Interplay between magnetic order and electronic band structure in ultrathin GdGe ₂ metalloxene films

Dimensionality can strongly influence the magnetic structure of solid systems. Here, we predict theoretically and confirm experimentally that the antiferromagnetic (AFM) ground state of bulk gadolinium germanide metalloxene, which has a quasi-layered defective GdGe₂ structure, is preserved in the ultrathin film limit. Ab initio calculations demonstrate that ultrathin GdGe₂ films present in-plane intra-layer ferromagnetic coupling and AFM inter-layer coupling in the ground state. Angle-resolved photoemission spectroscopy finds the AFM-induced band splitting expected for the 2 and 3 GdGe₂ trilayer (TL) films, which disappear above the Néel temperature. The comparative analysis of isostructural ultrathin DyGe₂ and GdSi₂ films confirms the magnetic origin of the observed band splitting. These findings are in contrast with the recent report of ferromagnetism in ultrathin metalloxene films, which we ascribe to the presence of uncompensated magnetic moments.