Iron-Oxypnictide superconductors: Synthesis and physical property characterization

We had reported superconductivity in the SmFe_1-xCo_xAsO (x =0.0 to 1.0) and NdFeAsO_0.8F_0.2 systems[^1,2]. These compounds were synthesized by a simple and versatile single-step solid state reaction route showing superconductivity with T_c of 14 K and 50 K respectively. The parent compounds SmFeAsO and NdFeAsO are nonsuperconducting showing spin density wave (SDW) like antiferromagnetic ordering at about 140–150 K. The partial substitution of Co³⁺at Fe²⁺ site results in the appearance of superconductivity in SmFeAsO. Whereas in NdFeAsO_0.8F_0.2 system, the carriers are introduced by O^2- site F^1- substitution or by introducing the O^1-X oxygen vacancies, which in turn as a result of charge neutrality provide mobile carriers to the superconducting FeAs layer. In this paper we report the synthesis and physical property characterization such as electrical resistivity, magnetization, and specific heat measurements in zero and applied magnetic field, on the above two iron-oxypnictide compounds. A comparison in physical property characterization of the two systems is also discussed in detail.