Effect of Erbium substitution on temperature and field dependence of thermally activated flux flow resistance in Bi-2212 superconductor

Thermally activated flux flow (TAFF) regime of Er doped Bi2Sr2Ca1−xErxCu2O8+δ (x=0.0, 0.1, 0.3) polycrystalline systems have been investigated using magneto-transport measurements up to 70 kOe magnetic field. High quality single phase samples have been prepared by standard solid state reaction method. The activation energy or pinning strength (U0) have been calculated using thermally activated flux flow (TAFF) model by linear fitting from the semi-logarithmic curve of ln ρ vs 1/T. It has been observed that activation energy (U0) decreases with Er substitution and U0 follows power law dependence with magnetic field for all three samples. Irreversibility lines (IL) have been drawn from the magneto-transport data for all three samples and it is observed that IL shifts to lower temperature with higher Er concentration. It is confirmed from the above results that pinning strength becomes weaker with Er doping. Finally, the variation of U0 have been shown with temperature by re-plotting -T(ln (ρ/ρ100)) vs T for three samples showing non-linear dependence with temperature.