Intrinsic and extrinsic antiferromagnetic damping in NiO

In antiferromagnetic spintronics where manipulation of the antiferromagnetic spins is a central technological challenge, it is important to understand the dynamic properties, especially their THz spin dynamics and the magnetic damping. Here, we investigate thoroughly the antiferromagnetic spin dynamics in NiO by broadband THz spectroscopy and find the remarkable difference in the damping constants $\alpha =5.0\pm 0.4\times {10}^{-4}$ and $7.4\pm 0.4\times {10}^{-4}$, respectively, for mono- and polycrystalline NiO, indicating the existence of strong extrinsic contributions to the damping, such as two-magnon scattering. Our results shed light on the mechanism of the antiferromagnetic dissipative dynamics and give important insights for developing antiferromagnetic and THz spintronics devices.