Temperature dependence of the magnetization of aBi2Sr2CaCu2O8+δsingle crystal close toTc

The magnetization M(T,H) of a ${\mathrm{Bi}}_2$ ${\mathrm{Sr}}_2$ ${\mathrm{CaCu}}_2$ ${\mathrm{O}}_{8+\mathrm{\delta }}$ single crystal has been measured above and below the superconducting transition temperature in externally applied magnetic fields H up to 50 kOe for H∥c. We find that M(T,H) is independent of H at a particular temperature ${\mathit{T}}^{\mathrm{*}}$ for external fields exceeding 10 Oe, and exhibits a two-dimensional (2D) scaling behavior as a function of [T-${\mathit{T}}_{\mathit{c}}$(H)]/(HT${)}^{1/2}$. The parameters ${\xi }_{\mathit{a}\mathit{b}}$(0)≊21.4 Å and ${\xi }_{\mathit{c}}$(0)≊0.4 Å are estimated from fitting the experimental data to a full Lawrence-Doniach model calculation of the fluctuation-induced magnetic susceptibility. From the same analysis, we obtain ${\mathit{dH}}_{\mathit{c}2}$/dT≊-14 kOe/K in the range 5 kOeH