Physical property characterization of single step synthesized NdFeAsO _0.80F _0.20 bulk 50 K superconductor

We report an easy single step synthesis route of title compound NdFeAsO _0.80F _0.20 superconductor having bulk superconductivity below 50 K. The title compound is synthesized via solid-state reaction route by encapsulation in an evacuated (10 ^-3 Torr) quartz tube. Rietveld analysis of powder X-ray diffraction data shows that compound crystallized in tetragonal structure with space group P4/nmm. R(T)H measurements showed superconductivity with T _c (R = 0) at 48 K and a very high upper critical field (H _c2) of up to 345 T. Magnetic measurements exhibited bulk superconductivity in terms of diamagnetic onset below 50 K. The lower critical field (H _c1) is around 1000 Oe at 5 K. In normal state i.e., above 60 K, the compound exhibited purely paramagnetic behavior and thus ruling out the presence of any ordered FeO _x impurity in the matrix. In specific heat measurements a jump is observed in the vicinity of superconducting transition (T _c ) along with an upturn at below T = 4 K due to the AFM ordering of Nd ⁺³ ions in the system. The Thermo-electric power (TEP) is negative down to T _c, thus indicating dominant carriers to be of n-type in NdFeAsO _0.80F _0.20 superconductor. The granularity of the bulk superconducting NdFeAsO _0.8F _0.2 sample is investigated and the intra and inter grain contributions have been individuated by looking at various amplitude and frequencies of the applied AC drive magnetic field.