Phonon anomalies associated with spin reorientation in the Kagome ferromagnet Fe₃Sn₂

We present polarization- and temperature-dependent Raman data for the Kagome ferromagnet Fe₃Sn₂. Eight out of nine expected phonon modes were identified and analyzed using lattice dynamical calculations. The experimental energies compare well with those from the simulations. The analysis of the line widths indicates relatively strong phonon-phonon coupling in the range 0.1 to 1. The temperature-dependent frequencies of three A_1g modes show weak anomalies at approximately 100 K. The linewidths of all phonon modes follow the conventional exponential broadening up to room temperature except for the softest A_1g mode.  The widthof this mode exhibits a kink close to 100 K and becomes nearly constant for T > 100 K. These features are indicative of a spin reorientation taking place in the temperature range above 100 K  which might arise from spin-phonon coupling. The low-energy part of the electronic continuum in E_g symmetry depends strongly on temperature. The possible reasons include particle-hole excitation tracking the resistivity, a spin-dependent gap or spin fluctuations.