Microwave Absorption In The Mixed State Of Bi2sr2cacu2o8+Delta Single Crystals

We have measured the microwave absorption at 10GHz, in Bi2Sr2CaCu2O8+delta single crystals (T-c=88 K) in the mixed state. We show that in our geometry, the absorption reflects the dissipation of the r.f. currents along the (c) over cap axis. We find a temperature dependent characteristic field H*, beyond which the normal state dissipation is recovered : this field may be identified with the decoupling field B-D estimated by Daemen et al.