Enhancement of two-magnon scattering induced by a randomly distributed antiferromagnetic exchange field

We report a quantitative study of two-magnon scattering in Ni81Fe19/NiO bilayers with various NiO thicknesses dNiO. We found that the magnetic damping of the Ni81Fe19/NiO bilayer strongly depends on dNiO, which evidences that the amplitude of the two-magnon scattering increases with increasing the thickness of the antiferromagnetic layer. The enhancement of the two-magnon scattering in the Ni81Fe19/NiO bilayer is attributed to the increase of randomly distributed antiferromagnetic exchange fields. We calculated the spin-mixing conductance by eliminating the effect of the two-magnon scattering, and found that the value is at 8.1nm-2 for the Ni81Fe19/NiO interface. Our result gives further insight on the role of the two-magnon scattering in manipulating magnetic damping, which is crucial for generation and transmission of spin currents in ferromagnet/antiferromagnet systems.