Proximity effect as a probe of electronic correlations and exchange field in ferromagnet/superconductor nanostructures

Abstract

The proximity effect for thin bilayer F/S and trilayer F/S/F, where F is a ferromagnetic metal, and S is superconductor, is investigated on the base of new boundary-value problem for the Eilenberger function. For both systems the dependencies of critical temperature on an exchange field of the F metal, electronic correlations in the S and F metals, and thicknesses of layers F and S are derived. It is shown that the possibility of the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state observation is especially increased in the asymmetrical trilayers F/S/F ′ for which solitary reentrant superconductivity is predicted. We propose new method of probe of electronic correlations and exchange field. It allows us to predict the sign and value of the constant of electron–electron interaction in gadolinium and to explain a surprisingly high critical temperature ( T c ∼ 5 K ) in the short-periodic Gd/La superlattice.