Quantum description of ferromagnet metal nanoparticles

The quantum physics of normal metal nanoparticles can be understood simply by recognizing the discreteness of individual electron eigenenergies and the dominant role played by Coulomb interactions in determining the rate at which the chemical potential increases with electron number. Ferromagnetic metal nanoparticles, on the other hand, have collective magnetization degrees of freedom that are responsible for additional low energy excitations. We discuss some issues that arise in attempting to achieve a unified and consistent quantum description of both collective and quasiparticle physics in magnetic metal nanoparticles, especially when acknowledging the essential role of spin–orbit coupling and the magnetic anisotropy it produces.