Demystifying unconventional Hall effects in anisotropic chiral magnets

The Hall effect provides crucial insights on the interplay of electronic structure with magnetism, spin transport, and ordered phases. Beyond conventional and anomalous Hall effects (AHE), the topological Hall effect (THE) has emerged as a probe for chiral spin textures, e.g. skyrmions [1,2]. Reports of THEs span across diverse materials,e.g.multilayers, alloys, and quantum materials. However, such measured Hall anomalies often exceed theoretical predictions by factors of 10-1000 [3], presenting a huge interpretational gap. There is an urgent need to reassess mechanisms underlying these unconventional Hall residues across material systems.

We first reveal a novel mechanism underlying sizable Hall nonlinearity across [Co/Pt]-based multilayers through ultra-sensitive concurrent magnetometry-transport experiments [4]. Minority spin textures geometrize the local current distribution, leading to non-destructive accumulation of AHE that modifies the global transport response of chiral magnets. This emergent Hall anomaly is independent of chirality or topology of spin textures. It offers acompelling alternative to prevailing transport models in chiral magnets.

Next, we investigate two magnetic quantum materials – epitaxialSrRuO₃/SrIrO₃ heterostructures and Cr₁₊δTe₂ films [6]. Quantitative magnetic force microscopy and transport studies reveal coexisting magnetic phases with distinct AHE signatures across both systems [6,7]. Our bespoke analytical framework enables nanoscale-resolved tracking of field- and temperature-evolution of magnetic order, uncovering strong correlations between phase heterogeneity and transport anomalies.

These insights highlight the critical role of local magnetism in reshaping electronic transport – distinct from prevailing mechanisms employing band- and real-space topology. We thus establish a unified framework for interpreting unconventional Hall signatures - generalizable to time-reversal symmetry-broken systems and ordered states across condensed matter and materials physics.