Computer simulation of the dynamics of one-dimensional Heisenberg magnets

Abstract

The intermediate spin-correlation function (S*_-q(0).S_q(t)) for classical linear chains of up to 120 antiferromagnetically coupled spins has been obtained by computer simulation as a function of wavevector q and time t. The spin correlations are calculated directly in reciprocal space. Chains in thermal equilibrium at 0.13, 0.24 and 0.44 times the molecular field transition temperature T_m=2JS(S+1)/3k have been analysed in detail at 21 wavevectors. Spin-wave frequencies and damping constants have been estimated using a fitted interpolation function. Appreciable deviations from a sinusoidal dispersion curve of linear spin-wave theory are found even at 0.13 T_m. Fourier transforms of the results to give the neutron-scattering function S(q, omega ) are presented and are shown to be in excellent agreement with the experimental results of Hutchings et al.