JETP Letters -- January 25, 2000 -- Volume 71, Issue 2 pp. 92-96

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c-Axis Penetration Depth in Bi2Sr2CaCu2O8 + delta Single Crystals Measured by ac-Susceptibility and Cavity Perturbation Technique

D. V. Shovkun,1 M. R. Trunin,1 A. A. Zhukov,1 Yu. A. Nefyodov,1 N. Bontemps,2 H. Enríquez,2 A. Buzdin,3 M. Daumens,3 and T. Tamegai4
1Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia
2Laboratoire de Physique de la Matière Condensée, Ecole Normale Supérieure, 75231 Paris, France
3Laboratoire de Physique Théorique, Université Bordeaux I, 33405 Talence Cedex, France
4Department of Applied Physics, The University of Tokyo, Hongo, Bunky-ku, 113-8656 Japan

(Received December 24, 1999)

The c-axis penetration depth Deltalambdac in Bi2Sr2CaCu2O8 + delta (BSCCO) single crystals as a function of temperature has been determined using two 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 Deltalambdac(T) [proportional] T in the temperature range T < 0.5Tc. Electrodynamic analysis of the impedance anisotropy has allowed us to estimate lambdac(0) [approximate] 50 mm in BSCCO crystals overdoped with oxygen (Tc [approximate] 84 K) and lambdac(0) [approximate] 150 mm at the optimal doping level (Tc [approximate] 90 K).

PACS: 74.72.Hs, 74.25.Ha