Double-reversal thickness dependence of critical current in superconductor-ferromagnet-superconductor Josephson junctions

TL;DR

This paper reports the first experimental observation of a double-reversal in the critical current's thickness dependence in superconductor-ferromagnet-superconductor Josephson junctions, revealing transitions between 0 and pi states.

Contribution

It provides the first experimental evidence of the two-node thickness dependence and develops a theoretical model incorporating spin-flip scattering to explain the observations.

Findings

Critical current exhibits two nodes as ferromagnet thickness varies.

Transitions between 0 and pi states are observed at specific thicknesses.

Theoretical calculations align well with experimental data.

Abstract

We report the first experimental observation of the two-node thickness dependence of the critical current in Josephson junctions with a ferromagnetic interlayer. Vanishings of the critical current correspond to transitions into pi-state and back into conventional 0-state. The experimental data allow to extract the superconducting order parameter oscillation period and the pair decay length in the ferromagnet. We develope a theoretical approach based on Usadel equations, which takes into account the spin-flip scattering. Results of numerical calculations are in good agreement with the experimental data.