Fluxoid dynamics in superconducting thin film rings

We have measured the dynamics of individual magnetic fluxoids entering and leaving photolithographically patterned thin film rings of the underdoped high-temperature superconductor Bi2Sr2CaCu2O8+δ, using a variable sample temperature scanning superconducting quantum interference device microscope. These results can be qualitatively described using a model in which the fluxoid number changes by thermally activated nucleation of a Pearl vortex in, and transport of the Pearl vortex across, the ring wall. © 2003 The American Physical Society.