  Topological magnetic excitations rooted in Dzyaloshinskii-Moriya interaction
(DMI) are promising information carriers for next-generation memory and
spintronic devices. The recently discovered two-dimensional (2D) magnets
provide fertile new platforms for revealing rich physical phenomena with
atomic-scale precision, as exemplified by the enhanced DMI associated with an
effective electric field that breaks the inversion symmetry. Here we use
first-principles calculations to establish a conceptually difierent
compositional engineering approach to induce giant DMI in a representative
CrMnI$_6$ 2D magnet, and the underlying mechanism is rooted in the spontaneous
inversion symmetry breaking in the bipartite system. Using atomistic magnetics
simulations, we further reveal that bimeronic excitations can emerge upon
cooling a spin random state or perturbing a ferromagnetic state. Strikingly,
the bimeron can exhibit unidirectional soliton-like propagation, and such a
ratchet phenomenon is highly desirable for racetrack memories. These findings
may prove instrumental in developing novel devices for quantum information
based on 2D magnets.
