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

c-Axis Penetration Depth in Bi₂Sr₂CaCu₂O_8 +  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 _c in Bi₂Sr₂CaCu₂O_8 +  (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 _c(T) T in the temperature range T < 0.5T_c. Electrodynamic analysis of the impedance anisotropy has allowed us to estimate _c(0) 50 mm in BSCCO crystals overdoped with oxygen (T_c 84 K) and _c(0) 150 mm at the optimal doping level (T_c 90 K).

PACS: 74.72.Hs, 74.25.Ha