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arXiv · 1112.0261

Phonon softening near structural transition in BaFe2As2 observed by inelastic x-ray scattering

Jennifer L. Niedziela·D. Parshall·K. A. Lokshin·A. S. Sefat·A. Alatas·T. Egami
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Abstract

In this work we present the results of an inelastic x-ray scattering experiment detailing the behavior of the transverse acoustic [110] phonon in BaFe2As2 as a function of temperature. When cooling through the structural transition temperature, the transverse acoustic phonon energy is reduced from the value at room temperature, reaching a maximum shift near inelastic momentum transfer q=0.1. This softening of the lattice results in a change of the symmetry from tetragonal to orthorhombic at the same temperature as the transition to long-range antiferromagnetic order. While the lattice distortion is minor, the anisotropy in the magnetic exchange constants in pnictide parent compounds is large. We suggest mechanisms of electron-phonon coupling to describe the interaction between the lattice softening and onset of magnetic ordering.

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Jennifer L. Niedziela, D. Parshall, K. A. Lokshin, A. S. Sefat, A. Alatas, T. Egami. 2011-12-01. Phonon softening near structural transition in BaFe2As2 observed by inelastic x-ray scattering. https://doi.org/10.1103/physrevb.84.224305

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