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arXiv · 0705.1432

Effective temperature and Gilbert damping of a current-driven localized spin

A. S. Nunez·R. A. Duine
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Abstract

Starting from a model that consists of a semiclassical spin coupled to two leads we present a microscopic derivation of the Langevin equation for the direction of the spin. For slowly-changing direction it takes on the form of the stochastic Landau-Lifschitz-Gilbert equation. We give expressions for the Gilbert damping parameter and the strength of the fluctuations, including their bias-voltage dependence. At nonzero bias-voltage the fluctuations and damping are not related by the fluctuation-dissipation theorem. We find, however, that in the low-frequency limit it is possible to introduce a voltage-dependent effective temperature that characterizes the fluctuations in the direction of the spin, and its transport-steady-state probability distribution function.

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A. S. Nunez, R. A. Duine. 2008-02-04. Effective temperature and Gilbert damping of a current-driven localized spin. https://doi.org/10.1103/physrevb.77.054401

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