We report on the observations of spontaneous spin polarized moments in 7.4 nm Pb/PbO nanoparticles, which give rise to re-entrantlike temperature profiles for the magnetic susceptibility and magnetization in the superconducting phase that develops below 6.86 K. Results reveal the existence of a magnetic component below T(C) and superconductivity remains at low temperatures. A 30-fold increase in the critical magnetic field is also found. Superconductivity mainly arises from the 5 nm Pb core, whereas the 1.2 nm PbO shell contributes to the appearance of a net magnetic moment in the 7.4 nm Pb/PbO core/shell particles. (C) 2011 American Institute of Physics. [doi:10.1063/1.3561766]
