CURRENT-VOLTAGE CHARACTERISTICS OF BI2SR2CA2CU3O10+X AG MULTIFILAMENTARY TAPES IN ZERO APPLIED MAGNETIC-FIELD/

Current-voltage characteristics of multifilamentary Bi2Sr2Ca2Cu3O10/Ag tapes (short samples) produced by the 'powder in tube' technique were measured at different temperatures close to the mean-field critical t emperature, and in zero applied magnetic field. After performing the r equired corrections due to the current flowing in the silver matrix, t he I-V curves were interpreted in terms of current-induced unbinding o f the thermally created vortex-antivortex pairs. Two possible mechanis ms for appearance of a finite critical current in zero applied magneti c field are discussed: the Jensen-Minnhagen quasi-two-dimensional (2D) approach, that takes into account the interlayer Josephson coupling, and a model of size limitation of vortex fluctuations. From our analys is, it seems that the latter model is more suitable for this kind of s uperconducting material, due probably to an accentuated intrinsic anis otropy.