Two-Dimensional Room-Temperature Magnetism in Janus Mn₂I₃S₃ and Cr₂I₃Se₃ Monolayers with Tunable Magnetic Properties by Strain Engineering

Exploring room-temperature intrinsic magnetism in two-dimensional (2D) materials for nanoscale spintronic devices has garnered significant interest. Achieving a high Curie temperature and substantial spin polarization in 2D ferromagnetic materials remains challenging. Drawing inspiration from the substantial enhancement of the Curie temperature observed in ferromagnetic CrIS monolayers by manipulating the covalent nature of Cr–S bonds, our study systematically delves into the electronic structure and magnetic properties of Janus M 2 X 3 Y 3 (M = V, Cr, Mn, Fe, and Co; X = Cl, Br, I; Y = S, Se, and Te) monolayers through first-principles calculations. Our findings reveal that 15 kinds of these monolayers exhibit dynamic and thermodynamic stability while displaying diverse electronic and ferromagnetic characteristics. Notably, Mn 2 I 3 S 3 demonstrates half-metallicity and in-plane magnetic anisotropy, while Cr 2 I 3 Se 3 exhibits a half-semiconductor and perpendicular magnetic anisotropy. Consequently, Mn 2 I 3 S 3 transforms from in-plane to perpendicular magnetic anisotropy through strain manipulation. Cr 2 I 3 Se 3, under strain, transforms from a half-semiconductor to a bipolar magnetic semiconductor. The strong coupling caused by the M–Y bonds makes them have a Curie temperature higher than room temperature. The unique magnetic properties exhibited by the 2D Janus Mn 2 I 3 S 3 and Cr 2 I 3 Se 3 magnets hold promise for applications in spintronics. Our study provides a foundational understanding for future experimental explorations in this exciting research area.