Cerium hexaboride attracts attention of solid-state community for almost 50 years. Nowadays, this material is considered as a unique example of a system with orbital ordering resulting in formation of low-temperature magnetic phase with quadrupolar order, the so-called antiferroquadrupole phase. In crystal electric field 4f 1 state of Ce3+ splits into Γ7 doublet and Γ8 quartet, the latter is believed to be the ground state, as long as just Γ8 allows quadrupolar effects. An additional tool for studying rich physics of CeB6 appeared since the discovery in this material the ESR, which is specific to antiferroquadrupole (AFQ) phase and is missing in the paramagnetic phase. In the present review, we have brought together electron spin resonance and inelastic neutron scattering data, which allowed obtaining most detailed structure of the magnetic resonance modes in the AFQ phase in a wide-frequency range up to 0.6 THz. It is shown that apart paramagnetic resonance main mode with homogeneous precession of the magnetization, there are antiferromagnetic resonance modes as well, some of them existing in the AFQ phase. Analysis of the g factors demonstrates that available theories based on Γ8 ground state are facing difficulties with accounting experimental data, thus providing a challenge for developing of a theory correctly describing dynamic magnetic properties of this interesting material.

中文翻译：

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亚太赫兹和太赫兹范围内的重费米子金属 CeB6：电子自旋共振和中子散射研究

近 50 年来，六硼化铈引起了固态界的关注。如今，这种材料被认为是轨道有序系统的独特例子，导致形成具有四极有序的低温磁相，即所谓的反铁四极相。在晶体电场中，Ce3+ 的 4f 1 态分裂为 Γ7 双峰和 Γ8 四峰，后者被认为是基态，只要 Γ8 允许四极效应。自从在该材料中发现 ESR 以来，出现了一种用于研究 CeB6 丰富物理学的额外工具，它特定于反铁四极 (AFQ) 相并且在顺磁相中缺失。在本综述中，我们汇集了电子自旋共振和非弹性中子散射数据，这允许在高达 0.6 THz 的宽频率范围内获得 AFQ 相位中磁共振模式的最详细结构。结果表明，除了具有均匀磁化进动的顺磁共振主模外，还存在反铁磁共振模，其中一些存在于AFQ相中。g 因子的分析表明，基于 Γ8 基态的可用理论在计算实验数据方面面临困难，因此为开发正确描述这种有趣材料的动态磁特性的理论提供了挑战。其中一些存在于 AFQ 阶段。g 因子的分析表明，基于 Γ8 基态的可用理论在计算实验数据方面面临困难，因此为开发正确描述这种有趣材料的动态磁特性的理论提供了挑战。其中一些存在于 AFQ 阶段。g 因子的分析表明，基于 Γ8 基态的可用理论在计算实验数据方面面临困难，因此为开发正确描述这种有趣材料的动态磁特性的理论提供了挑战。