Two-Magnon Excitations: From Periodical Perturbations to Magnonic Crystals

Two-magnon scattering is a well-known effect e.g.\ in ferromagnetic resonance experiments leading to a linewidth broadening. Available theory so far was based on random defects acting as a dipolar scattering potential. Recently it was shown by Landeros and Mills [1] that this theory can be extended to handle two-magnon scattering in \emph{periodically} perturbed films, which can be easily created by lithographical patterning. These perturbed films are the intermediate step towards full magnonic crystals.
The extended model allows for analytically calculating the response function of 1D and 2D periodically perturbed ferromagnetic films in almost perfect agreement to FMR experiments as I will show. A striking feature e.g.\ is the mode splitting due to the two-magnon scattering which opens magnonic band gaps. This splitting can be tailored by the geometric and magnetic sample parameters.

This work was supported by the DFG grants FA 314/6-1, FA314/3-2.