Anomalous Hall effect induced by Berry curvature in the topological nodal-line van der Waals ferromagnet Fe4GeTe2

The exploration of nontrivial transport phenomena associated with the interplay between magnetic order and spin-orbit coupling (SOC), particularly in van der Waals (vdW) systems, has gained a resurgence of interest due to their easy exfoliation, ideal for two-dimensional (2D) spintronics. We report the near room temperature quasi-2D ferromagnet, Fe4GeTe2 from the iron-based vdW family (FenGeTe2, n = 3,4,5), exhibiting a large anomalous Hall conductivity (AHC), sigma xAy similar to 490 S2-1cm-1 at 2 K. The near quadratic behavior of anomalous Hall resistivity (rho xAy) with the longitudinal resistivity (rho xx) suggests that a dominant AHC contribution is coming from an intrinsic Berry curvature (BC) mechanism. Concomitantly, the electronic structure calculations reveal a large BC arising from SOC induced gapped nodal lines around the Fermi level, governing such large AHC property. Moreover, we also report an exceptionally large anomalous Hall angle (-10.6%) and Hall factor (-0.22 V-1) values which, so far, are the largest in compared to those for other members in this vdW family.