Covalent Mixing in the 2D Ferromagnet CrSiTe3 Evidenced by Magnetic X-Ray Circular Dichroism

Abstract

The low-temperature electronic structure of the van der Waals ferromagnet (Formula presented.) is investigated. This ferromagnetic semiconductor has a magnetic bulk transition temperature of 33 K, which can reach up to 80 K in single- and few-layer flakes. X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements, carried out at the Cr (Formula presented.) and Te (Formula presented.) edges in vacuo-cleaved single crystals, give strong evidence for hybridization-mediated superexchange between the Cr atoms. The observed chemical shift in the XAS, as well as the comparison of XMCD with the calculated Cr (Formula presented.) multiplet spectra, confirms a strong covalent bond between the Cr (Formula presented.) ((Formula presented.)) and Te (Formula presented.) states. Application of the XMCD sum rules gives a nonvanishing orbital moment, supporting a partial occupation of the (Formula presented.) states, apart from (Formula presented.). Also, the presence of a nonzero XMCD signal at the Te (Formula presented.) edge confirms a Te (Formula presented.) spin polarization due to mixing with the Cr (Formula presented.) bonding states. The results strongly suggest that superexchange, instead of the previously suggested single-ion anisotropy, is responsible for the low-temperature ferromagnetic ordering of 2D materials such as (Formula presented.) and (Formula presented.). This demonstrates the interplay between electron correlation and ferromagnetism in insulating 2D materials.