Superconductor-ferromagnet-superconductor π-junctions

Superconductor-ferromagnet-superconductor (SFS) pi-junctions(1) were investigated experimentally. The transitions to pi-state and back to the conventional 0-state were found to result from temperature decrease or ferromagnetic interlayer thickness increase. Thickness dependence of the critical current was studied and nonmonotonic behavior was observed. The SF-proximity effect was also examined on SF-bilayers. It is shown that, due to the spatial oscillations of the induced superconducting order parameter in the ferromagnet, the critical temperature of the SF-bilayer has a minimum when the thickness of the ferromagnetic layer is close to a quarter of the oscillation period.