Dynamic magnetic information storage or retrieval – Head – Magnetoresistive reproducing head
Reexamination Certificate
1995-10-10
2001-04-17
Korzuch, William R. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Magnetoresistive reproducing head
Reexamination Certificate
active
06219205
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to magnetic transducers employing giant magnetoresistance (GMR) and in particular to a shielded GMR transducer.
DESCRIPTION OF THE PRIOR ART
As magnetic recording devices such as disk drives evolve towards ultra-high areal recording densities of 1 GB/in
2
(gigabytes per square inch) and beyond, the requirements for the linear bit density and track density capabilities of the recording head becomes increasingly more stringent. Narrow read gap length and track width are necessary to satisfy these requirements.
Because MR sensors are somewhat fragile and hence susceptible to mechanical, chemical and electrical damage during fabrication and assembly, there have been efforts to dispose such sensors in a recessed location in a transducer so as to be physically separated from the extension of the transducer. Since such a recessed location was believed to result in a reduction in the magnetic flux reaching the sensor, flux guides have been suggested to increase the amount of flux available at the sensing surface of the sensor. Such flux guide structures are described in the publication entitled
The Study Of Recessed MR Sensors With Un
-
Laminated and Multi
-
Laminated Flux
-
Guides,
C. Tsang et al, presented at the 1992 Intermag Conference, New Orleans, April 1992, and also described in the references identified in that publication. In that publication, a single-layer flux guide used therein has significant domain activity, leading to undesirable Barkhausen head noise. A more complicated multi-layer lamination flux guide is required to solve this problem, but even with this measure, an additional 40% signal loss is introduced by the fluxguide.
In another prior art approach a hard carbon overcoat is applied to the air bearing surface of the transducer to protect the sensor material and improve the head/disk wear and head flying properties. However, such an overcoat increases the head/disk spacing and can lead to signal amplitude loss and pulse widening, thereby reducing the signal-to-noise ratio, the detectable flux changes per inch and the tracks per inch.
SUMMARY OF THE INVENTION
The present invention utilizes a shielded read transducer with a GMR sensor, either a spin-valve device or a multi-layer device, recessed from the air bearing surface of the transducer. The recessed gap area is filled with a dielectric material which can be identical to the dielectric material in the gaps of the sensor itself. The present invention eliminates the problems described above with prior art transducers and compensates for any signal loss resulting from the space between the sensor and the ABS when using GMR sensors. Current GMR development provides sensors with very large sensitivity, and the present invention takes advantage of this feature to achieve a high data recording density. GMR materials can be vulnerable to corrosion damage, but the dielectric layer used herein effectively protects the sensor.
The structure of this invention has the following advantages:
(1) The presence of the recess reduces or prevents electrostatic discharge (ESD) between the active portion of the sensor and the disk. The structure also reduces contact with thermal asperities on the disk, especially during low-flying of the air bearing slider and transducer or contact of the transducer relative to the rotating disk or medium. Additionally, the structure protects the sensor materials, such as FeMn or TbCo, from corrosion, and protects the sensor materials from lapping exposure and contact with air.
(2) Read head saturation is reduced and the sensor is maintained in a linear dynamic range resulting from a reduction of flux in the transducer.
(3) The PW
50
, which is a measure of the readback pulse width at 50% amplitude, is reduced from that produced in a non-recessed head, thereby achieving a higher linear readback density.
(4) The structure also results in improved off-track symmetry, thereby reducing cross-talk and improving servo linearity by reducing incoming longitudinal flux.
REFERENCES:
patent: 4639806 (1987-01-01), Kira et al.
patent: 4807073 (1989-02-01), Takeura et al.
patent: 5168408 (1992-12-01), Lazzari
patent: 5446613 (1995-08-01), Rottmayer
Rottmayer Robert Earl
Yuan Samuel W.
Kallman Nathan N.
Korzuch William R.
Read-Rite Corporation
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