Abstract
A RLC electric circuit with magnetic core is studied experimentally and theoretically as a promising design of a metamaterial cell. Laminates made of multilayered ferromagnetic films are used as the magnetic core. The wire coiled around the core allows the frequency dependence of permeability to be adjusted according to needs of a particular task by creating a region of intensive magnetic loss below the ferromagnetic resonance frequency of the bare core. The theoretic analysis is based on the quasi-statics of magnetic fields and electric currents. The intensity of the loss peak is proportional to the value of μ′2/μ″, where μ′ and μ″ are the frequency-dependent components of permeability of the core material. The magnetic spectra of cells with cores made of laminates of NiFe films and FeCo films have been measured. It is shown that the application of the winding allows the magnetic loss peak to be shifted from 1 GHz to 0.3 GHz for NiFe and from 5 GHz to 0.7 GHz for FeCo. The effective imaginary permeability at the resonant frequency increases by the factors of 5 and 6, correspondingly. The theory agrees well with the measured data.
Highlights
The intensity and the shape of high-frequency magnetic loss peaks of magnetic materials is of great importance for technical applications of these
In publications dealing with metamaterials, such circuits are referred to as split ring resonators (SRR), see, e.g., Ref. 20
It is shown that the resonance frequency in the metamaterial cells with magnetic core can be controlled by concentrating magnetism of the core material in the desired frequency range around this very downshifted frequency
Summary
The intensity and the shape of high-frequency magnetic loss peaks of magnetic materials is of great importance for technical applications of these. As compared to the magnetic loss peak of the same magnetic sample without coil, the loss peak of the sample with wiring is shifted to lower frequencies Such materials have been studied in Ref. 10, where the effective permeability, μ=μ′–iμ′′, was measured as a function of the number of coil turns for a metamaterial cell made of a wire coil wound on a ferrite core,. That is why relatively large cell thicknesses, about 13 mm, are needed for high parameters of the metamaterial to be obtained Different geometries of such structures have been suggested.[11,12] Currently, metamaterials comprising ferromagnetic inclusions are widely employed as radar absorbers[13] and controllable electromagnetic materials,[14] with a full-wave simulation techniques typically employed instead of the equivalent circuit approach. Specific features of metamaterials with cores made of multilayer magnetic films are considered
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