High attenuation tunable microwave notch filters utilizing ferromagnetic resonance

We have constructed a series of microstrips for transmission of microwaves. These microstrips incorporate ferromagnetic and dielectric layers and therefore 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 magnetic field. For our devices, which incorporate Fe as the ferromagnetic material, the resultant FMR frequencies range from 10-20 GHz for applied fields up to only 1000 Oe. This frequency range is substantially higher than those found in devices utilizing a dielectric ferrimagnet such as YIG. We constructed devices using monocrystalline Fe films grown in a molecular beam epitaxy system. Our devices are of different construction than other Fe dielectric microstrips and show much improvement in terms of notch width and depth. We observed maximum attenuation on the order of 100 dB/cm, much larger than previously reported values of 4 dB/cm. (C) 2000 American Institute of Physics. [S0021- 8979(00)70308-2].