FeSe$_{0.5}$Te$_{0.5}$ thin films with critical current density above 1MA/cm$^{2}$

High quality FeSe$_{0.5}$Te$_{0.5}$ thin films have been prepared on various substrates, such as SrTiO$_{3}$, LaAlO$_{3}$ and YSZ, some with buffer layers. $T_{c}$'s as high as 20K with superconducting transition widths of about 1K were obtained. These $T_{c}$'s are much higher than those of bulk FeSe$_{0.5}$Te$_{0.5}$ ($\sim $15K). Our films carry high critical current densities $J_{c}$'s (above 1MA/cm$^{2})$ at liquid helium temperature. These films hold $J_{c}$'s above 1$\times$10$^{5}$A/cm$^{2}$ and very low $J_{c}$ anisotropies ($<$ 3) under magnetic fields as high as 30T at 4.2K. We have also prepared textured FeSe$_{0.5}$Te$_{0.5}$ thin films on a buffered metal template with results similar to the ones mentioned above. This shows that iron chalcogenides have a very promising future for high-field applications at liquid helium temperatures. Pinning force analysis indicates the presence of a point defect flux-pinning mechanism, suggesting a straightforward approach to conductor optimization.