Spin Screening And Inverse Proximity Effect In F/S Nanostructures

Abstract

It is shown that the short‐range oscillating spin polarization of conduction electrons around magnetic moment embedded in the superconducting film is screened in aggregate by the long‐range antiferromagnetic term, which owes its origin to the Cooper pairing. On this base new exchange model and boundary value problem for the proximity effect in ferromagnet/superconductor (F/S) nanostructures are proposed. In the framework of this model we investigate the possible variants of the mutual accommodation of inhomogeneous superconducting and magnetic order parameters in the F/S nanostructures. The F/S systems of the first type allow only homogeneous ferromagnetic ordering in the F layers, which for the weak exchange fields h < h c coexists with superconductivity in the S layers (FS phase). In the F/S systems of the second type the FS phase exists only for h < h c1. For the exchange fields h c1 < h < h c2 the superconducting layers S induce the nonuniform cryptoferromagnetic modulation (CFS phase) in the spin structure of the F films. This phenomenon can be called as the magnetic (or inverse) proximity effect. The conditions for the coexistence of the inhomogeneous magnetism and superconductivity in the F/S nanostructures EuO/A1, EuO/V, EuS/A1, and LaCaMnO/YBaCuO are investigated and the nontrivial experimental data are interpreted.