The supercell is randomly filled with the five elements in the fcc-lattice positions. In the starting configuration, all layers are precisely on top of each other. The displacements of all elements in the final configuration have been revealed by a simultaneous fit of the independent experimental spectra with reverse Monte Carlo simulations. Image: A.Kuzmin/University of Latvia and A. Smekhova/HZB.
The supercell is randomly filled with the five elements in the fcc-lattice positions. In the starting configuration, all layers are precisely on top of each other. The displacements of all elements in the final configuration have been revealed by a simultaneous fit of the independent experimental spectra with reverse Monte Carlo simulations. Image: A.Kuzmin/University of Latvia and A. Smekhova/HZB.

High-entropy alloys are being considered for various different applications. Some materials from this group are suitable for hydrogen storage, while others have proved of use for noble-metal-free electrocatalysis, radiation shielding and supercapacitors.

The microscopic structure of high-entropy alloys is very diverse and changeable; in particular, the local ordering and presence of different secondary phases can significantly affect macroscopic properties such as hardness, corrosion resistance and magnetism. The so-called Cantor alloy, which consists of the elements chromium, manganese, iron, cobalt and nickel mixed in equimolar proportions, can be considered as a suitable model system for the whole class of these materials.

Scientists from Helmholtz-Zentrum Berlin für Materialien und Energie (HZB), the Federal Institute for Materials Research (BAM) and the Ruhr University in Bochum, all in Germany, and the University of Latvia in Riga, have now studied the local structure of this model system in detail. Using X-ray absorption spectroscopy (EXAFS) at BESSY II, they were able to precisely track each individual element and their displacements from the ideal lattice positions for this system, with the help of statistical calculations and the reverse Monte Carlo method. They report their findings in a paper in the Journal of Alloys and Compounds.

The researchers uncovered peculiarities in the local environment of each element. Despite all five elements of the alloy being distributed at the nodes of the face-centred cubic lattice and having very close statistically averaged interatomic distances (2.54–2.55Å) with their nearest neighbours, the researchers found large structural relaxations solely for chromium atoms. In addition, they didn’t detect any evidence of secondary phases at the atomic scale. Finally, they correlated the macroscopic magnetic properties studied with conventional magnetometry at HZB CoreLab with the revealed structural relaxations of chromium.

"The results describe the arrangement of individual atoms at the atomic scale and how the complex magnetic order that we revealed may occur," explains HZB physicist Alevtina Smekhova, who supervised the experiments at HZB.

This story is adapted from material from HZB, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.