Surface density oscillations in disordered binary alloys: X-ray reflectivity study of Cu3Au(001)

3 Au(001) surface using Synchrotron radiation and show that the intensity distribution along the specular rod exhibits the same features as in the case of liquid metals which has been discussed in recent literature. The results are discussed within the framework of the distorted wave Born approximation which allows a straightforward easy-to-apply scheme to analyze such reflectivity data in the entire -range including the total external reflection regime. The data analysis gives a direct evidence for an oscillating average density profile which is analoguous to the socalled surface layering at liquid surfaces. The experimental values for the thermal roughness indicate that surface roughness is suppressed in the ordered phase and allowed to softly grow with temperature above the bulk order-disorder phase transition. The presented experimental and theoretical study of X-ray reflectivity from binary alloys demonstrates the potential of this technique for the study of surface roughening, surface layering and surface segregation phenomena at solid and liquid surfaces. Received: 14 August 1996/Accepted: 7 October 1996