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Sendust Films with Body-Centered-Cubic Metal Seed Layers

IP.com Disclosure Number: IPCOM000114876D
Original Publication Date: 1995-Feb-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 119K

Publishing Venue

IBM

Related People

Westwood, JD: AUTHOR

Abstract

Disclosed is a fabrication process that provides Sendust films having improved soft anisotropic magnetic properties and expands the range of Sendust alloy compositions over which such soft anisotropic properties can be obtained. In order to stabilize the magnetic domain structure, the prior art provides laminated Sendust films including two or more Sendust layers separated by thin nonmagnetic spacer layers. However, in a multilayer structure the magnetic properties of the individual Sendust layers deteriorate with decreasing layer thickness less than about 1.5 micrometers.

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Sendust Films with Body-Centered-Cubic Metal Seed Layers

      Disclosed is a fabrication process that provides Sendust films
having improved soft anisotropic magnetic properties and expands the
range of Sendust alloy compositions over which such soft anisotropic
properties can be obtained.  In order to stabilize the magnetic
domain structure, the prior art provides laminated Sendust films
including two or more Sendust layers separated by thin nonmagnetic
spacer layers.  However, in a multilayer structure the magnetic
properties of the individual Sendust layers deteriorate with
decreasing layer thickness less than about 1.5 micrometers.

      Technical Description - Sendust alloys have compositions at or
near 9.6% Si, 5.5% Al with the balance being Fe (% by weight).
Critical magnetic properties of Sendust thin films, such as
magnetostriction, anisotropy field and coercivity, depend on the
composition.  Sendust films have low and/or negative magnetostriction
are desirable for use in magnetic recording head applications, but
such Sendust films generally exhibit poor coercivity and anisotropy.

      The properties of magnetic thin films, in general, depend
critically on the texture, grain size and phase.  The atomic
structure of Sendust is based on the Body-Centered-Cubic (BCC)
structure of alpha-Fe.  In Sendust, Al and Si occupy BCC sites of the
alpha-Fe, but ordering of Al and Si relative to Fe occurs leading to
the formation of various superlattice phases which affect the
magnetic properties of the Sendust.  Since Sendust is based on a BCC
structure, formation of a Sendust film over a metal seed layer have a
BCC structure with similar lattice parameters alters the nucleation
and subsequent growth of the of the film thereby providing the
Sendust with a desired structure and improved magnetic properties.

      Sendust films consisting of a BCC metal seed layer and a bulk
Sendust layer were deposited by RF diode sputtering.  The BCC metal
seed layers were sputtered from targets with greater than 99.9%
purity in thicknesses from 50 to 1200 Angstroms.  After the seed
layer deposition, a bulk Sendust layer approximately 2 micrometers
thick was deposited without breaking vacuum.  After deposition, all
films were annealed in a magnetic field under a nitrogen atmosphere.

      Table 1 lists BH loop properties for selected films.  H(sub)ce
and H(sub)ch are the easy and hard axis coercivity, respectively;
mu(sub)i and mu(sub)r are the initial and re...