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Interface-driven topological Hall effect in SrRuO3-SrIrO3 bilaye:Professor Yoshinori Tokura, Professor Masashi Kawasaki, Department of Applied Physics , and other researchers.

Electron transport coupled with magnetism has attracted attention over the years. Among them, recently discovered is topological Hall effect (THE), originating from scalar spin chirality, that is, the solid angle subtended by the spins. THE is found to be a promising tool for probing the Dzyaloshinskii-Moriya (DM) interaction and consequent magnetic skyrmions. This interaction arises from broken inversion symmetry and hence can be artificially introduced at interface; this concept is lately verified in metal multilayers. However, there are few attempts to investigate such DM interaction at interface through electron transport. We clarified how the transport properties couple with interface DM interaction by fabricating the epitaxial oxide interface. We observed THE in epitaxial bilayers consisting of ferromagnetic SrRuO3 and paramagnetic SrIrO3 over a wide region of both temperature and magnetic field. The magnitude of THE rapidly decreases with the thickness of SrRuO3, suggesting that the interface DM interaction plays a significant role. Such interaction is expected to realize a 10-nm-sized Néel-type magnetic skyrmion. The present results established that the high-quality oxide interface enables us to tune the effective DM interaction; this can be a step toward future topological electronics.



Structure and basic physical properties of the SrRuO3-SrIrO3 bilayers. (A) Temperature (T) dependence of resistivity (ρ, top panel), MR (middle panel), and out-of-plane magnetization measured at 0.05 T (bottom panel) for the (SrRuO3)m-(SrIrO3)2 bilayers (m = 4, 5, 6, and 7). (B) Schematics of Bloch- and Néel-type skyrmions. (C) Schematics and an atomically resolved HAADF-STEM image of the studied bilayer structure. In the STEM image, SrTiO3 is capped on top of the SrIrO3 layer to protect the surface from electron beam radiation. uc, unit cells. (D) Anomalous Hall conductance (σHA) as a function of magnetization (M), which was varied through temperature.


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