Observation of Microwave Magnetoabsorption in the High-TcPhase of a Bi(Pb)-Sr-Ca-Cu-O Superconductor

Abstract
Microwave responses at 22.9 GHz of a high-TcBi(Pb)-Sr-Ca-Cu-O superconductor have been studied under magnetic fields up to 12 kG and temperatures of 4–130 K. The microwave magnetoabsorption curve systematically depends on the “magnetic history” after zero-field cooling. We show that the sharp change of microwave absorption in the low field range is not attributed to zero field ESR, but is probably caused by many Josephson junctions in the ceramic sample. By reducing contribution from Josephson junctions, the lower critical fieldHc1bcan be estimated from the magnetoabsorption curve.