Shield design for magnetoresistive sensor

Details Shield design for magnetoresistive sensor Shield design for magnetoresistive sensor

2001-05-24

2003-07-22

Klimowicz, William (Department: 2652)

Dynamic magnetic information storage or retrieval

Head

Magnetoresistive reproducing head

Reexamination Certificate

active

06597545

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to magnetoresistive sensors. More specifically, the present invention relates to magnetic shields used in magnetoresistive sensors.
BACKGROUND OF THE INVENTION
The present invention relates to magnetoresistive (MR) sensors. More specifically, the present invention relates to a magnetoresistive sensor having improved stability during operation.
Magnetic storage systems are used to store information in a magnetic format for subsequent retrieval. Various technologies are available for reading back the stored information. One newer technology is the use of a magnetoresistive sensor for such read back.
Magnetoresistive sensors are responsive to a change in resistivity caused by the presence of magnetic fields and are increasingly being employed as read back elements in the heads of magnetic disc drives. They are particularly advantageous because the change in resistivity is independent of disc speed and depends only on the magnetic flux. Further, the sensor output is easily scaled by adjusting the sense current. Various types of magnetoresistive sensors include AMR, GMR and tunnel junction sensors. The sensor is mounted in the head parallel to the plane of the disc and to the direction of disc rotation. Magnetic flux from the disc surface causes a change in electrical resistivity. A sense current is passed through the sensor active layer and the magnetic flux can be detected by measuring the change in voltage across the element as a result of the changing resistivity.
One problem encountered with magnetoresistive sensors is Barkhausen noise which is caused by an irreversible motion of magnetic domains in the presence of an applied field, i.e., coherent rotation of the magnetization vector is non uniform and suppressed, and depends upon domain wall behavior. Barkhausen noise generated in the magnetoresistive element may be eliminated by creating a single magnetic domain in the active region of the magnetoresistive sensor. Reduction of such Barkhausen noise generated in the magnetoresistive element is described in U.S. Pat. No. 4,803,480 entitled DOUBLE-GAP MAGNETORESISTIVE HEAD HAVING AN ELONGATED CENTRAL WRITE/SHIELD POLE COMPLETELY SHIELDING THE MAGNETORESISTIVE SENSOR STRIP IN THE READ GAP which was issued Feb. 7, 1989 to Mowry.
The present invention provides a solution to these and other problems and offers other advantages over the prior art.
SUMMARY OF THE INVENTION
The present invention relates to magnetoresistive sensors that have a magnetic shield which addresses the above mentioned problems.
In accordance with one embodiment of the invention, a magnetoresistive sensor includes a magnetic shield and a shield “flux thief.” The sensor can be used in a magnetic storage device and includes a magnetoresistive sensor element, electrical contacts coupled to the magnetoresistive element and a transducer in a magnetic storage device, comprising a magnetoresistive sensor element and electrical contacts coupled to the magnetoresistive element configured to sense a response of the magnetoresistive element to a magnetic field. A magnetic shield adjacent the magnetoresistive element is configured to shield the magnetoresistive element from stray magnetic fields. The shield has a substantially stable magnetic domain pattern. A shield flux thief is spaced apart from the shield and reduces a demagnetization field in the shield during fabrication of the magnetoresistive sensor element.


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