Vortex dynamics in Bi2+xSr2-(x+y)LayCuO6+δ and Bi2Sr2CaCu2Oy irradiated with heavy-ions:: correlation between the Bose-glass behavior and the coupling of pancake vortices

Vortex dynamics is investigated in Bi2+xSr2-(x+y)LayCuO6+delta (Bi-2201) and Bi2Sr2CaCu2Oy (Bi-2212) irradiated with 3.5 GeV Xe-136(31+) ions through the relation between the frequency and the loss peak temperature in ac susceptibility in order to seek the Bose-glass transition. The Bose-glass behavior is observed at fields below about half of matching filed, B-Phi/2 in irradiated Bi-2212, On the contrary to irradiated Bi-2212, the Bose-glass behavior is not observed in irradiated Bi-2201. This is due to the extremely weak coupling of pancake vortices along the c axis in Bi-2201 in spite of the presence of columnar defects. The pancake vortices in Bi-2201 irradiated with heavy-ions are almost decoupled, resulting in the occurrence of thermally activated flux flow or creep. (C) 1998 Published by Elsevier Science B.V. All rights reserved.