Effect of shell permutation on electromagnetic properties of ZnFeO4/(PANI, SiO2) core/double-shell nanostructured disks

Abstract

ZnFe2O4/PANI/SiO2 (ZPS) and ZnFe2O4/SiO2/PANI (ZSP) core/double-shell nanostructured disks comprising PANI conducting dielectric shell and SiO2 insulating dielectric shell on a disk-shaped ZnFe2O4 magnetic core are prepared to study the effect of shell permutation on their electromagnetic properties. The complex relative permittivity (εr=εr′−jεr″) and permeability (μr=μr′−jμr″) of ZPS and ZSP are measured, and the reflection loss (RL) is determined, together with the ZnFe2O4 core, in the 1–18 GHz range. εr′ and εr″ in ZPS and ZSP are smaller than the core because of the induction of disordered dipolar polarizations at various interfaces involving the insulating SiO2 shell. Two obvious dielectric and magnetic abnormalities are observed in ZPS and ZSP. First, εr″ is weakened in the dipolar polarization-rich ZPS when compared to the ZSP of relatively less dipolar polarization. Second, μr′ and μr″ in ZPS become the largest in the 1.5–10.8 and 5.6–18 GHz ranges, respectively, while μr″ in ZSP remains the lowest and changes to be negative in the 10–18 GHz range, among all samples. An electromagnetic energy transformation mechanism is proposed to explain the observed abnormalities and their effects on absorption.