Writing and Detecting Topological Charges in Exfoliated Fe_5-x GeTe₂

Fe5-xGeTe2 is a promising two-dimensional (2D) van der Waals (vdW) magnet for practical applications, given its 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 Fe5-xGeTe2, 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 t approximate to 30 nm where the formation of TST is maximized, inducing large magnitudes for the topological charge density (similar to 6.45 x 10(20) cm(-2)), and the concomitant anomalous (rho(A,max)(xy) similar or equal to 22.6 mu Omega cm) and topological (rho(u,T)(xy) 1 similar or equal to 5 mu Omega cm) Hall resistivities at T approximate to 120 K. These values for rho(A,max)(xy) and rho(u,T)(xy) 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.