Magnetoresistive spin valve sensor with improved pinned ferromagnetic layer and magnetic recording system using the sensor

Claim 2

A magnetoresistive sensor comprising: a first layer and a second layer of ferromagnetic material separated by a spacer layer of nonmagnetic material, the magnetization direction of said first layer of ferromagnetic material being at an angle relative to the magnetization direction of said second layer of ferromagnetic material at zero applied magnetic field, the second layer of ferromagnetic material comprising first and second ferromagnetic films antiferromagnetically coupled to one another and an antiferromagnetically coupling film located between and in contact with the first and second ferromagnetic films for coupling the first and second ferromagnetic films together antiferromagnetically so that their magnetizations are aligned antiparallel with one another and remain antiparallel in the presence of an applied magnetic field; and means for maintaining the magnetization of one of the ferromagnetic films in the second ferromagnetic layer in a fixed direction in the presence of an applied magnetic field, whereby while the magnetization of the first layer is free to rotate in the presence of an applied magnetic field the magnetization directions of the first and second ferromagnetic films in the second layer remain fixed and antiparallel to one another.

Claim 3

A magnetoresistive sensor as in claim 1 wherein the antiferromagnetically coupling film in the second ferromagnetic layer consists essentially of Ru.

Claim 4

A magnetoresistive sensor as in claim 2 wherein the Ru film has a thickness in the range of approximately 3-6 Angstroms.

Claim 5

A magnetoresistive sensor as in claim 2 wherein the first and second ferromagnetic films in the second ferromagnetic layer consist essentially of Ni--Fe.

Claim 6

A magnetoresistive sensor as in claim 1 wherein the first and second ferromagnetic films in the second ferromagnetic layer consist essentially of Fe, and wherein the antiferromagnetically coupling film in the second ferromagnetic layer consists essentially of Cr.

Claim 7

A magnetoresistive sensor as in claim 1 wherein the first and second ferromagnetic films in the second ferromagnetic layer are made of a material selected from the group consisting of Co, Fe, Ni, and their alloys, and wherein the antiferromagnetically coupling film in the second ferromagnetic layer is made of a material selected from the group consisting of Ru, Cr, rhodium (Rh), iridium (Ir), and their alloys.

Claim 8

A magnetoresistive sensor as in claim 1 wherein the second ferromagnetic layer has essentially zero net magnetic moment.

Claim 9

A magnetoresistive sensor as in claim 1 wherein the first and second films in the second ferromagnetic layer have substantially the same thickness.

Claim 10

A magnetoresistive sensor as in claim 1 wherein the ferromagnetic film adjacent to the spacer layer is thinner than the other ferromagnetic film in the second ferromagnetic layer.

Claim 11

A magnetoresistive sensor as in claim 1 wherein the magnetization maintaining means comprises an exchange bias layer of antiferromagnetic material adjacent to and in contact with one of the ferromagnetic films in the second ferromagnetic layer.

Claim 12

A magnetoresistive sensor as in claim 10 wherein the antiferromagnetic layer comprises a material selected from the group consisting of iron-manganese and nickel-manganese.

Claim 13

A magnetoresistive sensor as in claim 1 wherein the nonmagnetic spacer layer comprises a material selected from the group consisting of silver, gold, copper, and alloys of silver, gold, and copper.

Claim 14

A spin valve magnetoresistive sensor comprising: a substrate; and a layered structure formed on the substrate, the layered structure comprising: a free ferromagnetic layer having a preferred axis of magnetization in the absence of an applied magnetic field; a nonmagnetic spacer layer adjacent to the free ferromagnetic layer; a first pinned ferromagnetic film adjacent to the spacer layer and having an axis of magnetization at an angle to the magnetization axis of the free ferromagnetic layer; a second pinned ferromagnetic film having a direction of magnetization generally antiparallel to the magnetization direction of the first pinned ferromagnetic film; an antiferromagnetically coupling film located between and in contact with the first and second pinned ferromagnetic films for coupling the first and second pinned ferromagnetic films together antiferromagnetically so that their magnetizations are aligned antiparallel with one another and remain antiparallel in the presence of an applied magnetic field; and an exchange bias layer of antiferromagnetic material adjacent to and in contact with the second pinned ferromagnetic film for pinning the magnetization of the second pinned ferromagnetic film in a fixed direction and thereby pinning the magnetization of the first pinned ferromagnetic film antiparallel to the magnetization of the second pinned ferromagnetic film to which it is antiferromagnetically coupled.

