Memory effects in the dynamics of the vortex lattice in YBCO crystals; the role of correlated defects

Abstract

Memory effects (ME) in the solid vortex lattice (VL) are observed in a wide range of superconducting materials. Experiments in twinned<br />Y Ba2Cu3O7 (YBCO) crystals in a DC magnetic field tilted respect to the twin planes indicate that ME in these samples cannot be<br />ascribed to an equilibration process. However, how extensive is this behaviour, has not been explored so far. In this work we study<br />the role of correlated defects in ME by performing angular ac susceptibility measurements in YBCO crystals. We conclude that, when<br />uncorrelated disorder prevails, either in twinned or untwinned samples, ME have their origin in the oscillatory character of the vortex<br />dynamics.