OBSERVATION OF VORTEX MOVEMENTS IN A BI2212 SINGLE-CRYSTAL UNDER APPLICATION OF A TRANSPORT CURRENT BY MEANS OF THE BITTER PATTERN TECHNIQUE

The high-resolution Bitter pattern technique has been used to observe vortex movements of Bi2Sr2CaCu2Oy single crystals. A transport current is applied to the sample parallel to the ab plane, and a de magnetic field is applied normal to the nb plane at the Ni decoration. The Ni d ecoration pattern can be observed using a scanning electron microscope (SEM) and an atomic force microscope (AFM). Through observation of th e Ni pattern, we can identify vortex movements while the transport cur rent is being applied. The vortices move randomly with a small transpo rt current of less than 40% of J(c), and they move in a line with a la rge transport current nearly equal to J(c). The vortex movement was no t observed in the sample on applying a transport current larger than 1 .5 J(c).