Writing and Detecting Topological Charges in Exfoliated Fe_5-xGeTe₂

Fe_5-<i>x</i>GeTe₂ is a promising two-dimensional (2D) van der Waals (vdW) magnet for practical applications, given its remarkable magnetic properties. These include Curie temperatures above room temperature, and topological spin textures – TST (both merons and skyrmions), responsible for a pronounced anomalous Hall effect (AHE) and its topological counterpart (THE), which can be harvested for spintronics. Here, we show that both the AHE and THE can be amplified considerably by just adjusting the thickness of exfoliated Fe_5-<i>x</i>GeTe₂, with THE becoming observable even in zero magnetic field due to a field-induced unbalance in topological charges. Using a complementary suite of techniques, including electronic transport, Lorentz transmission electron microscopy, and micromagnetic simulations, we reveal the emergence of substantial coercive fields upon exfoliation, which are absent in the bulk, implying thickness-dependent magnetic interactions that affect the TST. We detected a ‘magic’ thickness <i>t</i> ~30 nm where the formation of TST is maximized, inducing large magnitudes for the topological charge density (~6.45 x 10²⁰ cm^-2), and the concomitant anomalous (<i>ρ_xy</i>^A ≈ 22.6 μΩ cm) and topological (<i>ρ_xy</i>^T≈ 15 μΩ cm) Hall resistivities at <i>T</i> ~ 120 K. These values are higher than those found in magnetic topological insulators and, so far, the largest reported for 2D magnets. The hitherto unobserved THE under zero magnetic field could provide a platform for the writing and electrical detection of TST aiming at energy-efficient devices based on vdW ferromagnets. are higher than those found in magnetic topological insulators and, so far, the largest reported for 2D magnets. The hitherto unobserved THE under zero magnetic field could provide a platform for the writing and electrical detection of TST aiming at energy-efficient devices based on vdW ferromagnets.