UC Davis

Strong superconducting pinning effects are observed from magnetic landscapes produced by arraysof circular rings with varying magnetic remanent states. The collective and the background pinningof superconducting Nb films is strongly enhanced by the stray magnetic field produced by an arrayof circular Ni rings magnetized to form “onion” (bidomain) states. On the other hand, whenthe same rings are magnetized into vortex (flux-closed) states, or are randomly magnetized, thesuperconducting pinning is much smaller. The greatest pinning is produced when thesuperconducting vortex lattice motion is along a direction in which there is a strong magnetic fieldvariation.