Fluctuation diamagnetism in a zero-dimensional superconductor

The diamagnetic transition of ensembles of single-crystal aluminum particles with radii less than the superconducting coherence length ${\xi }_0$ has been measured over a wide range of temperature, field, and average radius. The particles are sufficiently small that the Ginzburg critical region is experimentally accessible. Fluctuation effects are observed inside and outside this critical region. The data agree with recent exact theoretical calculations based on the Ginzburg-Landau functional.