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Nonlinear Microwave Response of MgB2 Thin Films



James C. Booth, Kenneth Leong, S. Y. Lee, J. H. Lee, B. Oh, H. N. Lee, S. H. Moon


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 fabricated MgB2 thin films on sapphire substrates patterned into coplanar-waveguide (CPW) transmission lines. Linear measurements yield the surface resistance and absolute value of the penetration depth, as well as the characteristic impedance of our MgB2 transmission lines. The nonlinear response of the same transmission lines was then measured by harmonic generation. Assuming that the measured nonlinear response is due to kinetic inductance effects, we were 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 YBa2Cu3O7-d (YBCO) thin films at comparable reduced temperatures. We find that for sufficiently low reduced temperatures the pair-breaking current density in MgB2 thin films rivals that in YBCO.
Superconductor Science and Technology


magnesium diboride, microwave properties, nonlinear response, thin film superconductor


Booth, J. , Leong, K. , Lee, S. , Lee, J. , Oh, B. , Lee, H. and Moon, S. (2003), Nonlinear Microwave Response of MgB<sub>2</sub> Thin Films, Superconductor Science and Technology, [online], (Accessed April 20, 2024)
Created December 1, 2003, Updated April 26, 2019