A study of the magnetic and electromagnetic properties of γ-Fe2O3–multiwalled carbon nanotubes (MWCNT) and Fe/Fe3C–MWCNT composites

A ferromagnetic γ-Fe2O3–MWCNT composite was prepared by a reverse microemulsion technique, and was transformed to a Fe/Fe3C–MWCNT composite by further heat-treatment in H2 atmosphere at 950 °C. TEM result suggests that MWCNTs are both surface decorated and filled with γ-Fe2O3 or Fe/Fe3C nanoparticles. The saturation magnetization and anisotropy field are particularly strong for Fe/Fe3C–MWCNT. The reflection loss of Fe/Fe3C–MWCNT is better than that of γ-Fe2O3–MWCNT at all frequencies between 2 and 18 GHz, resulting from enhanced magnetic loss and better matched characteristic impedance, rather than electric loss, as shown by the complex relative permeability image and permittivity image. The microwave absorbing properties can be modulated simply by manipulating the thickness of the prepared Fe/Fe3C–MWCNT composite for application in different frequency bands.