Vortex pinning and irreversibility fields in FeS1–xSex (x = 0, 0.06)

Abstract

We report strong vortex pinning and large irreversibility fields in single crystals of tetragonal FeS1–xSex (x = 0, 0.06). Vortex dynamics is characterized by crossover in field dependence of the depinning energy U0, indicative of single flux surface pinning to the region of collective flux pinning on point-like defects. The close proximity of the irreversibility lines to the upper critical field (Hc2) is consistent with strong pinning in FeS and FeS0.94Se0.06, pointing that new materials with building-blocks of FeS4 tetrahedra are likely to host high critical currents.