Pure spin currents are very promising for information transfer and processing for future low-power “green” electronics. There is a strong interest in using yttrium iron garnet (YIG) to generate pure spin currents, either via spin pumping or the spin Seebeck effect (SSE). This interest originates from the fact that the damping in YIG materials is lower than in any other known magnetic materials. The development of YIG-based, nanoscale spin batteries, however, demands YIG films that have a thickness in the nanometer range and at the same time exhibit low damping similar to single-crystal YIG materials. The growth of such YIG films will be discussed in the first part of this presentation. The second part will report on the exploration of optimal regimes for spin-wave spin pumping using YIG thin films, which will provide significant implication for the future development of high-efficient spin batteries. In previous work on using spin pumping or the SSE to produce spin currents, the experiments all required the use of an external magnetic field to bias the magnetic film, in addition to a microwave source for the excitation of magnetization precession or an electrical heating/cooling device for the establishment of a temperature gradient. The third part of this presentation will report on the generation of pure spin currents via the light-induced SSE in a self-biased hexagonal ferrite thin film, which demonstrates a spin battery that requires neither a magnetic field nor a microwave source nor a heating/cooling device, but light only.
