c-axis penetration depth in Bi2Sr2CaCu2O8+delta single crystals measured by ac-susceptibility and cavity perturbation technique

The c-axis penetration depth Delta lambda(c) in Bi2Sr2CaCu2O8 + delta (BSCC O) single crystals as a function of temperature has been determined using t wo techniques, namely, measurements of the ac-susceptibility at a frequency of 100 kHz and the surface impedance at 9.4 GHz. Both techniques yield an almost linear function Delta lambda(c)(T) proportional to T in the temperat ure range T < 0.5T(c). Electrodynamic analysis of the impedance anisotropy has allowed us to estimate lambda(c)(0) approximate to 50 mu m in BSCCO cry stals overdoped with oxygen (T-c approximate to 84 K) and lambda(c)(0) appr oximate to 150 mu m at the optimal doping level (T-c approximate to 90 K). (C) 2000 MAIK "Nauka / Interperiodica".