Investigating the magnetoelastic properties in FeSn and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Fe</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>Sn</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math> flat band metals
Yu Tao, Luke Daemen, Yongqiang Cheng, Jöerg C. Neuefeind, Despina Louca
Abstract
Topological quantum magnets FeSn and ${\mathrm{Fe}}_{3}{\mathrm{Sn}}_{2}$ were studied using neutron scattering and first-principles calculations. Both materials are metallic but host dispersionless flat bands with Dirac nodes at the $K$ point in reciprocal space. The local structure determined from the pair density function analysis of the neutron-diffraction data provided no evidence for electron localization in both compounds, consistent with their metallic nature. At the same time, in FeSn, an anomalous suppression in the $c$-axis lattice constant coupled with changes in the phonon spectra were observed across ${T}_{N}$ indicating the presence of magnetoelastic coupling and spin-phonon interactions. In addition, it was observed that spin waves persisted well above ${T}_{N}$, suggesting that the in-plane ferromagnetic spin correlations survive at high temperatures. In contrast, no lattice anomaly was observed in ${\mathrm{Fe}}_{3}{\mathrm{Sn}}_{2}$. The inelastic signal could be mostly accounted for by phonons, determined from density-functional theory, showing typical softening on warming.