Reversible hydrogen-ion control of the antiferromagnetic anisotropy in α-Fe₂O₃

Antiferromagnetic insulators are a ubiquitous class of magnetic materials, holding the promise of low-dissipation spin-based computing devices that can display ultra-fast switching and are robust against stray fields. However, their imperviousness to magnetic fields also makes them difficult to control in a reversible and scalable manner. Here we demonstrate a novel proof-of-principle ionic approach to drive a 90° spin-reorientation reversibly in the earth-abundant antiferromagnetic insulator α-Fe₂O₃ (hematite) – now an emerging spintronic material that hosts exotic topological antiferromagnetic spin-textures and long magnon-diffusion lengths. We use a low-temperature catalytic-spillover process involving the incorporation (or removal) of hydrogen from α-Fe₂O₃, post-growth, driving pronounced changes in its magnetic anisotropy, Néel-vector orientation and canted magnetism via electron injection and localized strains. We explain these effects with a detailed magnetic anisotropy model and first-principles calculations. Tailoring our work for future applications, we demonstrate control of the room-temperature spin-state by reversibly doping hydrogen in Rh-substituted α-Fe₂O₃.