Photo-Magnonics

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 magnetostatic 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.