Observation of Re-entrant Resistance in NbN/NbO/Co Trilayer
Transport measurements on a niobium nitride (NbN) film covered with a ferromagnetic cobalt layer are reported here. The sample shows a superconducting transition (T SC) at 6.5 K. In the superconducting state, a dip in resistance is observed at a temperature referred to as T MIN. Below T MIN, resistance reappears, with a magnitude of about 1% of the normal-state resistance. The observed resistance is found to decrease on increasing the applied current (I). A possible reason for re-entrant resistance might be the vortex dynamics in NbN superconducting layer due to the stray fields created by the Co layer. Further confirmation of the observed behavior is obtained from the plot of resistance versus probe current measured at various temperatures in close vicinity of T SC.
KeywordsSuperconductor Ferromagnetic Vortices