Effect of antimony substitution in iron pnictide compounds

TL;DR

This study investigates how substituting arsenic with antimony affects the structural and electronic properties of iron pnictides, revealing changes in magnetic and superconducting transition temperatures and solubility limits.

Contribution

It provides new insights into the effects of antimony substitution on the crystallography and physical properties of 1111- and 122-iron arsenides.

Findings

SDW transition temperature decreases with Sb content in LaFeAsO.

Superconducting transition temperature initially increases with Sb substitution.

No solubility of Sb observed in 122-iron arsenides.

Abstract

In the present study we have examined the effect of negative chemical pressure in iron pnictides. We have synthesized substitution series replacing arsenic by antimony in a number of 1111- and 122-iron arsenides and present their crystallographic and physical properties. The SDW transition temperature in LaFeAs$_{\mathrm{1-x}}$Sb$_{\mathrm{x}}$O decreases with increasing antimony content, while the superconducting transition temperature in LaFeAs$_{\mathrm{1-x}}$Sb$_{\mathrm{x}}$O$_{\mathrm{0.85}}$F$_{\mathrm{0.15}}$ initially increases with Sb substitution. 1111-compounds with samarium instead of lanthanum have a smaller unit cell volume. In these phases, no Sb solubility is observed. There is also no apparent solubility of antimony in the 122-iron arsenides.