Thermal fluctuations in the high-temperature superconductor CaLaBaCu3O7-δ

Magnetization measurements on a polycrystal of CaLaBaCu3O7-δ in high magnetic fields (20 to 50 kOe) are reported. The sample has a zero-field transition temperature Tc0 = 77 K and a transition width of 2.0 K. The results show large fluctuation effects, which can be explained by Ginzburg-Landau fluctuation theory for a two-dimensional system. The magnetization displays good scaling behavior as a function of [T - Tc(H)]/(TH)1/2. The experimental data were fitted by using a theoretical model based in the lowest Landau levels approximation, showing good agreement. We also analyze fluctuation effects in conductivity measurements at zero magnetic field. (orig.)