Giant Magnetoresistacne in Conducting Polymers and Their Nanocomposites

In this talk, the fundamentals of giant magnetoresistance (GMR) in the conducting polymers and their nanocomposites are presented. Both positive and negative GMR can be obtained in the conducting polymers and their nanocomposites for the highly disorderedly localized system in the Mott variable range hopping regime. The obtained positive GMR in the silica/polyaniline nanocomposites is analyzed by the wave-function shrinkage model and negative GMR is interpreted by the forward interference model. The results have found that the GMR is related to the changed localization length (a₀), density of states at the Fermi level (N(E_F)), and average hopping length R_hop. An observed transition from positive to negative GMR in the silicon/polyaniline nanocomposites is around magnetic field of 5.5 T. The theoretical analysis reveals that both the wave-function shrinkage model and the forward interference model contribute to the positive GMR and only forward interference model is responsible for the observed negative GMR.