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Layered ferromagnet-superconductor structures: the $π$ state and proximity effects

Klaus Halterman·Oriol T. Valls
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Abstract

We investigate clean mutilayered structures of the SFS and SFSFS type, (where the S layer is intrinsically superconducting and the F layer is ferromagnetic) through numerical solution of the self-consistent Bogoliubov-de Gennes equations for these systems. We obtain results for the pair amplitude, the local density of states, and the local magnetic moment. We find that as a function of the thickness $d_F$ of the magnetic layers separating adjacent superconductors, the ground state energy varies periodically between two stable states. The first state is an ordinary "0-state", in which the order parameter has a phase difference of zero between consecutive S layers, and the second is a "$π$-state", where the sign alternates, corresponding to a phase difference of $π$ between adjacent S layers. This behavior can be understood from simple arguments. The density of states and the local magnetic moment reflect also this periodicity.

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Klaus Halterman, Oriol T. Valls. 2003-07-16. Layered ferromagnet-superconductor structures: the $π$ state and proximity effects. https://doi.org/10.1103/physrevb.69.014517

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