Critical current densities in Bi2Sr2CaCu2O8+d

Critical current densities and upper critical fields were measured for a single crystal of the high-Tc oxide superconductor, Bi2Sr2CaCu2O8+d, within the ab basal plane and along the c-axis. The anisotropy in critical current densities was observed to be Jcperpendicular/Jcparallel = 10 in agreement with the anisotropy in resistivity for the normal state. The magnetic field dependence of the critical current densities can be interpreted by the anisotropy in the upper critical fields. The scaling of the critical current density with the magnetic field was found. The critical current density scaled to zero at fields Bc2 in the ab plane and along the c-axis which were in good agreement with the upper critical fields measured by transport. The anisotropy in flux pinning force density along the b axis. Fp parallel b, and along the a-axis, Fp parallel a, was found to be Fp parallel b/Fp parallel a = 3. The data provided strong evidence for flux pinning by the modulated structure in this system