Dresden 2006 – wissenschaftliches Programm

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MA: Magnetismus

MA 27: Spin-Dynamics, Magnetization Reversal II

MA 27.6: Vortrag

Donnerstag, 30. März 2006, 11:30–11:45, HSZ 403

Spin-wave eigenmodes of an infinite thin film withperiodically modulated exchange bias field — •B. Hillebrands¹, C. Bayer¹, M.P. Kostylev¹, and S.O. Demokritov² — ¹Fachbereich Physik and Forschungsschwerpunkt MINAS, TUKaiserslautern, Germany — ²Institut für AngewandtePhysik, Westfälische Wilhelms-Universität Münster,Germany

We propose a method to modify the spin-wave spectrum of a technologically relevant exchange bias bilayer system. It is based on a periodical suppression of the exchange bias field on the micrometer scale which induces a superlattice in the internal field. This periodic modification can experimentally be realized by focussed ion beam [1]. We will calculate semi-analytically the spin-wave eigenmodes and -frequencies of such a superlattice. The calculation method is based on the Green’s function approach and on Bloch’s theorem. We identify two different kinds of eigenmodes of this system. The first kind are propagating spin waves which have a band gap at the edge of the Brillouin zone. The second one are localized within the wells of the internal field and are nearly dispersion free. We further show that, by choosing an appropriate periodicity of the superlattice, the band gaps can be introduced at desired frequencies and so this system corresponds to a one-dimensional magnonic crystal. The proposed method might be of real practical interest for applications as it tailors the spin wave frequencies in thin films without a change in the topography. This work was supported by the EC projects ULTRASWITCH and NEXBIAS and by the DFG.

[1] K. Potzger, et al., IEEE Trans. Magn. 41, 10 (2005).