Abstract
Magnetization measurements with the magnetic field parallel to the c-axis were performed on overdoped t 2-x Pb x S 2 CaCu 2 O 8+δ single crystals. Different from undoped Bi 2 Sr 2 CaCu 2 O 8+δ single crystal, a pronounced anomalous peak with maximum peak field over 5000 G can be observed in enlarging temperature window from 0.2T c to 0.9T c ; both the anomalous magnetization peak H 2p and the sharp onset of the anomalous magnetization peak H on exhibit strong temperature dependence up to the vicinity of T c . The temperature dependence of H on and H 2p 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 H on and thermal disorder induced pancake vortex decoupling transition at H 2P . © 2000 THE PHYSICAL SOCIETY OF THE REPUBLIC OF CHINA.