Large anomalous Hall and Nernst effects in the ferromagnetic semimetal candidate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Mn</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">Sn</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>
Jianli Bai, Qingxin Dong, Bin-Bin Ruan, Libo Zhang, Qiaoyu Liu, Jingwen Cheng, Pinyu Liu, Cundong Li, Yingrui Sun, Yu Huang, Zhi‐An Ren, Genfu Chen
Abstract
Recent theoretical calculations have shown that ${\mathrm{Mn}}_{3}{\mathrm{Sn}}_{2}$, a well-known magnetocaloric material with multiple magnetic transitions, possesses both nodal lines and nodal surfaces in its electronic structures, making it an excellent platform for studying anomalous transport properties in magnetic topological candidates. In this work, we performed comprehensive electrical, thermal, and thermoelectric measurements on ${\mathrm{Mn}}_{3}{\mathrm{Sn}}_{2}$ single crystals. The electrical resistivity $\ensuremath{\rho}(T)$ shows an abnormal peak near the Curie temperature, ${T}_{\mathrm{C}2}\ensuremath{\sim}227$ K, and a negative resistivity slope above ${T}_{\mathrm{C}2}$, which are probably related to a large spin-fluctuation scattering. The Seebeck coefficient ${S}_{xx}(T)$ shows a sign reversal below 80 K although the Hall coefficient is always positive, which might be ascribed to the magnon-drag effect. Below ${T}_{\mathrm{C}1}\ensuremath{\sim}262$ K, a significant anomalous Hall effect is observed, and the anomalous Hall resistance $({\ensuremath{\rho}}_{\mathrm{xy}}^{A})$ peaks at around 7 \textmu{}\ensuremath{\Omega} cm at 200 K. ${\ensuremath{\rho}}_{\mathrm{xy}}^{A}$ exhibits a quadratic dependence on the longitudinal resistivity ${\ensuremath{\rho}}_{xx}$, and the anomalous Hall conductivity ${\ensuremath{\sigma}}_{\mathrm{xy}}^{A}$ remains nearly temperature independent below 200 K, suggesting the dominance of the intrinsic Berry-phase mechanism. Correspondingly, we also detect a large anomalous Nernst effect, with the anomalous Nernst coefficient reaching approximately $1\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{V}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ at 200 K. Despite ${\mathrm{Mn}}_{3}{\mathrm{Sn}}_{2}$ exhibiting robust ferromagnetism, its anomalous Hall angle (2.5%), anomalous Nernst angle (6.5%), and large anomalous Nernst coefficient $(1.65\phantom{\rule{4pt}{0ex}}\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{V}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{T}}^{\ensuremath{-}1})$ surpass those observed in typical ferromagnetic materials. Our results experimentally demonstrate the existence of topologically nontrivial states in ${\mathrm{Mn}}_{3}{\mathrm{Sn}}_{2}$.