NONLINEAR RESPONSE OF HTSC THIN-FILM MICROWAVE RESONATORS IN AN APPLIED DC MAGNETIC-FIELD

The non-linear microwave surface impedance, Z(s) = R-s + iX(s), of pat terned YBCO thin films, was measured using a suspended line resonator in the presence of a perpendicular DC magnetic field, H-DC, of magnitu de comparable to that of the microwave field, H-rf. Signature of the v irgin state was found to be absent even for relatively low microwave p ower levels, The microwave loss was initially found to decrease for sm all applied H-DC before increasing again. Also, non-linearities inhere nt in the sample were found to be substantially suppressed at low powe rs at these applied fields, These two features together can lead to si gnificant improvement in device performance.