  The antisymmetric interlayer exchange interaction, i.e., interlayer
Dzyaloshinskii-Moriya interaction (IL-DMI) has attracted significant interest
since this long-range chiral spin interaction provides a new dimension for
controlling spin textures and dynamics. However, the role of IL-DMI in the
field induced and spin-orbit torque (SOT) induced switching of synthetic
ferrimagnets (SFi) has not been uncovered. Here, we exploit interlayer chiral
exchange bias fields in SFi to address both the sign and magnitude of the
IL-DMI. Depending on the degree of imbalance between the two magnetic moments
of the SFi, the amount of asymmetry, addressed via loop shifts of the
hysteresis loops under an in-plane field reveals a unidirectional and chiral
nature of the IL-DMI. The devices are then tested with SOT switching
experiments and the process is examined via both transient state and steady
state detection. In addition to field-free SOT switching, we find that the
combination of IL-DMI and SOT give rise to multi-resistance states, which
provides a possible direction for the future design of neuromorphic computing
devices based on SOT. This work is a step towards characterizing and
understanding the IL-DMI for spintronic applications.
