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

Time-resolved scanning transmission x-ray microscopy (TR-STXM) has been used for the directimaging of spin wave dynamics in thin film yttrium iron garnet (YIG) with spatial resolution inthe sub 100 nm range. Application of this x-ray transmission technique to single crystalline garnetfilms was achieved by extracting a lamella (13x5x0.185μm3) of liquid phase epitaxy grown YIG thinfilm out of a gadolinium gallium garnet substrate. Spin waves in the sample were measured alongthe Damon-Eshbach and backward volume directions of propagation at gigahertz frequencies andwith wavelengths in a range between 100 nm and 10μm. The results were compared to theoreticalmodels. Here, the widely used approximate dispersion equation for dipole-exchange spin wavesproved to be insufficient for describing the observed Damon-Eshbach type modes. For achieving anaccurate description, we made use of the full analytical theory taking mode-hybridization effectsinto account.