  The recent emergence of two-dimensional (2D) van der Waals ferromagnets has
provided a new platform for exploring magnetism in the flatland and for
designing 2D ferromagnet-based spintronics devices. Despite intensive studies,
the anomalous Hall effect (AHE) mechanisms in 2D van der Waals ferromagnets
have not been investigated yet. In this paper, we report the AHE mechanisms in
quasi-2D van der Waals ferromagnet Fe0.29TaS2 via systematically measuring
Fe0.29TaS2 devices with thickness from 14 nm to bulk single crystal. The AHE
mechanisms are investigated via the scaling relationship between the anomalous
Hall and channel conductivities. As the Fe0.29TaS2 thickness decreases, the
major AHE mechanism changes from extrinsic scattering to intrinsic
contribution. The crossover of the AHE mechanisms is found to be highly
associated with the channel conductivities as the Fe0.29TaS2 thickness varies.
