Reversible intrinsic-extrinsic crossover of the anomalous Hall effect in PrAlSi via Al/Si ratio tuning
The anomalous Hall effect (AHE) in magnetic Weyl semimetals arises from distinct microscopic origins-intrinsic Berry curvature and extrinsic scattering mechanisms-yet reversible switching between these regimes within a single material platform remains elusive. Here, we demonstrate that off-stoichiometric tuning of the Al/Si ratio (from ~1.05 to ~0.75) reversibly drives an intrinsic-extrinsic-intrinsic crossover of the AHE in PrAlSi single crystals. Across four compositions spanning a narrow Si variation (PrAl0.93Si0.89 to PrAl0.79Si1.06), the anomalous Hall conductivity (AHC) exhibits a non monotonic arch (170-1413- 507-164 Ω-1cm-1). The intermediate composition PrAl0.90Si0.94 (Al/Si ~0.96) exhibits high carrier mobility, multi carrier transport, yielding a giant AHC of 1413 Ω-1cm-1 dominated by extrinsic skew-scattering. The Si-poor and Si-rich compositions exhibit lower AHC values and intrinsic Berry-curvature-dominated AHE, establishing a composition-driven intrinsic-extrinsic-intrinsic crossover. Deviating from the intermediate composition suppresses mobility and reverses carrier type from hole-like to electron-like. The Al/Si ratio thus serves as a chemical knob that primarily modulates the Fermi level via compositional band filling, while off-stoichiometry-induced chemical disorder plays a subordinate role in determining the AHE mechanism. These results position off-stoichiometric PrAlSi as a tunable platform where subtle compositional variation reversibly switches the AHE mechanism.