Self-biased planar millimeter wave notch filters based on magnetostatic wave excitation in barium hexagonal ferrite thin films

The use of M-type barium hexagonal ferrite (BaM) 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. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3504256]