Weak localization in FeSe1-xTex superconducting thin films

We have investigated the magneto-resistivity (MR) of FeSe1-xTex superconducting films on MgO substrate. The MR of pure FeSe and slightly Te-substituted films demonstrates regular Lorentz-type magnetic field dependence, MR similar to B-2. In highly Te-substituted samples, however, negative MR contribution due to the weak-localization effect gradually dominates at low temperature, which is consistent with the evolution of the temperature dependence of resistivity from a metallic to a weakly semiconductor-like behavior. Furthermore, the negative MR weakens and turns positive as temperature approaches the superconducting transition temperature, which is evidence for the Maki-Thompson correction in the weak-localization regime. The experimental data can be described very well by the weak-localization theory with the existence of scattering by some magnetic moments. The fitting parameters demonstrate that disorder most likely comes from the excess iron