Anomalous microwave response of hightemperature superconducting thinfilm microstrip resonator in weak dc magnetic fields
Abstract
We have studied an anomalous microwave (mw) response of superconducting YBa _{2}Cu _{3}O _{7 δ} (YBCO) microstrip resonators in the presence of a weak dc magnetic field, H_{dc}. The surface resistance ( R_{s}) and reactance ( X_{s}) show a correlated nonmonotonic behavior as a function of H_{dc}. R_{s} and X_{s} were found to initially decrease with elevated H_{dc} and then increase after H_{dc} reaches a crossover field, H_{c}, which is independent of the amplitude and frequency of the input mw signal within the measurements. The frequency dependence of R_{s} is almost linear at fixed H_{dc} with different magnitudes (< H_{c}, = H_{c} and > H_{c}). The impedance plane analysis demonstrates that r_{H}, which is defined as the ratio of the change in R_{s}( H_{dc}) and that in X_{s}( H_{dc}), is about 0.6 at H_{dc}< H_{c} and 0.1 at H_{dc}> H_{c}. The H_{dc} dependence of the surface impedance is qualitatively independent of the orientation of H_{dc}.
 Publication:

Physica C Superconductivity
 Pub Date:
 December 1999
 DOI:
 10.1016/S09214534(99)005341
 arXiv:
 arXiv:condmat/9908429
 Bibcode:
 1999PhyC..328...60R
 Keywords:

 Condensed Matter  Superconductivity;
 Condensed Matter  Materials Science
 EPrint:
 REVTex 3.1, 5 pages, 6 EPS figures, submitted to Physica C