Tunable microwave band-stop filters using ferromagnetic resonance

摘要

In this paper, we present some results on FeCoB-based microwave band-stop filters. These structures, prepared on GaAs substrates, are compatible in size and growth process with on-chip high-frequency electronics. The band-stop filters have been realized with microstrips which incorporate ferromagnetic and dielectric layers to absorb microwave energy at the ferromagnetic resonance (FMR) frequency. The absorption notch in transmission can be tuned to various frequencies by varying an external applied magnitic field. For our devices, which incorporate FeCoB as the ferromagnetic material, the resultant FMR frequencies range from 12-22 GHz for applied fields up to only 1000 Oe. Comparatively, the frequency range of those devices using permalloy and Fe is substantially lower than FeCoB-based devices for applied the same fields. We constructed devices using monocrystalline FeCoB films grown in a sputtering system. Our devices are of different construction than other dielectric microstrips and show much improvement in terms of notch width and depth. The maximum attenuations of 3.5 dB/cm and 90dB/cm are observed respectively in two different structures.