Phonon manipulating magnon transports in magnetic multi-layers through coupled Boltzmann approach

The collective elementary excitations of magnetic order, magnons, the quanta of spin-wave, are bosonic and carry spin angular momentum. Becoming an ideal spintronic device information carrier with low energy dissipations in ferromagnetic materials(like YIG). The scattering of phonons, in particular, the surface acoustic wave SAW, excites and regulates magnon and couples the transport channels of phonons and magnetrons through the magnetoelastic action. Which emerges a new method of magnons controlling. In this paper, within the framework of non-equilibrium Boltzmann transport, we address on the physical mechanism of how coupled phonons regulate and enhance the effects of magnon flow and propagation distance; as well as, the conversion mechanism of spin/magnon/phonon in magnetic multilayer film materials. We also study frequencies of coupled phonons that affect magnon's relaxation in k-space and by using external gradient field methods to control magnon transport. Based on quantum exchange interaction, we established a non-equilibrium magnon/spin/phonon three-phase coupled Boltzmann equations to calculate the transport behavior in the multi-layer film system. The physical core content of this paper focuses on non-equilibrium magnon propagation, coupled phonon excitation magnon, and material parameter controlling.