Fermi surface of a disorderedCu−Al-alloy single crystal studied by high-resolution Compton scattering and electron diffraction

Abstract

We have measured high resolution Compton scattering profiles for momentum transfer along a series of 28 independent directions from Cu 0.842 Al 0.158 disordered alloy single crystals with normals to the surfaces oriented along the [100], [110], and [111] directions. The experimental spectra are interpreted via parallel first-principles KKR-CPA (Korringa-Kohn-Rostoker coherent-potential approximation) computations of these directional profiles. The Fermi surface determined by inverting the Compton data is found to be in good agreement with the KKR-CPA predictions. An electron diffraction study of the present Cu 0.842 Al 0.158 sample is additionally undertaken to gain insight into short-range ordering effects. The scattering pattern displays not only the familiar diffuse scattering peaks, but also shows the presence of weak streaks interconnecting the four diffuse scattering spots around the (110) reciprocal lattice points. This study provides a comprehensive picture of the evolution of the shape of the Fermi surface of Cu with the addition of Al. Our results are consistent with the notion that Fermi surface nesting is an important factor in driving short-range ordering effects in disordered alloys.

Electron momentum density in Ni75Cu25and Ni75Co25disordered alloys: a high-resolution Compton-scattering study

“…Compton scattering is widely used to determine the ground-state electronic properties of solids [1]. As the method is not sensitive to defects or impaired by high impurity concentration it can be successfully applied to study disordered, nondilute alloys [2][3][4][5][6][7][8][9]. On the other hand, the high resolution (of the order of 0.1 au, atomic units of momentum) currently attainable in synchrotron-based Compton scattering experiments coupled with high statistical accuracy makes the method a sensitive tool to probe subtle fermiological properties of materials.…”

Comments on reconstruction of Fermi surface from high-resolution Compton data

“…A typical example of this case is a recent work by Kwiatkowska et al [13], in which the Fermi surface sections of a Cu 0.842 Al 0.158 disordered alloy are determined by searching the Fermi breaks in the momentum density reconstructed from 28 directional profiles measured with an overall experimental momentum resolution of 0.13 atomic units (a.u.). Together with the Fermi surface sections of a Cu 0.725 Pd 0.275 [14] which were previously determined in the same manner, they discussed the relation between the nesting features of the Fermi surface and the shortrange order exhibited in these disordered alloys through the generalized susceptibility.…”