Phase Diagrams of the Mixed‐Spin XXZ Heisenberg Model on a Square‐Octagon Lattice

Abstract

This article investigates the magnetic properties and phase diagrams of a mixed spin‐1 and spin‐1/2 system on a 2D square‐octagon lattice within the quantum XXZ Heisenberg model using the Oguchi approximation. The sublattice magnetizations and total magnetization are analyzed as a function of temperature, providing insights into the thermal behavior of this mixed‐spin system. Additionally, the effect of the crystal field parameter on the magnetic properties is examined, revealing critical phenomena and phase transitions in the system. The influence of the anisotropy parameter is also explored, demonstrating its essential role in shaping the nature of the phase transitions and the emergence of tricritical behavior. The results contribute to a deeper understanding of the interplay between exchange interaction, crystal field, thermal fluctuations, and quantum effects in complex lattice systems.