A silicene-based 4f magnet probed by X-ray photoemission spectroscopy

The honeycomb silicene lattice, the Si counterpart of graphene, provides a building block to form 2D and layered materials with unconventional properties. In particular, silicene-based EuSi2 is a fascinating material morphing from a 3D antifferomagnet to a 2D ferromagnet, from a metal to a semiconductor demonstrating colossal negative magnetoresistance. However, the electronic structure of the material supporting these transformations remains a mystery - the results of computational studies are controversial. Here, we probe the band structure of EuSi2 employing X-ray photoemission spectroscopy. Ultrathin films of EuSi2 are synthesized on silicon by molecular beam epitaxy and characterized by diffraction techniques. Photoemission spectra, including those at the Eu 3d resonance, provide information on both the core levels and the valence band of EuSi2. A key characteristic is the position of the 4f states responsible for EuSi2 magnetism with respect to the Fermi level; its experimental value (about 1.3 eV) resolves the controversy in theoretical studies. The results shed light on the structure of the 4f magnet EuSi2 and form a basis for studies of related materials.& COPY; 2023 Elsevier B.V. All rights reserved.