Electric-Field-Triggered Electromagnetic Polarizations in the Close-Packed Fe at C Nanocapsules

We investigated microwave absorption properties of the close-packed Fe at C nanocapsules under an external electric-field stimulus. The results indicate that the reflection parameter (S
₁₁
) linearly increases as the applied voltage ranging from 0 to 12 V at 18 to 26.5 GHz (K-band) frequencies, while the transmission parameter (S
₂₁
) remains constant. Such tunability is a consequence of the energy transfer between the permeability and the permittivity, physically originating from the multiple dielectric polarizations at the core at shell interfaces, ascribed to the electric-field induced asymmetric distribution of localized charge. The present finding might open up a new avenue for designing smart microwave absorbers targeted to complex serving environments.