Spin Diffusion in 2D XY Ferromagnet with Dipolar Interaction
  In the ordered phase of 2D XY ferromagnet the dipolar interaction between spins induces a strong, relevant interaction between spin-waves. We study quasi-excitations of the interacting spin-wave 'liquid' in the long wavelength limit. We employ the Janssen-De-Dominicis method for classical Langevin equation to find the transformation of the spin-wave excitation into a new soft-mode excitation in the intermediate range of wavelengths; and into an anomalous anisotropic diffusion mode excitation at long wavelengths. The dissipation of a spin-wave at short wavelengths is found to be highly anisotropic. 
A.Kashuba (Landau Institute for Theoretical Physics), Ar.Abanov and   V.L.Pokrovsky (Texas AM University)