Correlation functions of a Heisenberg ferromagnet in the paramagnetic region

An approximate closed system of equations for the correlation functions of a Heisenberg ferromagnet above the critical temperature and in zero magnetic field is obtained. The equations make it possible to express not only the static but also the dynamic characteristics of the spin system in terms of parameters of the microscopic theory. The expression obtained for the spectral density describes in the same approximation the low-frequency diffusion part of the spectrum as well as the high-frequency oscillations that can exist in magnetic systems in the paramagnetic region.