Inversion of the proximity effect in atomic-scale ferromagnet/superconductor/ferromagnet trilayers

Abstract

Atomic thickness ferromagnet/superconductor/ferromagnet (F/S/F) trilayers are studied theoretically in the framework of the Green’s functions formalism. The superconducting critical temperature is determined for an arbitrary orientation of the exchange field in the ferromagnetic layers, and this temperature is shown to be always higher for the antiparallel configuration. The superconducting order parameter is calculated at all temperatures, for both the parallel and antiparallel alignment; it appears that at low temperatures, the superconducting gap can be higher in the parallel configuration, in contrast with the critical temperature. This anomalous behavior of the gap is called here “inversion of the proximity effect.” We clarify the conditions for this inversion. Similar inversion takes place for the case of half-metal F-layers. Finally, we show that the electronic paramagnetism in the F-layers is enhanced by its interaction with the superconductor. For the parallel alignment the electronic spin polarization in the S-layer is also increased below the critical temperature.

Source-reported materials — not catalogue approval

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