Complex Susceptibility of La1.9Sr0.1CuO4-δ

Abstract

The response of superconducting La_1.9Sr_0.1CuO_4-δ against a small ac magnetic field is studied in terms of complex susceptibility χ=χ'-iχ''. The superconducting transition shows two types of characteristics: One is insensitive to the change in the amplitude h ₀(5-1000 mOe) of the external ac field, and the other is very sensitive to it. In the latter case, the transition width is appreciably broadened and the peak height of χ'' is enhanced as h ₀ increases. Besides, no frequency dependence is found below 500 Hz. These behaviors are qualitatively similar to that of the multiconnected network consisting of weak-link junctions.