范德华化合物Mn$_{2}$P$_{2}$S$_{6}$和MnNiP$_{2}$S$_{6}$的磁各向异性与低能自旋动力学
Magnetic anisotropy and low-energy spin dynamics in the van der Waals compounds Mn$_{2}$P$_{2}$S$_{6}$ and MnNiP$_{2}$S$_{6}$
AI总结：
本文通过高场高频电子自旋共振技术研究了Mn$_{2}$P$_{2}$S$_{6}$和MnNiP$_{2}$S$_{6}$单晶，发现增加Ni含量显著改变了磁各向异性、磁振子能隙及自旋涨落，并揭示了Mn$_{2}$P$_{2}$S$_{6}$中自旋波激发的场诱导维度交叉行为。
摘要：
我们报告了对单晶范德华化合物Mn$_{2}$P$_{2}$S$_{6}$和MnNiP$_{2}$S$_{6}$进行的详细的高场高频电子自旋共振（HF-ESR）光谱研究。对磁激发的分析表明，与Mn$_{2}$P$_{2}$S$_{6}$相比，增加Ni含量会在有序态中产生更大的磁振子能隙，并在顺磁态中产生更大的g因子值及其各向异性。研究发现，所研究的化合物具有强烈的各向异性，各自具有独特的基态和磁有序类型。在含Ni样品中，g因子偏离自由电子值更大，表明交换各向异性是稳定具有特定各向异性的某种磁有序类型的重要贡献者。在高于磁有序温度时，我们分析了自旋-自旋关联，导致了缓慢涨落的短程有序的发展。与Mn$_{2}$P$_{2}$S$_{6}$相比，它们在MnNiP$_{2}$S$_{6}$中表现得更为明显。MnNiP$_{2}$S$_{6}$中增强的自旋涨落归因于不同类型磁有序之间的竞争。最后，对Mn$_{2}$P$_{2}$S$_{6}$中低于有序温度时磁振子能隙随温度变化的临界行为的分析表明，该化合物中自旋波激发的特征经历了从类3D到2D XY区域的场诱导交叉。
英文摘要：
We report the detailed high-field and high-frequency electron spin resonance (HF-ESR) spectroscopic study of the single-crystalline van der Waals compounds Mn$_{2}$P$_{2}$S$_{6}$ and MnNiP$_{2}$S$_{6}$. Analysis of magnetic excitations shows that in comparison to Mn$_{2}$P$_{2}$S$_{6}$ increasing the Ni content yields a larger magnon gap in the ordered state and a larger g-factor value and its anisotropy in the paramagnetic state. The studied compounds are found to be strongly anisotropic having each the unique ground state and type of magnetic order. Stronger deviation of the g-factor from the free electron value in the samples containing Ni suggests that the anisotropy of the exchange is an important contributor to the stabilization of a certain type of magnetic order with particular anisotropy. At temperatures above the magnetic order, we have analyzed the spin-spin correlations resulting in a development of slowly fluctuating short-range order. They are much stronger pronounced in MnNiP$_{2}$S$_{6}$ compared to Mn$_{2}$P$_{2}$S$_{6}$. The enhanced spin fluctuations in MnNiP$_{2}$S$_{6}$ are attributed to the competition of different types of magnetic order. Finally, the analysis of the temperature dependent critical behavior of the magnon gaps below the ordering temperature in Mn$_{2}$P$_{2}$S$_{6}$ suggests that the character of the spin wave excitations in this compound undergoes a field induced crossover from a 3D-like towards 2D XY regime.
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