Ferromagnetic MnSn Monolayer Epitaxially Grown on Silicon Substrate

Two-dimensional (2D) ferromagnetic materials have been exhibiting promising potential in applications, such as spintronics devices. To grow epitaxial magnetic films on silicon substrate, in the single-layer limit, is practically important but challenging. In this study, we realized the epitaxial growth of MnSn monolayer on Si(111) substrate, with an atomically thin Sn/Si(111)-2\sqrt 3 \times 2\sqrt 3-buffer layer, and controlled the MnSn thickness with atomic-layer precision. We discovered the ferromagnetism in MnSn monolayer with the Curie temperature (T_\rm c) of \sim 54 K. As the MnSn film is grown to 4 monolayers, T_\rm c increases accordingly to \sim 235 K. The lattice of the epitaxial MnSn monolayer as well as the Sn/Si(111)-2\sqrt 3 \times 2\sqrt 3 is perfectly compatible with silicon, and thus an sharp interface is formed between MnSn, Sn and Si. This system provides a new platform for exploring the 2D ferromagnetism, integrating magnetic monolayers into silicon-based technology, and engineering the spintronics heterostructures.