Fast long-wavelength exchange spin waves in partially compensated Ga:YIG

Spin waves in yttrium iron garnet (YIG) nano-structures attract increasing attention from the perspective of novel magnon-based data processing applications. For short wavelengths needed small-scale devices, group velocity is directly proportional to spin-wave exchange stiffness constant $\lambda_\mathrm{ex}$. Using wave vector resolved Brillouin Light Scattering (BLS) spectroscopy, we measure $\lambda_\mathrm{ex}$ Ga-substituted YIG thin films and show that it about three times larger than for pure YIG. Consequently, overcomes one wavenumbers $k > 4$ rad/$\mu$m, ratio between velocities reaches a value around 3.4 all 20$ rad/$\mu$m. As revealed by vibrating-sample magnetometry (VSM) ferromagnetic resonance (FMR) Ga:YIG with thicknesses down 59 nm have low Gilbert damping ($\alpha < 10^{-3}$), decreased saturation magnetization $\mu_0 M_\mathrm{S}~\approx~20~$mT pronounced out-of-plane uniaxial anisotropy H_{\textrm{u1}} \approx 95 $ mT which leads an easy axis. Thus, opens access fast isotropic transport nano-scale systems independently dipolar effects.