Tailoring spin waves in 2D transition metal phosphorus trichalcogenides via atomic-layer substitution

The family of two-dimensional (2D) van der Waals transition metal phosphorus trichalcogenides has received renewed interest due to their intrinsic 2D antiferromagnetism, which proves them as unprecedented and highly tunable building blocks for spintronics and magnonics at the single-layer limit. Herein, motivated by the exciting potential of atomic-substitution demonstrated by Janus transition metal dichalcogenides, we investigated the crystal, electronic and magnetic structures of selenized Janus monolayers based on MnPS₃ and NiPS₃ from first-principles. In addition, we calculated the magnon dispersion and performed real-time real-space atomistic dynamic simulations to explore the propagation of spin waves in MnPS₃, NiPS₃, MnPS_1.5Se_1.5 and NiPS_1.5Se_1.5. Our calculations predict a drastic enhancement of magnetic anisotropy and the emergence of large Dzyaloshinskii-Moriya interactions, which arise from the induced broken inversion symmetry in the 2D Janus layers. These results pave the way for the development of Janus 2D transition metal phosphorus trichalcogenides and highlight their potential for magnonic applications.