  In this work, the magnetism of the single crystal Cr$_{1/3}$NbS$_{2}$, which
exhibits chiral magnetic soliton lattice (CSL) state, is investigated. The
magnetization displays strong magnetic anisotropy when the field is applied
perpendicularly and parallel to the $c$-axis in low field region ($H<H_{S}$,
$H_{S}$ is the saturation field). The critical exponents of Cr$_{1/3}$NbS$_{2}$
are obtained as $\beta=$ 0.370(4), $\gamma=$ 1.380(2), and $\delta=$ 4.853(6),
which are close to the theoretical prediction of three-dimensional Heisenberg
model. Based on the scaling equation and the critical exponents, the $H-T$
phase diagram in the vicinity of the phase transition is constructed, where two
critical points are determined. One is a tricritical point which locates at the
intersection between the CSL, forced ferromagnetic (FFM), and paramagnetic (PM)
states. The other one is a critical point situated at the boundaries between
CSL, helimagnetic (HM), and PM states.
