Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 30: Electron Theory

MA 30.13: Vortrag

Donnerstag, 28. Februar 2008, 17:45–18:00, H 1028

Electron theory of dissipative spin dynamics — •Jonas Seib, Daniel Steiauf, and Manfred Fähnle — Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart

Within the breathing Fermi surface model the damping of the magnetization dynamics is related to the change of the Fermi surface with changing magnetic configuration, given by the orientations of the atomic magnetic moments: This change requires a scattering of the electrons among the single-electron states in reciprocal space, and this in turn requires time. The theory yields a Gilbert-type equation of motion for the magnetization with the damping scalar of the original Gilbert equation replaced by a damping matrix. This damping matrix depends on a relaxation time describing the scattering, and on the change of single-electron energies when the directions of the atomic magnetic moments are changing. These derivatives of single-electron energies can be calculated within electron theory. For collinear configurations the breathing of the Fermi surface is caused by spin-orbit coupling, and the derivatives can been calculated with a torque-operator method [1]. For noncollinear situations, also interatomic exchange interaction is the origin of a breathing Fermi surface, and a new Harris-Foulkes approach [2] can be used to calculate the change of single-electron energies. Numerical results for the damping matrix in collinear configurations as obtained by the two methods are compared. A preview on damping in noncollinear situations is given.

[1] D. Steiauf and M. Fähnle, Phys. Rev. B 72, 064450 (2005).

[2] P. Bruno, Phys. Rev. Lett. 90, 087205 (2003).