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External H Field Source With Magnetic Head Readback for Measurement of Disk Bulk Magnetic Properties

IP.com Disclosure Number: IPCOM000102908D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Related People

Severson, JM: AUTHOR

Abstract

Magnetic read heads work well to sense the magnetic state of a recording film; however, it is very difficult to maintain them as a calibrated H field source. By providing a calibrated H field in the recording direction from an external magnet and using a magnetic read head to sense the flux state on a disk, the disk coercivity and coercive squareness can be measured.

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External H Field Source With Magnetic Head Readback for Measurement of Disk Bulk Magnetic Properties

      Magnetic read heads work well to sense the magnetic state of a
recording film; however, it is very difficult to maintain them as a
calibrated H field source.  By providing a calibrated H field in the
recording direction from an external magnet and using a magnetic read
head to sense the flux state on a disk, the disk coercivity and
coercive squareness can be measured.

      The external H field source in the recording direction is
provided by a ring head magnet 1 shown in the figure.  A magnetic
read/write head 2 is used to sense the flux state on a disk 3 via
monitoring the output from a recorded signal.  The external H field
is varied from 0 to a level which fully erases the recorded signal.
By plotting the output from read head 2 versus the applied H field,
the amount of field required to switch disk 3 is determined. This is
the coercive force.  Also, the slope of the read/write head output
versus the applied H field is measured.  This determines the coercive
squareness of media 3.  The magnetic moment associated with media 3
is determined from the maximum amplitude from recording head 2 and an
appropriate calibration factor.  This measurement does not require
the use of external H field source 1.

      Disclosed anonymously.