Abstract. The natural resonance appears at 16 GHz for (Fe, Ni)/C nanocapsules with (Fe, Ni) alloys as cores and graphite as shells. Reflection loss (RL) exceeding 10 dB was obtained in the whole Ku-band (12.4–18 GHz) for an absorber thickness of 2.0 mm, while it exceeds 20 dB over the 13.6–16.6 GHz range. In addition, the bandwidth does not change dramatically for the thicknesses of …