Electrical Transport in Polyaniline-Barium Ferrite Nanocomposites with Negative Giant Magnetoresistance

The barium ferrite/polyaniline (BaFe12O19/PANI) nanocomposites with room temperature negative giant magnetoresistance (GMR) are fabricated by the surface-initiated polymerization (SIP) method. The maximum negative GMR value is -7.1% in BaFe12O19/PANI nanocomposites with a BaFe12O19 loading of 20 wt % at a magnetic field of 9 T. The electrical transport mechanism of these samples is investigated by thermally activated transport (TAT) model at the high temperature range (180-290 K) and Mott variable range hopping (VRH) mechanism at the low temperature range (50-180 K). The results reveal that the electrical transport of pure PANI and BaFe12O19/PANI nanocomposites obeys the 3-D VRH mechanism. The estimated activation energy (E) (related to the energy required for charge carrier hopping process) for pure PANI and BaFe12O19/PANI nanocomposites with a BaFe12O19 loading of 10, 20, 30, and 40 wt % is calculated to be 38.5, 47.0, 52.1, 53.8, and 66.8 meV, respectively, according to the TAT model. With the aim of explaining the negative GMR phenomenon in BaFe12O19/PANI nanocomposites, the forward interference model is introduced, demonstrating the localized length of carriers varies with the applied magnetic field