Peak effect and vortex channeling in heavily Pb-substituted Bi2Sr2CaCu2O8+ with planar defects

Vortex states in heavily Pb-substituted Bi 2 Sr 2 CaCu 2 O 8+ y (BSCCO) with planar defects (PDs) from overdoped to underdoped region is studied using micro Hall probes. Angular dependence of magnetization reveals that in a restricted angle and field region, magnetization first increases when the field is tipped away from the c axis and then decreases again. This is understood as a manifestation of vortex channeling along the PDs. In addition, we observe an enhancement of magnetization (peak effect) at nearly constant c -axis component of the field and the peak field is almost independent of temperature and the doping level. The peak field has systematic correlation with the average spacing of PDs suggesting that a kind of matching effect is responsible for this phenomenon.