Spin diffusion in Heisenberg Ferromagnets in the high temperature limit

A study is made of the time dependence of the memory function given by the mode-mode theory for the Heisenberg Ferromagnet in the high temperature limit. For very long times this function is found to go as $\text{t}{}^{\mathrm{<mtext>?5</mtext><mtext>2</mtext>}}$ exp (-Dq²t/2). This leads to the conclusion that spin diffusion is not predicted in the asymptotic time region, in contrast to what has been stated before.