Magnetism of Nanoclusters and Nanocluster-Assembled Materials You Qiang University of Idaho Department of Physics Since the Stern-Gerlach Experiment demonstrated space Quantization in 1922, molecular (cluster) beam physics has developed into a strong and active branch of condensed matter physics. Free clusters of simple metals and molecules have been thoroughly investigated and well understood, such as magnetism of free transition metals. For most technological application, such as GMR, TMR and extremely high-density storage, the properties of deposited or embedded nanoclusters are more important than those free ones. There is now a big challenge to synthesize nanomaterials using free nanoclusters as building blocks. Our newly developed cluster source can produce monodispersed nanoclusters with a mean size range from 1 to 100 nm and very high intensity (>5 A/s). The nanocluster beam, combined with two atom beams from magnetron sputtering, is used to deposit simultaneously or alternately nanoclusters films or multilayers. The new nanomaterials are synthesized by controlling independently the incident cluster size, concentration and nanostructures to have a wide variety of controlled optical, electronic, magnetic, mechanical and chemical properties for many technological applications. I will focus on magnetic properties of them. Cluster size distribution and nano-crystalline structures have been studied by TOF, AFM, SEM and HRTEM. Magnetic properties of nanoclusters and nanocluster-assembled materials have been investigated by SQUID and MFM. An interesting dependence of magnetization was found on the cluster size and the volume fraction of Co (or Fe) clusters in Cu, SiO2 and Fe (or Co). First-principle calculations are used to analyze the experimental data in terms of the cluster-matrix interface effects and the intercluster exchange interactions. For further understanding the nature of these cluster-assembled films, the magnetic x-ray circular dichroism (MXCD) measurements have been performed. A more enhanced magnetic moment and orbital moment will be discussed. Finally I will give some possible applications of cluster films: (1) CoPt or FePt nanocluster-assembled materials for perpendicular recording media, (2) core-shell structured clusters as bio-magnetic sensors, (3) room temperature ferromagnetic semiconductor nanoclusters (Co or Ni doped-ZnO) for spintronics and optical applications.