%0 Journal Article
%T Magnetism dependent phonon anomaly in LaFeAsO observed via inelastic x-ray scattering
%A S. E. Hahn
%A G. S. Tucker
%A J. -Q. Yan
%A A. H. Said
%A B. M. Leu
%A R. W. McCallum
%A E. E. Alp
%A T. A. Lograsso
%A R. J. McQueeney
%A B. N. Harmon
%J Physics
%D 2012
%I arXiv
%R 10.1103/PhysRevB.87.104518
%X 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 observed in spin-polarized calculations. Magneto-structural effects similar to those observed in the AFe_2As_2 materials are confirmed present in LaFeAsO. The presence 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.
%U http://arxiv.org/abs/1206.1096v1