Identifying Band Structure Changes of FePS3 across the Antiferromagnetic Phase Transition

Magnetic 2D materials enable interesting tuning options of magnetism. As an example, the van der Waals material FePS₃, a zig-zag-type intralayer antiferromagnet, exhibits very strong magnetoelastic coupling due to the different bond lengths along different ferromagnetic and antiferromagnetic coupling directions enabling elastic tuning of magnetic properties. The likely cause of the length change is the intricate competition between direct exchange of the Fe atoms and superexchange via the S and P atoms. To elucidate this interplay, we study the band structure of exfoliated FePS₃ by μm scale ARPES (angular resolved photoelectron spectroscopy), both, above and below the Néel temperature T_N. We found three characteristic changes across T_N. They involve S 3p-type bands, Fe 3d-type bands and P 3p-type bands, respectively, as attributed by comparison with density functional theory calculations (DFT + U). This highlights the involvement of all the atoms in the magnetic phase transition providing independent evidence for the intricate exchange paths.