Anomalous magneto-elastic coupling in Au-doped BaFe2As2

We used polarization-resolved Raman scattering to study magneto-elastic coupling in Ba(Fe_1-xAu_x)₂As₂ crystals as a function of light Au-doping, materials for which temperatures of the structural transition (T_S) and of the magnetic ordering transition (T_N) split. We study the appearance of the A_g (As)phonon intensity in the XY scattering geometry that is very weak just below T_S, but for which the intensity is significantly enhanced below T_N. In addition, the A_g (As) phonon shows an asymmetric line shape below T_N and an anomalous linewidth broadening upon Au-doping in the magnetic phase. We demonstrate that the anomalous behavior of the A_g (As) phonon mode in the XY scattering geometry can be consistently described by a Fano model involving the A_g (As) phonon mode interacting with the B_2g symmetry-like magnetic continuum in which the magneto-elastic coupling constant is proportional to the magnetic order parameter.

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• Read more on Phys. Rev. B 102, 014501 (2020)