Intrinsic Raman Spectra of Self-intercalated van der Waals Magnets Cr_1+δTe₂

Chromium tellurides (Cr_1+δTe₂) are self-intercalated van der Waals (vdW) magnets that exhibit fundamentally intriguing and technologically important properties, including high-temperature ferromagnetism, topological spin textures, exotic Hall effects, and more. While significant efforts have been devoted to understanding the relation between magnetism and self-intercalation, less is known about how the intrinsic lattice vibrations are influenced by the intercalated Cr in the vdW gap. Previously, the study of vibrational properties of Cr_1+δTe₂ by Raman spectroscopy is complicated by rapid oxidation of the surface under ambient conditions, which obscures the intrinsic Raman modes. In this work, we develop experimental approaches to minimize surface oxidation, enabling the detection of intrinsic Raman spectra. Comparing the observed Raman peaks with density functional theory calculations, we assign the corresponding vibrational modes in the parent and intercalated structural phases. This work provides a basis for distinguishing intrinsic phonon modes from oxidation related features and for understanding lattice dynamics in intercalated chromium tellurides.