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Browse Prior Art Database

Method of Detecting Gap Defects with Magnetic Stability Measurements of MR Read Sensors

IP.com Disclosure Number: IPCOM000107344D
Original Publication Date: 1992-Feb-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 3 page(s) / 102K

Publishing Venue

IBM

Related People

Kahwaty, VN: AUTHOR [+2]

Abstract

In the case of an MR read head or an interleaved magnetic tape recording head using MR read sensors, a method of detecting gap defects without visual inspection is disclosed. It is found that gap defects will produce Barkhausen noise in MR sensors which can be detected by MR stability measurement techniques immediately after the head surface contour is established. In addition, ideas for applying these techniques to write gaps is disclosed.

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This is the abbreviated version, containing approximately 52% of the total text.

Method of Detecting Gap Defects with Magnetic Stability Measurements of MR Read Sensors

       In the case of an MR read head or an interleaved magnetic
tape recording head using MR read sensors, a method of detecting gap
defects without visual inspection is disclosed.  It is found that gap
defects will produce Barkhausen noise in MR sensors which can be
detected by MR stability measurement techniques immediately after the
head surface contour is established.  In addition, ideas for applying
these techniques to write gaps is disclosed.

      For recording heads the process of visual gap inspection is
difficult, expensive, and is usually conducted only on a sample
basis; hence, many gap defects can escape and will result in failures
at head test or may result in poor reliability heads.  This is a
continuing magnetic head defect problem and yield detractor.  Also
this problem could contribute to reduced magnetic tape head field
reliability. For a recording head using MR read sensors, it is found
that gap defects will produce Barkhausen noise in MR sensors which
can be detected by MR stability measurement techniques immediately
after the head surface contour is established.

      After establishing a stable MR read process it is found that
unstable MRs can be produced by head gap defects. Therefore, heads
with gap defects can frequently be found by finding unstable MR
elements.  This is achieved using a stability measurement technique
which drives the head with various exciting and disturbing magnetic
fields to excite possible unstable states in the MR element.  The
measurement can be conducted immediately after establishing the head
surface contour and should take an average of less than 1 minute for
an 18-element head.  This will have the effect of screening out
defective gaps early in the process and avoid continuing expensive
head fabrication steps.  It is possible to combine testing of heads
for resistance, amplitude, bias point, and distortion...