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MA: Fachverband Magnetismus
MA 34: Magnetization / Demagnetization Dynamics III
MA 34.14: Talk
Wednesday, March 28, 2012, 18:30–18:45, H 1012
Photo-magnonics: Influence of antidot-lattice symmetry on spin-wave Bloch states — •Benjamin Lenk, Nils Abeling, Jelena Panke, and Markus Münzenberg — I. Physikalisches Institut, Georg-August-Universität Göttingen
Femtosecond laser pulses are used to optically excite (pump) and subsequently measure (probe) magnetization dynamics on thin (50 nm) CoFeB films. On timescales as long as nanoseconds spin waves are observed that can be manipulated with periodic structures. In our case, two-dimensional arrays of antidots provide a periodic “potential” to the excited spin waves which then propagate along selected directions of the lattice. On the way towards spin-wave logic devices an understanding of the respective mechanisms for magnonic manipulation is of crucial importance. The structured CoFeB films show magnonic modes with Bloch-like character. Their dispersion ω ( Hext ) is used to determine the wave vector which turns out to be π/a, where a is the lattice parameter of the antidot structure. It is shown that the propagation direction remains in nearest-neighbor direction even if the structure’s symmetry changes. Moreover, hexagonal lattices yield the possibility to tune the wave vector to π/2a.
In our contribution, we focus on the influence of the symmetry and prove the population of spin-wave Bloch states at the Brillouin zone boundary. These findings together with the low intrinsic damping of the material under consideration provide the basis for propagation experiments on antidot waveguides, first corresponding results are presented.