Fluctuating diamagnetism in the critical region of the superconducting transition in lead nanoparticles

High resolution SQUID magnetization measurements in Lead nanoparticles are presented and discussed in terms of the fluctuation-related diamagnetism in the critical region of the transition to the superconducting state, where the first-order fluctuation theory breaks down. Exact expressions of the magnetization are derived from the Ginzburg-Landau functional in zerodimensional condition (i.e. for grain size lesser than the coherence length) and are used to achieve insights on the properties of the critical fluctuating diamagnetism.