Extraordinary magnetic field behavior of SIFS Josephson junctions with an inhomogeneous transparency of the FS interface

Within the framework of the Usadel equations the Josephson effect in a superconductor-insulator-ferromagnet-superconductor (SIFS) structure with spatially heterogeneous transparency of the SF interface has been studied. It is shown that at a certain thickness of the F-layer a step-like variation of the transparency leads to the formation of a region of size $\sim\xi_F$ (coherence length in a ferromagnet) where the Josephson supercurrents of different signs may flow. This may lead to a dependence of the junction critical current on the external magnetic field qualitatively different from the Fraunhofer pattern typically observed in usual Josephson junctions.