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Magnetic Properties of Transition Metal-Dendrimer Nanocomposites Richard A. Fry, Robert D. Shull, Srinivas Uppuluri1, and Lajos Balogh1 Metallurgy Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8552, U.S.A. 1 University of Michigan Center for Biologic Nanotechnology, University of Michigan, Ann Arbor, MI 48109-0533, U.S.A. ABSTRACT Magnetic nanocomposites have been successfully prepared by encapsulating nanosized entities of iron, cobalt, and nickel compounds in poly(amido-amine) (PAMAM) dendrimer hosts. Problems related to the instability of the magnetic structures under the influence of an external electromagnetic field have been overcome by using a solid polystyrene matrix to embed the dendrimer hosts containing the magnetic guests. SQUID magnetometry measurements on these nanocomposites showed that after subtraction of the diamagnetic polymer background, at 300 K all samples exhibited paramagnetic behavior, with susceptibilities of 1.14, 1.68, and 0.70 × 10-6 m3/kg for Fe-, Co-, and Ni-containing samples respectively. The temperature dependence for T