Andreev bound states in superconductor/ferromagnetic junctions

Assuming tunneling perpendicular to the layers, Andreev bound states are studied theoretically in atomic-scale S/F superlattices, where S is a conventional superconductor, and F is a ferromagnet. The nonmonotonic dependence of the critical current on the exchange field h in F layers is a consequence of (pi) -phase formation. The shape of the spectra of spin-splitted densities of states (DOS) depends strongly on h and on the transfer integral t between the layers; for an appropriate choice of these parameters zero-energy bound states (ZES) may appear. Considering in-plane tunneling in high-T_c S/F/S Josephson weak links with thin, ferromagnetic metal barrier, DOS is calculated assuming that the a-axes of the crystals in two S electrodes are misoriented for an angle (theta) . In the anisotropic d-wave case the number of peaks in DOS, corresponding to the Andreev bound states, can be greater than in the isotropic s-wave case. DOS strongly depends on h, (theta) , and on the macroscopic phase difference (phi) across the link.