Magnetic excitations above the critical temperature

We present a simple but physically motivated approximation scheme for the dynamical spin correlation function of the Heisenberg model above the critical temperature. Built upon the spin-diffusion theory, it describes the short-wavelength and high-frequency excitations as magnonlike modes which exist within clusters of highly correlated spins. The modes are damped by both the finite size and the finite lifetime of the clusters. The agreement between the theory and the neutron scattering data on a variety of systems is reasonably good.