We have observed vortices of the high-temperature superconductor using the
Bitter technique. Hopping movement of vortices of Y-123 and Bi-2212 single
crystal was observed in the temperature range of 50-90 K (T-c) by the therm
al energy. We estimated pinning potential by migration length, The pinning
potential, we have also observed the vortex pattern of Y-123 QMG sample inc
luding Y-211 phase. We found that vortex existed in the grain boundary of Y
-211 and Y-123 phase. (C) 2001 Elsevier Science B.V. All rights reserved.