  In this paper, we study the domain wall motion induced by vertical current
flow in asymmetric magnetic tunnel junctions. The domain wall motion in the
free layer is mainly dictated by the current-induced field-like torque acting
on it. We show that as we increase the MTJ asymmetry, by considering dissimilar
ferromagnetic contacts, a linear-in-voltage field-like torque behavior is
accompanied by an enhancement in the domain wall displacement efficiency and a
higher degree of bidirectional propagation. Our analysis is based on a
combination of a quantum transport model and magnetization dynamics as
described by the Landau-Lifshitz-Gilbert equation, along with comparison to the
intrinsic characteristics of a benchmark in-plane current injection domain wall
device.
