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The Formation of High-Coercivity, Oriented, Nanophase Cobalt Precipitates in Al2O3 Single Crystals by Ion Implantation

Published online by Cambridge University Press:  21 February 2011

S. Honda ,
F. A. Modine ,
T. E. Haynes ,
A. Meldrum ,
J. D. Budai ,
K. J. Song ,
J. R. Thompson  and
L. A. Boatner
S. Honda
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, N 37831, lb4@ornl.gov
F. A. Modine
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, N 37831, lb4@ornl.gov
T. E. Haynes
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, N 37831, lb4@ornl.gov
A. Meldrum
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, N 37831, lb4@ornl.gov
J. D. Budai
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, N 37831, lb4@ornl.gov
K. J. Song
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, N 37831, lb4@ornl.gov Also at the University of Tennessee, Knoxville, TN
J. R. Thompson
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, N 37831, lb4@ornl.gov Also at the University of Tennessee, Knoxville, TN
L. A. Boatner
Affiliation:
Solid State Division, Oak Ridge National Laboratory, Oak Ridge, N 37831, lb4@ornl.gov
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Abstract

Ion-implantation and thermal-processing methods have been used to form nanophase magnetic precipitates of metallic cobalt that are embedded in the near-surface region of single crystals of Al2O3. The Co precipitates are isolated, single-crystal particles that are crystallographically oriented with respect to the host Al2O3 lattice. Embedded nanophase Co precipitates were formed by the implantation of Co+ at an energy of 140 keV and a dose of 8 × 1016 ions/cm2 followed by annealing in a reducing atmosphere. The implanted/annealed Co depth profile, particle size distributions and shapes, and the orientational relationship between the nanophase precipitates and the host crystal lattice were determined using RBS/channeling, transmission electron microscopy, and x-ray diffraction. Magneto-optical effects arising from Co precipitates formed in the near-surface region of Al2O3 were observed and characterized using magnetic circular dichroism. Magnetic properties of the Co-particle/host nanocomposites were investigated in the temperature range of 77 to 295 K in applied fields of up to 10 kG using a superconducting quantum interference device (SQUID) magnetometer. Implantation of the Co particles by Pt or Xe ions produced a large anisotropic increase in their coercivity. Accordingly, these magnetic nanoparticle systems may be of interest for magnetic data storage applications. Details of the magnetic properties of the Co/Al2O3 nanocomposites including their retentivity, coercivity, saturation field, and magnetic anisotropy are presented.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 581: Symposium F – Nanophase & Nanocomposite Materials II , 1999 , 71
Copyright
Copyright © Materials Research Society 2000

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References

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