Control over magnetic spectrum of multilayer magnetic film metamaterial

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.