Coexistence of superconductivity and superparamagnetism in Pb-Co electrodeposited nanowires

Pb-Co nanowires were electrodeposited in 100 nm nominal pore diameter polycarbonate membranes. Above the TC of Pb we modelled the behaviour of the wires with a Langevin function, obtaining a Co volume of (1.06±0.01)×10^-7 cm³ divided into clusters of ≈10 atoms in size. The magnetic response of the wires in the 3 K to 10 K interval, which comprises T_C, was modelled by adding spherical superconducting Pb grains to the Co clusters; the Pb grains were found to be (87±6) nm in diameter. The Co clusters were not interacting and were not magnetically screened by the superconducting Pb.