Thermally activated flux flow in FeSe0.5Te0.5 superconducting single crystal

The current-voltage (J-E) isotherms of single crystal FeSe0.5Te0.5 sample have been measured at several temperatures near the transition temperature (T-c) and under applied magnetic fields (H). A power law (E similar to J(beta)) has been used to fit the data and evaluate the activation energy U-o (T) using beta = U-o/k(B)T. At low current density (J<>J(c) vortex flux flow (FF) behavior is expected. The effects of applied magnetic field on FF and TAFF also been investigated. We found that U-o(FF) was reduced with by about an order of magnitude in magnetic fields as low as similar to 1.5 Tesla -the reduction in U-o(TAFF) is even faster than in U-o(FF)-hence reflecting the low pinning nature (defects, vacancies etc.) of FeSe0.5Te0.5 superconductor.