Decoupled superconductivity in the four- and five-layered ferromagnet-superconductor nanostructures and control devices

The ferromagnet/superconductor (F/S) tetra- and pentalayer consisting of rather dirty metals are considered with regard for the boundary conditions. The dependences of critical temperatures Tc versus the thicknesses of the F layers are investigated. The clearest manifestation of decoupled superconductivity for the F′/S′/F″/S″ tetralayer is the rise of a hierarchy of transition temperature Tc, and different S′ and S″ layers can have different critical temperatures. The same is valid for nonsymmetrical case of the F′/S′/F″/S″/F‴ pentalayer. The complicated phase diagram of the tetralayer is discussed. The inverse action of superconductivity on magnetism leads to preferable mutual antiferromagnetic orientation of magnetizations of the F′ and F″ layers, if the inner S′ layer is in the superconducting state. Conceptual scheme of the new nanoelectronics control device, that has up to seven different states and combine in one sample the advantages of two different recording channels, is proposed.