Reentrant superconductivity in Nb/Cu1-xNix bilayers

We report on the first observation of a pronounced reentrant superconductivity phenomenon in a superconductor/ferromagnet layered system. The results were obtained using a superconductor/ferromagnetic-alloy bilayer of Nb/Cu1-xNix. 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)approximate to 4 nm. Increasing the Cu1-xNix 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-like state in the ferromagnetic layer.