Nonuniform superconducting state in superconductor/ferromagnet nanoscale layered system

Abstract

Superconducting Nb/Ni bilayers, prepared by magnetron sputtering are investigated in the range of temperatures 1.3-10K. For specimens with constant Nb layer thickness a non- monotonic behavior of the critical temperature upon increasing of the Ni layer thickness with distinct oscillations of Tc(dNi) of the Ni layer is found. The results are interpreted in terms of Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) inhomogeneous superconducting state in the ferromagnetic Ni layer.