Effect of columnar defects on reversible magnetization of superconducting Bi2Sr2Ca2Cu3O10+ delta.

Abstract

$c$-axis-oriented superconducting ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{Ca}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{10+\ensuremath{\delta}}$ (Bi-2223) tapes have been irradiated with 5.8-GeV Pb ions to produce columnar defects along the $c$ axis. The magnetization $M$ as a function of field and temperature were measured for both the unirradiated and irradiated samples at matching field ${B}_{\ensuremath{\varphi}}$ values of 1.28, 2.0, and 4 T. In striking contrast to the conventional $log(B)$ dependence of the reversible $M$ in the London regime, the field dependence of the reversible $M$ for the irradiated samples exhibits some unusual characteristics. A large reduction in the value of $M$ was observed at $B<~{B}_{\ensuremath{\Phi}}$, while a maximum appears at $B>{B}_{\ensuremath{\Phi}}$. We explain this field dependence in terms of the London model modified by the localization of the vortex lines in the columnar defects. Based on this study, we obtained the single vortex pinning energy for Bi-2223 by these columnar defects.