Enhancement of the upper critical field in codoped iron-arsenic high-temperature superconductors

TL;DR

This study demonstrates that codoping in iron-arsenide superconductors significantly enhances the upper critical magnetic field, promising improved performance for high-field applications.

Contribution

First investigation of codoped (Sr/Ba)_(1-x)K_xFe_(2-y)Co_yAs_2 superconductors showing increased H_c2 compared to single-doped materials.

Findings

H_c2 extrapolated to 0 K reaches ~90 T in codoped samples

Codoping increases H_c2 compared to single-doped counterparts

Results suggest codoping as a method to optimize superconductors for high magnetic fields

Abstract

We present the first study of codoped iron-arsenide superconductors of the 122 family (Sr/Ba)_(1-x)K_xFe_(2-y)Co_yAs_2 with the purpose to increase the upper critical field H_c2 compared to single doped (Sr/Ba)Fe_2As_2 materials. H_c2 was investigated by measuring the magnetoresistance in high pulsed magnetic fields up to 64 T. We find, that H_c2 extrapolated to T = 0 is indeed enhanced significantly to ~ 90 T for polycrystalline samples of Ba_0.55K_0.45Fe_1.95Co_0.05As_2 compared to ~75 T for Ba_0.55K_0.45Fe_2As_2 and BaFe_1.8Co_0.2As_2 single crystals. Codoping thus is a promising way for the systematic optimization of iron-arsenic based superconductors for magnetic-field and high-current applications.