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External H Field Source With Kerr Effect Readback for Measurement of Thin Film Disk Bulk Magnetic Properties

IP.com Disclosure Number: IPCOM000102909D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Johnson, KE: AUTHOR [+2]

Abstract

A polarization rotation of a polarized beam of light reflected off a thin film disk surface is changed according to the magnetization direction and magnitude present in the magnetic film at that surface. This is known as the Kerr effect. Using this effect with an external calibrated magnetic field on a rotating disk, the required field to switch the magnetic direction of the media (coercive force) as well as the coercive squareness of the media can be determined.

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External H Field Source With Kerr Effect Readback for Measurement of Thin Film Disk Bulk Magnetic Properties

      A polarization rotation of a polarized beam of light reflected
off a thin film disk surface is changed according to the
magnetization direction and magnitude present in the magnetic film at
that surface.  This is known as the Kerr effect.  Using this effect
with an external calibrated magnetic field on a rotating disk, the
required field to switch the magnetic direction of the media
(coercive force) as well as the coercive squareness of the media can
be determined.

      The external H field source in the recording direction is
provided by a ring head magnet 1, as shown in the figure. A polarized
laser beam source 2 and cross polarization detector 3 are located on
both sides of a rotating disk 4. A field large enough to magnetize
the recording media in one direction is applied.  The field is then
applied in the reverse direction starting at a low level and
incremented to the point where the recording media 4 is magnetized
completely in the opposite direction.  The phase of the polarized
laser beam 2 is monitored by the phase detector 3 at each level of H
field applied from external magnet 1. The field required to switch
the media (coercive force) and the rate at which the media switches
(coercive squareness) are determined from a plot of the phase of the
polarized laser beam versus the applied H field.

      Disclosed anonymously.