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 a spatially heterogeneous transparency of the SF interface has been studied. It is shown that, at a certain thickness of the F layer, a stepwise variation of the transparency leads to the formation of a region of size ∼ξ F (coherence length in a ferromagnet), where the Josephson supercurrents of different signs may flow. This may lead to the dependence of the junction critical current on the external magnetic field qualitatively different from the Fraunhofer pattern typically observed in usual Josephson junctions.