Magnetization, Susceptibility and Critical Currents of $(Tl_{2-x}Re_{x})Ba_{2}CaCu_{2}O_{y}$ Thin Films

The magnetization and the AC susceptibility vs. the temperature as well as the applied magnetic field of the thin film $(Tl_{2-x}Re_{x})Ba_{2}CaCu_{2}O_{y}$ with x=0 and 0.15 on R-plane sapphire substrate with $CeO_{2}$ buffer layer were measured and analyzed. XRD measurements show c-axis as well as a-b plane oriented Tl-1212 and superconducting pure phase. The zero critical temperature of the Tl-Re sample is 99.9 K and is practically the same as the critical temperature of the rhenium free sample: 99.5 K. The Tl-Re superconductor exhibits two peaks of the absorption part of AC susceptibility in the vicinity of the critical temperature in contrary to the rhenium free sample. The first peak placed in higher temperature is related to intragranular properties while the second peak is connected with the intergranular one. The critical current densities versus temperature were calculated from AC susceptibility as well as from the magnetization loops measurements using the Bean's critical state model. The Tl-Re film exhibits the higher critical current in comparison to the rhenium free thallium based film.