Evidence of Topological Hall Effect in Pt/Antiferromagnetic-Insulator Bilayers*

Topological Hall effect has been a primary indicator of spin textures in magnetic materials. We observe unambiguous the evidence of topological Hall effect in Pt/Cr₂O₃ bilayers grown on Al₂O₃(0001) and Al₂O₃(11-20), where Cr₂O₃ epitaxial film is an antiferromagnetic insulator. The Pt/Cr₂O₃ bilayers exhibit clear topological Hall resistivity for Cr₂O₃ thicknesses below 6 nm near and above room temperature, which is above the Néel temperature of Cr₂O₃, revealing the key role of thermal fluctuations in the formation of spin textures. The similarity of topological Hall signals in (0001) and (11-20)-oriented Cr₂O₃ films indicates that the emergence of spin textures is insensitive to crystalline orientation. This first observational evidence of topological Hall effect in HM/AFI bilayers significantly expands our materials base to include the large family of AF insulators for the exploration of AF-based skyrmion technology.