Study of the electrodynamic response of SmBa2Cu3O7-delta thin films in the microwave region

We present some experimental results on the temperature dependence of the surface resistance R-s and magnetic penetration depth lambda of thin films of SmBa2Cu3O7-delta. The samples, 0.25 mum thick, were grown by a dc sputtering technique on (100)K LaAlO3 single crystal substrates, with critical temperatures ranging between 87 and 88 K. Accurate measurements of the surface impedance Z(S) were performed down to 4 K by means of a dielectrically loaded cavity operating in the microwave region (20 GHz). Both lambda and R-S show a monotonic temperature behavior, with no evidence of low temperature up-turn characteristic of other rare earth based cuprates like GdBa2Cu3O7-delta. At low temperatures, we observed an almost linear behavior of lambda with a slope of similar to0.3 nm/K up to 25 K, as expected in a d-wave pairing scenario. The real part of complex conductivity sigma(1) shows a bump at around 40 K, in agreement with previous reports.