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Nonlocal Drag of Magnons in a Ferromagnetic Bilayer
Journal article   Peer reviewed

Nonlocal Drag of Magnons in a Ferromagnetic Bilayer

Tianyu Liu, G Vignale and Michael E Flatté
Physical review letters, Vol.116(23), pp.237202-237202
06/10/2016
DOI: 10.1103/PhysRevLett.116.237202
PMID: 27341254
url
https://arxiv.org/pdf/1605.04336View
Open Access

Abstract

Quantized spin waves, or magnons, in a magnetic insulator are assumed to interact weakly with the surroundings, and to flow with little dissipation or drag, producing exceptionally long diffusion lengths and relaxation times. In analogy to Coulomb drag in bilayer two-dimensional electron gases, in which the contribution of the Coulomb interaction to the electric resistivity is studied by measuring the interlayer resistivity (transresistivity), we predict a nonlocal drag of magnons in a ferromagnetic bilayer structure based on semiclassical Boltzmann equations. Nonlocal magnon drag depends on magnetic dipolar interactions between the layers and manifests in the magnon current transresistivity and the magnon thermal transresistivity, whereby a magnon current in one layer induces a chemical potential gradient and/or a temperature gradient in the other layer. The largest drag effect occurs when the magnon current flows parallel to the magnetization; however, for oblique magnon currents a large transverse current of magnons emerges. We examine the effect for practical parameters, and find that the predicted induced temperature gradient is readily observable.

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