Pulsed laser deposition of novel HTS multilayers for passive and active device applications
Multilayered structures have been fabricated from binary combinations of the high-T/sub c/ superconductor YBa/sub 2/Cu/sub 3/O/sub 7- delta / (YBCO) and the ferrite BaFe/sub 12/O/sub 19/ (BFO) or the ferroelectric Sr/sub 0.5/Ba/sub 0.5/TiO/sub 3/ (SBT). The combination of YBCO and BFO was found to destroy the superconductivity of the YBCO layer. Vibrating sample magnetometer measurements of the BFO layer still indicated a large uniaxial anisotropy. The underlying YBCO layer of an SBT/YBCO bilayer still had high quality transport properties unaffected by the SBT layer (T/sub c/ approximately 91 K. J/sub c/(77 K) approximately 2*10/sup 6/ A/cm/sup 2/). A thin-film, normal metal/SBT transmission line, patterned in microstrip, demonstrated a wealth of temperature and electric field dependent dielectric information for the frequency range tested (f<or=3 GHz). At 100 K, the dielectric constant for zero applied field was 250 for frequencies less than 30 MHz; it was approximately 120 for 1 GHz<or=f<or=3 GHz, and it varied continuously with frequency between these values. For temperatures between 300 K and 11 K, frequencies less than about 0.5 GHz, and applied fields up to 200 kV/cm, a nearly linear change in field-induced phase difference was produced in the transmission line. Above this frequency the field dependence changed sign and essentially disappeared at approximately 1 GHz.<<ETX>>