Superconducting fluctuation diamagnetism above $T_c$ in ${\mathrm{YBa}}_1$${\mathrm{Cu}}_3$${\mathrm{O}}_7$, ${\mathrm{La}}_{1.8}$${\mathrm{Sr}}_{0.2}$${\mathrm{CuO}}_4$, and ${\mathrm{Bi}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Pb}}_{\mathit{x}}$${\mathrm{Sr}}_2$${\mathrm{CaCu}}_2$${\mathrm{O}}_{8+\mathrm{\delta }}$

Magnetic susceptibility data are presented for the title compounds. All show negative curvature below ∼2$T_c$. Data for grain-aligned ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_7$ are in excellent agreement with a new calculation of the superconducting fluctuation diamagnetism. We infer s-wave pairing and Ginzburg-Landau coherence lengths ${\xi }_{\mathrm{ab}}$(0)=13.6±0.8 Å and ${\xi }_c$(0)=1.23±0.19 Å. Both of the order-parameter bands are found to be essential in the fit. Part of the above negative curvature is inferred to arise from the normal-state background.