Nuclear magnetic resonance and relaxation in the spin-wave regime of the dipolar Heisenberg ferromagnet EuS

We have investigated the resonance frequency fᵣ, the longitudinal and the transverse relaxation rates T₁^-1, T₂^-1, of ¹⁵³Eu in fields up to 2 T for low temperatures, T{≤}4.2 K{}Tc=16.5 K. Based on exchange constants from neutron data, a detailed analysis of the field dependence of fᵣ reveals a magnetic anisotropy field Bₐ=4 mT parallel to [100], which is much smaller than that proposed in previous NMR work but which is consistent with early ferromagnetic-resonance results. T₁^-1 appears to be dominated by the dipole-induced two-magnon relaxation. First evidence for a significant on-site contribution of the Suhl-Nakamura interaction to T₂^-1 is provided, caused by the very small spin-wave stiffness in this material.