Influence of the magnon-phonon relaxation in the magnon transport under thermal gradient in yttrium iron garnet.

We investigate the influence of the magnon-phonon relaxation processes in the magnon transport under thermal gradient in the ferrimagnetic insulator yttrium iron garnet (YIG). Based on the Boltzmann equation we calculate the magnon contribution in the thermal conductivity in YIG and the longitudinal spin Seebeck effect in YIG/Pt films, including the influence of the magnon relaxation to the lattice through a phenomenological damping parameter. Our results are in good agreement with reported experimental data showing that besides the magnon-magnon relaxation processes, the magnon-phonon relaxation plays an important role in the thermal properties in YIG films.