Large topological Hall effect near room temperature in noncollinear ferromagnet LaMn2Ge2 single crystal

Nontrivial spin structures in itinerant magnets can give rise to the topological Hall effect (THE) due to the interacting local magnetic moments and conductive electrons. While, in series of materials, THE has mostly been observed at low temperatures far below room temperature (RT) limiting its potential applications. Here, we report the anisotropic anomalous Hall effect (AHE) near RT in $\mathrm{La}{\mathrm{Mn}}_{2}{\mathrm{Ge}}_{2}$, a noncollinear ferromagnetic compound with Curie temperature ${T}_{\mathrm{C}}\ensuremath{\sim}325\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. A large topological Hall resistivity of $\ensuremath{\sim}1.0\phantom{\rule{0.16em}{0ex}}\ensuremath{\mu}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}$ in a broad temperature range $(190\phantom{\rule{0.16em}{0ex}}\mathrm{K}lTl300\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ is realized as field ($H$) is parallel to the $ab$ plane $(H//ab)$ and current along the $c$ axis $(I//c)$, in contrast to the conventional AHE for $H//c$ and $I//ab$. The emergence of THE is attributed to the spin chirality of noncoplanar spin configurations stabilized by thermal fluctuation during spin-flop process. Moreover, the constructed temperature-field ($H\ensuremath{-}T$) phase diagrams based on the isothermal topological Hall resistivity reveal a field-induced transition from the noncoplanar spin configuration to polarized ferromagnetic state. Our experimental realization of large THE near RT highlights $\mathrm{La}{\mathrm{Mn}}_{2}{\mathrm{Ge}}_{2}$ as a promising system for functional applications in novel spintronic devices.