Anomalous Hall effect induced by Berry curvature in topological nodal-line van der Waals ferromagnet Fe${}_4$GeTe${}_2$

Abstract

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, Fe${}_4$GeTe${}_2$ from the iron-based vdW family (Fe${}_n$GeTe${}_2$, $n$=3,4,5), exhibiting a large anomalous Hall conductivity (AHC), ${\sigma }_{xy}^A$ $\sim$ 490 ${\Omega }^{-1}{\text{cm}}^{-1}$ at 2 K. The near quadratic behavior of anomalous Hall resistivity (${\rho }_{xy}^A$) 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 gaped nodal lines around the Fermi level, governing such large AHC property. Moreover, we also report an exceptionally large anomalous Hall angle ($\simeq$ 10.6\%) and Hall factor ($\simeq$ 0.22 V${}^{-1}$) values which so far, are the largest in compared to those for other members in this vdW family.

7 pages, 4 figures, supplementary