  The spin-1/2 Heisenberg model is formulated in terms of a mean-field
approximation (MFA) by using the matrix forms of spin operators
$\hat{S}_x,\hat{S}_y$ and $\hat{S}_z$ in three-dimensions. The considered
Hamiltonian consists of bilinear exchange interaction parameters
$(J_x,J_y,J_z)$, Dzyaloshinskii-Moriya interactions
$(\Delta_x,\Delta_y,\Delta_z)$ and external magnetic field components
$(H_x,H_y,H_z)$. The magnetization and its components are obtained in the MFA
with the general anisotropic case with $J_x\neq J_y \neq J_z$ for various
values of coordination numbers $q$. Then, the thermal variations of
magnetizations are investigated in detail to obtain the phase diagrams of the
model for the isotropic case with $J_x=J_y=J_z>0$. It is found that the model
exhibits ferromagnetic, paramagnetic, random phase regions and an extra
ferromagnetic phase at which the components of magnetizations present
branching.
