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

Based on the relaxation time approximation, the mean collision time for magnon scattering zc(T) is computed from the experimental spin Seebeck coefficient of a bulk YIG/ Pt bilayer. The scattering results to be composed by two processes: the low temperature one, with a T-1/2 dependence, is attributed to the scattering by defects and provides a mean free path around 10 mu m; the high temperature one, depending on T-4, is associated to the scattering by other magnons. The results are employed to predict the thickness dependence of the spin Seebeck coefficient for thin films.