A COMPARATIVE-STUDY ON THE MICROWAVE PENETRATION DEPTH OF VARIOUS Y1BA2CU3O7-DELTA THIN-FILMS USING A NONCONTACT METHOD

Microwave properties of various YBCO thin films in the form of stripli ne resonators are studied using a non-contact method. Q factors, inser tion losses and the resonant frequency shift of the resonators are mea sured in frequencies of 8 to 12 GHz at temperatures above the liquid n itrogen temperature. The resonant frequency shift to a lower value is observed upon an increase in temperature in all resonators, which is e xplained using the temperature dependence of the magnetic penetration depth in the form of lambda(T)=lambda(0)[1-(T/T-c)(n)](-1), with the v alue of n=2 or 4. The fitted values of lambda 0 with n=2 appear smalle r than the corresponding values with n=4, indicating that the same val ue of n is to be used if the magnetic penetration depths of different high-T-c superconducting (HTS) thin films are to be compared. The resu lts also show that the penetration depth of a YBCO film can be differe nt depending on the fabrication method as well as on the thickness of the film, implying that minimization of signal loss cannot be accompli shed simply by using a HTS film with a thickness more than a few magne tic penetration depths of a single crystal of YBCO.