On-Wafer Microwave Devices based on Magnetic Materials

We present a review of theoretical and experimental results for tunable microwave band-stop filters, band-pass filters, phase shifters, and a signal to noise enhancer, all based on a microstrip geometry and using a variety of magnetic thin films and layered structures.  These devices are compatible in size and growth process with on-chip high-frequency electronics.  For devices based on metallic ferromagnetic films of Fe and Permalloy, the operational frequency ranges from 5 to 35 GHz for external fields below 5 kOe.  For the band-stop filters, we observed power attenuation up to ∼100 dB/cm, and an insertion loss on the order of ∼2–3 dB, for both Permalloy and Fe-based structures.  We also will discuss the use of thin films of hexagonal ferrites, and liquid crystals/magnetic nano-rods colloids, and show these materials can be used to make on-wafer microwave devices.  The devices based on hexagonal ferrite operate in the frequency range 35-70 GHz while devices based on liquid crystal/magnetic nano-rods colloids operate in the frequency range 5 - 110 GHz. We will also review the properties of hexagonal ferrites doped Al and grown on Si substrates in details.