  Recently, two-dimensional ferromagnetism in the family of Chromium compounds
$\rm CrXTe_3 (X=Si, Ge)$ has attracted a broad research interest. Despite the
structural similarity in $\rm CrTe_6$ octahedra, the size effect of inserted Ge
or Si dimer contributes to significant differences in magnetism. Here, we
report a new quaternary van der Waals ferromagnetic material $\rm
CrGe_{\delta}Si_{1-\delta}Te_3$ synthesized by flux method. Ge substitution in
Si site results in the lattice expansion, further increasing the Curie
temperature and reducing the magnetic anisotropy. The critical behavior of $\rm
Cr_{0.96}Ge_{0.17}Si_{0.82}Te_3$ has been studied by specific heat as well as
magnetization measurements. And the extracted critical exponents are
self-consistent and well-obeying the scaling laws, which are closer to the 2D
Ising model with interaction decaying as $J(r)\approx r^{-3.44}$.
