GEOMETRICAL BARRIERS IN HIGH-TEMPERATURE SUPERCONDUCTORS

A theoretical description of vortex dynamics in thin flat samples is d erived and is found to compare favorably with experimental results. In perpendicular applied magnetic field the vortex penetration is delaye d significantly due to the presence of a potential barrier of geometri cal origin. This novel geometrical barrier effect results in hystereti c magnetization and in the existence of an irreversibility line in the absence of bulk pinning. Among the unique characteristics of the barr ier are a vortex concentration in the center of the sample and a zero- field peak in the magnetization loops.