Susceptibility of Fe atoms in Cu clusters

By putting a Kondo system of limited dimension inside an insulating matrix, the Kondo screening cloud is confined by the size of the system. This allows us to distinguish the bulk and nano-particle behaviors of such system. We have investigated the magnetic properties of 0.3 at. % Fe-doped Cu clusters with dimensions less than 20 nm embedded in a SiO 2 matrix. The magnetic measurements are consistent with the Kondo interaction, and net antiferromagnetic Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions between several Fe atoms in one cluster are estimated to have a very small effect. To understand the low-temperature susceptibility reduction, we compare Brillouin functions with exact quantum-mechanical solutions for interacting spin-1 particles and with the Kondo predictions for confined nanoparticles.