  Calculations of skyrmions in antiferromagnets (AFMs) are presented, and their
properties compared with skyrmions in corresponding ferromagnets (FMs). The
rates of skyrmion collapse and escape through the boundary of a track, as well
as the binding to and collapse at a non-magnetic impurity, are calculated as a
function of applied magnetic field. The activation energy for skyrmion
annihilation is the same in AFMs and corresponding FMs in the absence of an
applied magnetic field. The pre-exponential factor in the Arrhenius rate law
is, however, different because skyrmion dynamics is different in the two
systems. An applied magnetic field has opposite effects on skyrmions in the two
types of materials. In AFMs the rate of collapse of skyrmions as well as the
rate of escape through the edge of a magnetic strip decreases slightly with
increasing field, while these rates increase strongly for a skyrmion in the
corresponding FMs when the field is directed antiparallel to the magnetization
in the center of the skyrmion. A non-magnetic impurity is less likely to trap a
skyrmion in AFMs especially in the presence of a magnetic field. This, together
with the established fact that a spin polarized current moves skyrmions in AFMs
in the direction of the current, while in FMs skyrmions move at an angle to the
current, demonstrates that skyrmions in AFMs have several advantageous
properties over skyrmions in FMs for memory and spintronic devices.

Materials Science