Dynamics of classical spins with dipolar coupling in a rigid lattice at high temperatures

Abstract

Molecular-dynamics calculations have been performed on the auto- and pair time-correlation functions in a rigid lattice of magnetic dipoles coupled by a truncated dipolar interaction. The first six terms of the exact time expansion of the correlation functions calculated from first principles are also presented. The analytical forms of the autocorrelation functions are examined and compared to the predictions from a stochastic local-field model due to Kubo and Toyabe. The correlation functions are also used to probe the applicability of a theory of Blume and Hubbard to dipolar coupled spins. Generally, this theory describes the longitudinal dynamics rather well, whereas the transverse dynamics is less satisfactorily described.