Pure Inverse Spin Hall Effect in Ferromagnetic Ni ₈₀ Fe ₂₀ /Y ₃ Fe ₅ O ₁₂ (YIG) Heterostructures via the Longitudinal Spin Seebeck Effect

ABSTRACT Spin–charge interconversion in ferromagnetic metals provides an unconventional pathway to explore spin–orbit coupling beyond heavy nonmagnetic systems. While ferromagnetic Ni 80 Fe 20 has long been regarded as a spin source, its role as a spin‐current detector remains largely unexplored. Here, we demonstrate the direct detection of a pure inverse spin Hall effect (ISHE) in a Ni 80 Fe 20 layer interfaced with a ferrimagnetic insulator, yttrium iron garnet (Y 3 Fe 5 O 12 , YIG). A thermally generated spin current produced by the longitudinal spin Seebeck effect (LSSE) in YIG is converted into a transverse charge voltage within the Ni 80 Fe 20 layer. Importantly, systematic control experiments using Ni 80 Fe 20 /Al 2 O 3 bilayers, combined with symmetry‐controlled measurement geometries, quantitatively eliminate anomalous Nernst contributions, thereby establishing that the observed voltage originates intrinsically from the ISHE in ferromagnetic Ni 80 Fe 20 . These findings identify ferromagnetic metals as viable spin‐current detectors and provide a conceptually simple platform for investigating spin–orbit interactions and spin caloritronic phenomena without relying on heavy nonmagnetic metals.