Microstructure and temperature dependence of microwave penetration depth of Ag doped Y1Ba2Cu3O7-x thin films

We report the measurements of magnetic penetration depth lambda(T) of Ag-doped YBa2Cu3O7-delta (YBCO) thin films in the thickness range 1500-4000 A and temperature range 18-88 K. The films are in situ grown by laser ablation on <100> LaAlO3 substrates. The penetration depth measurements are performed by microstrip resonator technique. A correlation of lambda(T) with the film microstructure observed with atomic force microscopy has shown that lambda(T) depends critically on the film microstructure. Temperature dependence of magnetic penetration depth has also been studied for best quality films. The experimental results are discussed in terms of BCS theory (s-wave pairing) and d-wave Pairing with and without unitary scattering. The results are found to be best fitted. to the d-wave model with unitary scattering limit. Near T-c, we have also compare the (3D) XY critical regime and the Ginzburg-Landau (GL) behaviour. (C) 2004 Elsevier B.V. All rights reserved.