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 LaMn2Ge2, a noncollinear ferromagnetic compound with Curie temperature T-C similar to 325 K. A large topological Hall resistivity of similar to 1.0 mu Omega cm in a broad temperature range (190K < T < 300K) 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-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 LaMn2Ge2 as a promising system for functional applications in novel spintronic devices.

Automated summary

Nontrivial spin structures in itinerant magnets can lead to the topological Hall effect at near room temperature, as demonstrated in LaMn2Ge2 compound with noncollinear ferromagnetic configuration. Anisotropic anomalous Hall effect is realized in a broad temperature range due to the spin chirality of noncoplanar spin configurations stabilized by thermal fluctuation. The temperature-field phase diagrams based on the isothermal topological Hall resistivity reveal a field-induced transition from noncoplanar spin configuration to polarized ferromagnetic state.