VORTEX CONFIGURATION AND DYNAMICS IN BI2SR1.8CACU2OX THIN-FILMS BY LORENTZ MICROSCOPY

Vortices in Bi2Sr1.8CaCu2Ox thin films were directly observed by Loren tz microscopy as the sample temperature T was raised from 4.5 K under fixed magnetic fields H. Each time T was raised, vortices moved, event ually to settle in a new static configuration. Vortices began to form a regular lattice at a temperature depending on H. The vortex-lattice image remained visible until it gradually faded away around an irrever sibility temperature T(H). Careful examination of the disappearance t emperature indicates that the vortex lattice may persist up to some te mperature above T(H).