Silas Hoffman, Koji Sato, Yaroslav Tserkovnyak
The spin Seebeck effect, i.e., thermal spin angular momentum transfer between a paramagnetic metal and ferromagnetic insulator, is studied theoretically based on the stochastic Landau-Lifshitz-Gilbert (LLG) phenomenology. Magnons in the ferromagnet establish a nonequilibrium steady state by equilibrating with phonons via bulk Gilbert damping and electrons in the paramagnet via spin pumping, according to the fluctuation-dissipation theorem. Subthermal magnons and the associated spin currents are treated classically, while the appropriate quantum crossover is imposed on high-frequency magnetic fluctuations. We identify several lengthscales in the ferromagnet, which govern qualitative changes in the dependence of the spin Seebeck coefficient on the magnetic film thickness.
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http://arxiv.org/abs/1304.7295
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