Recently, several putative quantum spin liquid (QSL) states were discovered in ${\tilde S} = 1/2$ rare-earth based triangular-lattice antiferromagnets (TLAF) with the delafossite structure. A way to clarify the origin of the QSL state in these systems is to identify ways to tune them from the putative QSL state towards long-range magnetic order. Here, we introduce the Ce-based TLAF KCeS$_2$ and show via low-temperature specific heat and $\mu$SR investigations that it yields magnetic order below $T_{\mathrm N} = 0.38$ K despite the same delafossite structure. We identify a well separated ${\tilde S} = 1/2$ ground state for KCeS$_2$ from inelastic neutron scattering and embedded-cluster quantum chemical calculations. Magnetization and electron spin resonance measurements on single crystals indicate a strong easy-plane $g$~factor anisotropy, in agreement with the ab initio calculations. Finally, our specific-heat studies reveal an in-plane anisotropy of the magnetic field-temperature phase diagram which may indicate anisotropic magnetic interactions in KCeS$_2$.

中文翻译：

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$ {\ tilde S} = 1/2 $三角晶格反铁磁体KCeS $ _2 $中的远距离磁阶

近来，在具有假铜矿结构的稀土基三角晶格反铁磁体（TLAF）中发现了几种假定的量子自旋液体（QSL）状态。阐明这些系统中QSL状态起源的一种方法是，确定将其从推定的QSL状态调谐到远距离磁阶的方法。在这里，我们介绍了基于Ce的TLAF KCeS $ _2 $，并通过低温比热和$ \ mu $ SR研究表明，尽管具有相同的铜铁矿结构，但其产生的磁阶低于$ T _ {\ mathrm N} = 0.38 $ K 。我们从非弹性中子散射和嵌入式簇量子化学计算中确定了KCeS $ _2 $的分离良好的$ {\ tilde S} = 1/2 $基态。在单晶上的磁化和电子自旋共振测量表明很强的易平面$ g $〜因子各向异性，与从头算起的协议一致。最后，我们的比热研究揭示了磁场温度相图的面内各向异性，这可能表明KCeS $ _2 $中的各向异性磁相互作用。