  Ne\'el skyrmions originate from interfacial Dzyaloshinskii Moriya interaction
(DMI). Recent studies have explored using thin-film ferromagnets and
ferrimagnets to host Ne\'el skyrmions for spintronic applications. However, it
is unclear if ultrasmall (10 nm or less) skyrmions can ever be stabilized at
room temperature for practical use in high density parallel racetrack memories.
While thicker films can improve stability, DMI decays rapidly away from the
interface. As such, spins far away from the interface would experience
near-zero DMI, raising question on whether or not unrealistically large DMI is
needed to stabilize skyrmions, and whether skyrmions will also collapse away
from the interface. To address these questions, we have employed atomistic
stochastic Landau-Lifshitz-Gilbert simulations to investigate skyrmions in
amorphous ferrimagnetic GdCo. It is revealed that a significant reduction in
DMI below that of Pt is sufficient to stabilize ultrasmall skyrmions even in
films as thick as 15 nm. Moreover, skyrmions are found to retain a uniform
columnar shape across the film thickness despite the decaying DMI. Our results
show that increasing thickness and reducing DMI in GdCo can further reduce the
size of skyrmions at room temperature, which is crucial to improve the density
and energy efficiency in skyrmion based devices.
