We report a study of magnetic, structural, and transport properties of ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$ single crystals with different degrees of overdoping. The overdoping is achieved by high oxygen pressure (up to 190 bar) annealing. The parameters used to characterize the overdoping were the crystallographic c-axis lattice parameter and the superconducting transition temperature. The irreversibility line $H_{\mathrm{il}}$ and the characteristic field of the order-disorder transition of the vortex structure $H_{\mathrm{sp}}$ were obtained from dc magnetization with the applied magnetic field perpendicular to the ${\mathrm{CuO}}_2$ planes. The large overdoped range has two well-defined regions: (i) close to the optimal doping the interlayer coupling is mainly electromagnetic and $H_{\mathrm{sp}}$ is given by ${\Phi }_0/{\lambda }_{\mathrm{ab}}^2\mathrm{}\left(0\right)\mathrm{}$ $\left[{\lambda }_{\mathrm{ab}}\mathrm{}\right(0)\mathrm{}$ is the in-plane penetration depth at $T=0\mathrm{}\hspace{0.5em}\mathrm{K}],$ and (ii) with further overdoping the Josephson interlayer coupling becomes relevant, so $H_{\mathrm{sp}}$ deviates from ${\Phi }_0/{\lambda }_{\mathrm{ab}}^2\mathrm{}\left(0\right)\mathrm{}$ and is fixed by the effective-mass anisotropy. All the results indicate an increase in the coupling between ${\mathrm{CuO}}_2$ planes with overdoping.

• Received 5 October 2000

DOI:https://doi.org/10.1103/PhysRevB.63.172505