Effect of interstitial iron on Jc and Hc2 anisotropy and magnetic relaxation of Fe1+yTe0.6Se0.4 single crystal

For a long time, the second peak effect in FeTe0.6Se0.4 has attracted the interest of researchers. The role of interstitial iron which is unique to FeTe0.6Se0.4 compared to FeSe superconductors, in the second peak effect remains unknown. In this study, we controlled the content of interstitial iron through flowing oxygen and prolonged vacuum annealing, and subsequently conducted investigations on the magnetic flux dynamics and superconducting properties with anisotropies. After reducing the interstitial iron content, Tc increased from 12.6 K to 13.8 K. The critical current density at 4.5 K increased from 1.2×105 A/cm2 to 1.76×105 A/cm2. At low fields (HMore