In recent years Josephson junctions with ferromagnetic F layers became one of the most desirable and actively developed devices in superconductive electronics. Magnetic properties of F-layer provide to create high-speed Josephson superconductive memory elements [1]. Moreover oscillating nature of superconductive proximity effect in the magnetics leads to appearance of π state in this type of Josephson junction. These π-junctions can be implemented in the RSFQ-circuits and significantly increase their performance [2]. In more complicated superconductor-ferromagnet hybrids the φ-state occurs with an arbitrary ground phase on the junction. These devices also can be implemented for memory elements [3] and different quantum systems [4].
Unfortunately, characteristic voltage, ICRN, of conventional SFS junctions and SF1F2S spin-valves is much smaller than that of tunnel SIS devices, which are widely used in superconductive electronics. This leads to deficient value of characteristic frequency and to difficulties in integration with other circuits.
As possible way to solve this task we considered Josephson SIsFS structures with complex interlayer consisting of tunnel barrier ‘I’, ferromagnetic layer ‘F’ and thin superconductor layer ‘s’ and we outlined operational modes of these junction. Due to superconductive support inside weak link this structure achieves both high frequency and has magnetic properties. Thus SIsFS can be used as high-speed π junction or memory element [5-6].
However pairing in the thin middle superconductive film ‘s’ suffers from proximity effect with ferromagnetic layer and stays in the critical regime. It means that state of that layer significantly depends from inhomogeneities in ferromagnetic layer. We study impact on current properties of different types of inhomogeneities including domains walls and normal phaseinclusions.
This work was supported by the Ministry of Education and Science of the Russian Federation, grant № 14Y26.31.0007
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