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

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.

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.

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.