Nanoscale magnetic materials have attracted increasing interests due to technological importance in magnetic data storage, chemical/biological sensing as well as catalytic applications. The ability to control the surface chemistry is important for these applications, which also governs the magnetic properties. In this presentation, recent results of an investigation of the synthesis, assembly and application of magnetic nanoparticles and their core@shell composite nanoparticles from the organic system will be described. The nanoscale magnets are derived from magnetic cores such as g-Fe2O3, Fe3O4 and gold shell. The interparticle ligand exchange–crosslinking-precipitation chemistry have been demonstrated at the gold shell for assembling thin films of Fe-oxide@Au nanoparticles. The resulting core@shell nanocomposites have been characterized using TEM, XRD, XPS, UV-Vis, DCP-AES, and SQUID techniques. While magnetization, remance magnetization, blocking temperature, and susceptibility were found to decrease after coating iron oxide seeds with Au shells, the coercivity was shown to increase with Au coating. Implications of the findings to the design of novel nanomagnets will be discussed.