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 Nb-Fe_0.1Si_0.9-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 π 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-π transition in metallic π junctions. This cusp is not related to the 0-π temperature-induced transition itself, but is caused by the different temperature dependencies of the opposing 0 and π supercurrents through the barrier.