Suppressed 3D conductivity in Mn doped Cu0.5Tl0.5Ba2Ca2−yMnyCu3O10−δ superconductors

Abstract

We have synthesised Mn-doped Cu0.5Tl0.5Ba2(Ca2−yMny)Cu3O10−δ superconducting samples and studied their Fluctuation Induced Conductivity (FIC) analysis. The Tc(R = 0) and magnitude of diamagnetism are suppressed with increased Mn-doping in the final compound. FIC analyses have shown a suppression of 3D Lawrence and Doniach (LD) regime and a significant enhancement of 2D LD regime of Mn-doping of y = 0.35. In the sample with Mn-doping of y = 0.5, the 3D LD regime vanishes altogether and only 2D LD regime is observed, showing the confinement of superconductivity in the two dimensional planes. The coherence length along the c-axis and the Fermi velocity of the carriers are suppressed with increased Mn doping. Using the Ginzburg-Landau (GL) number [NG] and GL equations, the thermodynamic critical magnetic field Bc(0), the lower critical field Bc1(0), the upper critical field Bc2(0), the critical current density Jc(0), and penetration depth λp.d are determined. The values of critical fields Bc(0) and Bc1(0) increases, despite suppression in the Tc(R = 0) with increased Mn-doping. The values of Jc(0), the penetration depth Λp.d, and inter-layer coupling are suppressed with enhanced Mn-doping. These observations suggested that Mn ions act as sub-nano-scale pinning centers between the CuO2 planes and their presence at the Ca-sites promote the de-coupling of CuO2 planes.