Realization of highly epitaxial (Y,Nd,Sm)Ba2Cu3O7-δ films for microwave applications

We report on the preparation and characterization of highly epitaxial (Y,Nd,Sm)Ba2Cu3O7-δ films deposited on LaAlO3 substrates. The samples have been obtained by a d.c. sputtering technique in high oxygen pressure. The effect of several deposition parameters on the structural and superconducting properties has been investigated by means of X-ray diffraction and transport measurements. Tc(ρ=0)>90 K have been obtained for the Y and Nd compounds while Tc(ρ=0)=87.3 K has been measured on the SmBa2Cu3O7-δ films. All the samples showed critical current densities Jc>106 A/cm2 at T=77 K. Microwave characterization by using planar microstrip resonators indicated at low temperatures (4.2 K) and low frequencies (1 GHz), surface resistances as low as 10 μΩ