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Llo Phase Formation in CoPt Thin Films

Published online by Cambridge University Press:  10 February 2011

R. A. Ristau ,
K. Barmak ,
K. R. Coffey  and
J. K. Howard
R. A. Ristau
Affiliation:
Department of Materials Science and Engineering, Lehigh University, Bethlehem, PA.
K. Barmak
Affiliation:
Department of Materials Science and Engineering, Lehigh University, Bethlehem, PA.
K. R. Coffey
Affiliation:
Sensormatic, Boca Raton, FL.
J. K. Howard
Affiliation:
IBM Storage Systems Division, San Jose, CA.
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Abstract

The high magnetic anisotropy and high coercivity of equiatomic CoPt thin films make them attractive as potential materials for magnetic recording applications. Magnetic coercivity (Hc) over 10 kOe has been measured in films in which the as-deposited fee phase has been partially transformed to the atomically ordered Ll0 phase. Very high Hc has been related to high volume fraction and small size of the Ll0 precipitates. A better understanding of the Ll0 phase formation and quantification of volume fraction is critical to optimizing the magnetic properties of this material.

As we have previously reported, an increase in Hc was observed with an increase in Ll0 volume fraction in 10 nm thick, equiatomic CoPt films. In our current investigation we have observed that, at anneal temperatures far from the order/disorder transition temperature, e.g. at T = 0.6 Tc, numerous, very fine Ll0 precipitates are seen, some of which cluster at the parent phase grain boundaries. At T = 0.85 Tc, very few, larger Ll0 regions were seen. As precipitates of the ordered phase grow to impingement, antiphase boundaries (APB) are formed. This is consistent with a heterogeneous nucleation and growth mechanism for the formation of the Ll0 phase throughout the temperature range studies.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 475: Symposium M – Magnetic Ultrathin Films, Multilayers, and Surfaces – 1997 , 1997 , 119
Copyright
Copyright © Materials Research Society 1997

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References

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