Spin Wave Frequency and Critical Dynamics of Ferromagnets Below T_C
  Employing mode-coupling theory we show that the amplitude of the spin wave frequency scaling function for the isotropic Heisenberg Hamiltonian is universal. Theoretical and experimental values for Fe, Ni, Co, EuO, and EuS agree quite well. Recent measurements of the longitudinal line width in Ni are explained quantitatively. 
H. Schinz, and F. Schwabl