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Phys. Rev. Lett. 74, 2010–2013 (1995)

[Issue 11 – 13 March 1995 ]

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X-Ray Intensity Fluctuation Spectroscopy Observations of Critical Dynamics in Fe₃Al

S. Brauer and G. B. Stephenson

IBM Research Division, T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598

M. Sutton, R. Brüning, and E. Dufresne

Center for the Physics of Materials and Department of Physics, McGill University, Montréal, Québec, Canada, H3A 2T8

S. G. J. Mochrie

Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

G. Grübel, J. Als-Nielsen, and D. L. Abernathy

European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble Cedex, France

We have carried out intensity fluctuation spectroscopy measurements using coherent x rays to study the dynamics of critical fluctuations in a binary alloy at equilibrium. An intense coherent hard x-ray beam, produced from an undulator source, was scattered from a single crystal of Fe₃Al held at temperatures near the B2-DO₃ order-disorder transition. A speckle pattern was observed at the (1 / 2 1 / 2 1 / 2) superlattice reflection. Below T_c it was essentially static, while above T_c it fluctuated in time. The behavior of the normalized time correlation function is consistent with predictions of theory.

©1995 The American Physical Society

URL: http://link.aps.org/abstract/PRL/v74/p2010
DOI: 10.1103/PhysRevLett.74.2010
PACS: 61.10.Lx, 05.40.+j, 42.30.Ms, 64.60.Ht

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References

1. G. Grübel, J. Als-Nielsen, D. Abernathy, G. Vignaud, S. Brauer, G. B. Stephenson, S. G. J. Mochrie, M. Sutton, I. K. Robinson, R. Fleming, R. Pindak, S. Dierker, and J. F. Legrand, ESRF Newsletter, February 1994; see also Annex to the ESRF Annual Report 1993 (European Synchrotron Radiation Facility, Grenoble, 1994).
2. M. Sutton, S. G. J. Mochrie, T. Greytak, S. E. Nagler, L. E. Berman, G. A. Held, and G. B. Stephenson, Nature (London) 352, 608 (1991) [ADS][ INSPEC].
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8. The composition was chosen to be at the maximum in T_c to reduce any broadening of the transition due to composition inhomogeneity. The crystal was prepared by arc melting Fe and Al in a gettered Ar atmosphere and annealing the resulting ingot for several days at 1723 K to grow large ( ~10 mm) grains. Precautions were taken to avoid significant evaporation of Al during annealing. After cutting and orienting, the surface was prepared by mechanical polishing.
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12. In computing g⁽²⁾( tau )-1 from the data, all time-bins were of equal size and spacing, but some were not filled due to interruptions in the data accumulation. The sums were carried out over only filled bins, and normalized to the number of summed terms. For each data set, various sizes of time-bin were investigated and found to produce very similar correlation functions.
13. G. Grinstein (private communication).
14. K. Binder, Z. Phys. B 43, 119 (1981) [ INSPEC][SPIRES].

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