Growth, characterization, vortex pinning, and vortex flow properties of single crystals of the iron chalcogenide superconductor FeCr0.02Se

We report on the growth and characterization of single crystals of the iron chalcogenide superconductor FeCr0.02Se. There is an enhancement of the superconducting transition temperature (T-c) as compared to the T-c of the single crystals of the parent compound Fe1+xSe by about 25%. The superconducting parameters such as the critical fields, coherence length, penetration depth, and the Ginzburg-Landau parameter have been estimated for these single crystals. Analysis of the critical current data suggests a fluctuation in the electronic mean free path induced (delta l) pinning mechanism in this material. Thermally activated transport across the superconducting transition in the presence of external magnetic fields suggests a crossover from a single vortex pinning regime at low fields to a collective flux creep regime at higher magnetic fields. The nature of charge carriers in the normal state estimated from the Hall effect and thermal transport measurements could provide crucial information on the mechanism of superconductivity in Fe-based materials