高熵尖晶石钒酸盐中轨道有序的抑制与玻璃态磁性的出现
Suppression of orbital ordering and emergence of a glassy magnetic state in a high-entropy spinel vanadate
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中文总结 AI 辅助
本研究合成高熵尖晶石钒酸盐(Li0.2Mg0.2Mn0.2Co0.2Zn0.2)V2O4，发现其高构型熵抑制长程轨道有序，稳定了介于典型自旋玻璃与团簇玻璃间的异质玻璃态磁性，揭示了高熵磁体中多因素的共同作用。
中文摘要 AI 辅助
高熵氧化物为探索构型无序与关联电子态之间的相互作用提供了独特平台。我们报道了高熵尖晶石钒酸盐(Li$_{0.2}$Mg$_{0.2}$Mn$_{0.2}$Co$_{0.2}$Zn$_{0.2}$)V$_2$O$_4$的结构、热力学和磁学性质，其中轨道活性V离子占据烧绿石亚晶格。X射线衍射测量表明，立方尖晶石结构在低至5 K的温度下仍保持稳定，未检测到任何对称性降低。与常规尖晶石钒酸盐因轨道有序驱动而发生对称性降低的结构转变不同，本研究的化合物在高熵状态下表现出长程轨道有序的抑制。磁化率测量显示在约20 K以下发生玻璃态磁冻结，而比热测量在低至3 K时未发现与长程有序相关的异常。频率相关的交流磁化率揭示了显著的玻璃态动力学。基于Mydosh参数、动态标度律和Vogel-Fulcher定律的分析表明，其处于典型自旋玻璃与团簇玻璃行为之间的中间动力学区域。此外，Cole-Cole分析显示偏离单一德拜弛豫过程的系统偏差，表明在冻结区域附近存在异质磁弛豫动力学。我们的结果表明，在阻挫尖晶石钒酸盐中，高构型熵抑制了长程轨道有序并稳定了异质玻璃态磁性，凸显了几何阻挫、轨道自由度和构型无序在高熵磁体中的共同作用。
英文摘要
High-entropy oxides provide a unique platform for exploring the interplay between configurational disorder and correlated electronic states. We report on structural, thermodynamic, and magnetic properties of the high-entropy spinel vanadate (Li$_{0.2}$Mg$_{0.2}$Mn$_{0.2}$Co$_{0.2}$Zn$_{0.2}$)V$_2$O$_4$, in which orbital-active V ions occupy the pyrochlore sublattice. X-ray diffraction measurements reveal that the cubic spinel structure is preserved at temperatures down to 5 K without any detectable symmetry lowering. Unlike conventional spinel vanadates exhibiting a symmetry-lowering structural transition driven by orbital ordering, the compound that we study exhibits a suppression of long-range orbital ordering in the high-entropy state. Magnetic susceptibility measurements show glassy magnetic freezing at temperatures below $\sim$20 K, while specific-heat measurements reveal no anomaly associated with long-range ordering down to 3 K. Frequency-dependent ac susceptibility reveals pronounced glassy dynamics. Analyses based on the Mydosh parameter, dynamic scaling law, and Vogel--Fulcher law suggest an intermediate dynamical regime between canonical spin-glass and cluster-glass behavior. Furthermore, Cole--Cole analyses reveal systematic deviations from a single Debye relaxation process, indicating the presence of heterogeneous magnetic relaxation dynamics near the freezing regime. Our results demonstrate that, in a frustrated spinel vanadate, high configurational entropy suppresses long-range orbital ordering and stabilizes a heterogeneous glassy magnetic state, highlighting the combined roles of geometrical frustration, orbital degrees of freedom, and configurational disorder in high-entropy magnets.
