  The Mn3X family of compounds was the first in which a large anomalous Hall
effect (AHE) was predicted to arise from a purely antiferromagnetic structure,
due to the Berry curvature in momentum space. Nearly simultaneously with this
prediction, a large AHE was observed experimentally in one of the hexagonal
members of this family, Mn3Sn. Aligning antiferromagnetic domains, a necessary
step for observation of the AHE, is more challenging for the cubic members of
the Mn3X family, due to a combination of a smaller spontaneous ferromagnetic
moment and much stronger magnetic anisotropy. Here, we use a combination of
uniaxial stress and applied magnetic field to align domains of bulk
single-crystal Mn3Pt, and demonstrate for the first time a substantial AHE in a
bulk sample of a cubic member of the Mn3X family. The AHE remains locked in
with essentially no quantitative variation when the stress is ramped back to
zero, which shows that it is not a consequence of any stress-induced
ferromagnetic moment.
