Vortex pinning in Bi2Sr2CaCu2O8 tapes irradiated by ions.

Abstract

Vortex pinning due to columnar and point defects was studied in Bi-2212 tapes irradiated by 230-MeV ${\mathrm{Au}}^{14+}$ and 120-MeV ${\mathrm{O}}^{7+}$ ions. Remanent magnetization and critical current density were significantly increased after irradiation in the applied field not only perpendicular to but also parallel to the ab plane. The enhancement of them in the latter field direction was interpreted as kink motion caused by Josephson vortices across the ${\mathrm{CuO}}_{2}$ planes. Angular dependence of irreversibility field (${\mathit{H}}_{\mathrm{irr}}$) at 55 K showed line vortices [three dimensional (3D) vortices] for columnar defects after Au irradiation and it followed the scaling rule for point defects after O irradiation. The transition of vortices from 3D to 2D was critically influenced by ${\mathit{H}}_{\mathrm{irr}}$, namely, by a pinning potential. \textcopyright{} 1996 The American Physical Society.