Magnetic properties of polyvinyl alcohol-based composites containing iron oxide nanoparticles

This paper describes the magnetic behaviour of polymer nanocomposites conta ining nanoparticles (similar to 10 nm) of maghemite gamma-Fe2O3 and magneti te Fe3O4 in a polyvinyl alcohol matrix, The compositions were synthesised u sing an original method of in situ preparation, the reaction of oxide forma tion taking place inside the polymer matrix itself. It is the one-domain-pe r-particle nature of magnetism in the given polymer nanocomposites that was found to be responsible for such a distinctive feature as superparamagneti sm detected using Mossbauer spectroscopy and magnetisation measurements. A giant negative magnetoresistance was found in the highly filled composition s. As far as we know, this is the first time that this effect has been obse rved in polymer composites based on ferrite nanoparticles, Copyright (C) 19 99 John Wiley & Sons, Ltd.