Stripline resonator measurements of Zs versus Hrf in YBa2Cu3O(7-x) thin films

A report is presented on measurements of the surface impedance, ZS, of YBa2Cu3O(7-x) thin films using a stripline resonator. The films were deposited on LaAlO3 substrates by off-axis magnetron sputtering. The authors obtained ZS as a function of frequency from 1.5 to 20 GHz, as a function of temperature from 4 K to the transition temperature (about 90 K), and as a function of the RF magnetic field from zero to 300 Oe. At low temperatures the surface resistance, RS, of the films shows a very weak dependence on the magnetic field up to 225 to 250 Oe. At 77 K, RS is proportional to the square of the field. The The penetration depth shows a much weaker dependence on the field than does RS. The origins of the magnetic field dependence of ZS are also discussed. (I.E.)