Nonlocal magnon spin transport in a ferrimagnetic insulator

Magnons recently entered the field of spintronics as novel, long-distance spin information carriers. In this talk, I will show the experimental demonstration of the diffusive magnon transport in yttrium iron garnet (YIG), a ferrimagnetic insulator [1]. Magnons can be excited in two ways simultaneously: electrical injection as a result of the spin Hall effect in an adjacent heavy metal, and thermal generation due to the bulk spin Seebeck effect. Magnons excited in both methods can be described by diffusive transport over a magnon relaxation length, around 10 $\backslash $mu m at room temperature [2]. We studied the transport behavior of both types of magnons as a function of magnetic field, YIG thickness and temperature [3][4]. However, the study of magnon transport in different YIG thickness shows quantitative disagreement with the magnon diffusion model, suggesting more complex processes. [1] Cornelissen \textit{et al., Nature Phys}. \textbf{11},1022 (2015) [2] Cornelissen \textit{et al.}, \textit{Phys. Rev. B} \textbf{94}, 014412 (2016) [3] Cornelissen \textit{et al., Phys. Rev. B }\textbf{93}, 020403 (R) (2016); \textit{Phys. Rev. B }\textbf{94}, 180402(R) (2016) [4] Shan \textit{et al}., \textit{Phys. Rev. B }in press, arxiv:1608.01178; J. Shan \textit{et al}., in preparation