Abstract
Based on the Fermi surface breathing model of Kamberský, a phenomenological extension of the ab initio density-functional electron theory is used to derive an equation of motion for the spin dynamics in magnets. It is shown that even in the simple case of a homogeneous magnetization the damping term of the commonly used Gilbert equation with the damping scalar has to be replaced by a term of the form with a damping matrix which depends on the orientation of . Explicit calculations are performed for bulk, monolayers, and monatomic wires of Fe, Co, and Ni. The variation of with an orientation of is quite substantial already for the bulk materials (up to a factor of 4 in hcp Co) but most dramatic in the monolayers and monatomic wires in which for some orientations the damping is even zero. This represents an additional option for optimizing the magnetization reversal process in a magnetic nanostructure. It is shown that there is no simple relation between damping and magnetic anisotropy energy.
- Received 28 April 2005
DOI:https://doi.org/10.1103/PhysRevB.72.064450
©2005 American Physical Society