Local magnetization measurements on Bi2Sr2Ca2Cu3O10 tapes

Global transport measurements and local Hall-probe array measurements of a section of silver clad BSCCO tape, are reported. Transport measurements are in good agreement with the 'brick wall' model. The induction profiles obtained from magnetic measurements agree with the assumption of a uniform bulk current at low (40-60 K) temperatures. At higher temperatures and relatively high fields (700 G and up) local measurements seem to reveal the existence of surface currents. These currents are the result of small current loops, flowing within the grains, which result in a net current only at the edges of the sample. Thus, the local magnetic measurements do not agree with global transport ones, and we contend that the 'brick wall' model aptly describes the flow of transport currents, but fails to describe the flow of currents induced by an external magnetic field. (C) 1998 Published by Elsevier Science B.V. All rights reserved.