Temperature dependence of the mean magnon collision time in a spin Seebeck device

•The main scattering processes of YIG are defects or boundaries and other magnons.•Scattering by defects in a bulk YIG provides a mean free path around 10 microns.•The scattering at the boundaries is main process for films below 10 microns.•Collisions with magnons depends on T−4 as for the magnon-magnon scattering theory.