The H field dependence of magnon diffusion length basing on Boltzmann transport methods*

The urgent demand for high-capacity and high-speed logical storage device gives rise to the further study on spin and magnon. In this abstract, we construct a new magnon Boltzmann equation from full quantum magnon Hamiltionian in magnetic insulator system, which contains the factors related to boundary injection, temperature gradient and magnetic field gradient. In our methods, we first calculate the change of magnon accumulation and magnon current with thickness of magnetic oxide film, under interaction of interface with spin-magnon, which implies that there are two parts in the process of magnon transport: magnon diffusion and magnon relaxation. Second, we calculate the change of magnon current with distance, which explains the dependence of magnon diffusion length on magnetic field theoretically. We find that the magnon diffusion length is inversely proportional to H field which was first observed by experiment [1]. Last but not least, we predict the rate of change of magnon current corresponding to the anisotropy energy change in magnetic insulator with strong anisotropic exchange energy and anisotropy energy.
[1] L. Cornelissen etal, PRB 93, 020403(R) (2016)