  We report room temperature long-distance spin transport of magnons in
antiferromagnetic thin film hematite doped with Zn. The additional dopants
significantly alter the magnetic anisotropies, resulting in a complex
equilibrium spin structure that is capable of efficiently transporting spin
angular momentum at room temperature without the need for a well-defined, pure
easy-axis or easy-plane anisotropy. We find intrinsic magnon spin-diffusion
lengths of up to 1.5 {\mu}m, and magnetic domain governed decay lengths of 175
nm for the low frequency magnons, through electrical transport measurements
demonstrating that the introduction of non-magnetic dopants does not strongly
reduce the transport length scale showing that the magnetic damping of hematite
is not significantly increased. We observe a complex field dependence of the
non-local signal independent of the magnetic state visible in the local
magnetoresistance and direct magnetic imaging of the antiferromagnetic domain
structure. We explain our results in terms of a varying and
applied-field-dependent ellipticity of the magnon modes reaching the detector
electrode allowing us to tune the spin transport.