Claim 15

A spin valve magnetoresistive sensor comprising: a substrate; and a layered structure formed on the substrate, the layered structure comprising: a free ferromagnetic layer having a preferred axis of magnetization in the absence of an applied magnetic field; a nonmagnetic spacer layer adjacent to the free ferromagnetic layer; a first pinned ferromagnetic film adjacent to the spacer layer and having an axis of magnetization at an angle to the magnetization axis of the free ferromagnetic layer; a second pinned ferromagnetic film having a direction of magnetization generally antiparallel to the magnetization direction of the first pinned ferromagnetic film; an antiferromagnetically coupling film located between and in contact with the first and second pinned ferromagnetic films for coupling the first and second pinned ferromagnetic films together antiferromagnetically so that their magnetizations are aligned antiparallel with one another and remain antiparallel in the presence of an applied magnetic field; and an exchange bias layer of antiferromagnetic material adjacent to and in contact with the second pinned ferromagnetic film for pinning the magnetization of the second pinned ferromagnetic film in a fixed direction and thereby pinning the magnetization of the first pinned ferromagnetic film antiparallel to the magnetization of the second pinned ferromagnetic film to which it is antiferromagnetically coupled.

Claim 16

A spin valve magnetoresistive sensor as in claim 13 wherein the antiferromagnetically coupling film between the first and second pinned ferromagnetic films consists essentially of Ru.

Claim 17

A spin valve magnetoresistive sensor as in claim 14 wherein the Ru antiferromagnetically coupling film has a thickness in the range of approximately 3-6 Angstroms.

Claim 18

A spin valve magnetoresistive sensor as in claim 14 wherein the first and second pinned ferromagnetic films consist essentially of Ni--Fe.

Claim 19

A spin valve magnetoresistive sensor as in claim 13 wherein the first and second pinned ferromagnetic films consist essentially of Fe, and wherein the antiferromagnetically coupling film between the first and second pinned ferromagnetic films consists essentially of Cr.

Claim 20

A spin valve magnetoresistive sensor as in claim 13 wherein the first and second pinned ferromagnetic films are made of a material selected from the group consisting of Co, Fe, Ni, and their alloys, and wherein the antiferromagnetically coupling film is made of a material selected from the group consisting of Ru, Cr, rhodium (Rh), iridium (Ir), and their alloys.

Claim 21

A spin valve magnetoresistive sensor as in claim 13 wherein the first and second pinned ferromagnetic films have substantially the same thickness.

Claim 22

A spin valve magnetoresistive sensor as in claim 13 wherein the antiferromagnetically coupled first and second pinned ferromagnetic films have essentially zero net magnetic moment.

Claim 23

A spin valve magnetoresistive sensor as in claim 13 wherein the second pinned ferromagnetic film adjacent to the exchange bias layer is thicker than the first pinned ferromagnetic film.

Claim 24

A spin valve magnetoresistive sensor as in claim 13 wherein the exchange bias layer of antiferromagnetic material consists of a material selected from the group consisting of iron-manganese and nickel-manganese.

Claim 25

A spin valve magnetoresistive sensor as in claim 13 wherein the nonmagnetic spacer layer between the free ferromagnetic layer and the first pinned ferromagnetic film comprises a material selected from the group consisting of silver, gold, copper, and alloys of silver, gold, and copper.

Claim 26

A spin valve magnetoresistive sensor as in claim 13 wherein the first pinned ferromagnetic film includes a thin film of Co adjacent to the spacer layer.

Claim 27

A magnetic storage system comprising: a magnetic storage medium having a plurality of tracks for the recording of data; a magnetic transducer maintained close to the magnetic storage medium during relative motion between the magnetic transducer and the magnetic storage medium, the magnetic transducer including a magnetoresistive sensor comprising: a first layer and a second layer of ferromagnetic material separated by a spacer layer of nonmagnetic material, the magnetization direction of the first layer of ferromagnetic material being at an angle relative to the magnetization direction of the second layer of ferromagnetic material at zero applied magnetic field, the second layer of ferromagnetic material comprising first and second ferromagnetic films antiferromagnetically coupled to one another and an antiferromagnetically coupling film located between and in contact with the first and second ferromagnetic films for coupling the first and second ferromagnetic films together antiferromagnetically so that their magnetizations are aligned antiparallel with one another and remain antiparallel in the presence of an applied magnetic field; and means for maintaining the magnetization of one of the ferromagnetic films in the second ferromagnetic layer in a fixed direction in the presence of an applied magnetic field, whereby while the magnetization of the first layer is free to rotate in the presence of an applied magnetic field the magnetization directions of the first and second ferromagnetic films in the second layer remain fixed and antiparallel to one another; and means coupled to the magnetoresistive sensor for detecting resistance changes in the magnetoresistive sensor responsive to magnetic fields representative of data bits recorded in the magnetic storage medium intercepted by the magnetoresistive sensor.

