Microwave absorption study of a lead chevrel-phase compound

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.