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Longitudinal Read Sensor for Magnetic Disks

IP.com Disclosure Number: IPCOM000101645D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 116K

Publishing Venue

IBM

Related People

Korth, HE: AUTHOR

Abstract

The weak read-out signal of data stored in very narrow tracks is increased by arranging a number of sensor elements along a track on the read/write head. By an integrated CCD (charge-coupled device), for example, the signals may be averaged with an appropriate delay. Tracking may be done by comparing a leading and a trailing sensor element of opposite offset with the track center.

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Longitudinal Read Sensor for Magnetic Disks

       The weak read-out signal of data stored in very narrow
tracks is increased by arranging a number of sensor elements along a
track on the read/write head.  By an integrated CCD (charge-coupled
device), for example, the signals may be averaged with an appropriate
delay.  Tracking may be done by comparing a leading and a trailing
sensor element of opposite offset with the track center.

      To increase the storage density of magnetic disks, the width of
the data tracks has to be reduced.  It has been shown that it is
feasible to read data from and write it in a track having a width of
the order of 1 mm.  Compared with existing devices, this increases
the track density by more than one order of magnitude.

      The problem of writing and retrieving data in the contiguous
storage area of a disk is still to be resolved. It appears feasible
to build data write elements for a bit size of 1 mm2, using advanced
photolithography.  To limit the size of the magnetic domains, the
disk coating has to be appropriately structured.

      Reading out very narrow tracks is becoming increasingly
difficult.  The extension of the written bit decreases as the track
width is reduced.  In addition, the fraction of the field that can be
sensed by a read sensor is decreasing. This means straightforward
miniaturization is not sufficient for reading.

      A further problem is the generation of the track servo signal.
Laterally shifted bit patterns at sector headers are not readily
combinable with track structuring.  Optical track servo sensors
require additional hardware.

      On conventional thin-film magnetic head sliders, the read/write
elements are located at the trailing edge of the device.  These
elements are prepared photolithographically and have a width of some
20 mm and a gap of about 1 mm.

      By reducing the track width and thus the element width to a few
mm, it is feasible to attach the elements to a sidewall of the
slider, as shown in the figure.  Appropriate photolithographic
techniques permit defining transducer elements based on
electromagnetics, magneto- resistivity or the Hall effect.

      By using sidewall 2 of slider 1 for transducer 3, it is
possible to produce a number of sensors 4 in parallel. Track scanning
of these sensors 4 produces virtually identical signals.  Averaging
these signals with an appropriate delay (about 50 nanoseconds per mm
distance), yields an enhanced read-out signal.  Assuming 100 sensor
elements 4 are contained in a sensor array 5, then the signal will be
enhanced by a factor 100 and the signal-to...