Thermal stability of non-collinear antiferromagnetic Mn3Sn nanodot

D019-Mn3Sn, an antiferromagnet having a non-collinear spin structure in a kagome lattice, has attracted great attention owing to various intriguing properties such as large anomalous Hall effect. Stability of a magnetic state against thermal fluctuation, characterized in general by the thermal stability factor ?, has been well studied in ferromagnetic systems but not for antiferromagnets. Here, we study ? of the antiferromagnetic Mn3Sn nanodots as a function of their diameter D. To quantify ?, we measure the switching probability as a function of the pulse field amplitude and analyze the results based on a model taking account of two and sixfold magnetic anisotropies in the kagome plane. We observe no significant change in ? down to D = 300 nm below which it decreases with D. The obtained D dependence is well explained by a single-domain and nucleation-mediated reversal models. These findings provide a basis to understand the thermal fluctuation and reversal mechanism of antiferromagnets for device applications.