Heterogeneous interfacial polarization in Fe@ZnO nanocomposites induces high-frequency microwave absorption

We report on the microwave absorption properties of Fe@ZnO nanocapsules composed of a ferromagnetic Fe core and a dielectric ZnO shell. By integrating such heterogeneous components in each particle, it results in reciprocal resonances for the relatively complex permeability and permittivity at ∼15 GHz, contributing to efficient complementarities between the dielectric and magnetic losses. Therefore, more than 90% microwave power can be attenuated at 8.2-18 GHz. X-ray photoelectron spectra reveals that the origin of reciprocal resonances is induced by the electronic interactions at Fe and ZnO interfaces. The present work has important implications in the understanding the physical mechanism of dielectric behaviors at heterogeneous interfaces.