Probing the Source of the Interfacial Dzyaloshinskii-Moriya Interaction Responsible for the Topological Hall Effect in $\text{Metal}/{\mathrm{Tm}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ Systems

The interfacial Dzyaloshinskii-Moriya interaction (DMI) is responsible for the emergence of topological spin textures such as skyrmions in layered structures based on metallic and insulating ferromagnetic films. However, there is active debate on where the interfacial DMI resides in magnetic insulator systems. We investigate the topological Hall effect, which is an indication of spin textures, in ${\mathrm{Tm}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ films capped with various metals. The results reveal that Pt, W, and Au induce strong interfacial DMI and topological Hall effect, while Ta and Ti cannot. This study also provides insights into the mechanism of electrical detection of spin textures in magnetic insulator heterostructures.

Figure 1

Structural characterization of metal/TmIG structures. (a) Cross-sectional STEM image of a $\mathrm{Pt}/\mathrm{TmIG}$ (1.85 nm) bilayer on sGGG(111) viewed along the $[11\overline{2}]$ direction. (b) STEM image combined with an EDX color map that distinguishes Tm in the TmIG film from Ga in the sGGG substrate. (c) AFM image of a $\mathrm{Ta}/\mathrm{TmIG}$ (2 nm) bilayer on sGGG(111) with a roughness of 0.29 nm. (d) An optical microscope image of a Hall bar combined with a schematic to show the geometry of the applied field ($H$), current ($I$), and measured Hall voltage ($V_{\mathrm{xy}}$).

Figure 2

Hall measurements of bilayers. Hall resistivity of heavy-metal/TmIG bilayers with (a) Pt, (b) W, (c) Ta, and (d) Au. Prominent peaks are observed for (a) Pt and (b) W on TmIG, indicating the detection of the SH-THE arising from the topological spin textures. (c) Only the SH-AHE and OHE are present for the $\mathrm{Ta}/\mathrm{TmIG}$ bilayer. (d) Only the OHE is present for the $\mathrm{Au}/\mathrm{TmIG}$ bilayer.

Figure 3

Hall measurements of trilayers. (a) OHE-subtracted Hall resistivity and (b) SH-THE resistivity of a $\mathrm{Pt}(3\mathrm{nm})/\mathrm{Au}(1\mathrm{nm})/\mathrm{TmIG}(2\mathrm{nm})$ trilayer with a heavy metal (Au) spacer layer showing large SH-THE peaks. OHE-subtracted Hall resistivity of (c) a $\mathrm{Pt}(3\mathrm{nm})/\mathrm{Ti}(1\mathrm{nm})/\mathrm{TmIG}(2\mathrm{nm})$ trilayer with a Ti spacer layer and (d) a $\mathrm{Pt}(3\mathrm{nm})/\mathrm{Ta}(1\mathrm{nm})/\mathrm{TmIG}(2\mathrm{nm})$ trilayer showing only the SH-AHE features.

Figure 4

Spin-Hall topological Hall effect phase diagrams. Magnetic field versus temperature phase diagrams of spin Hall-topological Hall resistivity for (a) a $\mathrm{Pt}(3\mathrm{nm})/\mathrm{TmIG}(2\mathrm{nm})$ bilayer, (b) a $W(2\mathrm{nm})/\mathrm{TmIG}(2\mathrm{nm})$ bilayer, (c) a $\mathrm{Pt}(3\mathrm{nm})/\mathrm{Au}(1\mathrm{nm})/\mathrm{TmIG}(2\mathrm{nm})$ trilayer, and (d) a $\mathrm{Pt}(3\mathrm{nm})/\mathrm{Ti}(1\mathrm{nm})/\mathrm{TmIG}(2\mathrm{nm})$ trilayer.

Figure 5

Plots of $H_{\mathrm{SH}\text{−}\mathrm{THE},\max }$ versus temperature for the $\mathrm{W}(2\mathrm{nm})/\mathrm{TmIG}(2\mathrm{nm})$ and $\mathrm{Pt}(3\mathrm{nm})/\mathrm{TmIG}(2\mathrm{nm})$ bilayers as well as the $\mathrm{Pt}(3\mathrm{nm})/\mathrm{Au}(1\mathrm{nm})/\mathrm{TmIG}(2\mathrm{nm})$ trilayer, where $H_{\mathrm{SH}\text{−}\mathrm{THE},\max }$ is the magnetic field at which ${\rho }_{\mathrm{SH}\text{−}\mathrm{THE}}$ reaches the maximum as indicated in the inset. Each set of data is fit to an exponential function, $H_{\mathrm{SH}\text{−}\mathrm{THE},\max }=a+b{e}^{-E/(k_{B}T)}$, with $R>0.999$.