基于长程交换相互作用的单层 CrPS$_4$ 和 NiPS$_3$ 的磁性基态
Magnetic ground states of CrPS$_4$ and NiPS$_3$ monolayers from long-range exchange interactions
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中文总结 AI 辅助
研究单层 CrPS$_4$ 和 NiPS$_3$ 磁性，结合多种方法，用 LKAG 形式提取磁交换张量考虑长程相互作用，揭示其对磁行为的影响，为硫代磷酸盐单层定量预测自旋模型及描述二维范德华磁体提供框架。
中文摘要 AI 辅助
我们通过结合第一性原理计算、第二性原理自旋模型和蒙特卡罗模拟来研究单层 CrPS$_4$ 和 NiPS$_3$ 的磁性。与传统方法不同，我们使用 LKAG 形式直接从密度泛函理论中提取磁交换张量，并包含相互作用直至数值收敛。结果表明，长程交换相互作用定性地改变了两种材料的磁行为。在 CrPS$_4$ 中，它使先前预测的铁磁基态不稳定，稳定了自旋螺旋相，降低了临界温度。在 NiPS$_3$ 中，只有包含到第五壳层的交换相互作用时才出现实验观察到的锯齿状反铁磁序。这些结果表明硫代磷酸盐单层的定量预测自旋模型需要长程交换相互作用，并为准确描述二维范德华磁体提供了预测框架。
英文摘要
We investigate the magnetic properties of monolayer CrPS$_4$ and NiPS$_3$ by combining first-principles calculations, second-principles spin models, and Monte Carlo simulations. Unlike conventional approaches that truncate exchange interactions after only a few shells and determine them by fitting total energies, we extract the magnetic exchange tensors directly from density functional theory using the LKAG formalism and include interactions until numerical convergence is achieved. We show that long-range exchange interactions qualitatively modify the magnetic behavior of both materials. In CrPS$_4$, they destabilize the previously predicted ferromagnetic ground state and stabilize a spin-spiral phase, reducing the critical temperature to about 21\,K, in agreement with available experiments. The resulting magnetic phase diagram contains multiple collinear and non-collinear phases that can be tuned by temperature and external magnetic fields. In NiPS$_3$, the experimentally observed zigzag antiferromagnetic order only emerges when exchange interactions up to the fifth shell are included. These results demonstrate that quantitatively predictive spin models for thiophosphate monolayers require long-range exchange interactions and provide a predictive framework for accurately describing two-dimensional van der Waals magnets.
