Two dimensional magnetic materials have experimental critical exponents that often have different critical exponent, not belonging to the Ising universal class nor to the XY universal class, but their values lies in a “universal window”, bounded by the Ising and XY critical exponent. The XYhq model is introduced to study these materials. Theoretically, XYhq model has been studied by using renormalization group and numerical simulation. In this model, the authors have shown for q≤ 4, it has only the Ising phase transition; for q> 4, it has KT phase transition depending on the value of q. However, experimental critical exponents have unusual behavior even with anisotropy q ≤ 4. Therefore, we study the phase transition phenomena of XYh3 model depending on the intensity of anisotropic crystal fields (h3) using extensive Monte Carlo simulation. The results show that the phase transition of XYh3 depends on the intensity of h3 for h3> 0.01 the model has a second-order phase transition and the phase transition temperature decreases as the crystal field strength decreases; for h3 ≤ 0.01 The model still has a second-order phase transition, but the phase transition temperature is constant and equal to the KTphase transition temperature.
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