Evidence for two-dimensional superconducting fluctuations in CaLaBaCu3O7-delta

We report measurements of the magnetization and diamagnetic susceptibility of a polycrystal of LaBaCaCu3O7-delta. The sample has a zero-field transiti on temperature T-c0 = 77 K and a transition width of 2.0 K. The results sho w large fluctuation effects, which can be explained by Ginzburg-Landau fluc tuation theory for a two-dimensional (2D) system. The experimental data for the magnetization in high magnetic fields (20-50 kOe), were fitted by usin g a theoretical model based on the lowest-Landau-levels approximation, show ing good agreement. The weak-field fluctuation diamagnetic susceptibility a bove T-c, can be fitted well in terms of the 2D Lawrence-Doniach model.