  In chiral magnets with intrinsic inversion symmetry breaking, it has been
known that two spin waves moving in opposite directions can propagate at
different velocities, exhibiting a phenomenon called magnetochiral
nonreciprocity which allows for realizations of certain spin logic devices such
as a spin-wave diode. Here, we theoretically demonstrate that the spin-wave
nonreciprocity can occur without intrinsic bulk chirality in certain magnets
including easy-cone ferromagnets and easy-cone antiferromagnetic. Specifically,
we show that nonlocal injection of a spin current from proximate normal metals
to easy-cone magnets engenders a non-equilibrium chiral spin texture, on top of
which spin waves exhibit nonreciprocity proportional to the injected spin
current. One notable feature of the discovered nonreciprocal spin waves is its
gapless nature, which can lead to a large thermal rectification effect at
sufficiently low temperatures. We envision that nonlocal electric injection of
chirality into otherwise nonchiral magnets may serve as a versatile route to
realize electrically controllable magnetochiral phenomena in a wide class of
materials.
