Dual spin valve magnetoresistive sensor

Claim 2

A magnetoresistive sensor comprising: a substrate; and a layered structure formed on said substrate comprising, a first, a second and a third layer of ferromagnetic material, each of said layers of ferromagnetic material separated from the adjacent layer of ferromagnetic material by a layer of non-magnetic metallic material, said second layer of ferromagnetic material disposed between said first and third layers of ferromagnetic material, the direction of magnetization being fixed in said first and third layers of ferromagnetic material, the direction of magnetization in said second layer of ferromagnetic material being substantially perpendicular to said fixed directions of magnetization in said first and third layers of ferromagnetic material at zero applied magnetic field.

Claim 3

A magnetoresistive sensor as in claim 1 wherein each of said layers of ferromagnetic material further comprise at least one additional layer of material.

Claim 4

A magnetoresistive sensor as in claim 2 wherein said additional layer of material comprises at least one nanolayer of ferromagnetic material.

Claim 5

A magnetoresistive sensor as in claim 3 wherein each said layer of ferromagnetic material further comprises a nanolayer of a different ferromagnetic material disposed at the interface between said layer of ferromagnetic material and said layer of non-magnetic metallic material.

Claim 6

A magnetoresistive sensor as in claim 4 wherein each of said first and third layers of ferromagnetic material form a bilayer comprising a layer of a first ferromagnetic material and a nanolayer of a second ferromagnetic material, said nanolayer disposed at the interface between said first and third layers of ferromagnetic material and said layer of non-magnetic metallic material separating said first and third layers of ferromagnetic material, respectively, from said second layer of ferromagnetic material, and said second layer of ferromagnetic material forming a trilayer comprising a layer of a first ferromagnetic material and two nanolayers of a second ferromagnetic material, said nanolayers disposed at the interfaces between said second layer of ferromagnetic material and said layers of non-magnetic metallic material separating said second layer of ferromagnetic material from said first and third layers of ferromagnetic material, respectively.

Claim 7

A magnetoresistive sensor as in claim 3 wherein said nanolayer has a thickness in the range of about 0.5 Angstroms to about 20.0 Angstroms.

Claim 8

A magnetoresistive sensor as in claim 1 further comprising means for fixing the direction of magnetization in said first and third layers of ferromagnetic material.

Claim 9

A magnetoresistive sensor as in claim 1 further comprising a first layer of magnetically hard material adjacent to said first layer of ferromagnetic material, and a second layer of magnetically hard material adjacent to said third layer of ferromagnetic material, said first and second layers of magnetically hard material for providing a magnetic bias field in said first and third layers of ferromagnetic material, respectively, thereby fixing the direction of magnetization in said layers.

Claim 10

A magnetoresistive sensor as in claim 1 further comprising a first layer of antiferromagnetic material adjacent to and in contact with said first layer of ferromagnetic material, and a second layer of antiferromagnetic material adjacent to and in contact with said third layer of ferromagnetic material, said first and second layers of antiferromagnetic material for providing a magnetic bias field in said first and third layers of ferromagnetic material, respectively, thereby fixing the direction of magnetization in said layers.

Claim 11

A magnetoresistive sensor as in claim 9 wherein said first and second layers of antiferromagnetic material are comprised of a material selected from the group comprised of iron-manganese, nickel-manganese and iron-nickel-manganese.

Claim 12

A magnetoresistive sensor as in claim 10 wherein said first and second layers of antiferromagnetic material comprise iron-manganese.

Claim 13

A magnetoresistive sensor as in claim 9 wherein said first and second layers of antiferromagnetic material have a thickness within the range of about 50 Angstroms to about 200 Angstroms.

Claim 14

A magnetoresistive sensor as in claim 1 wherein said first, second and third layers of ferromagnetic material are comprised of a material selected from the group consisting of iron, cobalt and nickel and alloys of iron, cobalt or nickel.

Claim 15

A magnetoresistive sensor as in claim 13 wherein said first, second and third layers of ferromagnetic material are comprised of an alloy of nickel-iron.

Claim 16

A magnetoresistive sensor as in claim 1 wherein said first, second and third layers of ferromagnetic material have a thickness within the range of about 5 Angstroms to about 150 Angstroms.

Claim 17

A magnetoresistive sensor as in claim 1 wherein said non-magnetic metallic spacer layer has a thickness less than the mean free path length of conduction electrons in said non-magnetic metallic spacer layer.

