Field-antisymmetric currents in the ferromagnetic MnSb₂Te₄

Recent realizations of the nontrivial quantum anomalous Hall (QAH) and axion insulator states in intrinsic topological magnets of the Mn(Bi,Sb)₂Te₄ class made it apparent that when long-range magnetism and band topology combine the consequences of ubiquitous disorder can be particularly acute and yet surprising. Here, we tap into a pre-existing Sb/Mn interchange (antisite) disorder landscape in the ferromagnetic MnSb₂Te₄ (FM MST) by implementing the post-growth hydrogen intake-and-release technique we have recently developed [1]. This transforms a conventional field-symmetric longitudinal magnetoresistance R_xx (H) for H||c (MR) of the as-grown MST (FM1) into a field-antisymmetric MR (FAMR) in the hydrogen-altered FM2, with a doubled Curie temperature of ~50 K. We demonstrate that FAMR directly translates into a giant field-antisymmetric planar Hall effect (PHE) for H||ab, characteristic of a Weyl semimetal topological bandstructure in which strong antisymmetry of the chiral-anomaly driven in-plane is massively amplified at low fields. Our studies of magnetotransport for H||ab under the in-plane field rotation (angle φ) reveal that it exhibits angular (±φ) chirality, which when enhanced by hydrogenation drives the field-antisymmetric chiral currents for H||c. A strong hydrogen-tunable chirality amplification of the PHE in FM2 and the appearance of an unusual in-plane hysteresis loop will be presented and implications for the bandstructure tunability will be discussed.





[1] H. Deng et al, Nature Comms. 13, 2308 (2022).



Acknowledgement: NSF-DMR-2011738 and NSF-HRD-2112550.