Negative magnetoresistance of polymer nanocomposites on the basis of PP + Fe3O4 and PVDF + Fe3O4 in the magnetic field

In the present study, we report about the influence of an external permanent magnetic field on electrical resistivity and dielectric permittivity of PP + Fe3O4 and PVDF + Fe3O4 based nanocomposites. It was found that independent of the type of polymer the electric resistivity of both polymer nanocomposites decreases under the influence of a magnetic field and the negative magnitoresistive effect has been observed. Investigation of MR in PP + Fe3O4 and PVDF + Fe3O4 based nanocomposites showed that at room temperature the concentration dependence of MR is identical for both systems. However, the electrical resistance of the PVDF + Fe3O4 based nanocomposite was found to reduce strongly in comparison with that of the nanocomposite based on PP + Fe3O4 under the influence of a magnetic field. This could be explained by the fact that the diamagnetic anisotropy and the charge carriers’ density of these polymers are quite different from each other. Negative magnetoresistance of composite films with ferromagnetic nanoparticles incorporated in dielectric matrix is due to the tunneling transitions of electrons between neighboring nanoparticles. Decrease in dielectric permittivity under a magnetic field is consistent with negative magnetoresistive effect.