Multi‐Origin Driven Giant Planar Hall Effect in Topological Antiferromagnet EuAl ₂ Si ₂ with Tunable Spin Texture

In topological materials, the planar Hall effect (PHE) is often regarded as a hallmark of profound quantum phenomena—most notably the Adler‐Bell‐Jackiw chiral anomaly and Berry curvature—rendering it an indispensable tool for deciphering the topological essence of emergent phases. In this study, the PHE and anisotropic magnetoresistance (MR) is delved into the recently discovered layered topological antiferromagnet EuAl 2 Si 2 . The analysis of the robust PHE signal (≈3.8 µΩ cm at 2 K and 8 T) unveils a distinct interplay of mechanisms. While Berry curvature plays a minor role, the dominant contributions stem from classical orbital MR in the field‐induced ferromagnetic state and field‐suppressed spin fluctuations in the paramagnetic regime. These insights not only position EuAl 2 Si 2 —with its highly tunable spin texture—as an exemplary system for probing the intricate coupling between spin configurations and band topology in magnetotransport but also pave the way for designing novel materials with tailored PHE responses, highlighting significant application prospects in quantum sensing, spintronic devices, and topologically protected electronic systems.