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 in small-scale devices, the group velocity is directly proportional to the spin-wave exchange stiffness constant lambda (ex). Using wave vector resolved Brillouin light scattering spectroscopy, we directly measure lambda(ex) in Ga-substituted YIG thin films and show that it is about three times larger than for pure YIG. Consequently, the spin-wave group velocity overcomes the one in pure YIG for wavenumbers k > 4 rad/mu m, and the ratio between the velocities reaches a constant value of around 3.4 for all k > 20 rad/mu m. As revealed by vibrating-sample magnetometry and ferromagnetic resonance spectroscopy, Ga:YIG films with thicknesses down to 59 nm have a low Gilbert damping ( alpha < 10 - 3), a decreased saturation magnetization mu M-0(S) approximate to 20 mT, and a pronounced out-of-plane uniaxial anisotropy of about mu H-0(u1) approximate to 95 mT, which leads to an out-of-plane easy axis. Thus, Ga:YIG opens access to fast and isotropic spin-wave transport for all wavelengths in nano-scale systems independently of dipolar effects. (c) 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).