Atomic ordering of ferromagnetic alloys, such as Heusler compounds, vastly influences their magnetic properties and overall usability. However, in some cases x-ray diffraction cannot unambiguously determine the correct atomic structure, which hampers further research. In this paper, we analyze the atomic ordering using spectroscopic ellipsometry—a simple tabletop method that researchers can use in situ during sample deposition. The ${\mathrm{Co}}_2\mathrm{Fe}({\mathrm{Ga}}_{0.5}{\mathrm{Ge}}_{0.5})$ Heusler compound was chosen for the analysis, as the atomic ordering greatly influences its spin-polarizing capabilities. The ellispometric results are confronted with x-ray diffraction and with the help of $\mathit{ab}$ initio calculations the qualitative changes in the optical response are linked to the changes in atomic ordering.

• Received 3 January 2022
• Revised 4 August 2022
• Accepted 25 August 2022

DOI:https://doi.org/10.1103/PhysRevB.106.144102