Sharee J. McNab, Richard J. Blaikie
Materials Research Society Symposium - Proceedings
Microwave surface impedance measurements on PbMo6S8 show granular characteristics with fluxon absorption at fields well below the bulk Hc1. Such behavior is very similar to that of the high-temperature perovskite superconductors. Weakly modulated absorption signals, which have a maximum near Hc1* and change sign on reversal of the field sweep, are observed for both materials. Hc1* = (47π/c)λJc is the threshold for the establishment of a critical state, where Jc is the critical current for depinning and λ. a relaxation length. For modulation fields larger than a few Oersteds, the sign of the signal becomes independent of the direction of field sweep as for the high-temperature superconductors. In powdered samples the absorption contains a line spectrum similar to that obtained in powdered ceramic YBa2Cu3O7-δ. © 1988 Elsevier Science Publishers B.V.