Magnetic interactions in intercalated transition metal dichalcogenides: a study based on ab initio model construction

Transition metal dichalcogenides (TMDs), TX₂, where T is a transition metal atom and X is a chalcogen atom, are known to have a wide variety of magnetic structures by hosting other transition metal atoms (M) in the van der Waals gaps. To understand the chemical trend of the magnetic properties of the intercalated TMDs, M_xTX₂, we carried out a systematic first-principles study for 48 compounds with different hosts (TX₂), guests (M), and composition ratios (x). Starting with calculations based on spin density functional theory, we derive classical spin models by applying the Liechtenstein method to the ab initio Wannier-based tight-binding model. We show that the calculated exchange couplings are overall consistent with the experiments. In particular, when the composition rate x is 1/3, the chemical trend can be understood in terms of the occupation of the 3d-orbital in the intercalated transition metal. The present results give us a useful guiding principle to predict the magnetic structure of compounds that are yet to be synthesized.