Model calculation of size effects in orbital magnetism

Size effects in the orbital magnetic susceptibility of small metallic systems are investigated by considering some simple model systems. The atomlike properties at low temperatures gradually evolve towards a diamagnetism close to the bulk Landau value at high temperatures, with only small size-dependent deviations. For ${\mathit{k}}_{\mathit{B}}$T smaller than the energy-level spacing, the susceptibility of an ensemble average of different particles is expected to show orbital paramagnetism. This mechanism is proposed as an explanation for the observations of Kimura and Bandow.