  We analyze the spin dynamics of an individual magnetic atom (Mn) inserted in
a II-VI semiconductor quantum dot under resonant optical excitation. In
addition to standard optical pumping expected for a resonant excitation, we
show that for particular conditions of laser detuning and excitation intensity,
the spin population can be trapped in the state which is resonantly excited.
This effect is modeled considering the coherent spin dynamics of the coupled
electronic and nuclear spin of the Mn atom optically dressed by a resonant
laser field. This spin population trapping mechanism is controlled by the
combined effect of the coupling with the laser field and the coherent
interaction between the different Mn spin states induced by an anisotropy of
the strain in the plane of the quantum dot.
