Ultrafast phononic switching of magnetization

TL;DR

This paper demonstrates ultrafast magnetization switching in magnetic garnet films through resonant excitation of specific phonon modes, revealing a magneto-elastic mechanism distinct from thermal effects.

Contribution

It provides the first experimental evidence of phonon-mediated ultrafast magnetization switching via resonant excitation of longitudinal optical phonons.

Findings

Resonant excitation of longitudinal phonons switches magnetization.

Transverse phonon excitation causes thermal demagnetization.

Magneto-elastic coupling is key to ultrafast switching.

Abstract

Identifying an efficient pathway to change the order parameter via a subtle excitation of the coupled high-frequency mode is the ultimate goal of the field of ultrafast phase transitions. This is an especially interesting research direction in magnetism, where the coupling between spin and lattice excitations is required for magnetization reversal. Despite several attempts however, the switching between magnetic states via resonant pumping of phonon modes has not yet been demonstrated. Here we show how an ultrafast resonant excitation of the longitudinal optical phonon modes in magnetic garnet films switches magnetization into a peculiar quadrupolar magnetic domain pattern, unambiguously revealing the magneto-elastic mechanism of the switching. In contrast, the excitation of strongly absorbing transverse phonon modes results in thermal demagnetization effect only.