Anomalous Hall and Nernst effects in epitaxial films of topological kagome magnet ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$

The topological kagome magnet (TKM) ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ exhibits unusual topological properties, flat electronic bands, and chiral spin textures, making it an exquisite materials platform to explore the interplay between topological band structure, strong electron correlations, and magnetism. Here we report the synthesis of high-quality epitaxial (0001) ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ films with large intrinsic anomalous Hall effect close to that measured in bulk single crystals. In addition, we measured a large, anisotropic anomalous Nernst coefficient $S_{yx}$ of $1.26\mu \mathrm{V}{\mathrm{K}}^{-1}$, roughly 2–5 times greater than that of common ferromagnets, suggesting the presence of Berry curvature sources near the Fermi level in this system. Crucially, the realization of high-quality ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ films opens the door to explore emergent interfacial physics and create novel spintronic devices based on TKMs by interfacing ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ with other quantum materials and by nanostructure patterning.

Figure 1

(a) Crystal structure of ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ with stacking of ${\mathrm{Fe}}_3\mathrm{Sn}$ and Sn layers. (b) Sn layer with honeycomb lattice. (c) ${\mathrm{Fe}}_3\mathrm{Sn}$ layer with Fe kagome lattice.

Figure 2

(a) Representative XRD 2θ scan of a 60 nm (0001) ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ film. Inset of panel (a) show an XRD 2θ scan of a 28.5 nm ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ film showing the (0009) peak accompanied by clear Laue oscillations. (b) Triple-axis HR-XRD ω scan (rocking curve) of ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ (0009) peak in the inset of panel (a). Inset of panel (b) shows a double-axis HR-XRD ω scan. (c) In-plane φ scans of ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$, Ru, Pt, and ${\mathrm{Al}}_2{\mathrm{O}}_3$. (d) Fine φ scan of ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$. Inset of panel (d) shows an XRD reflectivity scan.

Figure 3

(a) Magnetic hysteresis loop (field in the $ab$ plane) for a 60 nm ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ film at $T=300\mathrm{K}$ (blue squares) and $T=10\mathrm{K}$ (red squares). (b) Hall resistivity as a function of field for a Pt(2.5 nm)/Ru(2 nm)/${\mathrm{Fe}}_3{\mathrm{Sn}}_2$(80 nm) film at $T=300\mathrm{K}$ (blue squares) and $T=10\mathrm{K}$ (red squares). Inset shows the first derivative of the Hall resistivity as a function of field. (c) Resistivity (left) and anomalous Hall resistivity (right) as a function of temperature for the Pt(2.5 nm)/Ru(2 nm)/${\mathrm{Fe}}_3{\mathrm{Sn}}_2$(80 nm) film, and for ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ with buffer contribution subtracted (bottom inset). Top inset shows a schematic circuit diagram showing contribution from buffer layer (Pt/Ru). (d) Anomalous Hall resistivity of ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ with buffer contribution subtracted as a function of ${\left({\rho }_{xx}\right)}^2{M}_S$, where ${\rho }_{xx}\left(M_S\right)$ is the resistivity (saturated magnetization) of ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$. The dashed linear lines are to guide the eyes and intercepts to the origin. Inset shows the anomalous Hall conductivity of ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ as a function of ${\left({\sigma }_{xx}\right)}^2{M}_S$.

Figure 4

(a) Schematic diagrams of ANE measurements for in-plane (left) and out-of-plane (right) temperature gradient. (b), (c) Nernst electric field $E_{yx}$ ($\mathbf{\nabla }{T}_x$, $H\left|\right|c$ axis) as a function of field for a (b) Pt(2.5 nm)/Ru(2 nm)/${\mathrm{Fe}}_3{\mathrm{Sn}}_2$(80 nm) film and (c) a 40 nm Py film. Inset of panel (b) shows $E_{yx}$ (left $y$ axis) and $\mathbf{\nabla }{T}_x$ (right $y$ axis) as a function of heating power. (d), (e) $E_{yz}$ ($\mathbf{\nabla }{T}_z$, $H\left|\right|ab$ plane) as a function of field for (d) ${\mathrm{Fe}}_3{\mathrm{Sn}}_2$ and (e) Py films.