Thickness-Driven Control of Room Temperature Ferrimagnetic Skyrmions and their Topological Hall signature in GdFe Single Layers
Magnetic skyrmions are nanoscale, topologically protected spin textures with exceptional potential for high density data storage and energy efficient computing. Among various skyrmion hosting systems, rare earth transition metal ferrimagnets offer a promising platform due to their tunable magnetic properties and intrinsically low net magnetization. Despite this, the fundamental control of ferrimagnetic skyrmions in single layer films remains unexplored. Here, we demonstrate a viable route for engineering room temperature skyrmions in GdFe single layers through precise control of film thickness (60 to 80 nm). Thickness variation enables the systematic tuning of key magnetic parameters, including perpendicular magnetic anisotropy and saturation magnetization, thereby allowing precise control over skyrmion size and density. Magnetic force microscopy (MFM) reveals a clear thickness dependent evolution of isolated skyrmion characteristics, where skyrmion size decreases while skyrmion density increases with increasing GdFe film thickness, in agreement with micromagnetic simulations. At the same time, magnetotransport measurements show a systematic enhancement in the topological Hall resistivity with thickness, further corroborating the increased skyrmion density observed in MFM. Scanning transmission electron microscopy reveals a compositional gradient across the film thickness, indicative of structural asymmetry and potential inversion symmetry breaking, contributing to the emergence of a bulk Dzyaloshinskii Moriya interaction. Notably, sub 60nm skyrmions with high areal density are stabilized at room temperature. This work provides a viable route to tailor the properties of ferrimagnetic skyrmions in single-layer GdFe films, paving the way for the development of high-density ferrimagnetic skyrmionic devices.