Critical properties of superconducting Ba1-xKxFe2As2

TL;DR

This study investigates the magnetic and superconducting properties of Ba1-xKxFe2As2 samples with different potassium doping levels, revealing critical field behaviors, high critical current densities, and superconducting transition characteristics under magnetic fields.

Contribution

It provides detailed measurements of critical fields, critical current densities, and transition behaviors in Ba1-xKxFe2As2, highlighting anomalous low-temperature HC1 increase and doping-dependent properties.

Findings

HC1 shows anomalous increase at low temperatures

Critical current density exceeds 10^4 A/cm^2 at 4.2 K and 5 T

dHC2/dT at TC is approximately -7.7 T/K and -5.6 T/K for x=0.40 and 0.50

Abstract

Magnetisation and magnetoresistance measurements have been carried out on superconducting Ba1-xKxFe2As2 samples with x=0.40 and 0.50. From low field magnetization data carried out at different temperatures below TC, HC1 has been extracted. The plot of HC1 versus temperature shows an anomalous increase at low temperatures. From high field magnetization hysterisis measurements carried out in fields up to 16 T at 4.2 K and 20 K, the critical current density has been evaluated using the Bean critical state model. The JC determined from the high field data is >104A/cm2 at 4.2 K and 5 T. The superconducting transitions were also measured resistively in increasing applied magnetic fields up to 12 Tesla. From the variation of the TC onset with applied field, dHC2/dT at TC was obtained to be -7.708 T/K and -5.57 T/K in the samples with x=0.40 and 0.50.