# Nanoscale X-Ray Imaging of Spin Dynamics in Yttrium Iron Garnet

## TL;DR

This study employs time-resolved scanning transmission x-ray microscopy to directly image and analyze spin wave dynamics in yttrium iron garnet thin films at nanoscale resolution, revealing limitations of existing dispersion models.

## Contribution

It demonstrates the application of TR-STXM to single crystalline YIG films and highlights the necessity of full analytical models for accurate spin wave dispersion analysis.

## Key findings

- Spin waves observed at gigahertz frequencies with wavelengths from 100 nm to 10 μm.
- Approximate dispersion equations are insufficient for Damon-Eshbach modes.
- Full analytical theory including mode-hybridization provides accurate descriptions.

## Abstract

Time-resolved scanning transmission x-ray microscopy (TR-STXM) has been used for the direct imaging of spin wave dynamics in thin film yttrium iron garnet (YIG) with spatial resolution in the sub 100 nm range. Application of this x-ray transmission technique to single crystalline garnet films was achieved by extracting a lamella (13x5x0.185 $\mathrm{\mu m^3}$) of liquid phase epitaxy grown YIG thin film out of a gadolinium gallium garnet substrate. Spin waves in the sample were measured along the Damon-Eshbach and backward volume directions of propagation at gigahertz frequencies and with wavelengths in a range between 100~nm and 10~$\mathrm{\mu}$m. The results were compared to theoretical models. Here, the widely used approximate dispersion equation for dipole-exchange spin waves proved to be insufficient for describing the observed Damon-Eshbach type modes. For achieving an accurate description, we made use of the full analytical theory taking mode-hybridization effects into account.