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We investigate the vibrational and magnetic properties of thin layers of chromium tribromide (CrBr3) with a thickness ranging from three to twenty layers (3 L to 20 L) revealed by the Raman scattering (RS) technique. Systematic dependence of the RS process efficiency on the energy of the laser excitation is explored for four different excitation energies: 1.96 eV, 2.21 eV, 2.41 eV, and 3.06 eV. Our characterization demonstrates that for 12 L CrBr3, 3.06 eV excitation could be considered resonant with interband electronic transitions due to the enhanced intensity of the Raman-active scattering resonances and the qualitative change in the Raman spectra. Polarization- resolved RS measurements for 12 L CrBr3 and first-principles calculations allow us to identify five observable phonon modes characterized by distinct symmetries, classified as the Ag and Eg modes. The evolution of phonon modes with temperature for a 20 L CrBr3 encapsulated in hexagonal boron nitride flakes demonstrates alterations of phonon energies and/or linewidths of resonances indicative of a transition between the paramagnetic and ferromagnetic state at Curie temperature (TC ≈ 50 K). The exploration of the effects of thickness on the phonon energies demonstrated small variations pronounces exclusively for the thinnest layers in the vicinity of 3 - 5 L. This observation is attributed to strong localization in the real space of interband electronic excitations, limiting the effects of confinement for resonantly excited Raman modes to atomically thin layers.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Vibrational properties, magnetic properties, CrBr3

Date published: 2024-03-29

Publisher: Springer Science and Business Media LLC

Journal:

• Scientific Reports (ISSN: 20452322) vol. 14 issue. 1 7484

Funding:

• National Science Centre, Poland 2020/37/B/ST3/02311
• National Science Centre, Poland 2023/48/C/ST3/00309
• Air Force Office of Scientific Research FA8655-21-1-7026
• Ministry of Education - Singapore EDUN C-33-18-279-v12, I-FIM
• JSPS KAKENHI 21H05233
• World Premier International Research Center Initiative MEXT

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1038/s41598-024-57622-w

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Updated at: 2025-02-23 22:48:43 +0900

Published on MDR: 2025-02-23 22:48:43 +0900