Doping dependence of crossing vortex lattice in Bi2Sr2CaCu2O8+y

Local magnetization hysteresis is studied in a highly anisotropic superconductor Bi2Sr2CaCu2O8+y under tilted magnetic fields using a micro Hall probe. At moderately high temperatures, we found novel multiple peak structures in the local magnetization hysteresis curves. These peaks appear only in the increasing branch of hysteresis curves when a magnetic field is applied nearly parallel to the superconducting plane. Possible origins of the novel peak structures are discussed on the basis of the evolution of the peaks with temperature. (C) 2004 Published by Elsevier B.V.