Synthesis and Para-conductivity Analyses of TlBa2(Ca 3 − y Mg y )Cu4 O 1 2 − δ Superconductors

Abstract

TlBa 2(Ca 3−yMg y)Cu 4O12−δ (y=0,0.5,1.0, 1.5,2) superconductors are synthesized at normal pressure, and the influence of doped Mg atoms on the superconductivity parameters at the microscopic level is investigated by carrying out para-conductivity analyses of conductivity data. The samples have shown tetragonal structure, and the unit cell volume decreases with increased Mg doping. The onset temperature of superconductivity [ Tc(onset)] and zero resistivity critical temperature [ Tc(R=0)] decreases with Mg. Maximum magnitude of diamagnetism is observed in the samples with Mg of y=2. The apical oxygen mode of the type Tl-O A-Cu(2) and CuO 2 planar oxygen modes are softened as observed in fourier transform infrared spectrometer (FTIR) absorption measurements. The fluctuation-induced conductivity (FIC) analyses of conductivity data have shown the enhancement of inter-plane coupling and coherence length along the c-axis. These analyses have shown an increase in the coherence length along the c-axis and the inter-layer coupling J. The enhancement of inter-plane may possibly be arising due to a small decrease in the value of the order parameter of the carriers from ∣ψ∣ 2=1 in the CuO 2 planes in Mg-doped samples. The values of Bc0(T), Bc1(T), Jc(0) are suppressed with the increased incorporation of Mg, which most likely arises due to the weak coupling of the grains induced by Mg doping.