**3.5 Summary and outlook**

Magnetic insulators with perpendicular anisotropy have become an important class of materials in the development of spintronic devices. For magnetic domain devices, the low-damping and large anisotropy features can enable high-speed domain-wall motion with a small current threshold, fueling the development of domain-wall memory and logic devices. Moreover, low-damping is significant for SOT oscillator applications, where the current threshold for self-oscillations decreases with damping. Recent experiments show that spin waves can be used to control magnetic domains through spin-orbit torques [60, 61]; this effect can be amplified and become more efficient in magnetic insulators. The strong magnetic anisotropy also allows the engineering of spin-wave dispersion relation without the need for large bias magnetic fields [62]. This will expand the horizon for magnonic and spin-wave devices, allowing the development of new magnon-photon coupling devices for quantum transduction and microwave photonic systems [63, 64].
