Inter- and Intragrain Magnetization of Thallium-Based Superconductors

Abstract

We report on magnetization and magnetic hysteresis measurements for the (Tl$\text{}_{0.6}$Bi$\text{}_{0.5}$)(Sr$\text{}_{0.9}$Ba$\text{}_{0.1}$)$\text{}_{2}$Ca$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{y}$ Ag-sheathed superconducting tape as well as for the powdered and bulk (Tl$\text{}_{0.6}$Pb$\text{}_{0.5}$)(Sr$\text{}_{0.9}$Ba$\text{}_{0.1}$)$\text{}_{2}$Ca$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{y}$ superconductors. For the investigated tape and bulk specimens the low field magnetization showed a deviation from the ideal linear M(H) dependence, which was attributed to the superposition of inter- and intragrain superconducting currents. Fitting of the theoretical magnetization curves to the experimental data allowed for the independent determination of the intragrain critical current densities for the superconducting grains and intergrain critical current densities for the weak link system at 77K