Dynamic magnetic information storage or retrieval – Head – Head accessory
Reexamination Certificate
1999-01-06
2001-02-20
Heinz, A. J. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head
Head accessory
C360S122000, C360S221000
Reexamination Certificate
active
06191919
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the field of magnetic heads having longitudinal channels in the tape bearing surface.
BACKGROUND ART
The storage capacity of magnetic media can be increased by reducing the width and center-to-center spacing of the data tracks. As track densities increase beyond 1000 tracks per inch, the center-to-center spacing between tracks falls below 25.4 micrometers. Track width is determined by the shape and width of the poles of the writing transducer. The dominating factor is usually the width of the trailing pole as seen by the magnetic medium. Using current fabrication techniques, the bottom poles of write transducers are wider than the top poles. This asymmetry between the top and bottom poles cause the track widths to differ depending on the direction that the magnetic medium moves across the poles. Fabricating the top poles and bottom poles with the same width to eliminate directional track width dependencies is desirable. However, the photolithographic masks, wet etching, and/or de-plating techniques that are currently used to define the poles make this goal difficult to achieve.
“Tenting” also becomes more important as the width of the tracks decrease. Tenting occurs when debris lifts a flexible magnetic medium, such as magnetic tape, away from the tape bearing surface and the transducers. For example, a 1 micrometer debris particle 20 to 30 micrometers away from a write transducer may produce sufficient head/tape separation to cause a signal dropout during recording. Similar dropouts may occur while attempting to read in the presence of debris. Transverse slots are incorporated in some magnetic heads to remove air trapped between the media and the head, thereby keeping the head in close contact with the media. The transverse slots are found both upstream and downstream of the transducers to account for magnetic medium motion in either direction. Loose debris from the media tends to accumulate in these slots. Changes in the magnetic medium direction, excessive debris accumulated in the slots, the stop/start motion of the magnetic medium, or any other disturbance can cause debris to break loose from the slots. Debris ejected from an upstream slot may be swept across, or near the transducers potentially causing a momentary dropout.
Several groups are working to reduce the asymmetrical fringe fields caused by the asymmetrical top and bottom poles used in disk drive applications. In the articles “Recording Studies on Sub-Micron Write Heads by Focused Ion Beam Trimming”, IEEE Transactions on Magnetics, Volume 33, No. 5, September 1997 by Gorman et al., and “Low Fringe-Field and Narrow-Track MR Heads”, IEEE Transactions on Magnetics, Volume 33, No. 5, September 1997 by Guo et al., a focused ion beam is used to mill two channels that remove the sides of the top pole and form notches in the bottom pole. The effect of trimming the poles minimizes the side-fringing effects to minimize the erase width of the write transducers. These magnetic heads are intended for use in disk dive applications where the magnetic head sits inside a clean sealed environment and do not make contact with the magnetic disk. As a result, the channels disclosed in these articles do not address the need to minimize tenting induced by debris.
DISCLOSURE OF INVENTION
The present invention provides a magnetic head having a pair of longitudinal channels that flank each transducer in a tape bearing surface. The channels reduce the effective height of debris in the channels near the transducers. The channel floors may have a transverse slope to direct debris away from the transducers. To account for debris that appears between channels, the tape bearing surface immediately upstream and downstream of the transducers is tapered to urge the debris into a channel. Transverse slots upstream and downstream of the transducers help with debris removal. The channels extend between the two transverse slots. The channels also overlap the end sections of the transducers to help define the shape and position of the transducers' active section. When applied to a two pole write transducer, the channels narrow and equalize the effective width of the top and bottom poles. Narrow equal-sized poles can write narrow data tracks with a track width that is independent of the direction of the magnetic medium.
Accordingly, it is an object of the present invention to provide a magnetic head assembly with channels in the tape bearing surface to account for debris trapped between the magnetic head and a magnetic medium. A pair of channels in a tape bearing surface flank each transducer. Each channel is oriented parallel to the axis of motion of the magnetic medium so that debris is directed in the channels from upstream to downstream of the transducers. The depth of the channel is selected to eliminate or at least reduce the effective height of the debris that passes near the transducers.
Another object of the present invention is to provide a magnetic head assembly that can read and write narrow data tracks from a magnetic medium, and write a track width that is independent of the magnetic medium's direction of motion. The magnetic head assembly has a pair of channels flanking and partially overlapping each transducer in the tape bearing surface. Formation of the channels allows the shape and position of the active section of the transducers to be established accurately.
These and other objects, features and advantages will be readily apparent upon consideration of the following detailed description in conjunction with the accompanying drawings.
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IEEE Transactions On Magnetics, vol. 33, No. 5, Sep. 1997 “Recording Studies of Sub-Micron Write Heads by Focused Ion Beam Trimming” by Gorman et al.
IEEE Transactions On Magnetics, vol. 33, No. 5, Sep. 1997 “Low Fringe-Field and Narrow-Track MR Heads” by Guo et al.
IEEE Transactions On Magnetics, vol. 34, No. 4 Jul. 4, 1998 “A New Write Head Trimmed at Wafer Level by Focused Ion Beam” by Koshikawa et al.
Cates James C.
Lakshmikumaran Anand V.
Brooks & Kushman P.C.
Heinz A. J.
Storage Technology Corporation
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