Surface spin disorder effects in magnetite and poly(thiophene)-coated magnetite nanoparticles

Chemically synthesized magnetite and poly(thiophene)-coated magnetite nanoparticles and the correlations between their magnetic, structural, and microstructural properties are investigated. A typical superparamagnetic behavior was observed for faceted nanoparticle agglomerates of magnetite and nanocomposite. In nanocomposites, the polymer layer causes a sharp decrease in the spin disorder, which reduces the anisotropy constant significantly. This happens because the intimate contact between magnetite and poly(thiophene) leads to charge transfer from the polymer to the core via polaron interactions, causing a structural rearrangement of the nanoparticles and suppression of the spin movement at the surface. As this dynamic interaction can tune the core dimensions, the magnetic properties of nanocomposites can be tuned by controlling the core size through polymer coating. These characteristics can be exploited to design high-performance magnetically tunable nanodevices and applied in many areas of biomedicine (DNA separation, drug targeting, immune detection, and magnetic nanoparticle hyperthermia in cancer treatment). (C) 2010 American Institute of Physics. [doi:10.1063/1.3488634]