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

TL;DR

This study synthesizes and characterizes SmFeAsO and fluorine-doped SmFeAs(O0.93F0.07), revealing how sintering affects microstructure, magnetic behavior, and superconductivity, with high critical fields suggested by magnetoresistivity data.

Contribution

It provides detailed structural, microstructural, and magnetic analysis of SmFeAsO and its fluorine-doped variant, highlighting effects of sintering and F-doping on properties.

Findings

Sintering improves grain connectivity but reduces sample purity.

F-doping suppresses magnetic order at 140 K and induces superconductivity.

High critical fields are indicated by magnetoresistivity measurements.

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.