Browse Prior Art Database

Metal Underlayer Disk

IP.com Disclosure Number: IPCOM000119728D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 91K

Publishing Venue

IBM

Related People

Matsui, T: AUTHOR [+3]

Abstract

Disclosed is a metal underlayer magnetic media by which an output is increased and an inductance is reduced in a magnetic recording device using a magnetic head for reading or writing the magnetic media.

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

Metal Underlayer Disk

      Disclosed is a metal underlayer magnetic media by which
an output is increased and an inductance is reduced in a magnetic
recording device using a magnetic head for reading or writing the
magnetic media.

      Fig. 1 shows a general structure of the metal underlayer media.
The medium shown in Fig. 1 consists of a substrate 1, a metal
underlayer 2, a magnetic layer 3 and a protective layer 4.  This
substrate 1 is made of smooth surface material such as ceramic or
glass.  In some cases there is an additional layer between the
magnetic layer 3 and the metal underlayer 2 for controlling the
magnetic properties of the recording layer.

      Fig. 2 is a schematic illustration showing a magnetic head core
and the equivalent magnetic circuit for the recording process using
the metal underlayer medium.  The following simple approximate
expression for the efficiency EF can be obtained by considering the
head and the medium as magnetic circuit.
      EF = 1 / { 1 + (Rc/Rg) + (Rc/Rl) + (Rc/Rm) }      (1)

      The magnetic reluctance Rm of the metal underlayer region is
given by
   Rm = Am / ( Pme * lm )                            (2) where Am  :
a uniform cross section in the metal underlayer region
       Pme :  effective permeability of the metal underlayer
       lm  :  the flux path length through the metal underlayer

      Equation (1) shows that the high efficiency requires a high
reluctance in the metal underlayer region.

      Then, by using a complex permeability, the following simple
approximate expression * for Rm can be obtained:
      Rm = k * Del * (f) ^ 0.5                         (3)
      k = k'* { Am/(lm * Pdc)} * { pai * (2 * Pdc/P) ^ 0.5 }
where Del : the metal underlayer thickness
       f   : signal frequency
       Pdc : initial permeability of metal unde...