Magnetic and Microwave Properties of Nanocomposites Containing Iron Particles Encapsulated in Carbon

The magnetic and microwave properties of nanocomposites containing iron particles encapsulated in a carbon shell (Fe@C), as well as carbon nanotubes (CNT), have been experimentally studied. The examination of magnetic properties of composites shows that the materials under study contain a ferromagnetic component. The availability of ferromagnetic ordering for the dielectric matrix-based nanocomposite sample with Fe@C particles has been confirmed by the measurement results of the transmission and the reflection coefficients of the microwaves, since the ferromagnetic resonance has been observed. Furthermore, in the fields less than the field of ferromagnetic resonance, there are the signs of the presence of ferromagnetic antiresonance. The ferromagnetic resonance leads to minima in the transmission and reflection coefficients, whereas the antiresonance, conversely, leads to maxima in the reflection coefficient. The measurement results have been compared with the theoretical calculations of the field dependence of microwave transmission and reflection coefficients.