Tuning the anomalous Hall effect of the high Curie temperature nodal-line metal Fe3Ga via Mn doping and associated band topology

The $\mathrm{F}{\mathrm{e}}_{3}\mathrm{Ga}$ alloy with $D{0}_{3}$ phase has been reported to exhibit remarkable anomalous transport properties arising from the topological nontrivial nodal lines. In this study, the effect of Mn doping on the magnetic, electronic, and anomalous transport properties of polycrystalline $\mathrm{F}{\mathrm{e}}_{3\ensuremath{-}x}\mathrm{M}{\mathrm{n}}_{x}\mathrm{Ga}$ ($x=0$, 0.4, 0.6, and 1) are investigated. As the Mn doping level increases, the saturated magnetization at 10 K gradually decreases, while the anomalous Hall resistivity ${\ensuremath{\rho}}_{xy}^{A}$ shows a significant increasing trend, reaching a maximum value of 7.2 \textmu{}\ensuremath{\Omega} cm in $\mathrm{F}{\mathrm{e}}_{2}\mathrm{MnGa}$. The analysis of anomalous Hall effect (AHE) based on the expanded scaling mechanism proposed by Tian et al. [Phys. Rev. Lett. 103, 087206 (2009)] suggests that the AHE in $\mathrm{F}{\mathrm{e}}_{3}\mathrm{Ga}$ is dominated by intrinsic mechanism, with an intrinsic anomalous Hall conductivity (${\ensuremath{\sigma}}_{xy}^{\mathrm{int}}$) of 288 S/cm. In samples with $x=0.4$, extrinsic impurity and phonon scattering cannot be neglected and ${\ensuremath{\sigma}}_{xy}^{\mathrm{int}}$ decreases to 174 S/cm. As $x$ increases to 0.6, the intrinsic mechanism vanishes and the extrinsic impurity and phonon-scattering mechanisms become dominant in the AHE. A further enhanced extrinsic scattering in the AHE is observed in $\mathrm{F}{\mathrm{e}}_{2}\mathrm{MnGa}$ at low temperature with an anomalous Hall conductivity of 237 S/cm at 10 K. From ab initio calculations, we notice a ${\ensuremath{\sigma}}_{xy}^{\mathrm{int}}$ peak of 2310 S/cm locates approximately \ensuremath{-}0.5 eV below Fermi level (${E}_{\mathrm{F}}$) in $\mathrm{F}{\mathrm{e}}_{3}\mathrm{Ga}$ alloy, originating from the six linked nodal rings. When one Fe atom is substituted by Mn, this peak shifts to 0.5 eV above ${E}_{\mathrm{F}}$ in $\mathrm{F}{\mathrm{e}}_{2}\mathrm{MnGa}$. We propose that partially doping Fe with Mn in $\mathrm{F}{\mathrm{e}}_{3}\mathrm{Ga}$ may tailor the large peak of ${\ensuremath{\sigma}}_{xy}^{\mathrm{int}}$ around ${E}_{\mathrm{F}}$.