Thermally activated phase slip and variable range hopping in Tm(Ba_(2-x)Pr_x)Cu_3O_(7+δ)

摘要

The magnetoresistance measurement of single phase polycrystalline TmBa_(2-x)Pr_xCu_3O_(7+). samples have been analyzed by the Ambegaokar and Halperine (AH) phase slip model. The magnetic field dependence of pinning energy power factors increase with the increase of Pr doping. The derived critical current density from the AH theory decreases with increasing magnetic field and Pr-doping for all superconducting samples. It shows that the Pr-doping plays the role of weak link. We have also investigated the normal state resistivity with the hopping model. We have found a CG-VRH cross-over with the increase of Pr content near metal insulator transition. The deacrease of the localization length of the carriers show that Pr-doping strongly localizes the carriers, and finally causes the suppression of superconductivity.