Enhanced Gilbert Damping in Thin Ferromagnetic Films

Yaroslav Tserkovnyak, Arne Brataas, Gerrit E. W. Bauer

Published 2001-10-11, updated 2002-08-14Version 2

Using a scattering matrix approach, the precession of the magnetization of a ferromagnet is shown to transfer spins into adjacent normal metal layers. This ``pumping'' of spins slows down the precession corresponding to an enhanced Gilbert damping factor in the Landau-Lifshitz equation. The damping is expressed in terms of the scattering matrix of the ferromagnet-normal metal interface, which is accessible to model and first-principles calculations. Our estimates for permalloy thin films explain the trends observed in recent experiments.