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

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.