  The doping of semiconductors with magnetic impurities gives rise not only to
a spin-spin interaction between quasi-free carriers and magnetic impurities,
but also to a local spin-independent disorder potential for the carriers. Based
on a quantum kinetic theory for the carrier and impurity density matrices as
well as the magnetic and non-magnetic carrier-impurity correlations, the
influence of the non-magnetic scattering potential on the spin dynamics in DMS
after optical excitation with circularly polarized light is investigated using
the example of Mn-doped CdTe. It is shown that non-Markovian effects, which are
predicted in calculations where only the magnetic carrier-impurity interaction
is accounted for, can be strongly suppressed in the presence of non-magnetic
impurity scattering. This effect can be traced back to a significant
redistribution of carriers in $\mathbf{k}$-space which is enabled by the
build-up of large carrier-impurity correlation energies. A comparison with the
Markov limit of the quantum kinetic theory shows that, in the presence of an
external magnetic field parallel to the initial carrier polarization, the
asymptotic value of the spin polarization at long times is significantly
different in the quantum kinetic and the Markovian calculations. This effect
can also be attributed to the formation of strong correlations which
invalidates the semiclassical Markovian picture and it is stronger when the
non-magnetic carrier-impurity interaction is accounted for. In an external
magnetic field perpendicular to the initial carrier spin, the correlations are
also responsible for a renormalization of the carrier spin precession
frequency.
