Strong Spin-Lattice Interaction in Layered Antiferromagnetic CrCl$_\textrm{3}$

TL;DR

This study reveals strong spin-lattice interactions in layered antiferromagnetic CrCl3, showing how magnetic order influences vibrational properties and structural phases, with implications for 2D magnetic materials.

Contribution

The paper provides the first comprehensive experimental and theoretical analysis of all Raman-active phonon modes in CrCl3, demonstrating clear signatures of spin-phonon coupling across magnetic phase transitions.

Findings

All eight Raman-active modes are unambiguously assigned.

Selected phonon modes are strongly enhanced due to interference effects.

Pronounced spin-phonon coupling signatures are observed across magnetic phase transitions.

Abstract

Understanding the coupling between lattice vibrations and magnetic order is crucial for controlling properties of two-dimensional magnetic materials. Here, we investigate the vibrational properties of bulk and thick-flake CrCl$_\textrm{3}$ using polarization-resolved Raman spectroscopy, complemented by photoluminescence, photoluminescence excitation, and optical absorption measurements. Symmetry analysis, supported by first-principles phonon calculations, enables the unambiguous assignment of all eight Raman-active modes, four $\textrm{A}_\textrm{g}$ and four $\textrm{E}_\textrm{g}$, previously predicted only theoretically. Excitation-energy-dependent measurements reveal that the strong enhancement of selected phonon modes originates primarily from interference effects rather than resonant Raman scattering. Temperature-dependent Raman spectroscopy further reveals pronounced signatures of spin-phonon coupling across the transition from a fully antiferromagnetic phase, through an intermediate regime with local, domain-like ferromagnetic order, to the paramagnetic phase, accompanied by a clear rhombohedral-to-monoclinic structural transition. Together, these results demonstrate how lattice, electronic, and magnetic degrees of freedom collectively govern the Raman response of CrCl$_\textrm{3}$.