ANOMALOUS MICROWAVE-ABSORPTION IN GDBCO POWDER - PI-JUNCTIONS AND THEPARAMAGNETIC MEISSNER EFFECT

We have observed anomalous microwave absorption (MWA) representative o f paramagnetic Meissner effect in GdBCO powder. The results are discus sed in terms of pi junction theory. The phase change in the MWA gives evidence for the change in behaviour of the pi junctions from para to dia state. The intragrain weak links with high J(c) are likely to be f orming pi junctions in the sample. It is expressed that the high frequ ency absorption is a better tool than the magnetization measurements t o investigate the ir junctions. Thermally induced vortex-antivortex pa ir formation and the flux compression caused by an inhomogeneous super conducting transition are ruled out as the possible mechanisms of the PME, from the microwave absorption study. (C) 1998 Elsevier Science B. V.