Robust coupling of superconducting order parameter in a mesoscale NbN-Fe-NbN epitaxial structure

Abstract

We report an unconventional and promising route to self-assemble distributed superconductor-ferromagnet-superconductor (S-F-S) Josephson junctions on single crystal [100] MgO. These structures consist of [110] epitaxial nanoplaquettes of Fe covered with superconducting NbN films of varying thickness. The S-F-S structures are characterized by a strong magnetoresistance (MR) anisotropy for the in-plane and out-of-plane magnetic fields. The stronger in-plane MR suggests decoherence of S-F-S junctions whose critical current follows a (1-T/T_c) and (1-T/T_c)^1/2 dependence for T ≈ T_c and T  T_c, respectively, in accordance with the theory of supercurrent transport in such junctions.