Spin spiral and topological Hall effect in Fe3Ga4

A new mechanism for the topological Hall effect (THE) was recently proposed for the spiral magnet ${\mathrm{YMn}}₆{\mathrm{Sn}}₆,$ which requires transverse conical spiral magnetism, induced by external magnetic field, combined with thermally excited helical spiral magnons. In principle, this mechanism should be applicable to other itinerant spiral magnets as well. In this paper, we show that another magnetic compound, ${\mathrm{Fe}}₃{\mathrm{Ga}}₄$, in which THE was observed experimentally before, in one of its phases satisfies this condition, and the proposed theory of thermal-fluctuation-driven THE is quantitatively consistent with the experiment. This finding suggests that this mechanism is indeed rather universal, and the effect may have been observed in other compounds before but overlooked.