部分补偿Ga：YIG中的快速长波交换自旋波
Fast long-wavelength exchange spin waves in partially-compensated Ga:YIG
摘要：
钇铁石榴石（YIG）纳米结构中的自旋波从基于磁振子的新型数据处理应用的角度吸引了越来越多的关注。对于小规模设备中所需的短波长，群速度与自旋波交换刚度常数$λ_\mathrm{ex}$成正比。利用波矢分辨布里渊光散射（BLS）光谱，我们直接测量$λ_\mathrm{ex}$在Ga取代YIG薄膜，并表明它是约三倍大于纯YIG。因此，对于波数$k > 4$ rad/ $μ$ m，自旋波群速度克服纯YIG中的自旋波群速度，并且对于所有$k > 20$ rad/ $μ$ m，速度之间的比率达到约3.4的恒定值。振动样品磁强计（VSM）和铁磁共振（FMR）谱表明，厚度小于59 nm的Ga：YIG薄膜具有较低的Gilbert阻尼（$α< 10^{-3}$）、较低的饱和磁化强度（$μ_0 M_\mathrm{S}~\approx~20~$ mT）和显著的面外单轴各向异性（约为$μ_0 H_{\textrm{u1}} \approx 95 $ mT），这导致了面外易磁化轴。因此，Ga：YIG打开了独立于偶极效应的纳米尺度系统中所有波长的快速和各向同性自旋波传输的通道。
英文摘要：
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 $λ_\mathrm{ex}$. Using wave vector resolved Brillouin Light Scattering (BLS) spectroscopy, we directly measure $λ_\mathrm{ex}$ 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/$μ$m, and the ratio between the velocities reaches a constant value of around 3.4 for all $k > 20$ rad/$μ$m. As revealed by vibrating-sample magnetometry (VSM) and ferromagnetic resonance (FMR) spectroscopy, Ga:YIG films with thicknesses down to 59 nm have a low Gilbert damping ($α< 10^{-3}$), a decreased saturation magnetization $μ_0 M_\mathrm{S}~\approx~20~$mT and a pronounced out-of-plane uniaxial anisotropy of about $μ_0 H_{\textrm{u1}} \approx 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.
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