0 and π phase Josephson coupling through an insulating barrier with magnetic impurities

We have studied the temperature and field dependencies of the critical current ${I}_{C}$ in the $\mathrm{Nb}\text{\ensuremath{-}}{\mathrm{Fe}}_{0.1}{\mathrm{Si}}_{0.9}\text{\ensuremath{-}}\mathrm{Nb}$ Josephson junction with a tunneling barrier formed by a paramagnetic insulator. We demonstrate that in these junctions coexistence of both the 0 and the $\ensuremath{\pi}$ states within one tunnel junction occurs, and leads to the appearance of a sharp cusp in the temperature dependence ${I}_{C}(T)$, similar to the ${I}_{C}(T)$ cusp found for the $0\text{\ensuremath{-}}\ensuremath{\pi}$ transition in metallic $\ensuremath{\pi}$ junctions. This cusp is not related to the $0\text{\ensuremath{-}}\ensuremath{\pi}$ temperature-induced transition itself, but is caused by the different temperature dependencies of the opposing 0 and $\ensuremath{\pi}$ supercurrents through the barrier.