Local magnetic relaxation measurements in YBa2Cu3O7−x crystals show evidence for plastic vortex-creep associated with the motion of dislocations in the vortex lattice. This creep mechanism governs the vortex dynamics in a wide range of temperatures and fields below the melting line and above the field corresponding to the peak in the ''fishtail'' magnetization. In this range the activation energy Upl, which decreases with field, drops below the elastic (collective) creep activation energy, Uel, which increases with field. A crossover in flux dynamics from elastic to plastic creep is shown to be the origin of the fishtail in YBa2Cu3O7−x.
@article{arxiv.supr-con/9606003,
title = {Plastic vortex-creep in YBa$_2$Cu$_3$O$_{7-x}$ crystals},
author = {Y. Abulafia and A. Shaulov and Y. Wolfus and R. Prozorov and L. Burlachkov and Y. Yeshurun and D. Majer E. Zeldov and H. Wühl and V. B. Geshkenbein and V. M. Vinokur},
journal= {arXiv preprint arXiv:supr-con/9606003},
year = {2009}
}