The existence of Superconductivity in Nb_(1.75)Ta_(0.25)PdS_5

摘要

Nb_2PdSs is a novel superconductor having promising potential for applications. Synthesis of this by solid state reaction, characterization using susceptibility and resistivity of Ta substituted Nb_2PdS_5 is reported in the present paper. Nb_(1.75)Ta_(0.25)PdS_5 shows a diamagnetic transition at 6K while the onset of superconducting transition in resistivity is found at 6.73K; the slight difference is attributed to Aslamazov-Larkin paraconductivity fluctuations. This can be ascertained from the fact that the transition seen in resistivity is so broad that the zero resistance state is elusive due to weak inter grain coupling. We also report temperature dependence of resistivity under magnetic fields up to 16T that shows considerable broadening in fields that can be attributed to the field induced resistive state with underlying vortex motion. The results are explained based on models like thermally activated flux flow (TAFF) in the light of Kramer's relation. The normal state just above T_c has a negative temperature co-efficient of resistivity reminiscent of the Anderson localization scenario. The estimated critical field of 27T is more than two times higher than that of Pauli limit.