PENETRATION DEPTH IN PB2SR2Y1-XCAXCU3O8-DELTA SINGLE-CRYSTALS

The electron paramagnetic resonance (EPR) study of free radical adsorb ed at the surface of high T-c Pb2Sr2Y1-xCa(x)Cu(3)O(8-delta) single cr ystals were performed. A broadening of the EPR linewidth below the tra nsition temperature Tc is due to the spatial distribution of the magne tic nux. The magnetic field penetration depth lambda can be determined by this method. The results are discussed in a frame of BCS and two-f luid models. The value of penetration depth extrapolated to zero tempe rature lambda(0) was estimated.