Large Anomalous Hall Effect at Room Temperature in a Fermi-Level-Tuned Kagome Antiferromagnet

Antiferromagnets are promising materials for ultrafast spintronic memory and logic applications. Of particular interest are the noncollinear kagome antiferromagnets Mn₃X (X = Ga, Ge, Sn) that surprisingly show anomalous Hall effect (AHE) despite the vanishing net moment. So far, extensive studies have focused on Mn₃Sn and Mn₃Ge. By contrast, there are only scarce studies on polycrystalline hexagonal Mn₃Ga and no report on the Mn₃Ga single crystal. Here, we show the first experimental realization of Ga-rich hexagonal Mn₃Ga single crystals that exhibit relatively large and highly anisotropic anomalous Hall conductivity of 150 S/m at 300 K, a value largely surpasses state-fo-the-art Mn₃Ge and Mn₃Sn. The observed AHE is associated with the chiral noncollinear arrangement of Mn moments within the kagome plane with a net moment of only 0.05 μ_B/f.u., which can be easily controlled by a moderate external field. Our ab initio band structure calculations suggest the off-stoichiometry promotes an upshift of the Fermi level in Ga-rich Mn₃Ga, leading to the enhanced AHE. This work demonstrated efficient Fermi level engineering of AHE in kagome antiferromagnet via off-stoichiometric substitutional alloying and identified Mn₃Ga as an extremely interesting material for antiferromagnetic spintronics.