Exchange symmetry and low-frequency asymptotics of Green's functions in spin s=1 magnets

Abstract

The paper contains the description of the dynamics of non-equilibrium processes of spin $s=1$ magnets in an external variable field. We have obtained nonlinear dynamic equations with sources and calculated low-frequency asymptotics of two-time Green's functions for ferro- and quadrupole magnetic states with $SO(3)$ and $SU(3)$ exchange symmetry of the Hamiltonian. It has been shown that for ferro- and quadrupole magnetic states singularities of Green's functions in wave vectors $1/k$, $1/k^2$ and frequencies $1/\omega, 1/\omega^2$ have well-known character. We set the exact form of the magnetic anisotropy of these Green's functions. For states with $SO(3)$ symmetry of the exchange Hamiltonian, we have found Green's functions with quadrupole degrees of freedom and compared them with Green's functions of magnets having exchange $SU(3)$ symmetry.