The magnetic properties of iron chalcogenides and pnictides have found much interest as magnetic fluctuations are suggested to drive the formation of Cooper pairs in iron-based superconductors. Here, we have studied the pressure dependence of the magnetic and electrical properties of the iron-selenide compound $\left[\mathrm{C}{\mathrm{s}}_6\mathrm{Cl}\right]\left[\mathrm{F}{\mathrm{e}}_{24}\mathrm{S}{\mathrm{e}}_{26}\right]$ by energy-domain synchrotron Mössbauer spectroscopy up to 17 GPa and by resistivity measurements up to 45 GPa. Similar to the binary superconductor $\mathrm{F}{\mathrm{e}}_{1+x}\mathrm{Se}$, the host-guest-type crystal structure of $\left[\mathrm{C}{\mathrm{s}}_6\mathrm{Cl}\right]\left[\mathrm{F}{\mathrm{e}}_{24}\mathrm{S}{\mathrm{e}}_{26}\right]$ contains edge-sharing $\mathrm{FeS}{\mathrm{e}}_4$ units, but its ground state is antiferromagnetically ordered. A complex hyperfine pattern suggests a nontrivial spin structure like a spin spiral with large magnetic moments in the range 2 to $3{\mu }_{\mathrm{B}}$ at ambient pressure. High pressure drastically suppresses the Néel temperature from 220 K at ambient pressure to below 30 K at 12 GPa. Between 5 and 10 GPa the complex magnetic hyperfine pattern collapses and a low-moment magnetic ground state emerges at higher pressures. A concomitant decrease of the resistivity by several orders of magnitude indicates that the electronic system becomes more itinerant. Full metallization occurs near 25 GPa, but no sign of superconductivity down to 1.5 K was found at any pressure. It is suggested that the insulating ground state of $\left[\mathrm{C}{\mathrm{s}}_6\mathrm{Cl}\right]\left[\mathrm{F}{\mathrm{e}}_{24}\mathrm{S}{\mathrm{e}}_{26}\right]$ corresponds to an orbitally selective Mott phase, which due to an increased bandwidth, is transformed into a Hund's metal state under pressure.

中文翻译：

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压力诱导的主客体化合物[Cs6Cl] [Fe24Se26]中的大矩磁阶崩溃和局限电子跃迁

铁硫属元素化物和磷化物的磁性已引起人们的极大兴趣，因为建议磁起伏来驱动铁基超导体中库珀对的形成。在这里，我们研究了硒化铁化合物的磁性和电学性质与压力的关系$\left[\mathrm{C}{\mathrm{s}}_6氯\right]\left[\mathrm{F}{\mathrm{Ë}}_{24}\mathrm{小号}{\mathrm{Ë}}_{26}\right]$通过能量域同步加速器Mössbauer光谱达到17 GPa，通过电阻率测量达到45 GPa。类似于二元超导体$\mathrm{F}{\mathrm{Ë}}_{\mathrm{1个}+X}硒$的主体-客体型晶体结构 $\left[\mathrm{C}{\mathrm{s}}_6氯\right]\left[\mathrm{F}{\mathrm{Ë}}_{24}\mathrm{小号}{\mathrm{Ë}}_{26}\right]$ 包含边缘共享 $\mathrm{硫化铁}{\mathrm{Ë}}_4$单位，但其基态是反铁磁有序的。复杂的超精细模式表明非平凡的自旋结构，如自旋螺旋，具有较大的磁矩，范围为2至$3{\mu }_{\mathrm{乙}}$在环境压力下。高压极大地抑制了Néel温度，从环境压力下的220 K降至12 GPa下的30 K以下。在5 GPa和10 GPa之间，复杂的磁性超精细模式崩溃，并且在较高压力下出现低矩的磁性基态。电阻率随之降低几个数量级，表明电子系统变得更加流动。完全金属化发生在25 GPa附近，但是在任何压力下都没有发现低至1.5 K的超导迹象。建议将绝缘基态$\left[\mathrm{C}{\mathrm{s}}_6氯\right]\left[\mathrm{F}{\mathrm{Ë}}_{24}\mathrm{小号}{\mathrm{Ë}}_{26}\right]$ 对应于轨道选择性莫特相位，由于带宽增加，莫特相位在压力下转变为洪德的金属态。