Anisotropy of the Gilbert damping constant in NiFe grown on the chiral antiferromagnet Mn3Sn

$D{0}_{19}\text{\ensuremath{-}}\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$ is a noncollinear antiferromagnet characterized by a unique ferroic ordering of cluster magnetic octupoles, which has attracted significant attention due to its strong ferromagneticlike responses. In this study, we study the magnetic properties of a $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$/NiFe bilayer. We characterize the damping constant of NiFe grown on an epitaxial $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn} (01\overline{1}0)$ layer, with kagome planes oriented perpendicular to the sample surface. The spin-mixing conductance of $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$/MgO (0.35 nm)/NiFe is calculated to be ${g}_{\mathrm{eff}}^{\ensuremath{\uparrow}\ensuremath{\downarrow}}=3.6\ifmmode\pm\else\textpm\fi{}0.6\ifmmode\times\else\texttimes\fi{}{10}^{18}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}2}$ when the magnetization of NiFe is directed out of the kagome plane of $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$, and ${g}_{\mathrm{eff}}^{\ensuremath{\uparrow}\ensuremath{\downarrow}}=1.5\ifmmode\pm\else\textpm\fi{}0.1\ifmmode\times\else\texttimes\fi{}{10}^{18}\phantom{\rule{0.16em}{0ex}}{\mathrm{m}}^{\ensuremath{-}2}$ when the magnetization of NiFe aligned within the kagome plane. The relatively large spin-mixing conductance cannot be solely attributed to the pure spin current injection from NiFe to $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$ due to spin pumping; rather, it results from the coupled spin dynamics between the magnetic moments of NiFe and $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$, mediated by exchange interaction at the interface. Moreover, the anisotropy in the Gilbert damping constant of NiFe is likely due to the exchange spring effect in the $\mathrm{M}{\mathrm{n}}_{3}\mathrm{Sn}$. This insight is crucial for the development of antiferromagnetic spintronic devices.