Crossover behaviors in magnetoresistance oscillations for Nb thin film with rectangular arrays of antidots

Superconducting Nb thin films with rectangular arrays of submicron antidots (holes) have been systemically investigated by transport measurements. A series of crossover behaviors is found in magnetoresistance oscillations, corresponding to three different superconducting states: the wire network-like state, the interstitial vortex state and the single-loop-like state. These states are identified by the field intervals and hysteretic effect. The crossover fields between them are found to be both temperature and geometry dependent. Furthermore, in dense arrays, the saturation number is distinctly larger than the theoretical calculation for a single insulating inclusion. Our results indicate that in the process of magnetic field penetration into nanostructured superconductors, the order parameters are strongly modulated and finally localized near the edges, resulting in changes of oscillation modes. Copyright (C) EPLA, 2012