| Issue |
Europhys. Lett.
Volume 45, Number 6, March II 1999
|
|
|---|---|---|
| Page(s) | 686 - 692 | |
| Section | Condensed matter: structure, mechanical and thermal properties | |
| DOI | https://doi.org/10.1209/epl/i1999-00222-0 | |
| Published online | 01 September 2002 | |
Surface vs. bulk order/disorder transition in a binary alloy. A He
diffraction study of the 
surface*
Istituto Nazionale di Fisica della Materia (INFM) and
CFSBT/CNR
Dipartimento di Fisica, Università di Genova
via Dodecaneso 33, I-16146, Genova, Italy
Received:
29
October
1998
Accepted:
14
January
1999
We present a helium diffraction study of the order/disorder phase transition
at the (001) surface of 
. We have measured the specular and the
superlattice (-1, 0) Bragg intensities in the 140 K 
K
temperature range. We have performed an accurate determination of the Debye-Waller
factor, including anharmonic contributions. Thanks to the extreme
surface sensitivity of helium diffraction, the superlattice peak intensity
provides an experimental determination of the long-range order parameter M
at the topmost surface layer. The surface critical temperature is found to
be 
= 
. The value of the critical exponent 
=
0.45 ± 0.05 is in good agreement with theoretical predictions within
the surface-induced disorder model.
PACS: 68.35.Rh – Phase transitions and critical phenomena / 34.50.-s – Scattering of atoms, molecules, and ions
© EDP Sciences, 1999
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