Claim 18

A magnetoresistive sensor as in claim 16 wherein said non-magnetic metallic spacer layer has a thickness within the range of about 10 Angstroms to about 40 Angstroms.

Claim 19

A magnetoresistive sensor as in claim 1 where in said first and second non-magnetic metallic spacer layers are comprised of a material selected from the group consisting of silver, gold, copper and alloys of silver, copper and gold.

Claim 20

A magnetoresistive sensor as in claim 18 wherein each said first and second non-magnetic metallic spacer layer comprises a thin film layer of copper.

Claim 21

A magnetoresistive sensor as in claim 1 wherein said directions of magnetization in said first and third layers of ferromagnetic material are aligned in a parallel orientation.

Claim 22

A magnetoresistive sensor as in claim 1 wherein each said first and third layers of ferromagnetic material comprises a ferromagnetic material having a different coercivity than the coercivity of the ferromagnetic material of the other layer.

Claim 23

A magnetic storage system comprising: a magnetic storage medium having a plurality of tracks for recording of data; a magnetic transducer maintained in a closely spaced position relative to said magnetic storage medium during relative motion between said magnetic transducer and said magnetic storage medium, said magnetic transducer including a magnetoresistive read sensor comprising: a layered structure formed on a substrate comprising, a first, a second and a third layer of ferromagnetic material, each of said layers of ferromagnetic material separated from the adjacent layer of ferromagnetic material by a layer of non-magnetic metallic material, said second layer of ferromagnetic material disposed between said first and third layers of ferromagnetic material, the direction of magnetization being fixed in said first and third layers of ferromagnetic material, the direction of magnetization in said second layer of ferromagnetic material being substantially perpendicular to said fixed directions of magnetization in said first and third layers of ferromagnetic material at zero applied magnetic field; and a first layer of antiferromagnetic material adjacent to and in contact with said first layer of ferromagnetic material, and a second layer of antiferromagnetic material adjacent to and in contact with said third layer of ferromagnetic material, said first and second layers of antiferromagnetic material for providing a magnetic bias field in said first and third layers of ferromagnetic material, respectively, thereby fixing the direction of magnetization in said layers; actuator means coupled to said magnetic transducer for moving said magnetic transducer to selected tracks on said magnetic storage medium; and detection means coupled to said magnetoresistive read sensor for detecting resistance changes in said magnetoresistive material responsive to magnetic fields representative of data bits recorded in said magnetic storage medium intercepted by said magnetoresistive sensor.

Claim 24

A magnetic storage system comprising: a magnetic storage medium having a plurality of tracks for recording of data; a magnetic transducer maintained in a closely spaced position relative to said magnetic storage medium during relative motion between said magnetic transducer and said magnetic storage medium, said magnetic transducer including a magnetoresistive read sensor comprising: a layered structure formed on a substrate comprising, a first, a second and a third layer of ferromagnetic material, each of said layers of ferromagnetic material separated from the adjacent layer of ferromagnetic material by a layer of non-magnetic metallic material, said second layer of ferromagnetic material disposed between said first and third layers of ferromagnetic material, the direction of magnetization being fixed in said first and third layers of ferromagnetic material, the direction of magnetization in said second layer of ferromagnetic material being substantially perpendicular to said fixed directions of magnetization in said first and third layers of ferromagnetic material at zero applied magnetic field; and a first layer of antiferromagnetic material adjacent to and in contact with said first layer of ferromagnetic material, and a second layer of antiferromagnetic material adjacent to and in contact with said third layer of ferromagnetic material, said first and second layers of antiferromagnetic material for providing a magnetic bias field in said first and third layers of ferromagnetic material, respectively, thereby fixing the direction of magnetization in said layers; actuator means coupled to said magnetic transducer for moving said magnetic transducer to selected tracks on said magnetic storage medium; and detection means coupled to said magnetoresistive read sensor for detecting resistance changes in said magnetoresistive material responsive to magnetic fields representative of data bits recorded in said magnetic storage medium intercepted by said magnetoresistive sensor.

Claim 25

A magnetic storage system as in claim 22 wherein said first and second layers of antiferromagnetic material are comprised of a material selected from the group consisting of iron-manganese and nickel-manganese.

Claim 26

A magnetic storage system as in claim 22 wherein said magnetoresistive sensor further comprises: a capping layer deposited over said second antiferromagnetic layer; and electrical lead means deposited over said capping layer for coupling said magnetoresistive sensor to said detection means.

