First-principles study of magnetic interactions and excitations in antiferromagnetic van der Waals material MPX₃ (M=Mn, Fe, Co, Ni; X=S, Se)

Abstract

Transition metal phosphorus trichalcogenides MPX3 (M = Mn, Fe, Co, Ni; X = S, Se), as layered van der Waals antiferromagnetic materials, have emerged as a promising platform for exploring two-dimensional (2D) magnetism. Based on density functional theory (DFT), we present a comprehensive investigation of the electronic and magnetic properties of MPX3. We calculated the spin exchange interactions as well as magnetic anisotropy energy (MAE). The numerical results reveal that J3 is antiferromagnetic (AFM) in all cases, and J2 is significantly smaller compared to both J3 and J1 . This behavior can be understood with regard to exchange paths and electron filling. Compared to other materials within this family, FePS3 and CoPS3 demonstrate significant easy-axis anisotropy. Using the obtained parameters, we estimated the Néel temperature TN and Curie-Weiss temperature θCW , 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.