Synthesis of high-entropy-alloy-type superconductors (Fe,Co,Ni,Rh,Ir)Zr2 with tunable transition temperature

TL;DR

This study synthesizes high-entropy-alloy-type superconductors TrZr2 with various compositions, demonstrating that the HEA site allows systematic tuning of the superconducting transition temperature, which varies with lattice parameters.

Contribution

It introduces a new class of HEA-type superconductors TrZr2 and shows how their Tc can be systematically tuned through composition and structural modifications.

Findings

All samples exhibit bulk superconductivity.

Transition temperature Tc varies with composition and lattice parameters.

HEA site enables systematic Tc tuning across a wide temperature range.

Abstract

We report on the synthesis and superconductivity of high-entropy-alloy-type (HEA-type) compounds TrZr2 (Tr = Fe, Co, Ni, Rh, Ir), in which the Tr site satisfies the criterion of HEA. Polycrystalline samples of HEA-type TrZr2 with four different compositions at the Tr site were synthesized by arc melting method. The phase purity and crystal structure were examined by Rietveld refinement of X-ray diffraction profile. It has been confirmed that the obtained samples have a CuAl2-type tetragonal structure. From analyses of elemental composition and mixing entropy at the Tr site, the HEA state for the Tr site was confirmed. The physical properties of obtained samples were characterized by electrical resistivity and magnetization measurements. All the samples show bulk superconductivity with various transition temperature (Tc). The Tc varied according to the compositions and showed correlations with the lattice constant c and Tr-Zr bond lengths. Introduction of an HEA site in TrZr2 is useful to achieve systematic tuning of Tc with a wide temperature range, which would be a merit for superconductivity application.