Spin dynamics in patterned magnetic multilayers with perpendicular magnetic anisotropy

The magnetization dynamics in nanostructures has been extensively studied in the last decades, and nanomagnetism has
evolved significantly over that time, discovering new effects, developing numerous applications, and identifying promising
new directions. This includes magnonics, an emerging research field oriented on the study of spin-wave dynamics and their
applications. In this context, thin ferromagnetic films with perpendicular magnetic anisotropy (PMA) offer interesting
opportunities to study spin waves, in particular, due to out-of-plane magnetization in remanence or at relatively weak
external magnetic fields. This is the only magnetization configuration offering isotropic in-plane spin-wave propagation within
the sample plane, the forward volume magnetostatic spin-wave geometry. The isotropic dispersion relation is highly
important in designing signal-processing devices, offering superior prospects for direct replicating various concepts from
photonics into magnonics. Analogous to photonic or phononic crystals, which are the building blocks of optoelectronics and
phononics, magnonic crystals are considered as key components in magnonics applications. Arrays of nanodots and
structured ferromagnetic thin films with a periodic array of holes, popularly known as antidot lattices based on PMA
multilayers, have been recently studied. Novel magnonic properties related to propagating spin-wave modes, exploitation of
the band gaps, and confined modes were demonstrated. Also, the existence of nontrivial magnonic band topologies has
been shown. Moreover, the combination of PMA and Dzyaloshinskii–Moriya interaction leads to the formation of chiral
magnetization states, including Néel domain walls, skyrmions, and skyrmionium states. This promotes the multilayers with
PMA as an interesting topic for magnonics and this chapter reviews the background and attempts to provide future
perspectives in this research field.