Intrinsic parameters of aT*-phaseSmLa0.8Sr0.2CuO4−δsingle crystal and the fluctuation effects deduced from magnetization data

Abstract

We report the result of a detailed study on the equilibrium thermodynamic properties from the reversible magnetization data of a ${T}^{*}$-phase ${\mathrm{SmLa}}_{0.8}{\mathrm{Sr}}_{0.2}{\mathrm{CuO}}_{4}$ single crystal ${(T}_{c}^{\mathrm{on}}\ensuremath{\approx}24 \mathrm{K}).$ The analysis of those data outside the critical fluctuation region was performed according to the Hao-Clem model, while the data in the critical region were analyzed on the basis of the nonperturbative two-dimensional Ginzburg-Landau lowest Landau level scaling theory developed by Te\ifmmode \check{s}\else \v{s}\fi{}anovi\ifmmode \acute{c}\else \'{c}\fi{} et al. The analysis outside the critical region yields a complete set of intrinsic parameters of this system consisting of the Ginzburg-Landau parameter $\ensuremath{\kappa},$ the thermodynamic critical field ${H}_{c},$ the magnetic field penetration depth $\ensuremath{\lambda},$ the Cooper pairs coherence length $\ensuremath{\xi},$ and the upper critical field ${H}_{c2}.$ We found that the values of ${H}_{c}(T)$ derived from the Hao-Clem model were generally smaller than those obtained from scaling analysis in the critical region. According to the result of analysis in the critical region, these differences are suggested to have their origin in the thermal fluctuation effect evidenced by the existence of a crossing point in the magnetization data at ${T}^{*}=23.25 \mathrm{K},$ right below the onset critical temperature.