Size effect of nanomagnetite on magnetoresistance of core-shell structured polyaniline nanocomposites

In this work, magnetoresistive nanomagnetite@polyaniline (Fe 3 O 4 @PANI) composites with a core-shell structure were prepared by in situ polymerization method with KH-550 as coupling agent. All the samples demonstrated the positive MR, and compared with PANI composites reinforced with small (diameter 80 nm) size or large (diameter 450 nm) size of Fe 3 O 4 , the PANI composites reinforced with medium (diameter 220 nm) size of Fe 3 O 4 exhibit the largest MR (8.41%) when the MK-F loading is 60 wt%. Moreover, the size effect of Fe 3 O 4 particles on the electrical conductivity and MR behavior was analyzed by the Mott VRH model and wave functional shrinkage model. The MR value of Fe 3 O 4 @PANI composites with different loading and size of Fe 3 O 4 particles mainly depends on localization length, density of state at Fermi level, and average hopping length. Moreover, the Fe 3 O 4 @PANI composites were systematically characterized by SEM, TEM, XRD, and FT-IR. This work could provide the guidance for fabrication of magnetic field sensors and information memory storage devices. Graphical Abstract The core-shell structured magnetite/polyaniline nanocomposites with tunable magnetoresistance by changing the size of magnetite nanoparticle.