  Intrinsic, two-dimensional ferromagnetic semiconductors are an important
class of materials for overcoming the limitations of dilute magnetic
semiconductors for spintronics applications. CrSiTe$_3$ is a particularly
interesting member of this class, since it can likely be exfoliated down to
single layers, where T$_C$ is predicted to increase dramatically. Establishing
the nature of the magnetism in the bulk is a necessary precursor to
understanding the magnetic behavior in thin film samples and the possible
applications of this material. In this work, we use elastic and inelastic
neutron scattering to measure the magnetic properties of single crystalline
CrSiTe$_3$. We find that there is a very small single ion anisotropy favoring
magnetic ordering along the $c$-axis and that the measured spin waves fit well
to a model where the moments are only weakly coupled along that direction.
Finally, we find that both static and dynamic correlations persist within the
$ab$-plane up to at least 300 K, strong evidence of this material's
two-dimensional characteristics that are relevant for future studies on thin
film and monolayer samples.
