Negative dielectric permittivity and high-frequency diamagnetic responses of percolated nickel/rutile cermets

Materials with negative permittivity have attracted considerable attention due to their promising applications in various electromagnetic equipment and electronic devices. Herein, percolative nickel/rutile cermets were sintered, of which the dielectric and magnetic properties were investigated in radio-frequency region. With nickel content increasing, electrical conductivity of the percolative cermets increased dramatically and the conduction mechanism changed from hopping to metallic behavior. Enhancement of positive permittivity in the percolating cermets was attributed to the increased interfacial polarization, while negative permittivity of the percolated cermets with nickel content exceeding percolation threshold was caused by plasma oscillation of delocalized electrons. Meanwhile, magnetic permeability of the epsilon-negative cermets was smaller than 1, which was resulted from the induced high-frequency diamagnetic response of eddy currents within the interconnected conductive networks. This work elucidated the anomalous dielectric and magnetic properties of percolated cermets and determined diamagnetism is an inherent nature of epsilon-negative metacomposites at high frequency.