Improvement of upper critical field by the compositionally-complex-alloy concept in A15 superconductor V3X (X: Al, Si, Ga, Ge, Sn)

TL;DR

This study demonstrates that applying the compositionally complex alloy concept to V3X superconductors significantly enhances their upper critical field, with the V3X alloys showing higher Bc2(0) than V3Ge due to multiple high-entropy phases.

Contribution

It introduces the use of compositionally complex alloys in A15 superconductors, revealing increased upper critical fields through high-entropy phase mixing.

Findings

V3X exhibits bulk superconductivity with Tc of 6.4 K.

Bc2(0) of V3X is approximately 8.8 T, ~50% higher than V3Ge.

Presence of at least five high-entropy phases in V3X.

Abstract

Compositionally complex alloys (CCAs) are a new category of high-entropy materials containing more than two high-entropy phases in an alloy sample. We applied the concept of CCA to a A15-type compound superconductor V3X where X site is occupied by Al, Si, Ga, Ge, and Sn. The V3X sample shows bulk superconductivity with a transition temperature (Tc) of 6.4 K, which is close to the Tc of V3Ge. The upper critical field (Bc2(0)) of V3X estimated from magnetic susceptibility is 8.8 T, which is ~50% higher than that of V3Ge (Bc2(0) = 5.8 T). The presence of at least five different A15 phases with high configurational entropy of mixing were revealed. We consider that the examined V3X sample is an example system of CCA-type superconducting intermetallic compound.