发表机构
University of Oxford; Princeton University（牛津大学; 普林斯顿大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过高灵敏扭矩测量，揭示了保持单斜结构的微小α-RuCl₃单晶在14K下的磁相图，与菱面体样品显著不同，并提出了最小磁结构模型。
AI 中文摘要
层状蜂窝状 $\alpha$-RuCl$_3$ 作为自旋轨道纠缠的 $j_{\rm eff}=1/2$ Ru$^{3+}$ 磁矩之间非常规合作磁性的候选材料已被广泛探索，这些磁矩由强阻挫的 Kitaev 及其他依赖于键的各向异性相互作用所稳定。迄今为止，大多数研究集中在相对较大的单晶上，这些单晶在冷却至 150 K 以下时经历从单斜到菱面体的结构相变，并在约 7 K 时发生向锯齿状磁序的磁转变。在此，我们研究了高质量、非常小（直径小于 100 $\mu$m）的单晶的磁性，这些单晶在冷却至低温时保持单斜结构，并在 14 K 时表现出尖锐的磁转变。利用高灵敏度的压电悬臂磁扭矩测量，在高达 16 T 的磁场中，我们报告了磁场在三个正交晶面内旋转时的磁相图的全面研究。我们通过几乎连续改变场的角取向和场大小收集的大量扭矩数据，能够通过原始扭矩数据及其相对于角度和场大小的高阶导数中的异常清晰检测相变。获得的磁相图与菱面体样品相比显示出许多差异，表现出降低的旋转对称性、抑制自发磁序所需的显著更高场强以及不同的场致相。我们将扭矩数据与适用于 $\alpha$-RuCl$_3$ 并允许单斜晶格对称性的磁哈密顿量的平均场计算进行了直接比较，并为磁相图的所有探索区域提出了最小磁结构模型。
英文摘要
The layered honeycomb $α$-RuCl$_3$ has been much explored as a candidate to display unconventional cooperative magnetism between spin-orbit entangled $j_{\rm eff}=1/2$ Ru$^{3+}$ magnetic moments stabilized by strongly-frustrated, Kitaev and other bond-dependent anisotropic interactions. Most studies so far have focused on relatively large single crystals that undergo a structural phase transition from monoclinic to rhombohedral upon cooling below 150 K and a magnetic transition to zigzag order around 7 K. Here we study the magnetism of high-quality, very small (sub 100 $μ$m diameter) single crystals, which remain monoclinic upon cooling to low temperatures and display a sharp magnetic transition at 14 K. Using highly-sensitive piezo-cantilever magnetic torque measurements in fields up to 16 T, we report a comprehensive study of the magnetic phase diagrams for magnetic field rotated in three orthogonal crystallographic planes. Our extensive torque data collected upon varying almost continuously the angular orientation of the field as well as the field magnitude, allows clear detection of phase transitions via anomalies in the raw torque data and its higher order derivatives with respect to both angle and field magnitude. The obtained magnetic phase diagrams show many differences compared to rhombohedral samples, displaying reduced rotational symmetry, substantially higher fields required to suppress the spontaneous magnetic order, and distinct field-induced phases. We provide a direct comparison of the torque data with mean-field calculations for magnetic Hamiltonians appropriate for $α$-RuCl$_3$ allowing for the monoclinic lattice symmetry and propose minimal magnetic structure models for all explored regions of the magnetic phase diagrams.
Comments21 pages, 20 figures
