VARIATION OF MICROWAVE LOSSES INDUCED BY DC AND RF MAGNETIC-FIELDS INGD123 THIN-FILMS

Using a 5GHz parallel plate resonator, several Gd123 thin films have b een studied. The low rf power dependence, the de field dependence and the power dependence in the presence of dc fields have been measured. Two films were modified by introducing intragranular defects by high e nergy irradiation of either Kr ions or alpha particles. By using a sim ple model, values for high frequency pinning constant kappa(p) were ex tracted. The dc screening current density J, was also measured. We exa mine whether the irradiation has improved the de and high frequency pi nning properties and the impart this has on the power dependence of th e surface resistance. Comparison between the de and the power dependen ce losses are made.