Magnetism in Free Clusters and in Mn12O12-Acetate Nanomagnets

Novel properties and behaviors have been found to emerge as the size of the material is reduced from the bulk to the nanometer or sub-nanometer regime [1]. These include atomic clusters containing ten to several thousand atoms, nanoscale materials, mono- and multi-layers, clusters deposited on surfaces, and the nanocrystal superlattices. The atomic arrangements and the physical, chemical, electronic, and the magnetic properties of these new materials can be vastly different from those of the individual atoms/molecules or the solids. This novelty arises not by a shear reduction in size, but by the occurrence of an entirely new class of phenomenon inherent to or becoming dominant at the reduced size. Further, the properties evolve with size, dimension and the composition. These developments have provided hope that novel materials with entirely new properties could be synthesized. This new era of nano-technology is expected to revolutionize the science and technology in the 21st century. It is, however, clear that the renewed promise rests on our ability to fundamentally understand the behavior of matter at small sizes or dimensions and to produce these materials in large quantities. It is important to note that for practical applications, the clusters or nano-particles have to be assembled to form nano-composites, deposited on substrates, or made to assemble in superlattices. A fundamental understanding of the role of interface is therefore critical to any applications.