Title: Atypical antiferromagnetic ordering in single crystalline quasi-2D honeycomb magnet YbI$_3$ Show Chinese title

Title: 典型反铁磁序在单晶准二维蜂窝状磁体镱碘化物 YbI$_3$中的异常秩序

Abstract: Here, we study YbI$_3$, a quasi-2D layered material with Yb atoms arranged on an ideal honeycomb network of edge-sharing YbI$_6$ octahedra, analogous to the low-temperature phase of $\alpha-$RuCl$_3$. High quality single crystals of YbI$_3$ are grown from Yb and I as starting precursors, using the vapor transport technique. The grown crystals are characterized by single crystal x-ray diffraction, Raman spectroscopy, magnetization, and heat capacity probes. The crystal-field split ground state of Yb$^{3+}$ in \Yb~ is a well-isolated Kramers doublet with an effective moment $\rm J_{eff} = 1/2$. Upon cooling, the low-temperature heat capacity of \Yb~ reveals a broad peak at $\rm T_1 = 0.95$~K due to short-range ordering of the Yb moments, followed by a sharp peak at $\rm T_2 = T_N = 0.6$~K due to long-range ordering. The magnetic behavior is found to be weakly anisotropic with $\chi^\parallel > \chi^\perp$, where $\chi^\parallel$ and $\chi^\perp$ refers to the in-plane ($H \parallel ab$) and out-of-plane ($H \perp ab$) susceptibilities. The 2~K isothermal magnetization saturates at $\rm \approx~1.5~\mu_B/Yb^{3+}$ (in-plane) and $\rm \approx~1~\mu_B/Yb^{3+}$ (out-of-plane), suggesting the anisotropy to be easy-plane type. Low-temperature heat capacity, well below T$_N$, is found to vary as T$^\alpha$ with $\alpha~\approx~2.5$, indicating a possible unconventional magnetic ground state for YbI$_3$. Show Chinese abstract

Abstract: 在这里，我们研究了YbI$_3$，这是一种准二维层状材料，其中Yb原子排列在一个理想的蜂窝网络上，该网络由共享边的YbI$_6$八面体组成，类似于$\alpha-$RuCl$_3$的低温相。 通过使用Yb和I作为起始前驱体，采用气相输运技术生长出高质量的单晶YbI$_3$。生长的晶体通过单晶X射线衍射、拉曼光谱、磁化率以及热容探针进行表征。 Yb$^{3+}$在\Yb 中的晶体场分裂基态是一个有效磁矩为$\rm J_{eff} = 1/2$的良好隔离的克勒默双重态。在冷却过程中，\Yb 的低温比热在$\rm T_1 = 0.95$K 处出现一个由于 Yb 磁矩短程有序引起的宽峰，随后在$\rm T_2 = T_N = 0.6$K 处出现一个由于长程有序引起的尖锐峰。 发现磁性行为表现为弱各向异性，其中$\chi^\parallel > \chi^\perp$，$\chi^\parallel$和$\chi^\perp$分别表示面内（$H \parallel ab$）和面外（$H \perp ab$）的磁化率。2 K等温磁化强度在$\rm \approx~1.5~\mu_B/Yb^{3+}$（面内）和$\rm \approx~1~\mu_B/Yb^{3+}$（面外）处饱和，表明各向异性为易面型。 在远低于 T$_N$的低温下，热容随 T$^\alpha$变化，指数$\alpha~\approx~2.5$表明 YbI$_3$可能具有非常规的磁基态。