Hydrogen Toggling between Yoshimori Spin Spirals and Elliptical Dzyaloshinskii–Moriya Skyrmions in Fe on Ir(110)

Skyrmions are particle-like spin textures that arise from spin spiral states in an external magnetic field. These spirals can originate from frustrated Heisenberg exchange or from the interplay of exchange and the Dzyaloshinskii-Moriya interaction, leading to atomic- and mesoscale textures. However, converting exchange-stabilized spin spirals into single skyrmions typically requires fields exceeding laboratory limits. Here, we demonstrate a strategy that uses hydrogen adsorption to expand the range of magnetic films hosting skyrmions. In two pseudomorphic Fe layers on Ir(110), spin-polarized scanning tunneling microscopy and <i>ab initio</i> calculations reveal that an exchange-stabilized Néel-type Yoshimori spin spiral with a 1.3 nm period transforms upon hydrogen adsorption into a Dzyaloshinskii-Moriya spiral with a 7-fold longer period of 8.5 nm. This transition enables elliptical skyrmions at moderate fields. Hydrogenation thus provides a nonvolatile mechanism to toggle between distinct magnetic states, offering a versatile platform for controlling spin textures.