Long-distance transport of magnon spin information in a magnetic insulator at room temperature

• Published in: Nature physics 2015-12, Vol.11 (12), p.1022-1026
• Main Authors: Cornelissen, L. J., Liu, J., Duine, R. A., Youssef, J. Ben, van Wees, B. J.
• Format: Article
• Language: English
• Subjects: 142/126; 639/766/119/1001; 639/766/119/997; Atomic; Classical and Continuum Physics; Complex Systems; Condensed Matter; Condensed Matter Physics; Diffusion; letter; Magnetism; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Physics; Theoretical; Yttrium
• ISSN: 1745-2473; 1745-2481; 1476-4636
• DOI: 10.1038/nphys3465

Although electron motion is prohibited in magnetic insulators, the electron spin can be transported by magnons. Such magnons, generated and detected using all-electrical methods, are now shown to travel micrometre distances at room temperature. The transport of spin information has been studied in various materials, such as metals 1 , semiconductors 2 and graphene 3 . In these materials, spin is transported by the diffusion of conduction electrons 4 . Here we study the diffusion and relaxation of spin in a magnetic insulator, where the large bandgap prohibits the motion of electrons. Spin can still be transported, however, through the diffusion of non-equilibrium magnons, the quanta of spin-wave excitations in magnetically ordered materials. Here we show experimentally that these magnons can be excited and detected fully electrically 5 , 6 , 7 in a linear response, and can transport spin angular momentum through the magnetic insulator yttrium iron garnet (YIG) over distances as large as 40 μm. We identify two transport regimes: the diffusion-limited regime for distances shorter than the magnon spin diffusion length, and the relaxation-limited regime for larger distances. With a model similar to the diffusion–relaxation model for electron spin transport in (semi)conducting materials, we extract the magnon spin diffusion length λ = 9.4 ± 0.6 μm in a thin 200 nm YIG film at room temperature.