In the framework of magnonics, all-optical femtosecond laser experiments are used to study spin waves and their relaxation paths. Magnonic crystal structures based on antidots allow the control over the spin-wave modes. In these two-dimensional magnetic metamaterials with periodicities in the wave-length range of dipolar spin waves, the spin-wave bands and dispersion are modified. Hence, a specific selection of spin-wave modes excited by laser pulses is possible. Different to photonics, the modes depend strongly on the strength of the magneto-static potential at around each antidot site – the dipolar field. While this may lead to a mode localization, also for filling fractions around or below 10 %, Bloch states are found in low damping ferromagnetic metals. In this chapter, an overview of these mechanisms is given and the connection to spin-wave band spectra calculated from an analytical model is established. Namely, the plane-wave method yields flattened bands as well as band gaps at the antidot lattice Brillouin zone boundary.
KeywordsSpin Wave Pump Pulse Probe Pulse Continuous Film Brillouin Zone Boundary
We would like to thank Jakob Walowski for the contribution of the experiment’s schematic shown in Fig. 6.1(a) and Georg Herink for careful proof-reading of the manuscript.