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.