Incorporation of ferromagnetic metallic films in planar transmission linesfor microwave device applications

We constructed a series of microstrip and co-planar microwave waveguides. T hese structures use metallic ferromagnets and therefore exhibit strongly fr equency-dependent attenuation and phase-shift effects. The lines have maxim um attenuation peaks occurring at the ferromagnetic resonance frequency, wh ich increases with applied magnetic field. Such properties are used in band -stop filters. The devices used monocrystalline Fe films grown by Molecular Beam Epitaxy and polycrystalline sputtered permalloy films. For our device s that incorporated Fe the band-stop frequencies ranged from 10-20 GHz for applied fields up to only 80 kA/m (1000 Oersted). For devices using permall oy, the band-stop frequency was in the 5-10 GHz range for applied fields le ss than 80 kA/m. The maximum power attenuation was about 100 dB/cm, much la rger than the previously reported values of 4 dB/cm. The resonance conditio n also affects the phase of the transmitted wave, strongly changing phase a bove and below the resonance frequency. The result is a phase-shifter that is tunable with applied magnetic field. We observed phase changes of over 3 60 degrees /cm with an applied field of less than 40 kA/m.