# US 7,411,765 B2 · CPP-GMR sensor with non-orthogonal free and reference layer magnetization orientation

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- Number: US 7,411,765 B2
- Document ID: US7411765B2
- Status: Granted
- Kind: B2
- Application number: 11/189,170
- Filed: 2005-07-25
- Published: 2007-01-25
- Granted: 2008-08-12
- Earliest claimed: 2005-07-18
- Assignees: Hitachi Global Storage Technologies Netherlands B.V.
- Inventors: Jeffrey Robinson Childress; Neil Smith
- Web page: https://patentgrep.com/patent/US7411765B2

## CPC

- G01R 33/093: {using multilayer structures, e.g. giant magnetoresistance sensors (thin magnetic films H01F10/00)}
- B82Y 25/00: Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
- G11B 5/3903: {using magnetic thin film layers or their effects, the films being part of integrated structures}
- G11B 5/3932: {Magnetic biasing films}
- H10N 50/10: Magnetoresistive devices
- G11B 2005/0016: {of magnetoresistive transducers}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

A CPP GMR sensor structure having free and reference layers, where the magnetic orientations of the free and reference layers are non-orthogonal. In one embodiment, a ferromagnetic free layer film has a bias-point magnetization nominally oriented in plane of the film thereof, in a first direction at an angle θfb with respect to a longitudinal axis being defined as the intersection of the plane of deposition of the free layer and the plane of the ABS. A ferromagnetic reference layer film has a bias-point magnetization nominally oriented in a plane of the film thereof, in a second direction at angle θrb with respect to said longitudinal axis that is not orthogonal to the said first direction.

## Claims

### Claim 1

A CPP spin-valve magnetic head having an air bearing surface (ABS), comprising:
a ferromagnetic free layer film having a bias-point magnetization nominally oriented in plane of the film therof, in a first direction at an angle θfb with respect to a longitudinal axis being defined as the intersection of the plane of deposition of the free layer and the plane of the ABS;
a ferromagnetic reference layer film having a bias-point magnetization nominally oriented in a plane of the film thereof, in a second direction at angle θrb with respect to said longitudinal axis that is not orthogonal to the said first direction; and
a nonmagnetic spacer layer between the free and reference layers.

### Claim 2 (depends on 1)

A head as recited in claim 1, wherein cos(θfb−θrb) is less than zero.

### Claim 3 (depends on 1)

A head as recited in claim 1, wherein cos(θfb−θrb) is less than about −0.2.

### Claim 4 (depends on 1)

A head as recited in claim 1, wherein cos(θfb−θrb) is less than about −0.5.

### Claim 5 (depends on 1)

A head as recited in claim 1, wherein the reference layer magnetization orientation angle θrb is approximately orthogonal to the said longitudinal axis, wherein the free layer orientation angle θfb is not nominally parallel to said longitudinal axis.

### Claim 6 (depends on 5)

A head as recited in claim 5, wherein the orientation θfb of the free layer magnetization is determined by the polarity and direction of demagnetization and interlayer coupling fields from the reference layer.

### Claim 7 (depends on 5)

A head as recited in claim 5, further comprising hard bias layers positioned on opposite sides of the free layer and having a magnetization direction oriented at an angle from the longitudinal axis of the free layer, wherein θfb is oriented in the first direction by magnetic fields emanating from the hard bias layers.

### Claim 8 (depends on 7)

A head as recited in claim 7, wherein the magnetization direction of the hard bias layers is oriented at an angle of about 5 to about 30 degrees from the said longitudinal axis, wherein the free layer magnetization is oriented in the first direction θfb by magnetic fields emanating from the hard bias layers.

### Claim 9 (depends on 1)

A head as recited in claim 1, wherein the free layer magnetization orientation θfb is substantially parallel to the said longitudinal axis, wherein the reference layer orientation angle θrb is non-orthogonal to the said longitudinal axis.

### Claim 10 (depends on 9)

A head as recited in claim 9, further comprising a ferromagnetic pinned layer film exchange pinned by an antiferromagnet to maintain the pinned layer bias-point magnetization in the film plane at an orientation angle θpb which is not orthogonal to the free layer orientation θfb, and wherein the reference layer orientation θrb is antiparallel to the orientation θpb of the pinned layer.

### Claim 11 (depends on 1)

A magnetic storage system, comprising:
magnetic media;
at least one head for reading from and writing to the magnetic media, each head having:
a sensor having the structure recited in claim 1;
a write element coupled to the sensor;
a slider for supporting the head; and
a control unit coupled to the head for controlling operation of the head.

### Claim 12

A CPP magnetic head having an air bearing surface (ABS), comprising:
a ferromagnetic pinned layer;
an antiparallel coupling layer above the pinned layer;
a ferromagnetic reference layer above the antiparallel coupling layer, the reference layer being antiparallel coupled to the pinned layer;
a spacer layer above the reference layer;
a ferromagnetic free layer above the spacer layer, a longitudinal axis being defined as the intersection of the plane of deposition of the free layer and the plane of the ABS;
wherein the free layer has a bias-point magnetization orientation nominally in the film plane in a first direction at an angle θfb with respect to said longitudinal axis; and
wherein the reference layer has a bias-point magnetization orientation θrb nominally in the film plane in a second direction at an angle that is not orthogonal to the first direction.

