Possible local order in the high entropy TrZr2 superconductors. (March 2023)

• Record Type: Journal Article
• Authors: Pugliese, G.M.; Tortora, L.; Tomassucci, G.; Kasem, R.Md.; Mizokawa, T.; Mizuguchi, Y.; Saini, N.L.
• Is Part Of: Journal of physics and chemistry of solids. Volume 174(2023)
• Publication Date: 2023-03
• Subjects: High entropy alloys -- Superconductivity -- Local structure; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2022.111154
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: We have investigated the local structure of Tr Zr 2 (Tr = transition metal) superconductor with variable configurational entropy using x-ray absorption spectroscopy. Temperature dependent Zr K-edge extended x-ray absorption fine structure (EXAFS) measurements are carried out on three different samples including the pristine CoZr 2, medium entropy Co0.33 Rh0.34 Ir0.33 Zr 2 and high entropy Co0.2 Fe0.2 Ni0.2 Rh0.2 Ir0.2 Zr 2 . We have found that the local bondlengths remain largely temperature independent or tend to show negative thermal expansion, instead the Zr–Zr bondlengths get stiffer with the configurational entropy. The x-ray absorption near edge structure (XANES) spectra at Zr K-edge and Ir L 3 -edge indicate Zr 4 d - Tr n d (n = 2, 3, 4) hybridization to be related with the superconducting transition temperature. The results provide important information on the local structure that can be useful to understand the physical properties of these materials and design new high entropy alloys (HEAs) superconductors. Highlights: The effect of mixing entropy in TrZr 2 superconductor has been studied. The local structure of TrZr 2 changes significantly with the mixing entropy. The bond lengths are temperature independent or show negative thermal expansion. The bond lengths are stiffer in presence of an overall increased local disorder. The Zr 4d – Tr nd hybridization is related with the superconducting transition temperature.