Coexisting ordered and disordered vortex phases in Bi2Sr2CaCu2O8+δ

A high temporal resolution magneto-optical system was employed to image the induction distribution on the surface of a Bi2Sr2CaCu2O8+delta crystal while the external magnetic field was ramped up at a constant rate. These data reveal coexistence of quasi-ordered and disordered vortex phases, near the order-disorder phase transition line. The coexistence region in the B-T phase diagram narrows down with increasing temperature or decreasing sweep rate. These observations clarify previous interpretations of phenomena associated with the fishtail, e.g. the shift of the fishtail onset to higher inductions for slower sweep rates and the absence of a fishtail at low temperatures. (C) 2003 Elsevier Science B.V. All rights reserved.