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

D019-Mn3Sn 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 Mn3Sn/NiFe bilayer. We characterize the damping constant of NiFe grown on an epitaxial Mn3Sn (011<overline>0) layer, with kagome planes oriented perpendicular to the sample surface. The spin-mixing conductance of Mn3Sn/MgO (0.35 nm)/NiFe is calculated to be g up arrow down arrow eff = 3.6 +/- 0.6 x 1018 m-2 when the magnetization of NiFe is directed out of the kagome plane of Mn3Sn, and g up arrow down arrow eff = 1.5 +/- 0.1 x 1018 m-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 Mn3Sn due to spin pumping; rather, it results from the coupled spin dynamics between the magnetic moments of NiFe and Mn3Sn, 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 Mn3Sn. This insight is crucial for the development of antiferromagnetic spintronic devices.