Quantum Size Effects in the Magnetic Susceptibility of a Metallic Nanoparticle

We theoretically study quantum size effects in the magnetic response of a spherical metallicnanoparticle (e.g. gold). Using the Jellium model in spherical coordinates, we compute the inducedmagnetic moment and the magnetic susceptibility for a nanoparticle in the presence of a static external magnetic field. Below a critical magnetic field the magnetic response is diamagnetic, whereasabove such field the magnetization is characterized by sharp, step-like increases of several tenths ofBohr magnetons, associated with the Zeeman crossing of energy levels above and below the Fermi sea. We quantify the robustness of these regimes against thermal excitations and finite linewidth ofthe electronic levels. Finally, we propose two methods for experimental detection of the quantumsize effects based on superconducting quantum interference devices.