  We investigate the static and ultrafast magneto-optical response of the
hexagonal chiral helimagnet $Cr_{1/3}NbS_{2}$ above and below the helimagnetic
ordering temperature. The presence of a magnetic easy plane contained within
the crystallographic ab-plane is confirmed, while degenerate optical pump-probe
experiments reveal significant differences in the dynamic between the parent,
$NbS_{2}$, and Cr-intercalated compounds. Time resolved magneto-optical Kerr
effect measurements show a two-step demagnetization process, where an initial,
sub-ps relaxation and subsequent buildup ($\tau > 50$ ps) in the
demagnetization dynamic scale similarly with increasing pump fluence. Despite
theoretical evidence for partial gapping of the minority spin channel,
suggestive of possible half metallicity in $Cr_{1/3}NbS_{2}$, such a long
demagnetization dynamic likely results from spin lattice-relaxation as opposed
to minority state blocking. However, comparison of the two-step demagnetization
process in $Cr_{1/3}NbS_{2}$ with other 3d intercalated transition metal
dichalcogenides reveals a behavior that is unexpected from conventional
spin-lattice relaxation, and may be attributed to the complicated interaction
of local moments with itinerant electrons in this material system.
