Reversible magnetic properties of c-axis-oriented superconducting Bi2Sr2Ca2Cu3O10

Magnetization measurements on c-axis-oriented bulk superconducting Bi2Sr2Ca2Cu3O10 have been carried out with the magnetic field applied parallel to the c axis. Fitting the results to the variation model for magnetization suggested by Hao and Clem shows that the Ginzburg-Landau parameter κ is nearly constant for 74≤T≤86 K, with the value of 170 at 74 K, and slowly increases with temperature from ∼86 to ∼100 K. κ diverges in the vicinity of Tc. This unusual temperature dependence of κ(T) could come from extended fluctuation effects and a limitation of the Hao-Clem theory, which may fail to describe this extremely anisotropic Bi-based superconductor. By fitting the data with the value of κ equal to 170, the deduced values of some of the superconducting parameters are Hc(0)=10 600 Oe, ξ(0)ab=10. 5±0.6, λ(0)ab=1940±13, dHc2/-3.68 T/K near Tc.