Critical Properties and Phase Transitions of the Mixed-Spin Anisotropic XXZ Heisenberg Model

Using the Oguchi approximation, we have examined the magnetic properties of a mixed-spin (1/2, 1) XXZ Heisenberg model with a crystal field. The focus is on the 3D Heisenberg system, for which the phase diagrams and magnetizations are obtained numerically. It is found that the model features second- and first-order phase transition lines, as well as tricritical and critical end-points. The critical behavior is discussed and compared with previous works on Heisenberg systems.