杂化钙钛矿中阳离子对压力驱动自旋态转变和协同效应的影响
Cationic Effect on Pressure driven Spin-State Transition and cooperativity in Hybrid Perosvkites
摘要：
已知一般组成ABX $_3$的混合或金属有机骨架（MOF）钙钛矿显示出可导致各种技术应用的令人感兴趣的性质。我们的第一性原理研究表明，他们也是潜在的候选人表现出合作的自旋态转变时，施加外部刺激。我们通过考虑两种特定的铁基MOF钙钛矿，即甲酸二甲铵铁，[CH $_{3}$ NH $_{2}$ CH $_{3}$ ][Fe（HCOO）$_3$ ]和甲酸羟铵铁，[NH $_{3}$ OH][Fe（HCOO）$_3$ ]来证明这一点。这两个化合物被发现进行高自旋（S=2）到低自旋（S=0）的转变在Fe（II）网站后，应用中等强度的流体静压，随着大滞后。这种自旋状态的转变是由电子，磁性和光学性质的变化发出的信号。我们发现的过渡压力和滞后的宽度是强烈依赖于A-网站的阳离子，二甲基铵或羟胺的选择，这意味着调谐的自旋开关性能可实现的胺阳离子的化学变化的结构。我们的发现为最近感兴趣的这一系列材料开辟了新的功能，这些材料在传感器和存储设备中具有重要用途。
英文摘要：
Hybrid or metal organic framework (MOF) perovskites of general composition, ABX$_3$, are known to show interesting properties which can lead to variety of technological applications. Our first principles study shows they are also potential candidates for exhibiting cooperative spin-state transitions upon application of external stimuli. We demonstrate this by considering two specific Fe-based MOF perovskites, namely Dimethylammonium Iron Formate, [CH$_{3}$NH$_{2}$CH$_{3}$][Fe(HCOO)$_3$] and Hydroxylammonium Iron Formate, [NH$_{3}$OH][Fe(HCOO)$_3$]. Both the compounds are found to undergo high-spin (S=2) to low-spin (S=0) transition at Fe(II) site upon application of moderate strength of hydrostatic pressure, along with large hysteresis. This spin-state transition is signaled by the changes in electronic, magnetic and optical properties. We find both the transition pressure and the width of the hysteresis to be strongly dependent of the choice of A-site cation, Dimethylammonium or Hydroxylammonium, implying tuning of spin-switching properties achievable by chemical variation of the amine cation in the structure. Our finding opens up novel functionalities in this family of materials of recent interest, which can have important usage in sensors and memory devices.
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