Nonlinear microwave properties of Nb3Sn sputtered superconducting films

We report on microwave measurements of the surface impedance Z(s) = R-s + iX(s) of Nb3Sn superconducting films deposited by planar magnetron sputtering on sapphire substrates. The samples show the A15 structure with maximum T-c(R = 0) of 17.4 K and residual resistivity ratios up to beta approximate to 3. The measurements are performed by a microstrip resonator technique using a meander line geometry. The power dependence of Z(s) is studied at different temperatures and frequencies in the range of 1-10 GHz using the fundamental and higher order modes of the resonator. The effect of a de magnetic field applied with different orientations is also studied. The data are analyzed in the context of a simple model able to describe most of the reported loss mechanisms. (C) 1997 American Institute of Physics.