Physical property characterization of single step synthesized NdFeAsO0.80F0.20 bulk 50 K superconductor
National Physical Laboratory (CSIR), Dr. K.S. Krishnan Marg, 110012 New Delhi, India
2 Department of Physics, University of Rajasthan, 302055, Jaipur, Rajasthan, India
Corresponding author: a email@example.com
Revised: 10 November 2010
Published online: 21 December 2010
We report an easy single step synthesis route of title compound NdFeAsO0.80F0.20 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 Tc (R = 0) at 48 K and a very high upper critical field (Hc2) of up to 345 T. Magnetic measurements exhibited bulk superconductivity in terms of diamagnetic onset below 50 K. The lower critical field (Hc1) 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 FeOx impurity in the matrix. In specific heat measurements a jump is observed in the vicinity of superconducting transition (Tc) 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 Tc, thus indicating dominant carriers to be of n-type in NdFeAsO0.80F0.20 superconductor. The granularity of the bulk superconducting NdFeAsO0.8F0.2 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.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2010