Doping dependence of the in-plane penetration depth and fishtail in Bi2Sr2Ca1-xYxCu2O8+delta single crystals

We report on the London penetration depth lambda(ab)(0), measurements, and second peak (H) over tilde determination in Bi2Sr2Ca1-xYxCu2O8+delta (Bi-22 12) crystals with different doping levels. By combining cationic substituti ons and oxygen pressure annealings, crystals with a doping state going from the underdoped to overdoped regime have been obtained. The corresponding l ambda(ab)(0) values, deduced from reversible magnetization measurements hav e allowed us to evidence a "boomerang" shape for the T-c[1/lambda(ab)(2)(0) ] curve in the 0.8 less than or equal to T-c/T(c)(max)less than or equal to 1 region. Moreover, other T-c[1/lambda(ab)(2)(0)] values for superconducti ng crystals of Hg- and Tl-based cuprates are found to fit well with this bo omerang path, demonstrating its universal nature. The overdoped side of the boomerang for the Bi-2212 crystals clearly shows that 1/lambda(ab)(2)(0) d ecreases as the doping level is increased. Since by the same time the chara cteristic held of the fishtail H monotonously increases, we have thus estab lished that H increases with 1/lambda(ab)(2)(0) decreasing. Consequently, t he linear relation (H) over tilde=Phi(0)/lambda(ab)(2)(0) predicted by the electromagnetic model cannot account alone for the present experimental res ults in the overdoped regime. [S0163-1829(98)04546-9].