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Published online by Cambridge University Press: 21 February 2011
Giant magnetoresistance (GMR) as large as 25% at 25°C has been observed for multilayer ultrathin films of iron oxide (Fe3O4) nanoclusters and polyimide molecules alternately adsorbed onto single crystal silicon and quartz substrates using a novel self-assembly technique. This process involves the alternate dipping of a substrate into an aqueous solution of anionic polyimide precursor (polyamic salt, PAA) followed by dipping it into an aqueous solution of cationic polydiallyldimethylammonium chloride (PDDA)-coated Fe3O4, nanoparticles. The regular formation of alternating monolayers is verified by UV-vis spectroscopy and contact angle measurements. Vibrating sample magnetometry indicates the formation of ultrasoft films.