Magnetic anisotropy in single-crystalline antiferromagnetic Mn2Au

Multiple recent studies have identified the metallic antiferromagnet Mn₂Au to be a candidate for spintronic applications due to apparent in-plane anisotropy, preserved magnetic properties above room temperature, and current-induced N\'eel vector switching. Crystal growth is complicated by the fact that Mn₂Au melts incongruently. We present a bismuth flux method to grow millimeter-scale bulk single crystals of Mn₂Au in order to examine the intrinsic anisotropic electrical and magnetic properties. Flux quenching experiments reveal that the Mn₂Au crystals precipitate below 5500.16em0ex^∘C, about 1000.16em0ex^∘C below the decomposition temperature of Mn₂Au. Bulk Mn₂Au crystals have a room-temperature resistivity of 16--19 Ω0.16em0excm and a residual resistivity ratio of 41. Mn₂Au crystals have a dimensionless susceptibility on the order of 10^-4 (SI units), comparable to calculated and experimental reports on powder samples. Single-crystal neutron diffraction confirms the in-plane magnetic structure. The tetragonal symmetry of Mn₂Au constrains the $ab$-plane magnetic susceptibility to be constant, meaning that χ₁₀₀=χ₁₁₀ in the low-field limit, below any spin-flop transition. We find that three measured magnetic susceptibilities χ₁₀₀, χ₁₁₀, and χ₀₀₁ are the same order of magnitude and agree with the calculated prediction, meaning the low-field susceptibility of Mn₂Au is quite isotropic, despite clear differences in $ab$-plane and $ac$-plane magnetocrystalline anisotropy. Mn₂Au is calculated to have an extremely high in-plane spin-flop field above 30 T, which is much larger than that of another in-plane antiferromagnet, Fe₂As (less than 1 T). The subtle anisotropy of intrinsic susceptibilities may lead to dominating effects from shape, crystalline texture, strain, and defects in devices that attempt spin readout in Mn₂Au.