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arXiv · 1811.11972

Efficient spin transport in a paramagnetic insulator

Koichi Oyanagi·Saburo Takahashi·Ludo J. Cornelissen·Juan Shan·Shunsuke Daimon·Takashi Kikkawa·Gerrit E. W. Bauer·Bart J. van Wees·Eiji Saitoh
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Abstract

The discovery of new materials that efficiently transmit spin currents has been important for spintronics and material science. The electric insulator $\mathrm{Gd}_3\mathrm{Ga}_5\mathrm{O}_{12}$ (GGG) is a superior substrate for growing magnetic films, but has never been considered as a conduit for spin currents. Here we report spin current propagation in paramagnetic GGG over several microns. Surprisingly, the spin transport persists up to temperatures of 100 K $\gg$ $T_{\mathrm{g}} = 180$ mK, GGG's magnetic glass-like transition temperature. At 5 K we find a spin diffusion length ${λ_{\mathrm{GGG}}} = 1.8 \pm 0.2 μ$m and a spin conductivity $σ_{\mathrm{GGG}} = (7.3 \pm 0.3) \times10^4$ $\mathrm{Sm}^{-1}$ that is larger than that of the record quality magnet $\mathrm{Y}_3\mathrm{Fe}_5\mathrm{O}_{12}$ (YIG). We conclude that exchange coupling is not required for efficient spin transport, which challenges conventional models and provides new material-design strategies for spintronic devices.

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Koichi Oyanagi, Saburo Takahashi, Ludo J. Cornelissen, Juan Shan, Shunsuke Daimon, Takashi Kikkawa, Gerrit E. W. Bauer, Bart J. van Wees, Eiji Saitoh. 2018-11-29. Efficient spin transport in a paramagnetic insulator. https://doi.org/10.1038/s41467-019-12749-7

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