Control of Spin-Wave Damping in Radio Frequency Components Using Spin Currents from Topological Insulators

Spin-waves are coherent excitations of magnetic moments. The frequency at which they oscillate can be tuned using an external magnetic field. Materials such as Yttrium Iron Garnet (YIG) that have magnetic order can be used to realize miniature devices that can be used as tunable filters, phase shifters, or frequency selective limiters. However, spin-waves suffer from damping that results in insertion loss. High frequencies require large external magnetic fields which would require large power supplies with heat sinks making the use of spin-waves for high frequency application impractical. Here, we present solutions to address both of these disadvantages that spin-waves have. We demonstrate that by creating undulations in ferromagnetic materials, high frequency spin-waves can be excited. We also show that by using topological insulators (TI) spin-wave damping can be reduced through transfer of angular momentum from surface spin currents from TI to YIG. The last solution that we demonstrate can be used to realize reduction of damping in RF components that utilize thin YIG films. Our results show that using 4 mA of current, insertion loss can be reduced by 6 dB