  Spin-polarized scanning tunneling microscopy (SPSTM) was used to directly
image nanoscale N\'eel skyrmions in a SrIrO3 / SrRuO3 bilayer system that are
among the smallest reported to date in any system. Off-axis magnetron
sputtering was used to cap epitaxial films of the oxide ferromagnet SRO with 2
unit cells of SrIrO3, intended to provide interfacial spin orbit coupling.
Atomic resolution STM imaging and tunneling spectroscopy were used to identify
island-like SrIrO3 grains and small regions of bare SrRuO3. Isolated skyrmions
were only observed in SrIrO3-covered regions of the film, and exhibited a
distribution of sizes and shapes with an average diameter of 3 nm. We found
that skyrmions must be fully contained within, but may be smaller than, any
given SrIrO3 region. Additionally, skyrmions were observed on SrIrO3 islands of
varying thickness without loss of SPSTM contrast, suggesting the magnetic
texture lies within the SrIrO3 island rather than the underlying ferromagnetic
SrRuO3. Density functional theory calculations suggest this could be due to a
small induced magnetic moment associated with IrO layers in the SrIrO3 film.
