Scaling behavior of the specific heat of a LuBa2Cu3O7-y single crystal near the Hc2 line.

Abstract

High-resolution specific-heat measurements have been performed on an untwinned single crystal of ${\mathrm{LuBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathit{y}}$ in an applied magnetic field, along the c axis, of up to 5 T. The zero-field data near the normal-superconducting transition temperature (${\mathit{T}}_{\mathit{c}}$=92.5 K) display a very large and sharp specific-heat anomaly. Among various models for scaling the magnetic field and temperature-dependent specific-heat data, a model which incorporates the two-dimensional nature of this transition provides the best description of our data. A narrow region of crossover to three-dimensional behavior is also observed.