We investigate the absorption of a spin current at a ferromagnetic-metal/Pt-oxide interface by measuring ferromagnetic resonance. The spin absorption was characterized by the magnetic damping of the heterostructure. We show that the magnetic damping of a Ni81Fe19 film is clearly enhanced by attaching Pt oxide on the Ni81Fe19 film. The damping enhancement disappears by inserting an ultrathin Cu layer between the Ni81Fe19 and Pt-oxide layers. These results demonstrate an essential role of the direct contact between the Ni81Fe19 and Pt oxide to induce sizable interface spin-orbit coupling. Furthermore, the spin-absorption parameter of the Ni81Fe19/Pt-oxide interface is comparable to that of intensively studied heterostructures with strong spin-orbit coupling, such as an oxide interface, topological insulators, and metallic junctions with Rashba spin-orbit coupling. This result illustrates strong spin-orbit coupling at the ferromagnetic-metal/Pt-oxide interface, providing an important piece of information for quantitative understanding of the spin absorption and spin-charge conversion at the ferromagnetic-metal/metallic-oxide interface.
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