Excess fluctuation conductivity and superconducting parameters of CaLa-doped Nd-123

摘要

Polycrystalline samples of Nd _(1-x)Ca _xBa _(2-x)La _xCu _3O _(7-δ) (with 0.0 ≤ x ≤ 0.15) were prepared by the standard solid state method. The co-doping effect was studied on the resistivity as a function of temperature and doping concentration x. The fluctuation conductivity was analyzed using the Aslamazov and Larkin model (AL). For all samples, three fluctuation regions; i.e. one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D), were clearly observed with decreasing temperature. A critical region was also observed for high doping concentration (x < 0.1). Superconductivity parameters such as the effective coherence length ξ _p, the coherence length along the c-axis ξ _c and ab plane ξ _(ab), the effective interlayer separation d, anisotropy parameter γ _a, and the upper critical magnetic field B _(c2) along the c-axis and ab plane were obtained. It was also found that CuO _x chains contribute to conducting.