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

TL;DR

This paper demonstrates a novel method for self-assembling superconductor-ferromagnet-superconductor Josephson junctions on MgO substrates, revealing strong magnetoresistance anisotropy and specific temperature dependencies of critical current.

Contribution

It introduces a new approach to create S-F-S Josephson junctions using epitaxial nano-plaquettes, advancing understanding of their magnetoresistance and supercurrent behavior.

Findings

Strong magnetoresistance anisotropy observed

Critical current follows specific temperature dependencies

Successful self-assembly of S-F-S junctions on MgO

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 nano-plaquettes of Fe covered with superconducting NbN films of varying thickness. The S-F-S structures are characterized by 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/Tc) and (1-T/Tc)1/2 dependence for T Tc and T<<Tc respectively, in accordance with the theory of supercurrent transport in such junctions.