  Intrinsic, two-dimensional (2D) ferromagnetic semiconductors are an important
class of materials for spintronics applications. Cr$_2$X$_2$Te$_6$ (X = Si and
Ge) semiconductors show 2D Ising-like ferromagnetism, which is preserved in
few-layer devices. The maximum magnetic entropy change associated with the
critical properties around the ferromagnetic transition for Cr$_2$Si$_2$Te$_6$
$-\Delta S_M^{max} \sim$ 5.05 J kg$^{-1}$ K$^{-1}$ is much larger than $-\Delta
S_M^{max} \sim$ 2.64 J kg$^{-1}$ K$^{-1}$ for Cr$_2$Ge$_2$Te$_6$ with an
out-of-plane field change of 5 T. The rescaled $-\Delta S_M(T,H)$ curves
collapse onto a universal curve independent of temperature and field for both
materials. This indicates similar critical behavior and 2D Ising magnetism,
confirming the magnetocrystalline anisotropy that could preserve the long-range
ferromagnetism in few-layers of Cr$_2$X$_2$Te$_6$.
