# US 7,612,970 B2 · Magnetoresistive sensor with a free layer stabilized by direct coupling to in stack antiferromagnetic layer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,612,970 B2 - Document ID: US7612970B2 - Status: Granted - Kind: B2 - Application number: 11/065,244 - Filed: 2005-02-23 - Published: 2006-08-24 - Granted: 2009-11-03 - Earliest claimed: 2005-02-23 - Assignees: Hitachi Global Storage Technologies Netherlands B.V. - Inventors: Hardayal Singh Gill; Kuok San Ho - Web page: https://patentgrep.com/patent/US7612970B2 ## CPC - G11B 5/39: using magneto-resistive devices {or effects} - 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) ## Abstract A magnetoresistive sensor having a free layer biased by an in stack bias layer that comprises a layer of antiferromagnetic material. The bias layer can be IrMnCr, IrMn or some other antiferromagnetic material. The free layer is a synthetic free layer having first and second magnetic layers antiparallel coupled across an AP coupling layer. The first magnetic layer is disposed adjacent to a spacer or barrier layer and the second magnetic layer is exchange coupled with the IrMnCr bias layer. The bias layer biases the magnetic moments of the free layer in desired directions parallel with the ABS without pinning the magnetic moments of the free layer. ## Claims ### Claim 1 A magnetoresistive sensor, comprising: a magnetic pinned layer structure; a magnetic free layer structure; a non-magnetic, electrically conductive spacer layer sandwiched between the free and pinned layer structures; and a bias layer comprising an antiferromagnetic material, the antiferromagnetic material being in contact with the free layer structure; wherein the free layer structure comprises a first free magnetic layer, a second free magnetic layer and a coupling layer sandwiched between the first and second free magnetic layers, the first free magnetic layer and the second free magnetic layer having magnetizations that are free to move in response to a magnetic field, and wherein the first free magnetic layer is adjacent to the spacer layer and the second free magnetic layer is in contact with the bias layer. ### Claim 2 (depends on 1) A sensor as in claim 1 wherein the second free magnetic layer is exchange coupled with the bias layer. ### Claim 3 (depends on 1) A sensor as in claim 1, wherein the bias layer has a thickness that is chosen to provide a desired amount of free layer biasing. ### Claim 4 (depends on 1) A sensor as in claim 1, wherein the bias layer comprises IrMnCr. ### Claim 5 (depends on 4) A sensor as in claim 4, wherein the bias layer has a thickness and a Cr content chosen to provide, in combination, a desired amount of free layer biasing. ### Claim 6 (depends on 1) A sensor as in claim 1 further comprising first and second electrically conductive magnetic shields in electrical communication with the free and pinned layers. ### Claim 7 (depends on 1) A sensor as in claim 1 wherein the free layer structure, pinned layer structure, and spacer layer are located between and electrically insulated from first and second magnetic shields. ### Claim 8 (depends on 1) A sensor as in claim 1 wherein the pinned layer structure is formed above the free layer structure. ### Claim 9 (depends on 1) A sensor as in claim 1 wherein the pinned layer structure is formed below the free layer structure. ### Claim 10 (depends on 1) A sensor as in claim 1 wherein the pinned layer is an AP coupled pinned layer. ### Claim 11 (depends on 1) A sensor as in claim 1 wherein the pinned layer structure is a simple pinned layer structure. ### Claim 12 A magnetoresistive sensor, comprising: a magnetic pinned layer structure; a magnetic free layer structure having a magnetization that is free to move in response to a magnetic field; a non-magnetic, electrically insulating barrier layer sandwiched between the free and pinned layer structures; and a bias layer comprising an antiferromagnetic material, the anriferromagnetic material being in contact with the free layer structure; wherein the bias layer comprises IrMnCr. ### Claim 13 (depends on 12) A sensor as in claim 12 wherein the free layer structure comprises a first free magnetic layer, a second free magnetic layer and a coupling layer sandwiched between the first and second free magnetic layers, and wherein the first free magnetic layer is adjacent to the barrier layer and the second free magnetic layer is in contact with the bias layer. ### Claim 14 (depends on 12) A sensor as in claim 12 wherein the second free magnetic layer is exchange coupled with the bias layer. ### Claim 15 (depends on 12) A sensor as in claim 12, wherein the bias layer has a thickness that is chosen to provide a desired amount of free layer biasing. ### Claim 16 (depends on 12) A sensor as in claim 12, wherein the bias layer has a thickness and a Cr content chosen to provide, in combination, a desired amount of free layer biasing. ### Claim 17 (depends on 12) A sensor as in claim 12 further comprising first and second electrically conductive magnetic shields in electrical communication with the free and pinned layers. ### Claim 18 (depends on 12) A sensor as in claim 12 wherein the free layer structure, pinned layer structure, and spacer layer are located between and electrically insulated from first and second magnetic shields. ### Claim 19 (depends on 12) A sensor as in claim 12 wherein the pinned layer structure is formed above the free layer structure. ### Claim 20 (depends on 12) A sensor as in claim 12 wherein the pinned layer structure is formed below the free layer structure. ### Claim 21 A magnetoresistive sensor, comprising: a free layer structure including a first free magnetic layer, a second free magnetic layer and a non-magnetic, electrically conducive spacer layer disposed between the first and second free magnetic layers the first free magnetic layer and the second free magnetic layer each having a magnetization that is free to move in response to a magnetic field; and a bias layer comprising an antiferromagnetic material, the antiferromagnetic material being exchange coupled with the second free magnetic layer. ### Claim 22 (depends on 21) A magnetoresistive sensor as in claim 21, wherein the second free magnetic layer comprises NiFe. ### Claim 23 (depends on 21) A magnetoresistive sensor as in claim 21, wherein the first free layer comprises Co and second free magnetic layers each comprises NiFe. ### Claim 24 (depends on 21) A magnetoresistive sensor as in claim 21, wherein the bias layer comprises IrMnCr. ### Claim 25 A magnetic data recording system, comprising: a magnetic medium; a slider; an actuator connected with the slider for moving the slider adjacent to a surface of the magnetic medium; and a magnetoresisitve sensor connected with the slider, the magnetoresistive sensor comprising: a free layer structure including a first free magnetic layer, a second free magnetic layer and a non-magnetic, electrically conducive spacer layer disposed between the first and second free magnetic layers the first free magnetic layer and second free magnetic layer each having a magnetization that is free to move in response to a magnetic field; and a bias layer comprising an antiferromagnetic material, the antiferromagnetic material being exchange coupled with the second free magnetic layer.