The effect of nano-sized superparamagnetic particles on the dielectric constant of polyimide

Abstract

We propose that dynamically induced internal fields be utilized in obtaining materials with low dielectric constant at high frequencies. We also demonstrate the validity of the proposal by measuring the effective dielectric constant of polyimide dispersed with nanosized Ni0.6Zn0.4Fe2O4 particles. The dielectric constant of a polyimide composite measured at 1 MHz increases as a function of Ni0.6Zn0.4Fe2O4 contents when the diameter of the embedded particles is approximately 20 nm. On the other hand, the measured dielectric constant of a composite containing superparamagnetic particles of diameter approximately 6 nm showed much smaller value than that of pure polyimide. These contrasting behaviors indicate that the induced internal fields are in operation, in reducing the dielectric constant, for a material with superparamagnetic particles.