Unusually high critical current of clean P-doped BaFe2As2 single crystalline thin film

TL;DR

This study reports that P-doped BaFe2As2 thin films exhibit exceptionally high critical current densities and elevated superconducting transition temperatures due to in-plane tensile strain, making them promising for high-field magnet applications.

Contribution

It demonstrates that strain and doping can significantly enhance the critical current density and Tc in P-doped BaFe2As2 thin films, revealing new potential for superconductor applications.

Findings

Critical current density over 6 MA/cm2 at 4.2 K

In-field Jc exceeds 0.1 MA/cm2 at 35 T for H||ab

Superconducting Tc over 30 K with low P content

Abstract

Microstructura lly clean, isov alently P-doped BaFe2As2 (Ba-122) single crystalline thin films have been prepared on MgO (001) substrates by molecular beam epitaxy. These films show a superconducting transition temperature (Tc) of over 30 K although P content is around 0.22, which is lower than the optimal one for single crystals (i.e., 0.33). The enhanced Tc at this doping level is attributed to the in-plane tensile strain. The strained film shows high transport self-field critical current densities (Jc) of over 6 MA/cm2 at 4.2 K, which are among the highest for Fe based superconductors (FeSCs). In-field Jc exceeds 0.1 MA/cm2 at m0H = 35 T for H||ab and m0H = 18 T for H||c at 4.2 K, respectively, in spite of moderate upper critical fields compared to other FeSCs with similar Tc. Structural investigations reveal no defects or misoriented grains pointing to strong pinning centers. We relate this unexpected high Jc to a strong enhancement of the vortex core energy at optimal Tc, driven by in-plane strain and doping. These unusually high Jc make P-doped Ba-122 very favorable for high-field magnet applications.