Why are spin wave excitations all important in nanoscale magnetism?

For a proper interpretation of magnetic phenomena in low dimensional magnets, higher order spin wave excitations are more important than in bulk magnetism. Three different types of experiments will be discussed: (i) In a so-called trilayer, two ferromagnetic films are coupled via a nonmagnetic spacer: FM1/ NM/FM2. The individual Curie temperatures can be shifted by 50 K or 100 K, just by tuning the NM thickness. This is impossible in 3D. (ii) Spin-wave excitations are the major route to understanding the T-dependence of the interlayer exchange coupling (IEC). (iii) The standard Gilbert damping is insufficient to describe the spin dynamics in nanomagnets. Magnon-magnon scattering, a reversible process in the magnetic subsystem, must first be disentangled in the spin dynamics, before determining the dissipative relaxation into the thermal bath.