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Unusual features in the nonlinear microwave surface impedance of Y-Ba-Cu-O thin films

A. P. Kharel·Anton V. Velichko·J. R. Powell·A. Porch·M. J. Lancaster·R. G. Humphreys
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Abstract

Striking features have been found in the nonlinear microwave (8 GHz) surface impedance $Z_s=R_s + jX_s$ of high-quality YBaCuO thin films with comparable low power characteristics [$R_{res}\sim 35--60 μΩ$ and $λ_L(15 K)\sim 130--260 nm$]. The surface resistance $R_s$ is found to increase, decrease, or remain independent of the microwave field $H_{rf}$ (up to 60 mT) at different temperatures and for different samples. However, the surface reactance $X_s$ always follows the same functional form. Mechanisms which may be responsible for the observed variations in $R_s$ and $X_s$ are briefly discussed.

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A. P. Kharel, Anton V. Velichko, J. R. Powell, A. Porch, M. J. Lancaster, R. G. Humphreys. 1999-04-09. Unusual features in the nonlinear microwave surface impedance of Y-Ba-Cu-O thin films. https://doi.org/10.1103/physrevb.58.11189

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