First-principles study of magnetic interactions and excitations in antiferromagnetic van der Waals material MPX 3 (M=Mn, Fe, Co, Ni; X=S, Se)

Transition metal phosphorus trichalcogenides MPX 3 (M = Mn, Fe, Co, Ni; X = S, Se), as layered van der Waals antiferromagnetic (AFM) materials, have emerged as a promising platform for exploring two-dimensional (2D) magnetism. Based on density functional theory, we present a comprehensive investigation of the electronic and magnetic properties of MPX 3 . We calculated the spin exchange interactions as well as magnetocrystalline anisotropy energy. The numerical results reveal that J 3 is AFM in all cases, and J 2 is significantly smaller compared to both J 3 and J 1 . This behavior can be understood with regard to exchange paths and electron filling. Compared to other materials within this family, FePS 3 and CoPS 3 demonstrate significant easy-axis anisotropy. Using the obtained parameters, we estimated the Néel temperature T N and Curie-Weiss temperature θ C W , and the results are in good agreement with the experimental observations. We further calculated the magnon spectra and successfully reproduce several typical features observed experimentally. Finally, we give helpful suggestions for the strong constraints about the range of non-negligible magnetic interactions based on the relations between magnon eigenvalues at high-symmetry k points in honeycomb lattices.