Magnetic irreversibility and zero resistance in granular Y358 superconductor

We report on magnetization and magnetoresistance measurements of polycrystalline Y₃Ba₅Cu₈O₁₈ superconductor (Y358), prepared by solid state reaction in order to study the correlation between the magnetic irreversibility line and the zero electric resistance as a function of applied field. The magnetization measurements were performed using a MPMS-XL SQUID magnetometer and the magnetoresistance measurements were made using a PPMS, both from Quantum Design, up to 1 T. The granular microstructure was confirmed by scanning electron microscopy. In this case the grain junctions are weaker than in the Y123 system and the effect of the applied field on the grain couplings is much stronger. Consequently, in our sample the zero resistance line shifts away from the irreversibility line and is lower by more than 15 K at 1 T. We explain our results in terms of the superconducting glass model and in comparison with results obtained in other materials from the YBaCuO family