Browsing by Author "Gilmore, Keith"

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Precession damping in itinerant ferromagnets
(Montana State University - Bozeman, College of Letters & Science, 2007) Gilmore, Keith; Chairperson, Graduate Committee: Yves U. Idzerda; Mark Stiles (co-chair)
Precession damping in metallic ferromagnets had been assumed to result from the spinorbit interaction. While several theories of spin-orbit damping had been postulated, no convincing numerical comparisons to data existed. We selected one promising theory and performed first-principles numerical calculations of damping for bulk iron, cobalt, and nickel. Comparison of minimal calculated and measured damping rates demonstrated a 70 % agreement for nickel, 60 % for iron, and 40 % for cobalt. We then relaxed the initial constraint of a universal electron-lattice scattering rate by allowing the scattering rate to be spin dependent. The spin dependent lifetime ratio was equated to the ratio of the spin resolved density of states at the Fermi level. This modification improved the agreement to 95 % for nickel, 70 % for iron, and 47 % for cobalt. With this level of agreement, we next constructed a simple effective field explanation for the damping process. As the magnetization rotates, the energy of the spin system gets pushed out of equilibrium and this excitation is quenched by electron-lattice scattering.