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

Memory effects (ME) in the solid vortex lattice (VL) are observed in a wide range of superconducting materials. Experiments in twinnedY Ba2Cu3O7 (YBCO) crystals in a DC magnetic field tilted respect to the twin planes indicate that ME in these samples cannot beascribed to an equilibration process. However, how extensive is this behaviour, has not been explored so far. In this work we studythe role of correlated defects in ME by performing angular ac susceptibility measurements in YBCO crystals. We conclude that, whenuncorrelated disorder prevails, either in twinned or untwinned samples, ME have their origin in the oscillatory character of the vortexdynamics.Fil: Bekeris, Victoria Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin