Variation of microwave losses induced by DC and RF magnetic fields in Gd123 thin films

Using a 5 GHz parallel plate resonator, several Gd123 thin films have been studied. The low RF power dependence, the DC 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 energy irradiation of either Kr ions or /spl alpha/ particles. By using a simple model, values for high frequency pinning constant /spl kappa//sub p/ were extracted. The DC screening current density J, was also measured. We examine whether the irradiation has improved the DC and high frequency pinning properties and the impact this has on the power dependence of the surface resistance. Comparison between the DC and the power dependence losses are made.