The two-dimensional (2D) van der Waals ferromagnetic semiconductors, such as CrI$_3$ and Cr$_2$Ge$_2$Te$_6$, the 2D metals, Fe$_3$GeTe$_2$ MnSe$_2$, have been obtained in recent experiments attracted a lot of attentions. superexchange interaction has suggested to dominate magnetic interactions these systems. In usual theoretical studies, expression Heisenberg models were fixed by hand due exper...