Magnetic Properties of Deposited CoPt Clusters and Nanoparticles

Magnetic properties of in situ prepared size selectedCoPt clusters deposited on magnetized substrates and of wetchemically synthesized 3.7 nm to 8.4 nm diameter CoPt nanoparticles on silicon in an externalfield of up to 7 T, were investigated with x-ray magnetic circulardichroism (XMCD). The magnetic moments were extracted using theXMCD sum rules, while some electronic properties, especially theoxidation state of the wetchemically prepared particles could beobtained 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 arein 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, theiroxidation state and the influence of aging was investigated in a time span of up to a 290 day.