  Solitonic magnetic excitations such as domain walls and, specifically,
skyrmionics enable the possibility of compact, high density,
ultrafast,all-electronic, low-energy devices, which is the basis for the
emerging area of skyrmionics. The topological winding of skyrmion spins affects
their overall lifetime, energetics and dynamical behavior. In this review, we
discuss skyrmionics in the context of the present day solid state memory
landscape, and show how their size, stability and mobility can be controlled by
material engineering, as well as how they can be nucleated and detected.
Ferrimagnetsnear their compensation points are important candidates for this
application, leading to detailed exploration of amorphous CoGd as well as the
study of emergent materials such as Mn$_4$N and Inverse Heusler alloys. Along
with material properties, geometrical parameters such as film thickness, defect
density and notches can be used to tune skyrmion properties, such as their size
and stability. Topology, however, can be a double-edged sword, especially for
isolated metastable skyrmions, as it brings stability at the cost of additional
damping and deflective Magnus forces compared to domain walls. Skyrmion
deformation in response to forces also makes them intrinsically slower than
domain walls. We explore potential analog applications of skyrmions, including
temporal memory at low density, and decorrelator for stochastic computing at a
higher density that capitalizes on their interactions. We summarize the main
challenges to achieve a skyrmionics technology, including maintaining
positional stability with very high accuracy, electrical readout, especially
for small ferrimagnetic skyrmions, deterministic nucleation and annihilation,
and overall integration with digital circuits with the associated circuit
overhead.
