Synthesis, crystal structure, microstructure, transport and magnetic properties of SmFeAsO and SmFeAs(O0.93F0.07)

Abstract

SmFeAsO and the isostructural superconducting SmFeAs(O0.93F0.07) samples were prepared. Characterization by means of Rietveld refinement of X-ray powder diffraction data, scanning electron microscope observation, transmission electron microscope analysis, resistivity and magnetization measurements were carried out. Sintering treatment strongly improves the grain connectivity, but, on the other hand, induces a competition between the thermodynamic stability of the oxy-pnictide and Sm2O3, hence worsening the purity of the sample. In the pristine sample both magnetization and resistivity measurements clearly indicate that two different sources of magnetism are present: the former related to Fe ordering at 140 K and the latter due to the Sm ions that orders antiferromagnetically at low temperature. The feature at 140 K disappears in the F-substituted sample and, at low temperatures a superconducting transition appears. The magnetoresistivity curves of the F-substituted sample probably indicates very high critical field values.

Submitted to: Superconductor Science and Technology

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• Superconductivity and Phase Diagram in the Iron-based Arsenic-oxides ReFeAsO1-delta (Re = rare earth metal) without F-Doping
• Very High Field Two-Band Superconductivity in LaFeAsO_0.89F_0.11
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• The optical phonon spectrum of SmFeAsO
• Effect of the chemical pressure on superconductivity and SDW in undoped and 15%F doped La1-yYyFeAsO compounds
• Resistivity saturation in PrFeAsO${}_{1-x}$F${}_y$ superconductor: An evidence of strong electron-phonon coupling
• Intrinsic ferromagnetic impurity phases in SmFeAsO1-xFx detected by muSR