# US 5,705,973 A · Bias-free symmetric dual spin valve giant magnetoresistance transducer

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- Number: US 5,705,973 A
- Document ID: US5705973A
- Status: Granted
- Kind: A
- Application number: 08/702,961
- Filed: 1996-08-26
- Granted: 1998-01-06
- Earliest claimed: 1996-08-26
- Assignees: Read-Rite Corporation
- Inventors: Samuel W. Yuan; Hua-Ching Tong; Francis H. Liu; Minshen Tan
- Web page: https://patentgrep.com/patent/US5705973A

## CPC

- G01R 33/093: {using multilayer structures, e.g. giant magnetoresistance sensors (thin magnetic films H01F10/00)}
- B82Y 10/00: Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
- 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}
- 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}
- H10N 50/10: Magnetoresistive devices
- G11B 5/3954: {the active elements transducing on a single track}
- G11B 2005/3996: {large or giant magnetoresistive effects [GMR], e.g. as generated in spin-valve [SV] devices}
- 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)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

A giant magnetoresistive dual spin valve sensor employs at least one magnetic biasing layer located adjacent to an antiferromagnetic layer in the spin valve structure which includes two pinned ferromagnetic layers. The antiferromagnetic layer simultaneously pins the biasing layer and the ferromagnetic layer nearest the antiferromagnetic layer. This structure eliminates the bias point offset present in prior dual spin valve sensors.

## Claims

### Claim 1

A dual gap magnetoresistive sensor comprising:
a free ferromagnetic layer;
first and second spacers adjacent to opposing first and second surfaces of said ferromagnetic layer respectively;
first and second pinned ferromagnetic layers adjacent to said first and second spacers respectively, wherein the directions of magnetization of said pinned layers are the same, and the direction of magnetization of said free layer is perpendicular to that of said pinned layers at zero applied magnetic field;
first and second antiferromagnetic layers adjacent to said first and second pinned ferromagnetic layers respectively; and
a magnetic biasing means disposed adjacent to at least one of said antiferromagnetic layers, the direction of magnetization of said biasing means being opposite to that of said pinned ferromagnetic layers;
so that any stray field generated by said pinned ferromagnetic layers is eliminated and the biasing level of the sensor is independent of sense current.

### Claim 2 (depends on 1)

A dual gap magnetoresistive sensor as in claim 1, wherein the moment thickness of said magnetic biasing means matches that of said pinned ferromagnetic layers for producing a self-biased sensor.

### Claim 3 (depends on 1)

A dual gap magnetoresistive sensor as in claim 1, wherein said ferromagnetic layers and said antiferromagnetic layers form a balanced symmetrical dual gap spin valve structure.

### Claim 4 (depends on 1)

A dual gap magnetoresistive sensor as in claim 1 wherein said magnetic biasing means includes magnetic biasing layers adjacent to each of said first and said second antiferromagnetic layers.

### Claim 5 (depends on 4)

A magnetoresistive sensor as in claim 4 in which said biasing layers have magnetic fields extending in the same direction.

### Claim 6 (depends on 5)

A magnetoresistive sensor as in claim 5 in which the direction of said magnetic fields of said biasing layers is opposite to the fixed direction of magnetization of said first and said second layers of pinned ferromagnetic material.

### Claim 7 (depends on 1)

A magnetoresistive sensor as in claim 1 wherein said magnetic biasing means comprises a single magnetic biasing layer adjacent to one of said layers of antiferromagnetic material, the direction of magnetization of said single magnetic biasing layer being opposite to the fixed direction of magnetization of said first and said second layers of said pinned ferromagnetic layers.