Magnetotransport and thermal properties characterization of 55 K superconductor SmFeAsO_0.85F_0.15

This report fairly underlines the magneto-transport, thermal properties characterization and bulk superconductivity in the FeAs-based SmFeAsO0.85F0.1. The phase formation and structure are confirmed by Rietveld analysis of room temperature powder X-ray diffraction (XRD) data. Electron microscopy was employed to unravel the micro structural details, such as perfection of the lattice and the grain morphology including size and boundaries. The electrical and magnetic measurements have been carried out to confirm the bulk superconductivity and understand the nature of electrical transport in the normal and superconducting state. The intra-grain critical current density (J(c)) with applied magnetic field is calculated from isothermal DC magnetization (MH) plots using conventional Bean critical state model. Superconductivity is observed at transition temperature (T-c) above 55 K without HPHT (high pressure high temperature) synthesis route. The value of J(c) is found to be around 5.26 x 10(4) A/cm(2) at 5 K in zero field. The dependence of thermally activated flux flow energy (U/k(B)) on the applied magnetic field has been observed. AC susceptibility measurements were performed for 55 K superconducting SmFeAsO0.85F0.15 sample at various amplitude of applied AC drive field and its granular nature is confirmed. The parent compound SmFeAsO is found to be magnetic with Fe spin density wave (SDW) like order below 150 K, on the other hand the F doped SmFeAsO0.85F0.15 sample is bulk superconducting at below 55 K. Both Fe (SDW) at 150 K for SmFeAsO and 55 K superconductivity in case of SmFeAsO0.85F0.15 sample has confirmed by Specific heat [C-p(T)] measurement too. Further Sm orders anti-ferro-magnetically at 4.5 K for non-superconducting and at 3.5 K for superconducting samples, also the entropy change is reduced significantly for the later than the former. Summarily complete physical property characterization for both non-superconducting SmFeAsO and 55 K superconductor SmFeAsO0.85F0.15 samples is provided and discussed in the current article. (C) 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License