Influence of point defects on the vortex state of disordered superconductors - art. no. 172505

We report on a strongly pinned entangled vortex liquid state in the presenc e of random point disorders in complex ternary (Nd-Eu-Gd)Ba2Cu3O7-delta twi nned single-domain melt-textured samples. The in-plane and out-of-plane res istance measurements show that vortex lines are correlated along the c axis with finite vortex correlation length in the pinned liquid state. This is due to the correlated pinning promoted by the twin boundary. The vortex cor relation length can be quenched by increasing the defect density by introdu cing more second-phase precipitates or oxygen defects favoring an entangled vortex liquid state depending on the defect density.