Magnetism-dependent phonon anomaly in LaFeAsO observed via inelastic x-ray scattering

TitleMagnetism-dependent phonon anomaly in LaFeAsO observed via inelastic x-ray scattering
Publication TypeJournal Article
Year of Publication2013
AuthorsHahn SE, Tucker GS, Yan JQ, Said AH, Leu BM, McCallum RW, Alp EE, Lograsso TA, McQueeney RJ, Harmon BN
Journal TitlePhysical Review B
Date Published03
Type of ArticleArticle
ISBN Number1098-0121
Accession NumberWOS:000316792300003
Keywordsbrillouin-zone integrations, high-temperature superconductivity, iron-pnictides

The phonon dispersion was measured at room temperature along (0,0, L) in the tetragonal phase of LaFeAsO using inelastic x-ray scattering. Spin-polarized first-principles calculations imposing various types of antiferromagnetic order are in better agreement with the experimental results than nonmagnetic calculations, although the measurements were made well above the magnetic ordering temperature, T-N. Splitting observed between two A(1g) phonon modes at 22 and 26 meV is only reproduced in spin-polarized calculations. Magnetostructural effects similar to those observed in the AFe(2)As(2) (A = Ca, Sr, Ba, Eu) materials are present in LaFeAsO. The inclusion of Fe spin is necessary to find reasonable agreement of the calculations with the measured spectrum well above T-N. On-site Fe and As force constants show significant softening compared to nonmagnetic calculations, however an investigation of the real-space force constants associates the magnetoelastic coupling with a complex renormalization instead of softening of a specific pairwise force. DOI: 10.1103/PhysRevB.87.104518

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