Plastic vortex-creep in YBa 2 Cu 3 O 7−x crystals
Y. Abulafia, A. Shaulov, Y. Wolfus, R. Prozorov, L. Burlachkov, Y. Yeshurun, D. Majer E. Zeldov, H. Wühl, V.B. Geshkenbein, V.M. Vinokur
Abstract
Local magnetic relaxation measurements in YBa
2
Cu
3
O
7−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
U
pl
, which decreases with field, drops below the elastic (collective) creep activation energy,
U
el
, which increases with field. A crossover in flux dynamics from elastic to plastic creep is shown to be the origin of the fishtail in YBa
2
Cu
3
O
7−x
.