Topas 3

The phase composition of the samples after electrical conductivity measurements was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. Powder XRD measurements were done on a Bruker D8 diffractometer at ambient temperature using Ni filtered Cu K_α radiation (accelerating voltage 40 kV, electron current 40 mA). The diffractometer operates in the θ/2θ mode. The powder was fixed with petroleum jelly on a single-crystal silicon sample carrier which was rotated during the measurement. The detection unit was a Lynxeye strip detector. Indexing of the phases was supported by the Inorganic Crystal Structural Database (ICSD). Rietveld refinement of the XRD patterns was done with the Topas3® software provided by Bruker AXS.
The scanning electron microscope Zeiss Supra 55 VP was used for metallographic investigations. The excitation energy of the electron beam was 15–20 kV; backscattered electrons (BSE) were detected to visualize the surfaces of the samples. Pure Co was also used for energy calibration of the EDX detector signal. An acceleration voltage of 20 kV was applied. The chemical compositions obtained from EDX differ from the corresponding average value up to ± 1 at.%.

The Rietveld refinements were performed by using TOPAS3 software developed by Bruker AXS GmbH. The full width at half maximum of silicon (Standard Reference Material 640c) 111 diffraction peak is about 0.015° at 2θ = 10° which is an instrumental resolution function of the diffractometer. All XRD patterns were refined in 2θ range from 10 to 60° with 0.006° per step identical to the resolution of the beamline BL02B2, SPring-8. The XRD pattern of fcc-AuRu₃ was well fitted by two components with space groups of Fm $\overline{3}$ m and P6₃/mmc. For hcp-AuRu₃, the pattern was fitted by one component of P6₃/mmc.

The small-angle X-ray diffraction
(SAXRD) measurements were performed with a Bruker Nanostar system
(Cu Kα radiation, parallel beam formed by cross-coupled Goebel
mirrors and 3-pinhole collimation system, area detector VANTEC 2000).
The temperature of the sample was controlled with a precision of 0.1
°C. Samples were prepared as a thin film on a Kapton tape substrate.
For all samples temperature-dependent measurements were performed
in the same manner—data were collected every 5 °C for
60 s. A quasi-monodomain sample was prepared by a mechanical shearing
at elevated temperatures (10 °C below the phase transition point)
on a heating table.
Fitting of the experimental diffractograms
and simulation of the patterns were done using Topas 3 software (Bruker).
Each procedure started with choosing the most probable symmetry of
the lattice. Then, the unit cell parameters, intensities of the (Pseudo-Voigt)
signals, and (1/x) background intensity were considered
as independently adjustable parameters.