Energy spectrum and damping of spin waves in a ferromagnet with uniaxial anisotropy

The ground state and magnon spectrum (excluding the region of magnetostatic oscillations) are found for a ferrodieleetric sample in the form of a triaxial ellipsoid. The treatment is based on a microscopic Hamiltonian of the ferrodielectric that takes into account isotropic exchange, Zeeman and dipole-dipole interactions, and also the energy of uniaxial magnetic anisotropy. The frequency of homogeneous precession of the magnetization is also determined. The Tyablikov–Bonch-Bruevich regular perturbation theory for the mass operator is used to calculate the damping due to three-magnon processes induced by the anisotropy; the line width of homogeneous ferromagnetic resonance is also estimated.