Advanced Epitaxial Ferrite Devices.

Using a class of materials referred to as hexagonal ferrites, magnetically tunable filters in the millimeter wave range becomes a practical possibility. Becuase of their large inherent magnetic anisotropy, the hexaferrites can be biased into the millimeter wave range with relatively small external fields. It was the purpose of this contract to explore the use of epitaxial films of hexagonal ferrites as an alternative to bulk grown single crystal material. Since epitaxial films can be grown with a damage-free surface, no mechanical handling would be required. Bandstop filters using this material were fabricated and the characteristics were measured. Using parallel resonance a bandstop response at 39.1 GHz was obtained with an unloaded Q of 400. In perpendicular resonance, the film was linearly tuned across the 50 to 60 GHz range with a variable field which did not exceed 2000 gauss. In both cases only a minimum of mechanical processing was used. Author