EVIDENCE FOR LINE VORTICES IN BI2SR2CACU2O8

Bi2Sr2CaCu2O8 (BSCCO) crystals were irradiated with 5.8-GeV Pb ions to produce columnar defects either along the c direction or at 45-degree s with respect to it. Magnetization curves of the irradiated BSCCO cry stals were measured with the applied field at different directions rel ative to the defects. The width of the magnetization curves, which ref lects the pinning strength, is found to be the largest for fields alon g the defects. This unidirectional enhancement clearly indicates the l ine nature of the vortices in BSCCO.