Au nanoparticles exhibit ferromagnetic spin polarization and show diameter dependence in magnetization. The magnetic moment per Au atom in the particle attains its maximum value at a diameter of about 3 nm in the magnetization-diameter curve. Because Au metal is a typical diamagnetic material, its ferromagnetic polarization mechanism is thought to be quite different from the ferromagnetism observed in transition metals. The size effect strongly suggests the existence of some spin-correlation effect at the nanoscale. The so-called “Fermi hole effect” is the most probable one given in the free-electron gas system. Ferromagnetism in Au nanoparticles is discussed using this model.

• Received 10 June 2003

DOI:https://doi.org/10.1103/PhysRevB.69.174411