Copper Oxide High Temperature Superconductors Bi <sub> 2 </ Sub> Sr <sub> 2 </ Sub> The Cacu <sub> 2 </ Sub> O <sub> 8 + ¦Ä </ Sub> Single Crystal Flux Power Studies

In this dissertation, we used the "flux transformer" electrode geometry on the Bi₂Sr₂CaCu₂O_8+δ and La_1.93Sr(0.07)CuO_4+δ single crystals, measured the transport properties and researched the vortex dynamics in high-T_c superconductors. Some important results were achieved.In chapter 1, we introduced the discovery and development of high-T_c superconductors briefly. Improving the critical current density is the key on the application of high-T_c superconductors. In order to improve the critical current density, we must research the vortex dynamics. The basic conceptions and equations were given.In chapter 2, we introduced the general phenomenon in high-T_c superconductors, e.g. the critical current peak. For YBa₂Cu₃O_7δ and2H-NbSe₂ single crystal, the peak is induced by the transition from elastic flow to plastic flow in the vortex solid state. But for Bi₂Sr₂CaCu₂O_8+δsingle crystal, the peak is ascribed to the shear-induced decoupling of Cu-O layers. From mentioned above, it was found that the vortex movement in Bi₂Sr₂CaCu₂O_8+δ. single crystal is different from that in otherhigh-T_c superconductors.In chapter 3, we used the "flux transformer" electrode geometry, measured the transport properties and researched the vortex dynamics on the Bi₂Sr₂CaCu₂O_8+δ single crystal. With the novel "flux transformergeometry", for the first time, we observed a surprising "platform" in the normal-superconductive transition under the magnetic field being parallel to the c axis. The model of resistive restoration mechanism was suggested as below. Under the magnetic field being parallel to the c axis, the appearance of resistivity is ascribed to the pancake vortex movement;...