Microstrip superconducting resonators loaded with yttrium iron garnet single crystals

This paper deals with an experimental study of a magnetically tunable microstrip superconducting resonator loaded with a single crystal of bulk yttrium iron garnet (YIG). Tunability of 200 MHz at a center frequency of 5:3 GHz was observed, and a quality factor of 965 was measured with minimum insertion loss of 19.5 dB for a half-wavelength microstrip line consisting of a YIG-YBCO-MgO composite structure. The dispersion characteristics of the resonator were calculated using the spectral domain method. We discuss the limit of the magnetic tunability in terms of our experimental results on the mixed states of TEM and magnetostatic wave (MSW) modes. Power dependence of the characteristics is also discussed. (C) 1998 Scripta Technica.