Spin-Phonon Interaction in Yttrium Iron Garnet

TL;DR

This paper investigates the spin-phonon interaction in yttrium iron garnet (YIG) using Raman spectroscopy and a new theoretical approach, revealing a positive correlation between interaction strength and phonon frequency.

Contribution

It introduces a symmetry-adapted parameter and a modified mean-field theory to quantify spin-phonon interactions in YIG for the first time.

Findings

Discovered a positive correlation between spin-phonon interaction strength and phonon frequency.

Classified phonon modes based on their symmetry using Raman measurements.

Developed a new theoretical framework for quantifying spin-phonon interactions in magnetic insulators.

Abstract

Spin-phonon interaction is an important channel for spin and energy relaxation in magnetic insulators. Understanding this interaction is critical for developing magnetic insulator-based spintronic devices. Quantifying this interaction in yttrium iron garnet (YIG), one of the most extensively investigated magnetic insulators, remains challenging because of the large number of atoms in a unit cell. Here, we report temperature-dependent and polarization-resolved Raman measurements in a YIG bulk crystal. We first classify the phonon modes based on their symmetry. We then develop a modified mean-field theory and define a symmetry-adapted parameter to quantify spin-phonon interaction in a phonon-mode specific way for the first time in YIG. Based on this improved mean-field theory, we discover a positive correlation between the spin-phonon interaction strength and the phonon frequency.