Signature for non-Stoner ferromagnetism in the van der Waals ferromagnet Fe3GeTe2

Abstract

The van der Waals ferromagnet $\mathrm{F}{\mathrm{e}}_{3}\mathrm{GeT}{\mathrm{e}}_{2}$ has attracted great research attention recently due to its extraordinary properties. Here, using high-resolution angle-resolved photoemission spectroscopy, we systematically investigate the temperature evolution of the electronic structure of bulk $\mathrm{F}{\mathrm{e}}_{3}\mathrm{GeT}{\mathrm{e}}_{2}$. We observe largely dispersive energy bands with exchange splitting that are in overall agreement with our density-functional theory calculation. Interestingly, the band dispersions barely change upon heating towards the ferromagnetic transition near 225 K, except for the reduction of quasiparticle coherence, which strongly deviates from the itinerant Stoner model. We suggest that the local magnetic moments may play a crucial role in the ferromagnetic ordering and the electronic structure of $\mathrm{F}{\mathrm{e}}_{3}\mathrm{GeT}{\mathrm{e}}_{2}$, which will shed light on the generic understanding of itinerant magnetism in correlated materials.