Anomalous Hall Effect in a Kagome Ferromagnet*

The ferromagnetic kagome lattice is theoretically known to possess topological band structures [1,2]. We have synthesized large single crystals of a kagome ferromagnet Fe$_3$Sn$_2$ which orders ferromagnetically well above room temperature [3]. We have studied the electrical and magnetic properties of these crystals over a broad temperature and magnetic field range.  Both the scaling relation of anomalous Hall effect and anisotropic magnetic susceptibility show that the ferromagnetism of Fe$_3$Sn$_2$ is unconventional.  We discuss these results in the context of magnetism in kagome systems and relevance to the predicted topological properties in this class of compounds.  [1] \emph{Phys. Rev. B} 87 144101 (2013) [2] \emph{Phys. Rev. Lett.} 106 236802 (2011)  [3] \emph{J. Phys: Cond. Mat.} 21 452202 (2009)