Doping-dependence of the vortex phase diagram of Bi2Sr2Ca2Cu3O10+δ

We study the effect of oxygen overdoping in the vortex phase diagram of B single crystals. In the overcloped regime we do find a smooth variation of T, with the annealing pressure, indicating that Bi2Sr2Ca2Cu3O10+delta is less sensitive to oxygen-doping than the bilayer Bi2Sr2Ca2Cu3O8+delta compound. Magnetic measurements reveal that oxygen overcloping produces a reduction of the liquid vortex region and increases the second-peak transition field. These findings imply that the coupling between CuO2 planes increases upon overdoping. We find that this anisotropy decrease is steeper in Bi2Sr2Ca2Cu3O10+delta than in Bi2Sr2Ca2Cu3O8+delta for the same doping level. (C) 2007 Elsevier B.V. All rights reserved.