### Claim 13 (depends on 12)

A head as recited in claim 12, wherein cos(θfb−θrb) is less than zero.

### Claim 14 (depends on 12)

A head as recited in claim 12, wherein cos(θfb−θrb) is less than about −0.2.

### Claim 15 (depends on 12)

A head as recited in claim 12, wherein cos(θfb−θrb) is less than about −0.5.

### Claim 16 (depends on 12)

A head as recited in claim 12, wherein θrb is substantially orthogonal to said longitudinal axis, wherein θfb is not nominally parallel to the longitudinal axis of the free layer.

### Claim 17 (depends on 16)

A head as recited in claim 16, wherein the orientation θfb of the free layer magnetization is determined by the polarity and direction of demagnetization and interlayer coupling fields from the reference and pinned layers.

### Claim 18 (depends on 16)

A head as recited in claim 16, further comprising hard bias layers positioned on opposite sides of the free layer and having a magnetization direction oriented at an angle from the longitudinal axis of the free layer, wherein θfb is oriented in the first direction by magnetic fields emanating from the hard.

### Claim 19 (depends on 18)

A head as recited in claim 18, wherein the magnetization direction of the hard bias layers is oriented at an angle of about 5 to about 30 degrees from the longitudinal axis of the free layer, wherein θfb is oriented in the first direction by magnetic fields emanating from the hard bias layers.

### Claim 20 (depends on 12)

A head as recited in claim 12, wherein the free layer magnetization orientation θfb is substantially parallel to the said longitudinal axis, wherein the reference layer orientation angle θrb is non-orthogonal to the said longitudinal axis.

### Claim 21 (depends on 20)

A head as recited in claim 20, further comprising an antiferromagnet layer which exchange pins the bias-point magnetization of the pinned layer in a nominal direction in the film plane at orientation angle θpb which is not orthogonal to the free layer orientation θfb, and wherein the reference layer orientation θrb is antiparallel to the orientation angle θpb of the pinned layer.

### Claim 22 (depends on 12)

A head as recited in claim 12, wherein the direction of the pinned layer magnetization is fixed in orientation by means other than that of exchange pinning to an antiferromagnet layer.

### Claim 23 (depends on 12)

A magnetic storage system, comprising:
magnetic media;
at least one head for reading from and writing to the magnetic media, each head having:
a sensor having the structure recited in claim 12;
a write element coupled to the sensor;
a slider for supporting the head; and
a control unit coupled to the head for controlling operation of the head.

### Claim 24

A dual CPP magnetic head having an air bearing surface (ABS), comprising:
a ferromagnetic free layer film having bias-point magnetization orientation nominally in the film plane in a first direction described by angle θfb with respect to a longitudinal axis defined by the intersection of the free layer film plane and a plane of the ABS;
a first ferromagnetic reference layer film having a magnetization orientation nominally in a plane of the film thereof in a second direction described by angle θr1 that is not orthogonal to the first direction;
a first spacer layer between the free and first reference layers;
a second reference layer positioned on an opposite side of the free layer than the first reference layer, the second reference layer having a magnetization orientation nominally in a plane of the film thereof in a third direction normally oriented in a third direction described by angle θr1 that is not orthogonal to the first direction; and
a second spacer layer between the free and second reference layers.

### Claim 25 (depends on 24)

A head as recited in claim 24, wherein the first and second reference layers are substantially similar in physical properties, and wherein θr1≅θr2, and wherein the first and second spacer layers are substantially similar in physical properties.

### Claim 26 (depends on 24)

A head as recited in claim 24, wherein cos(θfb−θr1) is less than zero.

### Claim 27 (depends on 24)

A head as recited in claim 24, wherein cos(θfb−θr1) is less than about −0.2.

### Claim 28 (depends on 24)

A head as recited in claim 24, wherein first and second reference layer magnetization directions θr1, θr2 are substantially orthogonal to the longitudinal axis of the free layer, wherein free layer magnetization direction θfb is not nominally parallel to the longitudinal axis of the free layer.

### Claim 29 (depends on 24)

A head as recited in claim 24, wherein the free layer magnetization direction θfb is substantially parallel to the longitudinal axis, wherein first and second reference layer magnetization directions θr1θr2 are non-orthogonal to the longitudinal.

### Claim 30 (depends on 24)

A magnetic storage system, comprising:
magnetic media;
at least one head for reading from and writing to the magnetic media, each head having:
a sensor having the structure recited in claim 24;
a write element coupled to the sensor;
a slider for supporting the head; and
a control unit coupled to the head for controlling operation of the head.

### Claim 31

A magnetic head, comprising:
a free layer;
a reference layer;
a pinned layer
a coupling layer between the pinned and reference layers; and
a spacer layer between the free and reference layers;
wherein the reference layer has a magnetization direction fixed by the pinned layer through a coupling layer,
wherein the antiferromagnetic layer fixes the direction of magnetization of the pinned layer,
wherein the direction of magnetization of the free layer is oriented relative to the direction of magnetization of the reference layer as determined by a parameter Q, Q being the scalar product of the unit magnetization vector of the free layer with the unit magnetization vector of the reference layer,
wherein a value of Q and the magnitude and polarity of the bias current are such that the sensor is not subject to spin-torque induced instability during operation.

### Claim 32 (depends on 31)

A head as recited in claim 31, wherein a value of Q is between about zero and about −0.6.