  As a candidate material for applications such as magnetic memory,
polycrystalline antiferromagnets offer the same robustness to external magnetic
fields, THz spin dynamics, and lack of stray field as their single crystalline
counterparts, but without the limitation of epitaxial growth and lattice
matched substrates. Here, we first report the detection of the average Neel
vector orientiation in polycrystalline NiO via spin Hall magnetoresistance
(SMR). Secondly, by applying strain through a piezo-electric substrate, we
reduce the critical magnetic field required to reach a saturation of the SMR
signal, indicating a change of the anisotropy. Our results are consistent with
polycrystalline NiO exhibiting a positive sign of the in-plane
magnetostriction. This method of anisotropy-tuning offers an energy efficient,
on-chip alternative to manipulate a polycrystalline antiferromagnets magnetic
state.
