Nanoscale Vacancy Gradients Enhanced Spin‐Charge Conversion at YIG/Heavy Metal Interfaces

Abstract Here, a nearly twofold increase​ in spin‐to‐charge conversion efficiency within YIG/heavy‐metal heterostructures, achieved through Ar + ion bombardment and chemical treatment, is demonstrated. By inducing a ​gradient distribution of Fe vacancies​ confined to a 2‐nm skin depth of single‐crystal YIG films, a strongly inversion‐broken interface amplifying the inverse Rashba‐Edelstein effect (IREE) is established. Structural characterization via STEM‐EDS/TOF‐SIMS confirms the depth‐resolved Fe vacancy gradient, while ferromagnetic resonance and inverse spin Hall effect measurements revealed a ​170% enhancement in the spin‐to‐charge conversion efficiency. Control experiments with Cu interlayers and Au cappings exclude contributions from bulk spin Hall mechanisms and magnetic proximity effects, thereby directly linking the enhancement to the interfacial IREE. This defect‐engineering strategy offers a scalable pathway for high‐efficiency spintronic devices compatible with YIG/heavy‐metal systems.