Superconducting transition temperature of co-doped Y_0.95Pr _0.05Ba₂(Cu_1-xMn_x)₃O _7-δ superconductors for x ≤0.02

Values of the superconducting transition temperature T_c extracted from the resistivity and ac susceptibility of Y_0.95Pr _0.05Ba₂(Cu_1-xMn_x)₃O _7-δ (x ≤0.02) are found to follow the same qualitative variation with the Mn content. Both lead, in particular, to lower T_c for the x=0.005 sample than those of the x=0.0, 0.0075 and 0.01 samples. Comparing T_c with difference of resistivities with and without Pr for various x, it has been argued that electronic effects-dominate over the potential scattering in suppressing T_c below x=0.02. Superconducting volume fraction f_g (as deduced through imaginary part χ′ of the ac susceptibility at the peak temperature) when considered in conjunction with the average grain size for the x=0.005 sample, indicates that the smaller size of the grains in x=0.005 sample leads to stronger fluctuations. This is an additional source for the larger T_c degradation in the x=0.005 sample.