Robust spin current generated by the spin Seebeck effect

Spin pumping (SP) and the spin Seebeck effect (SSE) are widely used to generate a spin-wave spin current from ferromagnetic insulators. In this work, the authors show that while SP is significantly reduced in a polycrystalline yttrium iron garnet (YIG), the SSE is insensitive to the crystal structure. This discovery not only offers new insights into the mechanisms between the coherently driven SP and the noncoherently excited SSE but also demonstrates that the robust spin current generated by the SSE is a uniquely powerful tool to study the physics of the pure spin current in spintronics.