Superconductivity in Bi 2 Sr 2 CaCu 2 O 8 + δ single crystals doped with Fe, Ni, and Zn

We report electrical conductivity and magnetization measurements on single crystals of the high-${\mathit{T}}_{\mathit{c}}$ superconductor ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{8+\mathrm{\ensuremath{\delta}}}$ with partial substitution of Fe, Ni, and Zn for Cu. Even concentrations of the doping element below 1 at. % cause a strong increase of the electrical resistivity, a definite increase of the London penetration depth, and a decrease of the correlation length. Concomitantly the critical current is lowered and the irreversibility line shifts towards lower field values with increasing concentration of the dopants. For the initial slope ${\mathit{dT}}_{\mathit{c}}$/dx we derive a value of -5 K/at. % independent of the substitutional element.