  Antiferromagnetic (AFM) skyrmions are envisioned as ideal localized
topological magnetic bits in future information technologies. In contrast to
ferromagnetic (FM) skyrmions, they are immune to the skyrmion Hall effect,
might offer potential terahertz dynamics while being insensitive to external
magnetic fields and dipolar interactions. Although observed in synthetic AFM
structures and as complex meronic textures in intrinsic AFM bulk materials,
their realization in non-synthetic AFM films, of crucial importance in
racetrack concepts, has been elusive. Here, we unveil their presence in a
row-wise AFM Cr film deposited on PdFe bilayer grown on fcc Ir(111) surface.
Using first principles, we demonstrate the emergence of single and strikingly
interpenetrating chains of AFM skyrmions, which can co-exist with the rich
inhomogeneous exchange field, including that of FM skyrmions, hosted by PdFe.
Besides the identification of an ideal platform of materials for intrinsic AFM
skyrmions, we anticipate the uncovered knotted solitons to be promising
building blocks in AFM spintronics.
