XI. MICROWAVE DEVICES EMPLOYING MAGNETIC WAVES Academic and Research Staff

We have undertaken a comprehensive program directed at developing and perfecting a novel class of microwave yttrium iron garnet (YIG) filters based upon our recent observations (in the Microwave and Quantum Mechanics Group of the Department of Electrical Engineering and Computer Science) of extremely sharp localized resonance in single crystals biased with spatially nonuniform fields. Such magnetically tunable filters would employ photolithographically derived planar microwave circuit elements for coupling energy into and out of the crystal, and it appears that multipole filters can be integrated within the same crystal to provide economy of scale and hence preclude costly time-consuming hand-alignment procedures. Magnetic resonance is normally very much broadened if a ferrimagnetic sample is immersed in a spatially nonuniform field, and experimentalists measuring fundamental resonance parameters take great pains to employ ellipsoidal sample shapes (usually small spheres) that are positioned in fields of very high uniformity. Therefore it is very remarkable that in our work in the Microwave and Quantum Magnetics Group we recently observed extremely sharp resonances of a highly localized character in single