Co3Sn2S2 has generated a growing interest as a rare example of the highly uniaxial anisotropic kagomé ferromagnet showing a combination of frustrated-lattice magnetism and topology. Recently, via precise measurements of the magnetization and AC susceptibility we have found a low-field anomalous magnetic phase (A-phase) with very slow spin dynamics that appears just below the Curie temperature (T C). The A-phase hosts high-density domain bubbles after cooling through T C as revealed in a previous in-situ Lorentz-TEM study. Here, we present further signatures of the anomalous magnetic transition (MT) at T C revealed by a study of the critical behaviors of the magnetization and magnetocaloric effect using a high-quality single crystal. Analyses of numerous magnetization isotherms around T C (≃177 K) using different approaches (the modified Arrot plot, Kouvel-Fisher method and magnetocaloric effect) result in consistent critical exponents that do not satisfy the theoretical predictions of standard second-order-MT models. Scaling analyses for the magnetization, magnetic entropy change and field-exponent of the magnetic entropy change, all consistently show low-field deviations below T C from the universal curves. Our results reveal that the MT of Co3Sn2S2 can not be explained as a conventional second-order type and suggest an anomalous magnetic state below T C.

中文翻译：

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Co3Sn2S2 kagomé 铁磁体磁相变的非常规临界行为

Co3Sn2S2 作为高度单轴各向异性 kagomé 铁磁体的罕见例子引起了越来越多的兴趣，该例子显示了受挫晶格磁性和拓扑结构的结合。最近，通过对磁化强度和交流磁化率的精确测量，我们发现了一个低场反常磁相（A 相），其自旋动力学非常缓慢，刚好低于居里温度 (TC)。如先前的原位 Lorentz-TEM 研究所示，A 相在通过 TC 冷却后具有高密度域气泡。在这里，我们通过使用高质量单晶对磁化和磁热效应的关键行为的研究揭示了 TC 异常磁跃迁 (MT) 的进一步特征。使用不同方法分析 TC (≃177 K) 周围的众多磁化等温线（修改后的 Arrot 图，Kouvel-Fisher 方法和磁热效应）导致一致的临界指数不满足标准二阶 MT 模型的理论预测。磁化强度、磁熵变化和磁熵变化的场指数的比例分析都一致地显示出低于 TC 与通用曲线的低场偏差。我们的结果表明，Co3Sn2S2 的 MT 不能解释为传统的二阶类型，并表明低于 T C 的磁态异常。所有这些都始终显示出通用曲线低于 TC 的低场偏差。我们的结果表明，Co3Sn2S2 的 MT 不能解释为传统的二阶类型，并表明低于 T C 的磁态异常。所有这些都始终显示出通用曲线低于 TC 的低场偏差。我们的结果表明，Co3Sn2S2 的 MT 不能解释为传统的二阶类型，并表明低于 T C 的磁态异常。