  Racetrack memory based on magnetic domain walls (DWs) motion exhibits
advantages of small volume and high reading speed. When compared to
current-induced DW motion, voltage-induced DW motion exhibits lower
dissipation. On the other hand, the DW in an antiferromagnet (AFM) moves at a
high velocity with weak stray field. In this work, the AFM DW motion induced by
a gradient of magnetic anisotropy energy under a voltage pulse has been
investigated in theory. The dynamics equation for the DW motion was derived.
The solution indicates that the DW velocity is higher than 100 m/s, and because
of inertia, the DW is able to keep moving at a speed of around 100 m/s for
several nano seconds after turning off the voltage in a period of pulse. The
mechanism for this DW inertia is explained based on the Lagrangian route. On
the other hand, a spin wave is emitted while the DW is moving, yet the DW is
still able to move at an ever increasing velocity with enlarging DW width. This
indicates energy loss from emission of spin wave is less than the energy gain
from the effective field of the gradient of anisotropy energy.
