In-plane anomalous Hall effect in the Weyl magnet MnSb₂Te₄

The anomalous Hall effect (AHE), driven by magnetism and spin-orbit coupling, is a key signature of topological phases and is usually observed for out-of-plane magnetic field, where the perpendicular alignment maximizes the influence of these effects on electronic transport. The emergence of an unusual AHE (1) under the in-plane magnetic field H in a non-magnetic Weyl system and (2) with in-plane magnetization M in a magnetically doped topological insulator have been predicted in theory, however thus far this phenomenon has not been explored in a magnetic Weyl system. Our transport experiments on the Weyl ferromagnet MnSb₂Te₄ (FM MST) reveal a finite anomalous Hall loop (ARL) centered at zero magnetic field when the field is fully aligned in-plane [1]. In FM MST this in-plane-field ARL is enhanced by tuning the tilt and rotation of the magnetic easy axis by an intake and release of H⁺, consistent with our DFT calculations. It is fundamentally due to an out-of-plane Berry curvature when M is tilted off the symmetry axis, highlighting that M-tilt alters rotational C_2z symmetry. To separate the effects of the in-plane H and M-component, we compare H⁺ intake/release process with that of Li+, introduced using N-butyllithium, as Li⁺ intercalation, guided by our DFT calculations, preserves the out-of-plane magnetic easy axis. We will present angle-resolved in-plane-field transport measurements under both H⁺ and Li⁺ modification of FM MST and will discuss how breaking or preserving of the C_2z symmetry will alter AHE.