Identification of complex energy hierarchy in the coupled trimer spin system Ba4LuRu3O12

The weakly coupled spin cluster systems provide a fertile ground to study both zero-dimensional quantum and three-dimensional collective magnetism. Such spin cluster systems feature that the lower-energy magnetic excitations, including transverse and longitudinal magnon modes, emerge with gapped localized excitations concomitantly. The newly discovered trimer spin system Ba4LuRu3O12 constitutes Ru3O12 trimers made of three face-sharing RuO6 octahedra. The magnetic susceptibility of Ba4LuRu3O12 shows an antiferromagnetic order at TN = 8 K. However, the Curie-Wiess analysis of the magnetic susceptibility reveals that the local spin alignment of the Ru3O12 trimers varies with temperature. With the aid of inelastic neutron scattering, we will elucidate the energy-level scheme of the interacting spin trimer system and the underlying mechanism for the alteration of the spin configuration.

弱耦合自旋团簇系统是研究零维量子体系与三维集体磁学的理想研究平台。此类自旋团簇系统的典型特征为：低能磁激发（包含横向与纵向磁振子模式（transverse and longitudinal magnon modes））会与带隙局域激发伴随出现。新近发现的三聚自旋系统（trimer spin system）Ba₄LuRu₃O₁₂，其结构为由三个共面连接的RuO₆八面体构成的Ru₃O₁₂三聚体。Ba₄LuRu₃O₁₂的磁化率（magnetic susceptibility）测试表明，该体系在奈耳温度（Neel temperature，TN）=8 K时呈现反铁磁有序（antiferromagnetic order）。然而，对其磁化率开展的居里-外斯分析（Curie-Wiess analysis）显示，Ru₃O₁₂三聚体的局域自旋排布随温度发生变化。本研究将借助非弹性中子散射（inelastic neutron scattering），阐明相互作用三聚自旋系统的能级结构以及自旋构型改变的内在机制。