Influence of magnetic losses on absorption of microwave electromagnetic radiation by nanocomposites based on carbon nanotubes with low concentration of ferromagnetic nanoparticles

Abstract

New magnetic nanocomposites based on carbon nanotubes (CNT) are very promising for high-frequency applications such as transmission lines, detectors, antennas, and absorbing materials. The absorbing properties of CNT nanocomposites are determined mainly by ohmic and dielectric losses. However, intercalated magnetic NP in a CNT matrix increase the absorption of nanocomposites because of magnetic losses. Experimental investigations are needed and theoretical approaches that consider various parameters of the nanocomposites must be developed for a deeper understanding of the interaction mechanisms of electromagnetic radiation and CNT nanocomposites. The goal of the present work was to establish the influence of changing the magnetic interaction between ferromagnetic NP intercalated into a CNT matrix on the microwave-absorbing properties of the nanocomposite. For this, the absorption of nanocomposites with a low concentration of ferromagnetic NP localized in the CNT matrix were studied by measuring the frequency dependences of the refl ection and transmission coeffi cients in the range 78–118 GHz. The concentration of ferromagnetic NP was set by the concentration CF of ferrocene [Fe(C5H5)2] in a ferrocene–o-xylene mixture during chemical vapor deposition (CVD) of the CNT. It was recently found that the NP magnetic anisotropy is substantial for CF < 1% and dominates over exchange coupling. The principal NP interaction mechanism for CF ≥ 1% is exchange coupling.