  We develop a new method to probe the local spin dynamic autocorrelation
function, using magnetic field dependent muon depolarization measurements. We
apply this method to muSR experiments in the dilute Heisenberg spin glass
AgMn(p at. %) at T>T_g where the correlations of the Mn local magnetic moment
are strongly non-exponential. Our results clearly indicate that the dynamics of
this spin glass cannot be described by a distribution of correlation times.
Therefore, we analyze the data assuming a local spin correlation function which
is the product of a power law times a cutoff function. The concentration and
temperature dependence of the parameters of this function are determined. Our
major conclusion is that in the temperature region close to Tg the correlation
function is dominated by an algebraic relaxation term.
