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Removal of Dielectric Overcoat in Optimal Magneto-Optic Disk Design

IP.com Disclosure Number: IPCOM000116566D
Original Publication Date: 1995-Oct-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 84K

Publishing Venue

IBM

Related People

McDaniel, TW: AUTHOR [+2]

Abstract

The design of multilayer film media for Magneto-Optic (MO) data storage has several objectives. Among them are the production and protection of a smooth, homogeneous, amorphous magnetic film for data storage, and the encapsulation of the magnetic film above and below with smooth, homogeneous, nonreactive films. The protective film on the light-entrant side of the MO film must be transparent and the protective film adjacent to the MO film on the light-exit side may be transparent. The transparent materials are typically dielectrics. The protective films also can serve as optical reflectance and phase-adjusting media for the purpose of enhancing the magneto-optic Kerr effect during data readout. Fig.

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Removal of Dielectric Overcoat in Optimal Magneto-Optic Disk Design

      The design of multilayer film media for Magneto-Optic (MO) data
storage has several objectives.  Among them are the production and
protection of a smooth, homogeneous, amorphous magnetic film for data
storage, and the encapsulation of the magnetic film above and below
with smooth, homogeneous, nonreactive films.  The protective film on
the light-entrant side of the MO film must be transparent and the
protective film adjacent to the MO film on the light-exit side may be
transparent.  The transparent materials are typically dielectrics.
The protective films also can serve as optical reflectance and
phase-adjusting media for the purpose of enhancing the magneto-optic
Kerr effect during data readout.  Fig.  1a shows a typical multifilm
structure of thickness adjustment to jointly optimize several
important functions of the MO medium, such as thermomagnetic writing,
MO readout performance, and archival stability.  A well-optimized
quadrilayer structure provides peak MO readout performance, since it
enables achievement of a high quality, antireflection configuration
on the light-entrant side of the MO film (thus ensuring maximal
interaction of the readout light beam and the MO film), and it also
provides for a proper phase matching, transparent layer between the
MO film and the reflecting mirror on the light-exit side of the
structure.  The phase matching ensures that multiple reflection and
transmission at the MO film enhances the Kerr and Faraday effects
fully.  Such a quadrilayer tends to exhibit enhanced Kerr rotation,
and diminished reflectance, with overall readout signal being
increased.  The two primary disadvantages of a quadrilayer structure
are (1) the need to use a very thin, homogeneous, partially
trans...