Reduction of interlayer coherence around 1/3 of matching field in Bose glass phase of YBa2Cu3O7-delta with columnar defects

Magneto-optical imaging in YBa2Cu3O7-delta with columnar defects (CDs) show s an asymmetric critical-state field profile., which is related to the misa lignment between the applied field and the CDs. This asymmetric profile is explained by the in-plane magnetization originated from vortex alignment al ong the CDs. This phenomenon is utilized as a powerful probe for the interl ayer coherence. The extracted ratio of the in-plane to the out-of-plane mag netization component disappears at around B-phi/3, where B-phi is the dose equivalent matching field. Moreover, the maximum enhancement of the irrever sible magnetization occurs at around B-phi/3 which is independent of temper ature, These results suggest a reduction of interlayer coherence well bello w B-phi in the Bose glass phase, and are consistent with the prediction of the simulation study. (C) 2001 Elsevier Science B.V. All rights reserved.