Spin polarized STM imaging of nanoscale Neel skyrmions in an SrIrO3/ SrRuO3 perovskite bilayer

Oxide heterostructures are an emerging materials platform for engineering the size, stability and motion of magnetic skyrmions in next-generation devices. Here we use off-axis sputtering to grow epitaxial thin films, comprising just two unit cells of SrIrO3 on ten unit cells of the oxide ferromagnet, SrRuO3. Spin polarized scanning tunneling microscopy reveals isolated skyrmions and directly establishes their Ne ' el character, attributed to non-collinear exchange interactions at the interface. Statistical analysis reveals a distribution of sizes and shapes, with an average diameter of 3 nm that is among the smallest reported to date in any system. Skyrmions were only observed in SrIrO3-covered regions of the film, but were otherwise independent of SrIrO3 grain area and thickness. To help explain these observations, we performed density functional theory calculations, which suggest SrIrO3 acquires an induced magnetic moment in proximity to SrRuO3 and thus may host columnar spin textures stabilized by the interface.