In this work, we apply the concept of solid solutions to the two 2D transition metal trihalides CrCl₃ and MoCl₃. While CrCl₃ belongs to the magnetically active CrX₃ family, the magnetism in MoCl₃ is intrinsically suppressed by the formation of aligned Mo–Mo dimers, which also distort the regular honeycomb lattice that is typical for the 2D transition metal trihalides. We report suitable synthesis conditions for the gapless solid solution and crystal growth by chemical vapor transport. The CrCl₃–MoCl₃ solid solution was initially synthesized at 650 °C for 100 h under addition of MoCl₅ as mineralizer, and bulk crystals were subsequently grown by vapor transport in a temperature gradient from 600 °C → 550 °C for 60 h. The obtained solid solution exhibits multiple composition-dependent phase transitions at room temperature, as confirmed by powder X-ray diffraction measurements. The possible presence of Mo–Mo dimers in the solid solution was further investigated by infrared, Raman, electron energy loss, and nuclear quadrupole resonance spectroscopies. The combined results indicate that the Mo–Mo dimers are present over a wide range of compositions. Their orientation changes from parallel alignment for compositions from 70% ≤ c(Mo³⁺) ≤ 100% to random orientation for samples with c(Mo³⁺) < 70% content, which significantly affects the course of lattice parameters. Finally, the magnetic properties of the powder samples show a correlation between the Mo³⁺ content and the transition temperature into the low-temperature phase.

中文翻译：

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CrCl3-MoCl3 固溶体中二聚体形成引起的结构和磁转变


在这项工作中，我们将固溶体的概念应用于两种二维过渡金属三卤化物 CrCl ₃ 和 MoCl ₃ 。虽然 CrCl ₃ 属于磁性活性 CrX ₃ 家族，但 MoCl ₃ 中的磁性本质上受到排列的 Mo-Mo 二聚体的形成的抑制，这也扭曲二维过渡金属三卤化物典型的规则蜂窝晶格。我们报告了通过化学气相传输进行无间隙固溶体和晶体生长的合适合成条件。添加 MoCl ₅ 作为矿化剂，在 650 °C 100 h 下初步合成 CrCl ₃ –MoCl ₃ 固溶体，随后生长块状晶体通过蒸气传输，温度梯度从 600 °C → 550 °C 持续 60 小时。粉末 X 射线衍射测量证实，所获得的固溶体在室温下表现出多种与成分相关的相变。通过红外、拉曼、电子能量损失和核四极共振光谱进一步研究了固溶体中可能存在的 Mo-Mo 二聚体。综合结果表明 Mo-Mo 二聚体存在于多种成分中。它们的取向从 70% ≤ c(Mo ³⁺ ) ≤ 100% 成分的平行排列变为 c(Mo ³⁺ ) < 70% 含量样品的随机取向，这显着影响晶格参数的过程。最后，粉末样品的磁性能显示了 Mo ³⁺ 含量与进入低温相的转变温度之间的相关性。