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arXiv · 1903.02790

Nonlocal Spin Transport as a Probe of Viscous Magnon Fluids

Camilo Ulloa·A. Tomadin·J. Shan·M. Polini·B. J. van Wees·R. A. Duine
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Abstract

Magnons in ferromagnets behave as a viscous fluid over a length scale, the momentum-relaxation length, below which momentum-conserving scattering processes dominate. We show theoretically that in this hydrodynamic regime viscous effects lead to a sign change in the magnon chemical potential, which can be detected as a sign change in the nonlocal resistance measured in spin transport experiments. This sign change is observable when the injector-detector distance becomes comparable to the momentum-relaxation length. Taking into account momentum- and spin-relaxation processes, we consider the quasiconservation laws for momentum and spin in a magnon fluid. The resulting equations are solved for nonlocal spin transport devices in which spin is injected and detected via metallic leads. Because of the finite viscosity we also find a backflow of magnons close to the injector lead. Our work shows that nonlocal magnon spin transport devices are an attractive platform to develop and study magnon-fluid dynamics.

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Camilo Ulloa, A. Tomadin, J. Shan, M. Polini, B. J. van Wees, R. A. Duine. 2019-03-07. Nonlocal Spin Transport as a Probe of Viscous Magnon Fluids. https://doi.org/10.1103/physrevlett.123.117203

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