  Spin waves in magnetic materials are promising information carriers for
future computing technologies due to their ultra-low energy dissipation and
long coherence length. Antiferromagnets are strong candidate materials due, in
part, to their stability to external fields and larger group velocities.
Multiferroic aniferromagnets, such as BiFeO$_3$ (BFO), have an additional
degree of freedom stemming from magnetoelectric coupling, allowing for control
of the magnetic structure, and thus spin waves, with electric field.
Unfortunately, spin-wave propagation in BFO is not well understood due to the
complexity of the magnetic structure. In this work, we explore long-range spin
transport within an epitaxially engineered, electrically tunable,
one-dimensional (1D) magnonic crystal. We discover a striking anisotropy in the
spin transport parallel and perpendicular to the 1D crystal axis. Multiscale
theory and simulation suggests that this preferential magnon conduction emerges
from a combination of a population imbalance in its dispersion, as well as
anisotropic structural scattering. This work provides a pathway to
electrically-reconfigurable magnonic crystals in antiferromagnets.
