Tunable negative permittivity and permeability in FeNiMo/Al2O3 composites prepared by hot-pressing sintering

FeNiMo/Al2O3 composites with different FeNiMo content were prepared by hot-pressing sintering. Interestingly, simultaneous negative permittivity and permeability were realised in FeNiMo/Al2O3 composites with 30% FeNiMo content in the frequency range of 860 MHz to 1 GHz and in the frequency range of 890 MHz to 1 GHz for composites with 40% FeNiMo content. Experimental results and theoretical simulations indicate that the negative permeability is caused by the domain wall resonance and gyromagnetic spin resonance, while the negative permittivity is attributed to the plasma oscillation of conduction electrons and LC resonance. The negative permittivity of the FeNiMo/Al2O3 composite induced by the plasma oscillation of conduction electrons was analyzed using the Drude model. The fitting results indicated that the plasma frequency of the composites was 8.99 GHz. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.