Molecular based spin-1/2 triangular lattice systems such as LiZn₂Mo₃O₈ have attracted research interest. Distortions, defects, and intersite disorder are suppressed in such molecular-based magnets, and intrinsic geometrical frustration gives rise to unconventional and unexpected ground states. Li₂AMo₃O₈ (A = In or Sc) is such a compound where spin-1/2 Mo₃O₁₃ clusters in place of Mo ions form the uniform triangular lattice. Their ground states are different according to the A site. Li₂InMo₃O₈ undergoes conventional 120° long-range magnetic order below T_N = 12 K whereas isomorphic Li₂ScMo₃O₈ exhibits no long-range magnetic order down to 0.5 K. Here, we report exotic magnetisms in Li₂InMo₃O₈ and Li₂ScMo₃O₈ investigated by muon spin rotation (μSR) and inelastic neutron scattering (INS) spectroscopies using polycrystalline samples. Li₂InMo₃O₈ and Li₂ScMo₃O₈ show completely different behaviors observed in both μSR and INS measurements, representing their different ground states. Li₂InMo₃O₈ exhibits spin wave excitation which is quantitatively described by the nearest neighbor anisotropic Heisenberg model based on the 120° spin structure. In contrast, Li₂ScMo₃O₈ undergoes short-range magnetic order below 4 K with quantum-spin-liquid-like magnetic fluctuations down to the base temperature. Origin of the different ground states is discussed in terms of anisotropies of crystal structures and magnetic interactions.

基于分子的自旋1/2三角晶格系统例如LiZn ₂ Mo ₃ O ₈引起了研究兴趣。在这种基于分子的磁体中，扭曲、缺陷和位点间无序被抑制，并且内在的几何挫败会产生非常规和意想不到的基态。 Li ₂ A Mo ₃ O ₈ ( A ＝In或Sc)是这样的化合物，其中自旋1/2 Mo ₃ O ₁₃簇代替Mo离子形成均匀的三角形晶格。根据 A 位点，它们的基态有所不同。 Li ₂ InMo ₃ O ₈在T _N = 12 K 以下经历传统的 120° 长程磁序，而同质 Li ₂ ScMo ₃ O ₈在低至 0.5 K 时不表现出长程磁序。在这里，我们报告了 Li ₂中的奇异磁性使用多晶样品通过μ子自旋旋转（ μSR ）和非弹性中子散射（INS）光谱研究InMo ₃ O ₈和Li ₂ ScMo ₃ O ₈ 。 Li ₂ InMo ₃ O ₈和Li ₂ ScMo ₃ O ₈在μ SR 和INS 测量中观察到完全不同的行为，代表它们不同的基态。 Li ₂ InMo ₃ O ₈表现出自旋波激发，这可以通过基于120°自旋结构的最近邻各向异性海森堡模型定量描述。 相比之下，Li ₂ ScMo ₃ O ₈经历低于4 K的短程磁序，并在低至基础温度时出现类似量子自旋液体的磁涨落。从晶体结构的各向异性和磁相互作用的角度讨论了不同基态的起源。