Abstract
The onset of vortex penetration into micron-sized disks and squares is studied using local magnetization measurements. The vortex penetration field is observed to exceed the lower critical field at all temperatures below the superconducting transition temperature The magnitude of is determined by sample size and geometry. Below 15 K, is approximately proportional to the sample width D, consistent with the Bean bulk pinning model. Above 15 K, is a function of the sample thickness-to-width ratio and agrees with the Bean-Livingston surface-barrier effect.
- Received 16 November 2001
DOI:https://doi.org/10.1103/PhysRevB.65.184506
©2002 American Physical Society