2017 Volume 52 Issue 6 Pages 443-447
Since the discovery of Fe-based superconductors (FBS), great progress in the growth of single crystals and thin films of these materials have been made. Now high-quality FBS thin films are available, which spurs progress in fundamental and application research. In this paper, we report on the transport properties of epitaxial SmFeAs(O,F) and Fe(Se,Te) thin films. We found vortex trapping and lock-in caused by the Sm(O,F) blocking layer in SmFeAs(O,F) when the magnetic field is close to the ab-plane. The vortex trapping is hallmarked by a drop of the exponent n in E~J n (E and J are electric field and current density), whereas a local peak within the dip of n is a sign of the vortex lock-in. Interestingly, vortex trapping and lock-in were also observed in Fe(Se,Te), albeit Fe(Se,Te) shows a low superconducting transition temperature and low anisotropy.
