MICROWAVE SURFACE-RESISTANCE IN LU1-XPRXBA2CU3O7-DELTA THIN-FILMS

We report microwave surface resistance R(s)(T) measurements on Lu1-xPr xBa2Cu3O7-delta thin films in situ grown by Pulsed Laser Deposition (P LD) technique, focussing on the effect of Pr doping in this system. An omalous peaks in R(S)(T) plots are observed for both dilute and strong doping concentrations of Pr (x similar to 0.07 and x similar to 0.2). Also ageing effects are observed in these films, with a decrease in r esidual surface resistance and vanishing of the peaks with ageing of t hese films. We interpret the peaks in R(S)(T) vs T curve due to the di fferent competing processes involving the temperature dependences of q uasi particle scattering time, pair condensation, penetration depth an d percolation effects. (C) 1997 Elsevier Science Ltd.