Growth and Characterization of ROBiS2 High-Entropy Superconducting Single Crystals.

Abstract

A series of high-entropy superconductors, ROBiS2 (R = La + Ce + Pr + Nd + Sm), have been successfully grown in the form of single crystals using CsCl flux. The obtained single crystals have a platelike shape with a size of 0.5–2.0 mm and a thickness of 70–450 μm, and they are cleavable along the c-plane. The c-axis lattice constants of the obtained ROBiS2 single crystals have similar values of 13.47–13.57 Å. The Ce in the obtained ROBiS2 single crystals was in a mixed-valence state, comprising both Ce3+ and Ce4+. On the other hand, Pr and Sm showed only the trivalent state. The superconducting transition temperatures of ROBiS2 single crystals were approximately 2–4 K. The superconducting transition temperature and superconducting anisotropies of R-site mixed high-entropy samples increased with a decrease in the mean ionic radius of the R-site. Moreover, a deviation in the tendency to exhibit superconducting properties was observed based on the difference in the R-site mixed entropy. R-site mixed entropy in ROBiS2 superconductors may affect their superconducting properties.