Giant magnetoresistance behavior of an iron/carbonized polyurethane nanocomposite

This letter describes the magnetoresistance (MR) behavior of the heat treated polyurethane composites reinforced with iron nanoparticles. The flexible nanocomposites were fabricated by the surface-initiated-polymerization method. The uniformly distributed nanoparticles within the polymer matrix, well characterized by field emission scanning electron microscopy, favor a continuous carbon matrix formation, rendering the transition from insulating to conductive composites. The coercive forces reflect strong particle loading and matrix dependent magnetic properties. By simply annealing in a reducing environment, the obtained nanocomposites possess a MR of 7.3% at room temperature and 14% at 130 K occurring at a field of 90 kOe. © 2007 American Institute of Physics