  The compensated magnetic order and characteristic, terahertz frequencies of
antiferromagnetic materials makes them promising candidates to develop a new
class of robust, ultra-fast spintronic devices. The manipulation of
antiferromagnetic spin-waves in thin films is anticipated to lead to new exotic
phenomena such as spin-superfluidity, requiring an efficient propagation of
spin-waves in thin films. However, the reported decay length in thin films has
so far been limited to a few nanometers. In this work, we achieve efficient
spin-wave propagation, over micrometer distances, in thin films of the
insulating antiferromagnet hematite with large magnetic domains whilst
evidencing much shorter attenuation lengths in multidomain thin films. Through
transport and magnetic imaging, we conclude on the role of the magnetic domain
structure and spin-wave scattering at domain walls to govern the transport. We
manipulate the spin transport by tailoring the domain configuration through
field cycle training. For the appropriate crystalline orientation, zero-field
spin-transport is achieved across micrometers, as required for device
integration.
