Dimensionality and pinning of magnetic vortices in the c-axis aligned Bi2Sr2CaCu2O8+delta and (Bi,Pb)(2)Sr2Ca2Cu3O10/Ag tapes irradiated by 5.8-GeV Pb ions

Powder-in-the Ag tube processed Bi2Sr2CaCu2O8+delta and (Bi,Pb)(2)Sr2Ca2Cu2O10 tapes were irradiated with 5.8-GeV Pb ions along the tape normal for the ion fluences of 0.68, 1.0, and 2.0 X 10(11) cm(-1). The angular (theta) dependence of critical current densities J(c)(theta,B,T) for these tapes was measured at temperature T=27 K and 55-80 K, Cusplike sharp peaks in J(c)(theta,B,T) were observed for T greater than or equal to 55 K when the applied magnetic field B is oriented parallel to the direction of the irradiation (theta=90 degrees), and J(c)(theta) did not scale with the perpendicular component of B, (B-perpendicular to=B sin theta). Based on this evidence, it was concluded that the magnetic vortices behave as linelike (three-dimensional) rather than the pancakelike [two-dimensional (2D)] objects in these irradiated superconductors. However, at 27 K, neither the peaks in J(c)(theta) nor the scaling of J(c)(theta) with B-perpendicular to was observed. We attribute this to the increased strength of the isotropic pinning by the small irradiation-induced defect debris relative to that of the columns and due to the increased interlayer coupling strength at reduced temperature, but not as evidence for the pancakelike 2D vortices at low temperatures, Also, for T greater than or equal to 55 K, the enhancement in the pinning strength qualitatively followed the theory by Nelson and Vinokur [Phys. Rev. Lett. 68, 2398 (1992); Phys. Rev, B 48, 13 060 (1993)].