Influence of Magnetism on Phonons in CaFe2As2 Via Inelastic X-ray Scattering

TL;DR

This study investigates how magnetism influences phonon behavior in CaFe2As2, revealing that including antiferromagnetic order in calculations aligns theoretical predictions with experimental phonon dispersion data.

Contribution

The paper demonstrates that spin-polarized ab initio calculations with antiferromagnetic order significantly improve phonon predictions in CaFe2As2.

Findings

Antiferromagnetic correlations persist in the tetragonal phase.

Spin-polarized calculations match experimental phonon dispersion.

Magnetism strongly affects phonon properties in CaFe2As2.

Abstract

In the iron pnictides, the strong sensitivity of the iron magnetic moment to the arsenic position suggests a significant relationship between phonons and magnetism. We measured the phonon dispersion of several branches in the high temperature tetragonal phase of CaFe2As2 using inelastic x-ray scattering on single-crystal samples. These measurements were compared to ab initio calculations of the phonons. Spin polarized calculations imposing the antiferromagnetic order present in the low temperature orthorhombic phase dramatically improve agreement between theory and experiment. This is discussed in terms of the strong antiferromagnetic correlations that are known to persist in the tetragonal phase.