Plasticity and memory effects in the vortex solid phase of twinned YBa2Cu3O7 single crystals

摘要

We report on marked memory effects in the vortex system of twinned YBa2Cu3O7single crystals observed in ac susceptibility measurements. We show that thevortex system can be trapped in different metastable states with variabledegree of order arising in response to different system histories. The pressureexerted by the oscillating ac field assists the vortex system in ordering,locally reducing the critical current density in the penetrated outer zone ofthe sample. The robustness of the ordered and disordered states together withthe spatial profile of the critical current density lead to the observed memoryeffects.