Stock material or miscellaneous articles – Composite – Of inorganic material
Reexamination Certificate
1999-06-21
2001-09-18
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Composite
Of inorganic material
C428S690000, C428S690000, C428S690000, C428S900000, C438S003000, C438S048000, C438S104000, C438S381000, C360S112000, C148S108000, C029S603080, C029S603140, C029S603150
Reexamination Certificate
active
06291087
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to magnetoresistive (MR) sensor elements employed within magnetic data storage and retrieval. More particularly, the present invention relates to simultaneously providing: (1) enhanced magnetoresistive (MR) resistivity sensitivity; and (2) enhanced magnetic exchange bias, within magnetoresistive (MR) sensor elements employed within magnetic data storage and retrieval.
2. Description of the Related Art
The recent and continuing advances in computer and information technology have been made possible not only by the correlating advances in the functionality, reliability and speed of semiconductor integrated circuits, but also by the correlating advances in the storage density and reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval.
Storage density of direct access storage devices (DASDs) is typically determined as areal storage density of a magnetic data storage medium formed upon a rotating magnetic data storage disk within a direct access storage device (DASD) magnetic data storage enclosure. The areal storage density of the magnetic data storage medium is defined largely by the track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium. The track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium are in turn determined by several principal factors, including but not limited to: (1) the magnetic read-write characteristics of a magnetic read-write head employed in reading and writing digitally encoded magnetic data from and into the magnetic data storage medium; (2) the magnetic domain characteristics of the magnetic data storage medium; and (3) the separation distance of the magnetic read-write head from the magnetic data storage medium.
With regard to the magnetic read-write characteristics of magnetic read-write heads employed in reading and writing digitally encoded magnetic data from and into a magnetic data storage medium, it is known in the art of magnetic read-write head fabrication that magnetoresistive (MR) sensor elements employed within magnetoresistive (MR) read-write heads are generally superior to other types of magnetic sensor elements when employed in retrieving digitally encoded magnetic data from a magnetic data storage medium. In that regard, magnetoresistive (MR) sensor elements are generally regarded as superior since magnetoresistive (MR) sensor elements are known in the art to provide high output digital read signal amplitudes, with good linear resolution, independent of the relative velocity of a magnetic data storage medium with respect to a magnetoresistive (MR) read-write head having the magnetoresistive (MR) sensor element incorporated therein.
Within the general category of magnetoresistive (MR) sensor elements, magnetically biased magnetoresistive (MR) sensor elements, such as longitudinal magnetic exchange biased magnetoresistive (MR) sensor elements, are even more desirable within the art of magnetoresistive (MR) sensor element fabrication insofar as magnetic biasing of a magnetoresistive (MR) layer within a magnetoresistive (MR) sensor element typically provides at least one of noise reduction and linear response enhancement within the magnetically biased magnetoresistive (MR) sensor element.
Similarly, as is also understood by a person skilled in the art, it is also desirable in the art of magnetoresistive (MR) sensor element fabrication to fabricate magnetoresistive (MR) sensor elements with enhanced magnetoresistive (MR) resistivity sensitivity. Within the context of the present invention, magnetoresistive (MR) resistivity sensitivity is intended as a measure of proportion of resistance change normalized to an absolute resistance of a magnetoresistive (MR) sensor element (i.e. dR/R) when measuring a magnetic signal within a magnetic data storage medium while employing the magnetoresistive (MR) sensor element. The magnetoresistive (MR) resistivity sensitivity of a magnetoresistive (MR) sensor element is alternatively known as the magnetoresistive (MR) coefficient of the magnetoresistive (MR) sensor element. Magnetoresistive (MR) sensor elements exhibiting enhanced magnetoresistive (MR) resistivity sensitivity are desirable within the art of magnetoresistive (MR) sensor element fabrication since such enhanced magnetoresistive (MR) resistivity sensitivity clearly inherently allows for detection within a magnetic data storage media of weaker magnetic signals with increased linear density and thus also inherently allows for an increased areal density of the magnetic data storage medium within a magnetic data storage enclosure which employs the magnetoresistive (MR) sensor element which exhibits the enhanced magnetoresistive (MR) resistivity sensitivity.
It is thus towards the goal of forming for use within magnetic data storage and retrieval magnetoresistive (MR) sensor elements simultaneously with enhanced magnetoresistive (MR) resistivity sensitivity and enhanced magnetic exchange bias that the present invention is directed.
Various magnetoresistive (MR) sensor elements which possess desirable properties, and/or methods for fabrication thereof, have been disclosed within the art of magnetoresistive (MR) sensor element fabrication.
For example, Nepela et al., in U.S. Pat. No. 5,309,305, discloses a dual stripe magnetoresistive (DSMR) sensor element with enhanced readout signal amplitude from the dual stripe magnetoresistive (DSMR) sensor element. The dual stipe magnetoresistive (DSMR) sensor element realizes the foregoing object by employing when forming the dual stripe magnetoresistive (MR) sensor element an antiferromagnetic magnetic exchange biasing of each patterned magnetoresistive (MR) layer within a pair of patterned magnetoresistive (MR) layers within the dual stripe magnetoresistive (MR) sensor element, and where the antiferromagnetic magnetic exchange biasing of each patterned magnetoresistive (MR) layer within the pair of patterned magnetoresistive (MR) layers is: (1) anti-parallel with respect to the other patterned magnetoresistive (MR) layer; and (2) perpendicular to the plane of a magnetic media layer from which magnetic data is read while employing the dual stripe magnetoresistive (DSMR) sensor element.
In addition, Shi et al., in U.S. Pat. No. 5,684,658, discloses a dual stripe magnetoresistive (DSMR) sensor element having a narrow read back width of the dual stripe magnetoresistive (DSMR) sensor element which in turn provides that the narrow read back width dual stripe magnetoresistive (DSMR) sensor element may be employed for reading digitally encoded magnetic data within narrowly spaced tracks within a magnetic data storage medium. The dual stripe magnetoresistive (DSMR) sensor element realizes the foregoing object by employing when forming the dual stripe magnetoresistive (DSMR) sensor element: (1) an offset of a first magnetoresistive (MR) layer with respect to a second magnetoresistive (MR) layer within the dual stripe magnetoresistive (DSMR) sensor element; (2) a parallel longitudinal magnetic biasing of the first magnetoresistive OR) layer and the second magnetoresistive (MR) layer within the dual stripe magnetoresistive (DSMR) sensor element; and (3) an anti-parallel electromagnetic biasing of the first magnetoresistive (MR) layer and the second magnetoresistive (MR) layer within the dual stripe magnetoresistive (DSMR) sensor element.
Further, Han et al., in U.S. Pat. No. 5,783,460, discloses a method for fabricating a dual stripe magnetoresistive (DSMR) sensor element, where there is minimized tolerance variations with respect to the width and/or alignment between a pair of magnetoresistive (MR) layers within the dual stripe magnetoresistive (DSMR) sensor element. To realize the foregoing object, the method employs a lift off stencil as an etch mask for forming from a trilayer stack layer comprising: (1) a blanket first magnetoresistive (MR) layer having form
Chang Jei-Wei
Horng Cheng
Ju Kochan
Torng Chyu-Jiuh
Xiao Rongfu
Ackerman Stephen B.
Headway Technologies Inc.
Kiliman Leszek
Saile George O.
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