Large anomalous Hall effect in a non-collinear antiferromagnet Mn$_{3}$Sn at room temperature

Recent development in theoretical and experimental studies have provided a framework for understanding the anomalous Hall effect using Berry-phase concepts, and this perspective has led to predictions that, under certain conditions, a large anomalous Hall effect may appear in spin liquids and antiferromagnets [1, 2]. In this talk, we will present experimental results showing that the antiferromagnet Mn$_{3}$Sn, which has a non-collinear 120-degree spin order, exhibits a large anomalous Hall effect [3]. The magnitude of the Hall conductivity is $\sim$ 20 $\Omega^{-1}$ cm$^{-1}$ at room temperature and $>$ 100 $\Omega^{-1}$ cm$^{-1}$ at low temperatures. We found that a main component of the Hall signal, which is nearly independent of a magnetic field and magnetization, can change the sign with the reversal of a small applied field, corresponding to the rotation of the staggered moments of the non-collinear antiferromagnetic spin order which carries a very small net moment of a few of m$\mu_{\rm B}$. [1] N. Nagaosa $et \ al$., Rev. Mod. Phys. $\bf{82}$, 1539 (2010). [2] Y. Machida $et \ al$., Nature $\bf{463}$, 210 (2010). [3] S. Nakatsuji, N. Kiyohara and T. Higo, Nature, doi:10.1038/nature15723, (2015).