Non-van der Waals MCrS₂ nanosheets with tunable two-dimensional ferromagnetism

Designing two-dimensional (2D) ferromagnetic materials with high Curie temperature is urgent for the development of spintronic technology. The exploration of non-van der Waals (vdW) ferromagnetic nanosheets play a vital role in enriching the 2D ferromagnetic materials family on account of the scarcity of vdW materials in nature. Herein, we report a non-vdW AgCrS 2 material with antiferro-to-ferro-magnetism transition when it thinned down to monolayer. Based on it, a universal ion-exchange strategy was employed to replace Ag + by the M (M = Li + , Na + , K + ) cations, acquiring a series of 2D non-vdW M x Ag 0.5− x CrS 2 materials with tunable ferromagnetism. The Curie temperature is higher than the AgCrS 2 nanosheet, and reaches up to 160 K when M is K + . The theoretical calculations verify the ferromagnetism of AgCrS 2 and M x Ag 0.5− x CrS 2 nanosheet originated from CrS 2 layer. The disorderly arranged M and Ag ions increase the asymmetry of the lattice structure of M x Ag 0.5− x CrS 2 , thereby strengthening the interlayer ferromagnetic coupling and raising the Curie temperature of the nanosheets. This work provides ideas for discovering more 2D ferromagnetic materials with high Curie temperature.