Dynamics of dilute magnets aboveTc

Nonperturbative contributions are shown to produce anomalously slow relaxation in dilute ferromagnets (or antiferromagnets), both in the paramagnetic and ‘‘Griffiths’’ phases. In the paramagnetic phase, the pseudoscaling form C(t)∼exp{-${\mathit{t}}^{\mathit{d}/(\mathit{d}+\mathit{z})}$f(t/${\xi }_{\mathit{p}}^{\mathit{d}+\mathit{z}}$)} is predicted for the spin autocorrelation function, with ${\xi }_{\mathit{p}}$ the correlation length of the nondilute system. In the Griffiths phase, C(t)∼exp{-A1nt${)}^{\mathit{d}/\left(\mathit{d}\mathrm{-}1\right)}$} and exp{-(Bt${)}^{1/2}$} are predicted for Ising Heisenberg systems, respectively, for t≫${\xi }_{\mathit{p}}^{\mathit{d}+\mathit{z}}$.