Thermally induced all-optical ferromagnetic resonance in thin YIG films

TL;DR

This paper demonstrates that all-optical ferromagnetic resonance can be applied to thin YIG films with metallic capping layers, enabling local magnetic property measurements through laser-induced heating and magnetization precession analysis.

Contribution

It introduces a novel application of AO-FMR to thin YIG films with metallic caps, allowing local magnetic characterization via laser heating-induced magnetization dynamics.

Findings

AO-FMR can be used in thin YIG films with metallic capping layers.

Magnetization precession is triggered by femtosecond laser heating.

Precession frequency depends on magnetic anisotropy and external field.

Abstract

All-optical ferromagnetic resonance (AO-FMR) is a powerful tool for local detection of micromagnetic parameters, such as magnetic anisotropy, Gilbert damping or spin stiffness. In this work we demonstrate that the AO-FMR method can be used in thin films of Yttrium Iron Garnet (YIG) if a metallic capping layer (Au, Pt) is deposited on top of the film. Magnetization precession is triggered by heating of the metallic layer with femtosecond laser pulses. The heating modifies the magneto-crystalline anisotropy of the YIG film and shifts the quasi-equilibrium orientation of magnetization, which results in precessional magnetization dynamics. The laser-induced magnetization precession corresponds to a uniform (Kittel) magnon mode, with the precession frequency determined by the magnetic anisotropy of the material as well as the external magnetic field, and the damping time set by a Gilbert damping parameter. The AO-FMR method thus enables measuring local magnetic properties, with spatial resolution given only by the laser spot size.