Thin films of the newly discovered superconductor MgB2 show promise for a number of different electronic applications. In order to evaluate the suitability of this new material for communication applications at microwave frequencies, we have measured both the linear and nonlinear microwave response of ex-situ MgB2 thin films on sapphire substrates patterned into coplanar waveguide transmission lines. Linear measurements yield the characteristic impedance of our CPW transmission lines, as well as the complex conductivity of the MgB2 film. The nonlinear response of transmission lines on the same film was measured by harmonic generation techniques. Assuming that the measured nonlinear response is due to kinetic inductance effects, we are able to directly determine the relevant pair-breaking current density in our MgB2 thin films by combining results from our linear and nonlinear measurements. Because the resulting pair-breaking current density is a material property independent of sample geometry, we can make quantitative comparisons of the nonlinear response of MgB2 thin films and YBCO thin films at comparable reduced temperatures. We find that the pair-breaking current density in MgB2 thin films rivals that in YBCO for sufficiently low reduced temperatures.
Proceedings Title: Extended Abstracts, 2003 Intl. Superconductive Electronics Conf. (ISEC)
Conference Dates: July 7-11, 2003
Conference Location: Sydney, AS
Pub Type: Conferences
magnesium diboride, nonlinear microwave, superconducting electronics