Claim 27

A magnetic storage system as in claim 24 wherein said capping layer comprises a material selected from the group consisting of tantalum and zirconium.

Claim 28

A magnetic storage system as in claim 24 further comprising means for providing a longitudinal bias field in an active portion of said magnetoresistive sensor.

Claim 29

A magnetic storage system as in claim 22 wherein said directions of magnetization in said first and third layers of ferromagnetic material are aligned in a parallel orientation.

Claim 30

A magnetoresistive sensor comprising a layered structure formed in a substrate including a first, a second and a third layer of ferromagnetic material, each of said layers of ferromagnetic material separated from the adjacent layer of ferromagnetic material by a layer of non-magnetic metallic material, said second layer of ferromagnetic material disposed between said first and third layers of ferromagnetic material, the direction of magnetization being fixed in said first and third layers of ferromagnetic material, the direction of magnetization in said second layer of ferromagnetic material being substantially perpendicular to said fixed directions of magnetization in said first and third layers of ferromagnetic material at zero applied magnetic field, said first and second layers of ferromagnetic material forming a first pair of ferromagnetic layers separated by a non-magnetic layer having a positive giant magnetoresistance therebetween and said second and third layers of ferromagnetic material forming a second pair of ferromagnetic layers separated by a non-magnetic layer having a negative giant magnetoresistance therebetween.

Claim 31

A magnetoresistive sensor comprising a layered structure formed in a substrate including a first, a second and a third layer of ferromagnetic material, each of said layers of ferromagnetic material separated from the adjacent layer of ferromagnetic material by a layer of non-magnetic metallic material, said second layer of ferromagnetic material disposed between said first and third layers of ferromagnetic material, the direction of magnetization being fixed in said first and third layers of ferromagnetic material, the direction of magnetization in said second layer of ferromagnetic material being substantially perpendicular to said fixed directions of magnetization in said first and third layers of ferromagnetic material at zero applied magnetic field, said first and second layers of ferromagnetic material forming a first pair of ferromagnetic layers separated by a non-magnetic layer having a positive giant magnetoresistance therebetween and said second and third layers of ferromagnetic material forming a second pair of ferromagnetic layers separated by a non-magnetic layer having a negative giant magnetoresistance therebetween.

Claim 32

A magnetoresistive sensor as in claim 28 wherein said directions of magnetization in said first and third layers of ferromagnetic material are aligned in an antiparallel orientation.

Claim 33

A magnetoresistive sensor as in claim 28 further comprising a layer of a first antiferromagnetic material adjacent to and in contact with said first layer of ferromagnetic material, and a layer of a second antiferromagnetic material adjacent to and in contact with said third layer of ferromagnetic material, said first and second layers of antiferromagnetic material for providing a magnetic bias field in said first and third layers of ferromagnetic material, respectively, thereby fixing the direction of magnetization in said layers.

Claim 34

A magnetoresistive sensor as in claim 30 were in said first and second antiferromagnetic materials have different blocking temperatures.

Claim 35

A magnetoresistive sensor as in claim 28 further comprising means for fixing the direction of magnetization in said first and third layers of ferromagnetic material.

Claim 36

A magnetoresistive sensor as in claim 32 wherein said means comprise a first layer of magnetically hard material adjacent to said first layer of ferromagnetic material, and a second layer of magnetically hard material adjacent to said third layer of ferromagnetic material, said first and second layers of magnetically hard material for providing a magnetic bias field in said first and third layers of ferromagnetic material, respectively, thereby fixing the direction of magnetization in said layers.

Claim 37

A magnetoresistive sensor as in claim 28 further comprising a first layer of antiferromagnetic material adjacent to and in contact with said first layer of ferromagnetic material, and a second layer of antiferromagnetic material adjacent to and in contact with said third layer of ferromagnetic material, said first and second layers of antiferromagnetic material for providing a magnetic bias field in said first and third layers of ferromagnetic material, respectively, thereby fixing the direction of magnetization in said layers.

Claim 38

A magnetoresistive sensor as in claim 28 wherein said first and third layers of ferromagnetic material comprise a ferromagnetic material having a high coercivity.

Claim 39

A magnetoresistive sensor as in claim 35 wherein each said first and third layers of ferromagnetic material comprises a ferromagnetic material having a different coercivity than the coercivity of the ferromagnetic material of the other layer.