高压合成B20-type化合物Mn $_{1-x}$（Co，Rh）$_x$ Ge的理论与实验研究
Theoretical and experimental study of high-pressure synthesized B20-type compounds Mn$_{1-x}$(Co,Rh)$_x$Ge
摘要：
寻找和开发自然界中没有的新材料是现代纯化学和应用化学的发展趋势之一。在目前的工作中，我们报告的实验和\textit{ab initio}密度泛函研究的高压合成系列化合物Mn $_{1-x}$（Co，Rh）$_x$ Ge。这些高压相在正常条件下保持亚稳态，从而保持其固有的非中心对称B20型结构和手性磁性。在这两个等价系统中特别感兴趣的是比较分析$3d$（Co）和$4d$（Rh）取代Mn的效果，因为$3d$轨道的特征在于比$4d$轨道更高的定位和电子相互作用。在$0 \leq x \leq 1$范围内追踪了Mn $_{1-x}$（Co，Rh）$_x$ Ge体系随浓度变化的行为。我们应用了一个敏感的实验和理论技术，允许细化的形状的磁化率$χ(T)$的温度依赖性，从而提供一个新的和详细的磁相图Mn $_{1-x}$ Co $_x$ Ge。结果表明，这两个系统表现出螺旋磁有序，非常强烈地依赖于组合物$x$。然而，Mn $_{1-x}$ Co $_x$ Ge的相图不同于Mn $_{1-x}$ Rh $_x$ Ge的相图，其特征在于在特定的浓度和温度区域中两个螺旋共存。
英文摘要：
The search and exploration of new materials not found in nature is one of modern trends in pure and applied chemistry. In the present work, we report on experimental and \textit{ab initio} density-functional study of the high-pressure-synthesized series of compounds Mn$_{1-x}$(Co,Rh)$_x$Ge. These high-pressure phases remain metastable at normal conditions, therewith they preserve their inherent noncentrosymmetric B20-type structure and chiral magnetism. Of particular interest in these two isovalent systems is the comparative analysis of the effect of $3d$ (Co) and $4d$ (Rh) substitution for Mn, since the $3d$ orbitals are characterized by higher localization and electron interaction than the $4d$ orbitals. The behavior of Mn$_{1-x}$(Co,Rh)$_x$Ge systems is traced as the concentration changes in the range $0 \leq x \leq 1$. We applied a sensitive experimental and theoretical technique which allowed to refine the shape of the temperature dependencies of magnetic susceptibility $χ(T)$ and thereby provide a new and detailed magnetic phase diagram of Mn$_{1-x}$Co$_x$Ge. It is shown that both systems exhibit a helical magnetic ordering that very strongly depends on the composition $x$. However, the phase diagram of Mn$_{1-x}$Co$_x$Ge differs from that of Mn$_{1-x}$Rh$_x$Ge in that it is characterized by coexistence of two helices in particular regions of concentrations and temperatures.
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