Magnetic materials based on manganese–zinc ferrite with surface-organized polyaniline coating

Core–shell composites of manganese–zinc (MnZn) ferrite and polyaniline (PANI) have been prepared by the oxidation of aniline with ammonium peroxydisulfate in the presence of ferrite. The various reaction conditions allowed controlling the thickness of PANI coating, 50–250 nm. Complex magnetic permeability spectra of MnZn ferrite of various particles sizes, 25–250 μm, and of their composites with PANI, have been studied in the frequency range 1 MHz–10 GHz. The formation of a polymer p-semiconducting nanolayer on the surface of a MnZn ferrite particle changes the character of the frequency dispersion of the permeability. The interfacial effects between MnZn ferrite and PANI nanofilm are responsible for the shifts of resonance frequency from MHz closer to GHz. This effect strongly depends on the specific area of the ferrite–PANI interface and, moreover, on the properties of the PANI overlayer.