In two dimensional magnets, the interplay of thermal fluctuations and spin anisotropy control the existence of long-range magnetic order. In the van der Waals antiferromagnets FePX3, orbital degeneracy in the t2g levels of the Fe2+ ions in octahedral coordination yields strong uniaxial anisotropy, which stabilizes magnetic order up to T≈100 K. Recent inelastic neutron scattering measurements around the magnetic ordering transition have shown the existence of a broad spectrum of magnetic fluctuations with nontrivial momentum dependence, which has been interpreted as evidence for localized entangled cluster excitations. In this paper, we offer an alternative interpretation using classical nonlinear spin dynamics simulations. We present stochastic Landau Lifshitz dynamics simulations that reproduce the neutron scattering measurements of Chen [] on FePSe3. These calculations faithfully explain the dynamical structure factor's momentum and energy dependence and point to a classical origin for the excitations observed in neutron spectroscopy and that the order-disorder transition can be understood in terms of thermal fluctuations overcoming the anisotropy energy. Published by the American Physical Society 2025

中文翻译：

---

量子簇激发的热诱导模拟及其对 FePSe3 中磁跃迁的影响

在二维磁体中，热波动和自旋各向异性的相互作用控制了长程磁序的存在。在范德华反铁磁体 FePX3 中，八面体配位中 Fe2+ 离子的 t2g 能级的轨道简并产生强烈的单轴各向异性，从而将磁序稳定在 T≈100 K 以下。最近围绕磁有序跃迁的非弹性中子散射测量表明，存在具有非平凡动量依赖性的宽谱磁涨落，这已被解释为局部纠缠簇激发的证据。在本文中，我们提供了使用经典非线性自旋动力学模拟的另一种解释。我们提出了随机的 Landau Lifshitz 动力学模拟，它再现了 Chen [] 在 FePSe3 上的中子散射测量。这些计算忠实地解释了动力学结构因子的动量和能量依赖性，并指出了在中子能谱中观察到的激发的经典起源，并且有序无序转变可以用克服各向异性能量的热波动来理解。 美国物理学会 2025 年出版