We report on the first observation of a pronounced re-entrant superconductivity phenomenon in superconductor/ferromagnetic layered systems. The results were obtained using a superconductor/ferromagnetic-alloy bilayer of Nb/Cu(1-x)Ni(x). The superconducting transition temperature T_{c} drops sharply with increasing thickness d_{CuNi} of the ferromagnetic layer, until complete suppression of superconductivity is observed at d_{CuNi}= 4 nm. Increasing the Cu(1-x)Ni(x) layer thickness further, superconductivity reappears at d_{CuNi}=13 nm. Our experiments give evidence for the pairing function oscillations associated with a realization of the quasi-one dimensional Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) like state in the ferromagnetic layer.
@article{arxiv.cond-mat/0602448,
title = {Re-entrant superconductivity in Nb/Cu(1-x)Ni(x) bilayers},
author = {V. Zdravkov and A. Sidorenko and G. Obermeier and S. Gsell and M. Schreck and C. Müller and S. Horn and R. Tidecks and L. R. Tagirov},
journal= {arXiv preprint arXiv:cond-mat/0602448},
year = {2016}
}