The Boltzmann Transport theory of Magnon with N-process Normal Scattering

Ferromagnetic insulators (FMIs) was most promising material for magnon devices to generate, process, and transport spin information over long distances. While, a precise magnon transport picture in FMIs thin film was still demanded. A novel complete picture of magnon transport in FMIs was builded with a new Boltzmann equation which combined magnon, phonon and spin-polarized electron system together. In three magnons scattering, we found the N-process scattering which due to dipole-dipole interaction, dominated the decay dynamics of magnon group. To conduct N-process scattering, a new spatial dependent magnon interaction field λ was introduced, which was discribing collective local field in magnons. We also found N-process scattering is the physical origin that why coherence magnons can transfer to thermal magnons in FI relaxation process. With those effects, we proposed a new method try to modify generation, amplification and controlling of magnon transport and the conversion to other particle(phonon). Furthermore, governing N-process scattering magnons which engendered by temperature gradient, could extend the global decay length of magnetic information.