Magnetic field, temperature and electric field dependence of magneto-transport for polyaniline nanofiber networks

We report large magnetoresistance (up to 55% at T = 2.5 K and H = 8 T) for polyaniline nanofiber networks. Magneto-transport behavior has been studied at low and high magnetic and electric fields for temperatures 2–250 K. A crossover from positive magnetoresistance (MR) to negative MR is observed at ∼ 87.5 K. Two competing mechanisms which account for the MR behavior are shrinkage of localized electron wavefunctions and destruction of the quantum interference of wavefunctions of electrons propagating along various paths during charge hopping processes in the applied magnetic field. We also observed that the magnitude of positive magnetoresistance decreases with increasing electric field which we propose is due to decrease in the activation energies in hopping process.