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Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

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Related Experiment Video

Updated: Jul 21, 2025

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

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Published on: June 28, 2016

Phonon Anharmonicity and Spin-Phonon Coupling in CrI₃.

Luca Tomarchio^1,2, Lorenzo Mosesso^1,2, Salvatore Macis^1,3

¹Department of Physics, Sapienza University, Piazzale Aldo Moro 5, 00185 Rome, Italy.

Materials (Basel, Switzerland)

|July 29, 2023

Summary

Chromium triiodide (CrI3) single crystals exhibit complex optical properties due to strong lattice anharmonicity and spin-phonon coupling. These interactions influence the vibrational spectrum of this van der Waals ferromagnet below its Curie temperature.

Keywords:

optical spectroscopy phonon anharmonicity spin–phonon coupling van der Waals ferromagnet

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Area of Science:

Condensed Matter Physics
Materials Science
Spectroscopy

Background:

Chromium triiodide (CrI3) is a van der Waals ferromagnet with a low Curie temperature (61 K).
Understanding its optical properties is crucial for exploring its magnetic and vibrational behaviors.
Spin-phonon coupling and lattice anharmonicity are key factors influencing material properties.

Purpose of the Study:

To investigate the temperature-dependent far-infrared optical properties of CrI3 single crystals.
To identify and characterize various excitations beyond standard phonon modes.
To elucidate the role of spin-phonon coupling and lattice anharmonicity in CrI3's optical response.

Main Methods:

Far-infrared optical spectroscopy (reflectance and transmittance measurements).
Temperature-dependent measurements were performed on CrI3 single crystals.
Analysis of spectral features in relation to crystalline symmetry, temperature, and magnetic properties.

Main Results:

Observed numerous excitations in the optical spectra of CrI3, in addition to expected phonon modes.
Spectra showed significant temperature dependence, particularly below the Curie temperature (61 K).
Evidence of strong lattice anharmonicity and significant spin-phonon coupling was found.

Conclusions:

The complex vibrational spectrum of CrI3 arises from the interplay of lattice anharmonicity and spin-phonon coupling.
These entangled interactions significantly influence the optical properties of this van der Waals ferromagnet.
The study highlights CrI3 as a platform for investigating coupled degrees of freedom in magnetic materials.