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Magnetic anisotropy in single-crystalline antiferromagnetic Mn2⁢Au

Publication Type
Journal
Journal Name
Physical Review Materials
Publication Date
Page Number
084413
Volume
8
Issue
8

Multiple recent studies have identified the metallic antiferromagnet Mn2⁢Au to be a candidate for spintronic applications due to apparent in-plane anisotropy, preserved magnetic properties above room temperature, and current-induced Néel vector switching. Crystal growth is complicated by the fact that Mn2⁢Au melts incongruently. We present a bismuth flux method to grow millimeter-scale bulk single crystals of Mn2⁢Au in order to examine the intrinsic anisotropic electrical and magnetic properties. Flux quenching experiments reveal that the Mn2⁢Au crystals precipitate below 550⁢∘⁢C, about 100⁢∘⁢C below the decomposition temperature of Mn2⁢Au. Bulk Mn2⁢Au crystals have a room-temperature resistivity of 16–19 µ⁢Ωcm and a residual resistivity ratio of 41. Mn2⁢Au 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 Mn2⁢Au constrains the 𝑎⁢𝑏-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 Mn2⁢Au is quite isotropic, despite clear differences in 𝑎⁢𝑏-plane and 𝑎⁢𝑐-plane magnetocrystalline anisotropy. Mn2⁢Au 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, Fe2⁢As (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 Mn2⁢Au.