Critical current density and mechanism of vortex pinning in KxFe2-ySe2 doped with S

TL;DR

This study investigates how sulfur doping affects the critical current density and vortex pinning mechanisms in KxFe2-ySe2 crystals, revealing optimal doping levels and the dominance of small normal point defects in vortex pinning.

Contribution

It provides new insights into the enhancement of critical current density through sulfur doping and identifies the dominant vortex pinning mechanism in these materials.

Findings

Optimal S doping significantly increases Jc.

Weak fishtail effect observed for H||c.

Vortex pinning dominated by small normal point defects.

Abstract

We report the critical current density Jc in KxFe2-ySe2-zSz crystals. The Jc can be enhanced significantly with optimal S doping (z=0.99). For K0.70(7)Fe1.55(7)Se1.01(2)S0.99(2), the weak fishtail effect is found for H||c. The normalized vortex pinning forces follow the scaling law with a maximum position at 0.41 of the reduced magnetic field. These results demonstrate that the small size normal point defects dominate the vortex pinning mechanism.