Observation of vortex movement in oxide superconductors by means of the Bitter pattern technique

The high-resolution Bitter pattern technique has been used to observe vorte x movement of oxide superconductors, Bi(2)Sr(2)CaCu(2)Oz (Bi2212). The Bitt er pattern was observed in field-cooled (FC) and zero-field cooled (ZFC) ex periments. We also examined vortex movement of the Bi2212 single crystal in which transport current was applied parallel to the c plane, and a de magn etic field applied normal to the c plane at the Ni decoration. The Ni decor ation pattern was observed using a scanning electron microscope (SEM) and a n atomic force microscope (AFM). Through observation of the Ni decoration p attern, we can identify vortex movement. The vortices moved into the sample on FC experiment, and the direction of vortex movement was approximately n ormal to the edge of the sample. We also found the vortex movement in a lin e under application of transport currents. They moved hopping among pinning centers due to Lorentz force.