Comparison of Gd addition effect on the superconducting properties of FeSe0.5Te0.5 bulks under ambient and high-pressure conditions

TL;DR

This study compares how Gd addition affects the superconducting properties of FeSe0.5Te0.5 bulks under ambient and high-pressure conditions, revealing that high-pressure synthesis enhances critical current density despite Gd's limited impact on transition temperature.

Contribution

It provides a systematic analysis of Gd doping effects combined with different synthesis methods on FeSe0.5Te0.5 superconductors, highlighting the role of high-pressure synthesis in improving critical current density.

Findings

High-pressure synthesis enhances Tc and Jc of parent compound.

Gd addition increases lattice parameter c but decreases Tc.

High-pressure Gd-added samples show improved Jc due to better grain connectivity.

Abstract

We have prepared a series of (FeSe0.5Te0.5 + xGd) bulk samples, with x = 0, 0.03, 0.05, 0.07, 0.1 and 0.2, through the convenient solid-state reaction method at ambient pressure (CSP). High gas pressure and high-temperature synthesis methods (HP-HTS) are also applied to grow the parent compound (x = 0) and 5-wt% of Gd-added bulks. Structural, microstructural, transport and magnetic characterizations have been performed on these samples in order to draw the final conclusion. Our analysis results that the HP-HTS applied for the parent compound enhances the transition temperature (Tc) and the critical current density (Jc) with the improved sample density and intergrain connections. The lattice parameter c is increased with Gd additions, suggesting a small amount of Gd enters the tetragonal lattice of FeSe0.5Te0.5 and the Gd interstitial sites are along the c-axis. A systematic decrease of the onset transition temperature Tc is observed with Gd additions, however, the calculated Jc of these Gd-added samples is almost the same as that of the parent compound prepared by CSP. It specifies that there is no improvement of the grain connections or pinning properties due to these rare earth additions. However, Gd-added FeSe0.5Te0.5 bulks prepared by HP-HTS have revealed a slightly improved critical current density due to improved grain connections and sample density but have a lower transition temperature than that of the parent compounds.