paper

Nonlinear Dielectric Microwave Losses in MgO Substrates

arXiv:cond-mat/0108346 · doi:10.1063/1.1447000

Abstract

We have investigated the nonlinear surface impedance and two-tone intermodulation distortion of nine epitaxial YBa2Cu3O7-d films on MgO substrates, using stripline resonators, at frequencies f=2.3-11.2GHz and temperatures T=1.7K-Tc. The power dissipation decreased by up to one order of magnitude as the microwave electric field was increased to about 100V/m for T<20 K, while the reactance Xs showed only a weak increase. The minimum of the losses correlated with a plateau in the intermodulation signal. The same features were observed for a Nb film on MgO. The anomalous response is due to nonlinear dielectric losses in the substrate, which can be described by defect dipole relaxation.

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