Spin wave band structure and microwave properties of the weak ferromagnet FeBo3

The transparent weak ferromagnet FeBO3is investigated using Brillouin scattering from thermal acoustic magnons and microwave resonance. A detailed analysis including dipole energy results in a comprehensive description of the various contributions to the magnon energy at small wavevectors. The linewidth of both the ferromagnetic resonance and parametrically generated spin waves is determined. The results allow a separation of homogeneous and inhomogeneous contributions. Random strain seems to be responsible for most of the ferromagnetic resonance linewidth at low temperature.