Exotic Proximity Effects in Superconductor/Ferromagnet Structure

Abstract

We study a possibility to obtain a new type of superconductivity (s-wave, triplet, odd in Matsubara frequencies) in superconductor/ferromagnet (S/F) structures. A special attention is paid to multilayered S/F structures with the magnetization vector inclined in neighboring F layers by an angle a. It is shown that not only a singlet, but also triplet component exists in the structure which penetrates into the F layers over a long distance. The long-range penetration of the triplet component insures the Josephson coupling. The sign of the Josephson coupling between the nearest S layers (Sand S +1) depends on chirality of the system, i.e., on sign of the product α α α +1. Therefore in-plane superconductivity in the structure is caused by the singlet component and transverse superconductivity is due to the triplet component (odd superconductivity). We also study ferromagnetism induced in the superconductor due to the inverse proximity effect. It turns out that the magnetization M induced in S is opposite to M in the ferromagnet and spreads over a distance of order of the correlation length.