The use of M-type barium hexagonal ferrite ͑BaM͒ thin films for self-biased planar millimeter wave notch filters was demonstrated for the first time. The BaM film was grown by pulsed laser deposition and showed a remanent to saturation magnetization ratio of 0.99 and a 60 GHz ferromagnetic resonance linewidth of about 300 Oe. The filter consisted of a BaM film element positioned on the top of a coplanar waveguide and showed a band-stop response at 53 GHz for zero external fields. This filtering response resulted from power absorption due to magnetostatic wave excitation in the BaM film.

A hexagonal ferrite thin film-based planar millimeter-wave phase shifter was demonstrated. The device made use of an M-type barium ferrite ͑BaM͒ thin film prepared by pulsed laser deposition and a coplanar waveguide geometry. The phase tuning relied on ferromagnetic resonance in the BaM film. The device showed a phase tuning rate of 43°/ ͑mm kOe͒ and an insertion loss of 3.1 dB/mm in the on-resonance regime. In off-resonance regimes, the device showed smaller loss and smaller tuning rates. The experimental results were confirmed by theoretical calculations.

A planar millimeter wave band-stop filter based on confined magnetostatic wave ͑MSW͒ excitations in an M-type barium hexagonal ferrite ͑BaM͒ film strip was demonstrated. The device consists of a BaM film strip on the top of a coplanar waveguide with the strip length along the signal line. For zero magnetic fields, the device shows a band-stop filtering response at 53 GHz. This response originates from the excitation of confined MSW modes across the BaM strip width. The filter operation frequency is tunable with low fields. This tuning relies on the change in the MSW dispersion with field.