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arXiv · 1812.00720

Microscopic theory of magnon-drag electron flow in ferromagnetic metals

Terufumi Yamaguchi·Hiroshi Kohno·Rembert A. Duine
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Abstract

A temperature gradient applied to a ferromagnetic metal induces not only independent flows of electrons and magnons but also drag currents because of their mutual interaction. In this paper, we present a microscopic study of the electron flow induced by the drag due to magnons. The analysis is based on the $s$-$d$ model, which describes conduction electrons and magnons coupled via the $s$-$d$ exchange interaction. Magnetic impurities are introduced in the electron subsystem as a source of spin relaxation. The obtained magnon-drag electron current is proportional to the entropy of magnons and to $α- β$ (more precisely, to $1 - β/α$), where $α$ is the Gilbert damping constant and $β$ is the dissipative spin-transfer torque parameter. This result almost coincides with the previous phenomenological result based on the magnonic spin-motive forces, and consists of spin-transfer and momentum-transfer contributions, but with a slight disagreement in the former. The result is interpreted in terms of the nonequilibrium spin chemical potential generated by nonequilibrium magnons.

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Terufumi Yamaguchi, Hiroshi Kohno, Rembert A. Duine. 2018-12-03. Microscopic theory of magnon-drag electron flow in ferromagnetic metals. https://doi.org/10.1103/physrevb.99.094425

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