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

Abstract

Microwave properties of various YBCO thin films in the form of stripline resonators are studied using a non-contact method. Q factors, insertion losses and the resonant frequency shift of the resonators are measured in frequencies of 8 to 12 GHz at temperatures above the liquid nitrogen temperature. The resonant frequency shift to a lower value is observed upon an increase in temperature in all resonators, which is explained 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 value of n=2 or 4. The fitted values of lambda 0 with n=2 appear smaller than the corresponding values with n=4, indicating that the same value 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 results also show that the penetration depth of a YBCO film can be different depending on the fabrication method as well as on the thickness of the film, implying that minimization of signal loss cannot be accomplished simply by using a HTS film with a thickness more than a few magnetic penetration depths of a single crystal of YBCO.