Competing magnetic states in a non-coplanar Kagome magnet

Non-collinear Kagome antiferromagnets (AFMs) Mn3X (X = Sn, Ga, Ge, Ir, Pt) can generate an anomalous Hall effect (AHE) despite vanishing net magnetization, enabled by broken time-reversal and inversion symmetries. However, strong in-plane anisotropy has limited studies of the AFM-AHE and electronic applications to coplanar spin configurations. Non-coplanar spin textures in these systems have been realized only in low temperature spin-glass states or at interfaces with heavy metals. Here, we report an intrinsic non-coplanar spin configuration persisting up to 400 K in cubic-phase Mn3Ge, originating from coexisting symmetric and antisymmetric exchange interactions. Competing magnetic states associated with this non-coplanar spin configuration give rise to an unconventional AHE with a magnetic-field-induced sign reversal and a hump-like feature. Our findings establish a platform for non-coplanar magnetism in AFM spintronics.

💡 Research Summary

In this work the authors demonstrate that a non‑coplanar spin texture can be stabilized in the cubic phase of Mn₃Ge (c‑Mn₃Ge) up to 400 K, and that this texture gives rise to an unconventional anomalous Hall effect (AHE) characterized by a magnetic‑field‑induced sign reversal and a pronounced hump‑like feature in the Hall conductivity. Thin films of Mn₃Ge were grown by magnetron sputtering on Ru‑buffered Al₂O₃(0001) substrates. Structural characterization using out‑of‑plane X‑ray diffraction, reciprocal‑space mapping, and cross‑sectional STEM‑HAADF revealed the coexistence of a hexagonal h‑Mn₃Ge layer (the thermodynamically stable phase) at the interface (≈3–5 nm) and a cubic c‑Mn₃Ge layer that grows epitaxially on top of it. Both phases share the same Kagome‑plane motif, which explains the six‑fold symmetry observed in pole‑figure measurements.

Transport measurements were performed on patterned Hall‑bars (100 nm thick c‑Mn₃Ge) over a temperature range of 2–400 K and magnetic fields up to ±14 T applied perpendicular to the film plane (along the