Magnetic and structural transitions in layered FeAs systems: AFe2As2 versus RFeAsO compounds

TL;DR

This study compares magnetic and structural phase transitions in layered FeAs compounds, revealing a first-order SDW transition at 205K in SrFe2As2 and stronger Fe-magnetism compared to similar materials, supported by experimental and theoretical analyses.

Contribution

It provides a comparative analysis of magnetic and structural transitions in SrFe2As2 and related compounds, highlighting differences in transition order and magnetic strength.

Findings

First-order SDW transition at 205K in SrFe2As2.

Stronger Fe-magnetism in SrFe2As2 and EuFe2As2.

High similarity in electronic structure across compounds.

Abstract

Resistivity, specific heat and magnetic susceptibility measurements performed on SrFe2As2 samples evidence a behavior very similar to that observed in LaFeAsO and BaFe2As2 with the difference that the formation of the SDW and the lattice deformation occur in a pronounced first order transition at T_0=205K. Comparing further data evidences that the Fe-magnetism is stronger in SrFe2As2 and in EuFe2As2 than in the other layered FeAs systems investigated up to now. Full potential LDA band structure calculations confirm the large similarity between the compounds, especially for the relevant low energy Fe 3d states. The relation between structural details and magnetic order is analyzed.