Claim 28

A magnetic storage system comprising: a magnetic storage medium having a plurality of tracks for the recording of data; a magnetic transducer maintained close to the magnetic storage medium during relative motion between the magnetic transducer and the magnetic storage medium, the magnetic transducer including a magnetoresistive sensor comprising: a first layer and a second layer of ferromagnetic material separated by a spacer layer of nonmagnetic material, the magnetization direction of the first layer of ferromagnetic material being at an angle relative to the magnetization direction of the second layer of ferromagnetic material at zero applied magnetic field, the second layer of ferromagnetic material comprising first and second ferromagnetic films antiferromagnetically coupled to one another and an antiferromagnetically coupling film located between and in contact with the first and second ferromagnetic films for coupling the first and second ferromagnetic films together antiferromagnetically so that their magnetizations are aligned antiparallel with one another and remain antiparallel in the presence of an applied magnetic field; and means for maintaining the magnetization of one of the ferromagnetic films in the second ferromagnetic layer in a fixed direction in the presence of an applied magnetic field, whereby while the magnetization of the first layer is free to rotate in the presence of an applied magnetic field the magnetization directions of the first and second ferromagnetic films in the second layer remain fixed and antiparallel to one another; and means coupled to the magnetoresistive sensor for detecting resistance changes in the magnetoresistive sensor responsive to magnetic fields representative of data bits recorded in the magnetic storage medium intercepted by the magnetoresistive sensor.

Claim 29

A system as in claim 25 wherein the antiferromagnetically coupling film between the first and second ferromagnetic films in the second ferromagnetic layer consists essentially of Ru.

Claim 30

A system as in claim 26 wherein the Ru antiferromagnetically coupling film has a thickness in the range of approximately 3-6 Angstroms.

Claim 31

A system as in claim 25 wherein the first and second ferromagnetic films in the second ferromagnetic layer consist essentially of Ni--Fe.

Claim 32

A system as in claim 25 wherein the first and second ferromagnetic films in the second ferromagnetic layer consist essentially of Fe, and wherein the antiferromagnetically coupling film between the first and second ferromagnetic films consists essentially of Cr.

Claim 33

A system as in claim 25 wherein the first and second ferromagnetic films in the second ferromagnetic layer are made of a material selected from the group consisting of Co, Fe, Ni, and their alloys, and wherein the antiferromagnetically coupling film is made of a material selected from the group consisting of Ru, Cr, rhodium (Rh), iridium (Ir), and their alloys.

Claim 34

A system as in claim 25 wherein the first and second ferromagnetic films in the second ferromagnetic layer have substantially the same thickness.

Claim 35

A system as in claim 25 wherein the antiferromagnetically coupled first and second ferromagnetic films have essentially zero net magnetic moment.

Claim 36

A system as in claim 25 wherein the nonmagnetic spacer layer between the free ferromagnetic layer and the adjacent pinned ferromagnetic film comprises a material selected from the group consisting of silver, gold, copper, and alloys of silver, gold, and copper.

Claim 37

A system as in claim 25 wherein the means for maintaining the magnetization of one of the ferromagnetic films in the second ferromagnetic layer in a desired direction comprises an exchange bias layer of antiferromagnetic material adjacent to and in contact with the second ferromagnetic film, the antiferromagnetic layer providing a bias field in the second ferromagnetic film for maintaining the magnetization in the second ferromagnetic film and the antiferromagnetically coupled first ferromagnetic film in a desired direction.

Claim 38

A system as in claim 34 wherein the exchange bias layer of antiferromagnetic material consists of a material selected from the group consisting of iron-manganese and nickel-manganese.

Claim 39

A magnetic recording disk drive comprising: a magnetic recording disk; a motor connected to the disk for rotating the disk; a spin valve magnetoresistive sensor for sensing magnetically recorded data on the disk, the sensor comprising: a free ferromagnetic layer having a preferred axis of magnetization in the absence of an applied magnetic field; a nonmagnetic spacer layer adjacent to the free ferromagnetic layer; a first pinned ferromagnetic film adjacent to the spacer layer and having an axis of magnetization generally perpendicular to the magnetization axis of the free ferromagnetic layer; a second pinned ferromagnetic film having a direction of magnetization generally antiparallel to the magnetization direction of the first pinned ferromagnetic film; an antiferromagnetically coupling film located between and in contact with the first and second pinned ferromagnetic films for coupling the first and second pinned ferromagnetic films together antiferromagnetically so that their magnetizations are aligned antiparallel with one another and remain antiparallel in the presence of an applied magnetic field; and an exchange bias layer of antiferromagnetic material adjacent to and in contact with the second pinned ferromagnetic film for pinning the magnetization of the second pinned ferromagnetic film in a fixed direction and thereby pinning the magnetization of the first pinned ferromagnetic film antiparallel to the magnetization of the second pinned ferromagnetic film to which it is antiferromagnetically coupled; a carrier supporting the spin valve magnetoresistive sensor, the carrier having a substrate onto which the sensor is attached; an actuator for moving the carrier generally radially across the disk so the sensor may access different regions of magnetically recorded data on the disk; means connecting the carrier to the actuator for maintaining the carrier near the disk; means electrically coupled to the sensor for detecting changes in resistance of the sensor caused by rotation of the magnetization axis of the free ferromagnetic layer relative to the fixed, generally perpendicularly oriented magnetizations of the antiferromagnetically coupled first and second pinned ferromagnetic films in response to magnetic fields from the magnetically recorded disk; and means for supporting the motor and actuator.

