CONDENSED MATTER PHYSICS, vol.25, no.3, 2022 (SCI-Expanded)
The spin-1/2 Heisenberg model is formulated in terms of a mean-field approximation (MFA) by using the matrix forms of spin operators (S) over cap (x), (S) over cap (y) and (S) over cap (z) in three-dimensions. The considered Hamiltonian consists of bilinear exchange interaction parameters (J(x), J(y), J(z)), Dzyaloshinskii-Moriya interactions (Lambda(x), Lambda(y), Lambda(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) +/- J(y) +/- J(z) for various values of coordination numbers... 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.