensor film whose magnetization rotates in response to magnitude of the applied magnetic field is antiferromagnetically coupled to said magnetic flux guide via a nonmagnetic intermediate layer made of Ru, Cr, Rh, Tr, or alloys thereof.

3. The magnetoresistive sensor according to claim 2, wherein said magnetic flux guide consists of a first magnetic flux guide portion and a second magnetic flux guide portion, said first magnetic flux guide portion and said second magnetic flux guide portion being continuous from said air bearing surface towards a depth direction and being magnetically connected at a farther position from said air bearing surface than the position of said magnetoresistive sensor film in the depth direction.

4. The magnetoresistive sensor according to claim 1, wherein said magnetic flux guide consists of a first magnetic flux guide portion and a second magnetic flux guide portion, said first magnetic flux guide portion and said second magnetic flux guide portion being continuous an said air bearing surface towards a depth direction and being magnetically connected at a farther position from said air bearing surface than the position of said magnetoresistive sensor film in the depth direction.

5. The magnetoresistive sensor according to claim 1, wherein said magnetic flux guide is provide with a longitudinal biasing layer for suppressing a Barkhausen noise.

6. The magnetoresistive sensor according to claim 1, wherein said magnetoresistive sensor film further comprises:

another ferromagnetic layer,

wherein said ferromagnetic layer and said another ferromagnetic layer have been laminated to each other via a tunnel barrier layer,

wherein a magnetization of said ferromagnetic layer rotating in response to the applied magnetic field, and a relative angle of the magnetization direction of said ferromagnetic layer to that of said another ferromagnetic layer varies to change electric resistance.

7. The magnetoresistive sensor according to claim 1, wherein said magnetoresistive sensor film further comprises:

another ferromagnetic layer;

wherein said ferromagnetic layer and said another ferromagnetic layer, have been laminated to each other via a nonmagnetic conductive layer, and

wherein a magnetization of said ferromagnetic layer rotating in response to the applied magnetic field, and a relative angle of the magnetization direction of said ferromagnetic layer to that of said another ferromagnetic layer varies to change electric resistance.

8. A magnetic head comprising:

a read-head, wherein said read-head comprises;

a magnetoresistive sensor film having a ferromagnetic layer whose magnetization rotates in response to magnitude of an applied magnetic field,

a pair of electrodes for flowing a signal sensing current to said magnetoresistive sensor film, and

a magnetic flux guide for guiding leakage flux from a magnetic recording medium to said magnetoresistive sensor film,

wherein said magnetic flux guide being antiferromagnetically coupled to said ferromagnetic layer of said magnetoresistive sensor film whose magnetization rotates in response to magnitude of the applied magnetic field.

9. The magnetic head according to claim 8, wherein said magnetoresistive sensor film further comprises:

another ferromagnetic layer,

wherein said ferromagnetic layer and said another ferromagnetic layer have been laminated to each other via a tunnel barrier layer,

wherein said ferromagnetic layer being a magnetoresistive sensor film whose magnetization rotates in response to magnitude of the applied magnetic field, and

wherein said magnetic flux guide is antiferromagnetically coupled to said ferromagnetic layer of said magnetoresistive sensor film via a nonmagnetic intermediate layer made of Ru, Cr, Rh, Ir, or alloys thereof to guide leakage flux from the magnetic recording medium to said magnetoresistive sensor film.

10. The magnetic head according to claim 8, wherein said magnetoresistive sensor film further comprises:

another ferromagnetic layer,

wherein said ferromagnetic layer and said another ferromagnetic layer have been laminated to each other via a tunnel barrier layer,

wherein a magnetization of said ferromagnetic layer rotates in response to magnitude of the applied magnetic field, and a relative angle of the magnetization direction of said ferromagnetic layer to said another ferromagnetic layer varying to change electric resistance, and

wherein said magnetic flux guide is antiferromagnetically coupled to said ferromagnetic layer via a nonmagnetic intermediate layer made of Ru, Cr, Rh, Ir, or alloys thereof to guide leakage flux from the magnetic recording medium to said magnetoresistive sensor film.

11. The magnetic head according to claim 8, wherein said magnetic flux guide is provided with a longitudinal biasing layer for suppressing a Barkhausen noise.

12. The magnetic head according to claim 8, wherein said magnetoresistive sensor film further comprises:

another ferromagnetic layer,

wherein said ferromagnetic layer and said another ferromagnetic layer have been laminated to each other via a nonmagnetic conductive layer,

wherein the magnetization of said ferromagnetic layer rotates in response to magnitude of the applied magnetic field, and a relative angle of the magnetization direction of said ferromagnetic layer to said another ferromagnetic layer varying to change electric resistance, and

wherein said magnetic flux guide is antiferromagnetically coupled to said ferromagnetic layer via a nonmagnetic intermediate layer made of Ru, Cr, Rh, Ir, or alloys thereof to guide leakage flux from the magnetic recording medium to said magnetoresistive sensor film.

13. A magnetic disk apparatus comprising:

a magnetic recording apparatus including;

a magnetic recording medium;

a magnetic head including a recording unit and a read-back unit;

driving means for letting said magnetic head make a relative motion to said magnetic recording media; and

read/write signal processing means,

wherein said read-back unit of said magnetic head comprises;

a magnetoresistive sensor film including a ferromagnetic layer whose magnetization rotates in response to magnitude of an applied magnetic field;

a pair of electrodes for flowing a signal sensing current to said magnetoresistive sensor film; and

a magnetic flux guide for guiding leakage flux from said magnetic recording medium to said magnetoresistive sensor film, said magnetic flux guide being antiferromagnetically coupled to the ferromagnetic layer of said magnetoresistive sensor film whose magnetization rotates in response to magnitude of the applied magnetic field.

14. The magnetic disk apparatus according to claim 13, wherein said magnetoresistive sensor film further comprises:

another ferromagnetic layer,

wherein said ferromagnetic layer, a nonmagnetic layer, said another ferromagnetic layer, and an antiferromagnetic layer have been formed in order, and

wherein said first-ferromagnetic layer and said magnetic flux guide being formed via the nonmagnetic intermediate layer made of Ru, Cr, Rh, Ir, or alloys thereof.

15. The magnetic disk apparatus according to claim 14, wherein said nonmagnetic layer is a tunnel barrier layer.