Claim 40

A magnetic recording disk drive comprising: a magnetic recording disk; a motor connected to the disk for rotating the disk; a spin valve magnetoresistive sensor for sensing magnetically recorded data on the disk, the sensor comprising: a free ferromagnetic layer having a preferred axis of magnetization in the absence of an applied magnetic field; a nonmagnetic spacer layer adjacent to the free ferromagnetic layer; a first pinned ferromagnetic film adjacent to the spacer layer and having an axis of magnetization generally perpendicular to the magnetization axis of the free ferromagnetic layer; a second pinned ferromagnetic film having a direction of magnetization generally antiparallel to the magnetization direction of the first pinned ferromagnetic film; an antiferromagnetically coupling film located between and in contact with the first and second pinned ferromagnetic films for coupling the first and second pinned ferromagnetic films together antiferromagnetically so that their magnetizations are aligned antiparallel with one another and remain antiparallel in the presence of an applied magnetic field; and an exchange bias layer of antiferromagnetic material adjacent to and in contact with the second pinned ferromagnetic film for pinning the magnetization of the second pinned ferromagnetic film in a fixed direction and thereby pinning the magnetization of the first pinned ferromagnetic film antiparallel to the magnetization of the second pinned ferromagnetic film to which it is antiferromagnetically coupled; a carrier supporting the spin valve magnetoresistive sensor, the carrier having a substrate onto which the sensor is attached; an actuator for moving the carrier generally radially across the disk so the sensor may access different regions of magnetically recorded data on the disk; means connecting the carrier to the actuator for maintaining the carrier near the disk; means electrically coupled to the sensor for detecting changes in resistance of the sensor caused by rotation of the magnetization axis of the free ferromagnetic layer relative to the fixed, generally perpendicularly oriented magnetizations of the antiferromagnetically coupled first and second pinned ferromagnetic films in response to magnetic fields from the magnetically recorded disk; and means for supporting the motor and actuator.

Claim 41

A disk drive according to claim 36 wherein the antiferromagnetically coupling film between the first and second pinned ferromagnetic films in the spin valve magnetoresistive sensor consists essentially of Ru.

Claim 42

A disk drive according to claim 37 wherein the Ru antiferromagnetically coupling film has a thickness in the range of approximately 3-6 Angstroms.

Claim 43

A disk drive according to claim 36 wherein the first and second pinned ferromagnetic films in the spin valve magnetoresistive sensor consist essentially of Ni--Fe.

Claim 44

A disk drive as in claim 36 wherein the first and second pinned ferromagnetic films consist essentially of Fe, and wherein the antiferromagnetically coupling film between the first and second pinned ferromagnetic films consists essentially of Cr.

Claim 45

A disk drive as in claim 36 wherein the first and second pinned ferromagnetic films are made of a material selected from the group consisting of Co, Fe, Ni, and their alloys, and wherein the antiferromagnetically coupling film is made of a material selected from the group consisting of Ru, Cr, rhodium (Rh), iridium (Ir), and their alloys.

Claim 46

A disk drive as in claim 36 wherein the first and second pinned ferromagnetic films have substantially the same thickness.

Claim 47

A disk drive as in claim 36 wherein the antiferromagnetically coupled first and second ferromagnetic films have essentially zero net magnetic moment.

Claim 48

A disk drive as in claim 36 wherein the nonmagnetic spacer layer comprises a material selected from the group consisting of silver, gold, copper, and alloys of silver, gold, and copper.

Claim 49

A disk drive sensor as in claim 36 wherein the first pinned ferromagnetic film includes a thin film of Co adjacent to the spacer layer.

Claim 50

A disk drive as in claim 36 wherein the exchange bias layer of antiferromagnetic material consists of a material selected from the group consisting of iron-manganese and nickel-manganese.