Spin polarization and orbital effects in superconductor-ferromagnet structures

Abstract

We study theoretically spontaneous currents and magnetic field induced in a superconductor-ferromagnet (S-F) bilayer due to direct and inverse proximity effects. There are two types of contributions to the induced currents. One is the Meissner current, which appears even in the absence of an external magnetic field due to the magnetic moment in the ferromagnet and to the magnetization in the superconductor. The second contribution is due to a space-dependent magnetization in the superconductor which is induced by the inverse proximity effect over a distance of the order of the superconducting correlation length ξS. In contrast, the magnetic induction B, caused by the Meissner currents, penetrates the S film over the London length λS. Even though λS usually considerably exceeds the correlation length, the amplitude and sign of B at distances much larger than ξS depend crucially on the strength of the exchange energy in the ferromagnet and on the magnetic moment induced in the S layer.

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