Growth-induced compositional control of room-temperature ferrimagnetic skyrmions and their topological Hall signature in Gd-Fe single layers

Magnetic skyrmions are nanoscale, topologically protected spin textures with strong potential for high-density data storage and energy-efficient computing. Among skyrmion-hosting systems, rare earth–transition metal ferrimagnets offer a promising platform due to their tunable magnetic properties and low net magnetization. Here, we demonstrate composition-mediated control of room-temperature skyrmions in amorphous single-layer Gd-Fe films grown with thicknesses of 60–80 nm. Depth-resolved scanning transmission electron microscopy combined with energy-dispersive x-ray spectroscopy reveals a growth-induced compositional gradient across the film thickness, giving rise to structural inversion asymmetry that promotes bulk Dzyaloshinskii–Moriya interaction. This compositional evolution systematically modifies the effective perpendicular magnetic anisotropy and saturation magnetization of the films. Magnetic force microscopy reveals a progressive reduction in skyrmion size accompanied by a significant increase in skyrmion density, in excellent agreement with micromagnetic simulations. Correspondingly, magnetotransport measurements show a systematic enhancement of the topological Hall resistivity, consistent with the increased skyrmion density. Notably, sub-60 nm skyrmions with a high density (∼26 μm−2) are stabilized at room temperature. These findings establish growth-induced compositional engineering as an effective strategy for tailoring ferrimagnetic skyrmions in single-layer Gd-Fe films, for spintronic applications.