Abstract
The wavevector and frequency-dependent relaxation shape function for a Heisenberg paramagnet is investigated within the framework of a memory function formalism, which, unlike previous treatments is applied to the spin-velocity relaxation function rather than the spin relaxation function itself. It is shown that the choice of a gaussian for this memory function gives results in good agreement with the selfconsistent calculations of Blume and Hubbard (1970) at infinite temperatures and with the computer simulation calculations of Evans and Windsor (1973) for RbMnF3 at T=1.17 TN. In all cases examined the results are an improvement on the three-pole approximation of Lovesey and Meserve (1973) based on the continued fraction representation. The connection between the two methods is pointed out.

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