X-RAY-INTENSITY FLUCTUATION SPECTROSCOPY OBSERVATIONS OF CRITICAL-DYNAMICS IN FE3AL

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 (12 12 12) superlattice reflection. Below Tc it was essentially static, while above Tc it fluctuated in time. The behavior of the normalized time correlation function is consistent with predictions of theory. © 1995 The American Physical Society.