Effects of Iron Contents on the Vortex State in Fe x Se0.5Te0.5
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We investigate the effects of iron content on the upper critical field (H c2) and the activation energy U(T) in thermally activated flux flow in Fe x Se0.5Te0.5 near the superconducting transition temperature T c . The variations in H c2(T) with temperature are analyzed using Ginzburg-Landau (GL), Werthamer-Helfand-Hohenberg (WHH) models along with the empirical relation (ER). The obtained values of H c2(0) depend strongly on the model and the criteria used to determine the transition temperature. However, the general trend is that that H c2(0) increases with the increasing Fe content. The activation energy U(T) is maximum for x = 1 and rapidly suppressed by excess or deficiency of iron. The low values of U(T) (∼10 meV) reflect the low vortex-pinning nature (due to defects, vacancies, etc.) in the Fe x Se0.5Te0.5 superconductor.
KeywordsFe-based superconductors Activation energy Werthamer-Helfand-Hohenberg (WHH) models
We would like to acknowledge the support of King Fahd University of Petroleum & Minerals for this work. We also would like to acknowledge the support of the Imam Abdulrahman Bin Faisal University to this work.
This project has been funded by NSTIP under project number 11-ADV1631-04.
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