Magneto-optical imaging of vortex lattice melting transition in Bi2Sr2CaCu2O8+y

Magneto-optical differential imaging technique is applied to the observatio n of the vortex lattice melting transition in Bi2Sr2CaCu2O8+y. Contrary to the naive expectation, the nucleation of the vortex liquid paddle occurs in a rather inhomogeneous manner. The front of the vortex solid-liquid interf ace propagates reflecting the intrinsic inhomogeneities of the crystal. Dir ect compositional mapping of the constituent atoms indicates that the chang e in the chemical composition have some correlation with the behavior of th e vortex solid-liquid interface. Changes in the superconducting parameters due to the variation of the local doping level could be the origin of such an effect. (C) 2001 Elsevier Science B.V. All rights reserved.