Magnon transport properties data

The spin Seebeck effect (SSE) in ferromagnetic insulators provides a simple method that employs heat to manipulate magnons, which could be used as carriers of information and energy conversion. However, a theory that can quantatively interpret experimental results is still lacking. In this manuscript, we first reviewed the important experimental results of the spin Seebeck effect in ferromagnetic insulator materials in the past few years, and through theoretical analysis, we develop the equations for magnon transport and find that the temperature-dependent longitudinal SSE is dominated by magnon-phonon scattering at low temperature region, rather than magnon-magnon scattering. The relaxation time of magnon-phonon scattering follows <i>T^-3.3</i> dependence. At very low temperature region, the magnon enters the ballistic transport process, the temperature dependence of the relaxation time is <i>T^-1/2</i>. The mode is in excellent agreement with the experimental results. In addition, we have also derived equations that explain the position dependence of SSE with an in-plane temperature gradient. The transverse distribution of the magnon temperature corresponding to the number of magnons is consistent with the experimental measurement, and the linear spatial distribution of the transverse SSE signal with position is given.