Fluctuations in single-crystal YBa2Cu3O6.5 : Evidence for crossover from two-dimensional to three-dimensional behavior
نویسندگان
چکیده
Magnetization measurements as a function of temperature are reported for YBa2Cu3O6.5 crystal (Tc 545.2 K) for fields between 0.2 and 3.5 T. All isochamps for H.1 T intersect at T2D ! .42.8 K, implying a fluctuation contribution to the magnetization. These curves collapse into a single curve when magnetization and temperature are scaled according to the predicted ‘‘two-dimensional ~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.
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