Spin polarized STM imaging of nanoscale Néel Skyrmions in an SrIrO₃/SrRuO₃ Perovskite Bilayer

Interfaces in perovskite heterostructures exhibit a range of emergent properties that have attracted considerable interest. We use spin-polarized scanning tunneling microscopy to directly image isolated nanoscale Néel Skyrmions in a SrIrO₃ /SrRuO₃ bilayer system that are among the smallest reported to date in any system. Atomically resolved imaging and tunneling spectroscopy identified island-like SrIrO₃ (SIO) grains and valleys of exposed SrRuO₃ (SRO)_. Statistically we found that Skyrmions must be fully contained within, but may be smaller than, any given SrIrO₃ region with an average diameter of 3 nm. Additionally, skyrmions were observed on SrIrO₃ islands of varying thickness without loss of SPSTM contrast, suggesting the magnetic texture lies within the SrIrO₃ island in addition to the underlying SRO. Density functional theory calculations suggest this is due to a small induced magnetic moment associated with IrO layers in the SIO film. Furthermore, we observed some skyrmions readily switch between the ferromagnetic and skyrmionic states, while other skyrmions are firmly pinned. No discernible surface defects seem to drive the pinning, suggesting an interfacial mechansim.