Microwave refraction coefficient in nanocomposites and nanostructures in magnetic field

摘要

Microwave refraction coefficient is studied for two types of composites and for metallic (CoFe)/Cu nanostructures. Nanocomposites of the first type are prepared on the base of artificial opal matrices with embedded particles of nickel-zinc ferrite and metallic cobalt. The introduced particles are sized from 5 to 60 nm. The composite material of the second type is prepared of permalloy flakes sized about 2 - 50 μm placed into epoxy amine matrix. At frequencies of centimeter and millimeter waveband the magnetic field dependences of transmission and reflection coefficients have been measured. The complex refractive coefficients are obtained as a function of magnetic field. The complex refraction coefficient can be expressed via the effective dielectric permittivity and magnetic permeability. Analysis of magnetic field dependences of refraction coefficient shows that strong variations are observed near ferromagnetic resonance. For metallic nanostructures there are also variations of the refraction coefficient caused by giant magnetoresistive effect.