Electromagnetic wave absorption by magnetic colloids with conductive filler in the centimeter range

Abstract

Placing non-magnetic microparticles in a magnetic colloid makes it possible to control them by means of a magnetic field, which allows the creation of tunable composite materials. The choice of microparticles with appropriate properties can enable the creation of materials with tunable absorption of electromagnetic microwaves, which may be of interest in device engineering and radar detection. An experimental and theoretical study of the interaction of super high frequency electromagnetic waves with magnetic colloids containing microparticles of conductive filler (aluminum) under the additional influence of a constant magnetic field has been carried out in this work. The studies were performed using a cell based on a coaxial cable in the frequency range of 5–18 GHz. It was found that the formation of chain structures of aluminum particles in the magnetic field leads to a significant increase in the absorption coefficient of electromagnetic energy. The character of the frequency dependence and the absolute values of the absorption and reflection coefficients depend on the volume concentration of the conductive filler in a complex way. To interpret the obtained results, numerical modeling of the investigated system in the effective medium approximation by the finite element method has been carried out. The anisotropic distribution of electromagnetic energy losses in the transmission line is demonstrated.