Evidence of the Topological Hall Effect in Pt/Antiferromagnetic Insulator Bilayers

Abstract

The topological Hall effect has been a primary indicator of nontrivial spin textures in magnetic materials. We observe the evidence of the topological Hall effect in $\mathrm{Pt}/{\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ bilayers grown on ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}(0001)$ and ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}(11\overline{2}0)$, where the ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ epitaxial film is an antiferromagnetic insulator. The $\mathrm{Pt}/{\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ bilayers exhibit topological Hall resistivity for ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ thicknesses below 6 nm near and above room temperature, which is above the N\'eel temperature of ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$, revealing the key role of thermal fluctuations in the formation of spin textures. The similarity of topological Hall signals in (0001)- and $(11\overline{2}0)$-oriented ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3}$ films indicates that the emergence of spin textures is insensitive to crystalline orientation.