  Skyrmions are emerging topological spin structures that are potentially
revolutionary for future data storage and spintronics applications. The
existence and stability of skyrmions in magnetic materials is usually
associated to the presence of the Dzyaloshinskii-Moriya interaction (DMI) in
bulk magnets or in magnetic thin films lacking inversion symmetry. While some
methods have already been proposed to generate isolated skyrmions in thin films
with DMI, a thorough study of the conditions under which the skyrmions will
remain stable in order to be manipulated in an integrated spintronic device are
still an open problem. The stability of such structures is believed to be a
result of ideal combinations of perpendicular magnetic anisotropy (PMA), DMI
and the interplay between geometry and magnetostatics. In the present work we
show some micromagnetic results supporting previous experimental observations
of magnetic skyrmions in spin-valve stacks with a wide range of DMI values.
Using micromagnetic simulations of cobalt-based disks, we obtain the magnetic
ground state configuration for several values of PMA, DMI and geometric
parameters. Skyrmion numbers, corresponding to the topological charge, are
calculated in all cases and confirm the occurrence of isolated, stable, axially
symmetric skyrmions for several combinations of DMI and anisotropy constant.
The stability of the skyrmions in disks is then investigated under magnetic
field and spin-polarized current, in finite temperature, highlighting the
limits of applicability of these spin textures in spintronic devices.
