Temperature dependence of the diffuse scattering fine structure in equiatomic CuAu

TL;DR

This study investigates how the fine structure of diffuse x-ray scattering in disordered CuAu varies with temperature, revealing differences from Cu3Au and providing insights into phase transition behaviors.

Contribution

It presents the first detailed analysis of temperature effects on diffuse scattering in CuAu, contrasting it with Cu3Au and applying an extended Ginzburg-Landau model.

Findings

Diffuse peak splitting in CuAu is temperature-insensitive.

No divergence of antiphase length-scale at transition temperature.

The mean-field instability point in CuAu is lower than in Cu3Au.

Abstract

The temperature dependence of the diffuse scattering fine structure from disordered equiatomic CuAu was studied using {\it in situ} x-ray scattering. In contrast to Cu$_3$Au the diffuse peak splitting in CuAu was found to be relatively insensitive to temperature. Consequently, no evidence for a divergence of the antiphase length-scale at the transition temperature was found. At all temperatures studied the peak splitting is smaller than the value corresponding to the CuAuII modulated phase. An extended Ginzburg-Landau approach is used to explain the temperature dependence of the diffuse peak profiles in the ordering and modulation directions. The estimated mean-field instability point is considerably lower than is the case for Cu$_3$Au.