  Due to the difficulty in detecting and manipulating magnetic states of
antiferromagnetic materials, studying their switching dynamics using electrical
methods remains a challenging task. In this work, by employing heavy metal/rare
earth-transition metal alloy bilayers, we experimentally studied
current-induced domain wall dynamics in an antiferromagnetically coupled
system. We show that the current-induced domain wall mobility reaches a maximum
close to the angular momentum compensation. With experiment and modelling, we
further reveal the internal structures of domain walls and the underlying
mechanisms for their fast motion. We show that the chirality of the
ferrimagnetic domain walls remains the same across the compensation points,
suggesting that spin orientations of specific sublattices rather than net
magnetization determine Dzyaloshinskii-Moriya interaction in heavy
metal/ferrimagnet bilayers. The high current-induced domain wall mobility and
the robust domain wall chirality in compensated ferrimagnetic material opens
new opportunities for high-speed spintronic devices.
