Magnetic field-controlled 0-$\pi$ transitions and their experimental signatures in superconductor-ferromagnet-superconductor junctions

TL;DR

This paper demonstrates that external magnetic fields can control 0-$$ transitions in superconductor-ferromagnet-superconductor junctions, revealing new experimental signatures and expanding control methods beyond temperature and layer thickness.

Contribution

The study introduces magnetic field control of 0-$$ transitions in SFS junctions and shows how to detect these transitions through flux-flow conductivity measurements.

Findings

Magnetic field can induce 0-$$ transitions in SFS junctions.

Transitions are detectable for large exchange energies by adjusting diffusion coefficients.

Flux-flow conductivity features reveal the 0-$$ transitions in experiments.

Abstract

Superconductor-ferromagnet-superconductor Josephson junctions are known to exist in the $0$ and $\pi$ states with the transitions between them controlled by the temperature and ferromagnetic interlayer thickness. We demonstrate that these transitions can be controlled also by the external magnetic field directed perpendicular to the layers. By varying the ratio of diffusion coefficients in superconducting and ferromagnetic layers, these field-controlled transitions can be made detectable for arbitrary large value of the exchange energy in the ferromagnet. We also show that the $0$-$\pi$ transitions in the perpendicular field can be observed as the specific features of the flux-flow conductivity dependencies on the ferromagnetic thickness in accordance with recent experimental results.