Phonon anomalies associated with spin reorientation in the Kagome ferromagnet Fe3Sn2

TL;DR

This study combines Raman spectroscopy and theoretical simulations to investigate phonon behavior in Fe3Sn2, revealing anomalies linked to spin reorientation and spin-phonon coupling around 100 K.

Contribution

It provides the first detailed analysis of phonon anomalies associated with spin reorientation in the Kagome ferromagnet Fe3Sn2 using combined experimental and theoretical approaches.

Findings

Identification of eight phonon modes consistent with simulations

Weak anomalies in A_{1g} phonon frequencies near 100 K

Linewidth behavior indicating spin-phonon coupling around 100 K

Abstract

Polarization- and temperature-dependent Raman data along with theoretical simulations are presented for the Kagome ferromagnet Fe_3Sn_2. Eight out of nine expected phonon modes were identified. 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. In contrast, the linewidths of all phonon modes follow the conventional exponential broadening up to room temperature except for the softest A_{1g} mode, whose width 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.