Vortex Dynamics in Ybco Single Crystals at High Temperatures

We have studied the vortex creep in YBaCuO single crystals at high temperatures, T>80 K, by dc-current resistivity measurements. The obtained results show single vortex creep for low magnetic fields, creep of vortex bundles in intermediate field region, whereas in high magnetic fields plastic creep mediated by motion of the flux-line-lattice (FLL) dislocation is observed. The effect of the FLL anisotropy and of the twin boundaries on vortex creep is discussed.