Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1998-09-28
2001-02-20
Korzuch, William R. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06191926
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to data storage systems. More specifically, the present invention relates to data storage systems using read heads which utilize the giant magnetoresistive (GMR) effect.
Magnetic sensors utilizing the GMR effect, frequently referred to as “spin valve” sensors, are known in the art. A spin valve sensor is typically a sandwiched structure consisting of two ferromagnetic layers separated by a thin non-ferromagnetic layer. One of the ferromagnetic layers is called the “pinned layer” because it is magnetically pinned or oriented in a fixed and unchanging direction by an adjacent antiferromagnet layer, commonly referred to as the “pinning layer,” through exchange coupling. The other ferromagnetic layer is called the “free” or “unpinned” layer because the magnetization is allowed to rotate in response to the presence of external magnetic fields.
One type of self pinned layer is known in the art as an artificial antiferromagnet layer (AAF). Such a layer is formed by three layers, a first ferromagnetic layer, a second ferromagnetic layer and a non-magnetic spacer layer separating the two ferromagnetic layers. The two ferromagnetic layers have magnetic vectors which are biased in antiparallel directions and in the plane of the sensor. This is described in, for example, U.S. Pat. No. 5,583,725, issued Dec. 10, 1996 to Coffey et al., entitled “SPIN VALVE MAGNETORESISTIVE SENSOR WITH SELF-PINNED LAMINATED LAYER AND MAGNETIC RECORDING SYSTEM USING THE SENSOR which is incorporated herein by reference.
SUMMARY OF THE INVENTION
A spin valve magnetoresistive sensor of the type used in a data storage system includes a free layer extending in a sensor plane. The free layer has a magnetization which changes in the presence of a magnetic field. An artificial antiferromagnet layer includes a first ferromagnetic layer extending in the sensor plane which has a first ferromagnetic layer vector. A second ferromagnetic layer extends in the sensor plane and includes a second ferromagnetic layer vector. A spacer layer of non-magnetic material extends in the sensor plane and is positioned between the first and second ferromagnetic layers. At least two permanent magnet poles are provided whereby the first and second magnetization vectors in the first and second ferromagnetic layers include vector components which are directed perpendicular to the sensor plane, i.e., in a “cross track” direction.
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“Linearity of Unshielded Spin-Valve Sensors”, by N. Sugaware et al.,American Institute of Physics, 1997, 3 pages, pp. 523-525.
“AMR Effect in Spin-Valve Structure”, by Y. Uehara et al.,IEEE Transactions on Magnetics, vol. 32, No. 5, Sep. 1996, pp. 3432-3433.
Everitt Brenda A.
van Ek Johannes
Korzuch William R.
Seagate Technology LLC
Westman, Champlin & Kelly, P.A
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