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Magnetically Resonant Thin Films And Resonant Heads for Magnetic And Magneto-Optic Recording

IP.com Disclosure Number: IPCOM000101384D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 78K

Publishing Venue

IBM

Related People

Re, ME: AUTHOR [+3]

Abstract

Constructive interference in magnetic/dielectric thin-film laminates can be used to make magnetically resonant structures wherein the magnetic permeability is significantly enhanced at a given frequency. Applications include magnetic heads as well as flux- and wave-guides.

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Magnetically Resonant Thin Films And Resonant Heads for Magnetic And Magneto-Optic Recording

       Constructive interference in magnetic/dielectric
thin-film laminates can be used to make magnetically resonant
structures wherein the magnetic permeability is significantly
enhanced at a given frequency.  Applications include magnetic heads
as well as flux- and wave-guides.

      The laminated structure has two components:  N magnetic layers
characterized by resistivity rm, thickness t, and permeability m,
separated by N - 1 dielectric layers, described by resistivity ri,
thickness d and dielectric constant e.  The magnetic layers supply
the magnetic permeability, and the dielectric layers provide
electrical isolation between the layers.  Each layer is then compared
to the skin depth of the material.

      In a magnetic film laminated with insulating interlayers, the
effective wavelength in the film of the applied field parallel to the
film surface is 1% or less of the free-space wavelength but much
larger than in the bulk (unlaminated) magnetic film.  A resonance in
the permeability occurs when half the effective wavelength in a
laminated magnetic structure approaches the structure width W.
Additional resonances occur at higher half-odd harmonics of the
effective wavelength.  The resonant frequencies are

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      Resonant magnetic structures may be useful for the following
applications:
(1) Heads for magneto-optical direct overwrite.
One way to achieve direct overwrite in magneto-optical recording is
to use a magnetic head to generate a high frequency ( > 5 MHz)
oscillating field.  By making the head magnetically resonant, the
effective permeability can be increased, reducing the power
requirements.
(2) Resonant or semi-resonant structures for thin-film magnetic heads
and f...