A THEORETICAL-ANALYSIS OF THE MICROWAVE-ABSORPTION NEAR ZERO-FIELD FOR HIGH-TC SUPERCONDUCTORS

Dispersive microwave absorption curves are detected from the recently developed high Tc superconductors by an electron spin resonance spectrometer as the d.c. magnetic field is swept from negative to positive across zero. The absorption lineshapes can be characterized by a complex surface impedance which is strongly influenced by the Josephson tunnelling current between grain boundaries. The analyzation for best fitting appraises a coherent length ζ(0°K = 15.3 Å, grain size d0 {reversed tilde equals} 1.5 μm, and superconduction electron density ns = 1021cm-3 which satisfactorily agrees with the values derived from other measurements. © 1990.