Micromagnetic theory of spin waves in rare-earth–transition-metal compounds

The micromagnetic theory is a simple and powerful method to calculate the spin-wave dispersion relation in the long-wavelength region. The calculation has been performed within the framework of the two-sublattice model which is the adequate micromagnetic description for rare-earth–transition-metal compounds. A magnetocrystalline anisotropy of the easy-axis type is assumed and the cases of ferromagnetic and ferrimagnetic coupling of the two sublattices are considered. The theoretical results are compared to neutron-scattering data obtained from R${\mathrm{Fe}}_2$, ${\mathit{R}}_2$ ${\mathrm{Fe}}_{17}$, ${\mathit{R}}_2$ ${\mathrm{Co}}_{17}$, and ${\mathit{R}}_2$ ${\mathrm{Fe}}_{14}$B, with R representing different rare-earth atoms.