Fluctuations in YBa₂Cu₃O₆.₅ single crystal: an evidence for 2D->3D crossover

Original · EN

Magnetization measurements as a function of temperature are reported for YBa₂Cu₃O₆.₅ crystal (Tc=45.2 K) for fields between 0.2 to 3.5Tesla. All isochamps for H>1 Tesla intersect at T₂D⋆≃ 42.8K, implying fluctuations contribution to the magnetization. These curves collapse into a single curve when magnetization and temperature are scaled according to the predicted ''2D scaling'' in the fluctuation regime. Surprisingly, the low field curves also intersect, at T₃D⋆≃ 43.4 K, and they obey a 3D scaling. We provide a theoretical picture of the magnetization in the fluctuation regime based on the Lawrence-Doniach model. Within this model we calculate the field and temperature dependence of the magnetization. The two intersection points and the 2D→ 3D crossover are consistent with the experimental observation.