Structural phase transitions in $f$-electron materials have attracted sustained attention both for practical and basic science reasons, including that they offer an environment to directly investigate relationships between structure and the $f$-state. Here we present results for UCr${}_2$Si${}_2$, where structural (tetragonal $\to$ monoclinic) and antiferromagnetic phase transitions are seen at $T_{\rm{S}}$ $=$ 205 K and $T_{\rm{N}}$ $=$ 25 K, respectively. We also provide evidence for an additional second order phase transition at $T_{\rm{X}}$ = 280 K. We show that $T_{\rm{X}}$, $T_{\rm{S}}$, and $T_{\rm{N}}$ respond in distinct ways to the application of hydrostatic pressure and Cr $\to$ Ru chemical substitution. In particular, hydrostatic compression increases the structural ordering temperature, eventually causes it to merge with $T_{\rm{X}}$ and destroys the antiferromagnetism. In contrast, chemical substitution in the series UCr${}_{2-x}$Ru${}_x$Si${}_2$ suppresses both $T_{\rm{S}}$ and $T_{\rm{N}}$, causing them to approach zero temperature near $x$ $\approx$ 0.16 and 0.08, respectively. The distinct $T-P$ and $T-x$ phase diagrams are related to the evolution of the rigid Cr-Si and Si-Si substructures, where applied pressure semi-uniformly compresses the unit cell and Cr $\to$ Ru substitution results in uniaxial lattice compression along the tetragonal $c$-axis and an expansion in the $ab$-plane. These results provide insights into an interesting class of strongly correlated quantum materials where degrees of freedom associated with $f$-electron magnetism, strong electronic correlations, and structural instabilities are readily controlled.

中文翻译：

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调整UCr2Si2中的结构相和反铁磁相变：静水压力和化学取代

结构相变 $F$-电子材料由于实用和基础科学的原因而引起了持续的关注，包括它们提供了一种直接研究结构与结构之间关系的环境。 $F$-州。在这里，我们呈现UCr的结果${}_2$硅${}_2$，其中结构（四边形 $\to$单斜）和反铁磁相变出现在$ T _ {\ rm {S}} $ $=$205 K和$ T _ {\ rm {N}} $ $=$25K。我们还提供了在$ T _ {\ rm {X}} $ = 280 K处进行第二阶相变的证据。我们证明了$ T _ {\ rm {X}} $，$ T _ {\ rm {S}} $，和$ T _ {\ rm {N}} $以不同的方式响应静水压力和Cr的施加$\to$汝化学取代。特别是，静水压缩会增加结构的有序温度，最终使其与$ T _ {\ rm {X}} $合并并破坏反铁磁性。相反，UCr系列中的化学取代${}_{2-X}$茹${}_X$硅${}_2$同时抑制$ T _ {\ rm {S}} $和$ T _ {\ rm {N}} $，使它们接近零温度$X$ $\approx$分别为0.16和0.08。独特的$Ť-P$ 和 $Ť-X$ 相图与刚性Cr-Si和Si-Si子结构的演变有关，其中施加的压力半均匀地压缩了晶胞和Cr $\to$ Ru置换导致沿四边形的单轴晶格压缩 $C$轴和扩展 $\mathrm{一种}b$飞机。这些结果提供了对有趣的一类强相关的量子材料的洞察力，其中自由度与$F$-电子磁性，强电子相关性和结构不稳定性易于控制。