Magnetic Properties of Deposited CoPt Clusters and Nanoparticles

Magnetic properties of in situ prepared size selected CoPt clusters deposited on magnetized substrates and of wetchemically synthesized 3.7 nm to 8.4 nm diameter CoPt nanoparticles on silicon in an external field of up to 7 T, were investigated with x-ray magnetic circular dichroism (XMCD). The magnetic moments were extracted using the XMCD sum rules, while some electronic properties, especially the oxidation state of the wetchemically prepared particles could be obtained from the x-ray absorption measurements. The magnetism of small deposited alloy clusters and particles may depend on their size, their composition and the substrate they are in contact with. To gain fundamental understanding size selected clusters of only a few atoms were deposited on a weakly and on a strongly exchange coupling substrate, while the composition and size of the clusters was varied between measurements. For the much larger, as prepared organic ligand covered wetchemically synthesized nanoparticles, their saturation magnetization, their oxidation state and the influence of aging was investigated in a time span of up to a 290 day.