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

Abstract

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 [Formula: see text]. Using wave vector resolved Brillouin light scattering spectroscopy, we directly measure [Formula: see text] 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/ μm, and the ratio between the velocities reaches a constant value of around 3.4 for all k > 20 rad/ μm. As revealed by vibrating-sample magnetometry and ferromagnetic resonance spectroscopy, Ga:YIG films with thicknesses down to 59 nm have a low Gilbert damping ([Formula: see text]), a decreased saturation magnetization [Formula: see text] mT, and a pronounced out-of-plane uniaxial anisotropy of about [Formula: see text] 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.

Self‐Imaging Based Programmable Spin‐Wave Lookup Tables

“…Making the Talbot length dependent on the parameter M = d /λ and the wavenumber k , we can also derive the formula for the time‐delay ( t d = z T / v gr ) of devices based on self‐imaging in the exchange interactions regime, where $$\omega \approx l_{ex}^2{\omega _{\rm{M}}}{k^2}$$, getting $$\[{t_{\rm{d}}} = \frac{{{z_{\rm{T}}}(M)}}{{{v_{gr}}}} = \frac{{\pi {M^2}}}{{\gamma {\lambda _{ex}}}}\frac{1}{{{k^2}}}\]$$To validate these predictions, we calculate the relationship between the Talbot length values and the group velocity characteristic for a given material ( t d = z T / v gr ) as a function of the wave vector. We perform this analysis assuming M = 3 and comparing results for films of thickness L = 5 nm made of three different materials, that is, YIG, permalloy (Py) and Ga‐substituted YIG (Ga:YIG), [ 41 ] see Figure 8a.…”

“…). [41] The solid lines represent the results obtained assuming dispersion relation described by Equation ( 2)) whereas the dashed lines represent the exchange approximation (Equation ( 5)). b) t d (k) dependencies for different M values.…”

“…To validate these predictions, we calculate the relationship between the Talbot length values and the group velocity characteristic for a given material (t d = z T /v gr ) as a function of the wave vector. We perform this analysis assuming M = 3 and comparing results for films of thickness L = 5 nm made of three different materials, that is, YIG, permalloy (Py) and Ga-substituted YIG (Ga:YIG), [41] see Figure 8a.…”

“…The time-delay t d (=z T /v gr ) dependence on the wave vector. a) t d (k) dependencies for the same ratio M = d/λ (here equals three) and three different materials, that is, YIG, Py (M S = 800 kA m −1 , A ex = 16 pJ m −1 ) and Ga-substituted YIG (M S = 15.9 kA m −1 , A ex = 1.37 pJ m −1 ) [41]. The solid lines represent the results obtained assuming dispersion relation described by Equation (2)) whereas the dashed lines represent the exchange approximation (Equation (5)).…”

Stripe Domains in Electrodeposited Ni90fe10 Thin Films

“…In addition, there is an increasing attention in magnetoelasticity since it can be exploited in spin waves generation [3][4][5][6]. Spin waves are collective excitations of the electron spin system, and they have been proposed for applications such as information transfer with low energy dissipation, high-speed technology or analog computing [3,[7][8][9][10]. In that sense, spin textures play a fundamental role for the stabilization and manipulation of spin waves, and therefore, a huge effort is performing for the development of tunable magnetic structures.…”