Understanding Damping Mechanisms via Spin Diffusion Length in Low-damping Li$_{0.5}$Al$_{1.0}$Fe$_{1.5}$O$_4$ Spinel Ferrite Thin Films

TL;DR

This study investigates magnon damping mechanisms in low-damping ferrimagnetic insulator thin films, revealing distinct temperature-dependent spin diffusion length behaviors for electrical and thermal magnons, linked to different scattering processes.

Contribution

It introduces Li$_{0.5}$Al$_{1.0}$Fe$_{1.5}$O$_4$ thin films as a model system to differentiate magnon scattering mechanisms via temperature-dependent spin diffusion length measurements.

Findings

Electrical SDL remains stable with temperature.

Thermal SDL decreases as temperature increases.

Different scattering mechanisms limit electrical and thermal magnons.

Abstract

The mechanisms underlying magnon damping are of fundamental and technological interest in low-damping materials. We find low-damping ferrimagnetic insulator Li$_{0.5}$Al$_{1.0}$Fe$_{1.5}$O$_4$ (LAFO) thin films to be a promising model system for probing these mechanisms because of its distinct temperature dependent spin diffusion length (SDL) trends for electrically and thermally generated magnons. With increasing temperature, the electrical SDL shows minimal change, while the thermal SDL decreases. We attribute these trends to distinct magnon populations and scattering mechanisms: thermally generated high $k$ magnons are limited by magnon-phonon scattering, whereas electrically generated low $k$ magnons are limited by relaxational scattering from magnetic impurities.