Dielectric-ferrite film heterostructures for magnetic field controlled resonance microwave components

An investigation of the composite “α-Al2O3 dielectric resonator-thick ferrite film” heterostructures magnetic field tunable microwave properties has been conducted. Thick high-density high-quality NiFe2O4 spinel and M-type hexaferrite BaFe12O19 films were deposited on the surface of the dielectric by tape-casting technique. Specific organic suspensions for ferrite films synthesis were developed; optimal conditions for pre-heat treatment and annealing have been defined. It was found, that magnetic field has a profound impact on microwave transmission characteristic of composite resonator, including peak absorption level and unloaded Q-factor. Both effects were attributed to increase of the magnetic part of the composite resonator internal losses at frequencies close to ferromagnetic resonance. Since qualitatively similar results were obtained for both cm-wave (with nickel ferrite) and mm-wave (with barium hexaferrite) resonators, the proposed method of electronic control over dielectric resonator properties can be successfully utilized in a very broad frequency range, basically, from few GHz to more than 100 GHz.