ANGULAR-DEPENDENCE OF THE MAGNETIZATION CURVES AND INTERLAYER JOSEPHSON COUPLING IN BI2SR2CACU2O8

Magnetization curves were measured for Bi2Sr2CaCu2O8 crystals which we re irradiated with 5.8 GeV Pb ions along the c direction or at 45-degr ees with respect to it. Each ion produces continuous columnar defect t hat crosses the sample and yields a unidirectional pinning center. The density of the defects in the various samples ranges from 10(10) to 2 .5 x 10(11) ions/cm2. In all the irradiated samples the width of the m agnetization curves is found to be the largest for fields along the de fects indicating that when the field is at other directions the vortic es are tilted away from the defects. This manifests the important role of the Josephson coupling between the CuO2 planes. We also report on accelerated flux escape around zero magnetization and around zero fiel d, particularly in samples with a high dose of irradiation.