Anomalous Magnetization Characteristics in the Overdoped Bi2¡ xPbxSr2CaCu2O8+± Single Crystal

Magnetization measurements with the magnetic field parallel to the c-axis were performed on overdoped Bi2¡ xPbxSr2CaCu2O8+ ± single crystals. Different from undoped Bi2Sr2CaCu2O8+ ± single crystal, a pronounced anomalous peak with maximum peak field over 5000 G can be observed in enlarging temperature window from 0.2Tc to 0.9Tc; both the anomalous magnetization peak H2p and the sharp onset of the anomalous magnetization peak Hon exhibit strong temperature dependence up to the vicinity of Tc. The temperature dependence of Hon and H2p implies that observed anomalous magnetization originates from a static disorder-induced transition from a relatively ordered vortex lattice (or Bragg glass) to a vortex glass (or disordered vortex solid) at Hon and thermal disorder induced pancake vortex decoupling transition at H2p.